Drivers of Activities

<< Previous Class

“World is made up of precisely two things: living beings and non living things, and then there are all kinds of activities around. Who or What drives these activities, which are happening all around?”, kicked off the 5th session on philosophy.

“As per some philosophies, it is some super power called God, who makes all the things happen around”, answered Vishay.

“But then does that mean, no one has any control on doing anything, it is all as per the super power”, quizzed Mitthyātva.

“Such philosophies believe so. But I don’t think that is practical. May be God has some control and remaining control is left to the individuals – the living beings”, replied Vishay.

“Yes, I know of many philosophies, which propound that doer is the individual, but the result provider is the super power”, intervened Tatva.

“There are a few who believe in no super power as well, and dictates that you are the sole controller of your destiny”, added Ātmā.

“But again, that may not be practical, as we have seen incidents which are totally out of one’s control, whatever one may do”, interrupted Vishay.

“I liked it. A really healthy debate”, praised the professor. “In fact, nothing really right or wrong about these philosophies. It is just that they have been put up from different perspectives, and they may be valid from that perspective.”

“That’s really interesting”, expressed Mitthyātva.

“Yes it is, indeed. And, how about incorporating various of these perspectives in say a unified philosophy?”, questioned the professor.

“O Wow! Don’t tell me that’s possible”, exclaimed Tatva.

Why just possible? In fact, there is a name for the technique of incorporating multiple perspectives.

What is it?

Anekāntvād (अनेकान्तवाद), which is one of the foundation pillars of the philosophy under discussion, all these days.

Okay, so what does it talk about the driver of the activities?

As per it, there is not just 1 or 2 but 5 samvāy (समवाय) or the so called drivers of activities.

Five?! We are already puzzled with two.

Don’t you worry. It would rather help us resolve the unanswered from other philosophies. And the five are:
+ kāl (काल) – time
+ swabhāv (स्वभाव) – the intrinsic property or nature
+ karm (कर्म) – the tiny particles, we learnt about in our previous session
+ purushārth (पुरुषार्थ) – one’s effort, we discussed in our previous session
+ niyati (नियति) – the pre-determined activity – the destiny, which can’t be changed

That seems complicated.

Let’s take some examples to simplify. Take for example a mango seed. We sow that for growing a mango plant, and then into a mango tree, to finally bear mangoes. We water it, manure it, for it to grow healthy and faster. Now, whatever be done, it would take a minimum time for the seed to sprout and come out as a sapling, one can’t make it faster – that is the kāl in action. After all these, what size of tree it grows into, what taste of mango it bears, … is all decided by the karm attached with the soul in the mango tree. Now, if one expects berry from the mango tree, it wouldn’t but give only mango – that is its swabhāv in action. Now, even after the first three in action, if one wouldn’t have done the purushārth of sowing the seed, it wouldn’t have even grown, forget about bearing fruits.

“So, purushārth is the most powerful – that’s why people say don’t stop putting in your effort”, quipped Ātmā.

Your second part is correct that don’t give up your effort, but not the first one. Actually, all the samvāy have their own roles to play. Sometimes one may seem to be more powerful than the other, but all of them have their importance – again that is what is anekāntvād.

If it is not *the* powerful, then what’s the point of doing purushārth?

Understand that you may need all the drivers for an activity to happen. So, skipping purushārth may cause it not to happen at all. Say you are all planned to become rich, you have the characteristics to earn (swabhāv), opportunities to earn (kāl), and karm supporting it – but then you don’t even attempt to earn. In such a scenario, given all possibilities of you becoming rich, you won’t become rich.

What if any of the others is not supporting?

Exactly. Note that, in this scenario, all may be important – and any one missing may lead to not becoming rich. But the challenge is our inability to know about the state of others. More importantly, out of all the samvāy, it is only purushārth, which is under one’s control, none others are – so this is our only key, and *the* key to control or drive the activity – and that’s why we should not stop putting in our effort.

“What is the role of niyati? That has not come in any of the above examples”, asked Tatva with curiosity.

Niyati is what people call the destiny – whatever may happen, if something has to happen, it would happen. For example, if the niyati of the mango seed was to not sprout, even after all the first four supporting samvāy, it would not sprout.

That’s dangerous.

Yes, it is. But typically, only very few things are niyati. And that’s why most of the times, it is not *the* most powerful one, as it may look like in the first go.

But, how is niyati decided? Is it set by a super power? And why is it set, in the first place?

It is set or rather attracted by no other super power but the soul itself. Niyati is basically driven by a special type of karm called nikāchit (निकाचित) karm, attracted & set by soul itself. And it is such, that its effects cannot be altered or removed without bearing them as is, unlike other karm.

But, why would the soul attract the nikāchit karm, in the first place?

As discussed earlier, as long as we do activity, there is continuous inflow & outflow of karm particles. However, if during the inflow, we (as in our soul) is in intense passion of anger, greed, ego, or deceit (AGED), these karm particles get transformed into nikāchit karm.

So, if our soul (as in we), through our purushārth, are never in intense passion of anger, greed, ego, or deceit (AGED), we’d never attract the nikāchit karm, avoiding any effect of niyati.

Yes, no more new niyati drivers. But, you’d have to bear the past ones, if you had already accumulated any.

Hmmm! So, that’s one more strong reason for being simple, devoid of anger, greed, ego, deceit, at least the intensest ones.

Excellent recall. And, finally note that the five drivers are for the activities of living beings. For non-living things, it is only the first two, others don’t make sense.    Send article as PDF   

Theory of Karm

<< Previous Class

“As discussed in our last class, karm (कर्म) particles are the impurities surrounding the soul, obstructing it to attain its state of complete knowledge. But what are these karm particles? Are they living or non-living? Do they decide the fate of soul? Can they ever be eliminated from the soul? If yes, how? Why in the first place are they surrounding the soul? I am sure you have one or more such queries bothering you”, jolted the professor.

“Yes”, came a chorus.

These and many more questions around karm are what are dealt in the theory of karm.

“So finally, are we going to learn how to attain the complete knowledge by eliminating the karm particles?”, asked Jāti.

Dear Jāti, it is a continual learning process, not just a pill to eliminate all karm particles. So, knowing the theory of karm is just the beginning into the process.

Great! at least we’ll begin today.

Karm particles are one of the tiniest granules of matter, and as such they are non-living.

“How does the living soul accumulate the non-living karm?”, asked Upyog.

If it is a pure living soul, it in fact cannot accumulate non-living karm, and that state of soul is what is called nirvāñ (निर्वाण) or moksh (मोक्ष), from which it never comes out. However, the worldly soul is already surrounded by karm ma and these karm leads to accumulating more karm – it is a vicious cycle.

“If it is a vicious cycle, would soul ever be able to come out of it”, asked Yog.

Good question. If left on its own, the karm wouldn’t allow soul to attain nirvān. However, soul has the ability of doing purushārth (पुरुषार्थ), i.e. “putting effort” to break the vicious cycle.

What kind of effort?

Effort to stop the inflow of karm, and effort to remove the existing karm.

How to do the effort?

For that, let’s first understand the process of inflow & accumulation. Any of our mental, vocal, or physical activity brings in the karm. So, stopping or reducing them, stops or reduces the inflow, e.g. taking vows to reduce our activities – the most common & profound activity being eating.

Is that why so many soul centred philosophies are centred around food restrictions?

Sort of – more precisely food control and management, as food is one major activity driver for all living beings.

So, does it directly relate fasting to removal of karm particles?

Yes, it does – just that it should be done with that intention alone – otherwise it may not be that effective.

“Intentions? Do they have any role?”, asked surprised Karm.

In fact, they are the ones having the major role, as intentions trigger thoughts, and thoughts drive the appropriate effort.

Isn’t putting effort an action in itself?

Putting effort to remove karm is an action indeed.

Then, wouldn’t it further accumulate more karm?

It would, but accumulate only good karm particles, eliminating the bad ones.

“Does it mean, it is good to have good karm particles?”, quizzed Yog.

Not really, as even they would obstruct the soul from reaching its pure form. But once all the bad ones are gone, the good ones cannot stay for long – they would eventually go off. And a thing to understand is that more important than the accumulation of karm particles is the strength with which they are bonded with. As it is almost inevitable to reach zero activity, so karm particles would keep on accumulating, till almost our soul gets into pure form. But, if they are accumulated with the least possible bonding strength, they could all be cleared very easily, in lesser go’s.

And how do we control the bonding strength?

The bonding strength depends on the level of kasāy during the bonding.

“What is this kasāy?”, asked Guñasthān.

It is the glue for karm particles. The foursome of Anger, Greed, Ego, Deceit is collectively termed as kasāy. So, having the less of these in our character, enables easy removal of our karm. One may remember them as the acronym AGED. I hope all of you understand these four emotions.

I believe anger is best understood but least worked upon. Greed is want of something more than one’s need, even at cost of others. Ego is the “only me” thought. Deceit is cheating.

More or less correct. And with that I believe you understand why various philosophies talk about being simple, devoid of anger, greed, ego, deceit.

You mean being devoid of AGED paves the path towards complete knowledge.

Yes. Shed anger, be peaceful. Shed greed, be satisfied. Shed ego, be accommodative. Shed deceit, be straightforward. And head towards achieving complete knowledge, and henceforth the state of pure soul.

Next Class >>    Send article as PDF   

Types of Knowledge

<< Previous Class

“Today, we’ll talk about the types of knowledge. Before we start, you may ask any doubts from our last two sessions”, stated the professor.

“In the previous session, you mentioned that all souls already have the complete knowledge. Then, what do you really mean by types of knowledge? Is completeness also of different types?”, quizzed Sharīr.

Excellent. That’s correct that every soul’s complete knowledge is just one – there is no categorization of it.

Then, what do we mean by types of knowledge?

Hope you also remember the discussion, that just having knowledge doesn’t mean having the ability to use it.

Yes – the worldy bounds and limitations, restricts the ability of the soul to use its complete knowledge.

Exactly. So these types or rather levels of knowledge are classified based on the ability of the soul to use its knowledge. Accordingly, knowledge is broadly categorized into five types:

  1. Mati (मति)
  2. Shrut (श्रुत)
  3. Awadhi (अवधि)
  4. Manh Paryav (मन:पर्यव)
  5. Keval (केवल)

Okay, so these are basically levels of exercisable/usable knowledge.

You may say so. Mati knowledge is the most basic form, we perceive through our sense organs and processed/analysed by our mind. Mind (मन) is not just what one relates to brain, but it actually is spread throughout our sense organs and body.

Is Mati, the common sense, we talk about?

Let’s not get into that, as that’s a very loose term we use. Common for one may not be common for others. Basically, the knowledge of sound, colour & form/shape, smell, taste, touch could be assimilated as Mati knowledge.

“So, does it mean that, living beings only with all 5 working sense organs have Mati knowledge?”, asked Yog.

Not really. Every living being has it in some form or the other. Depending on its sense organs, or rather capability of sense organs, a particular one may be used / exhibited more profundly than others. In that sense, you may have heard / read about blind people recognizing colours using touch, and similar other cases.

Wow! This foundation that knowledge is within, would possibly answer many such miracles around us.

Yes. In fact, as you dive deeper into the non-observables, the more you’d realise that there is nothing called a miracle, but just connection of some missing dots.

So can we conclude that, what all observable knowledge we currently know, can be called as Mati knowledge?

Don’t be so impatient. Let me first explain the next one – Shrut knowledge. Then, we shall draw some conclusions. Mati is just the basic form of recognition, but it lacks relation. Hence, we may be able to know using Mati, but may not be able to share/exchange/communicate the knowledge with others. The knowledge which enables us to do that is called Shrut knowledge.

“We communicate using languages. So, are they a form of Shrut knowledge?”, asked Upyog.

Yes, one of the forms, or at least a medium for it. And the language could be anything – written, spoken, pictures, or for that matter even sign. However, Shrut is more than just language – it knowledge about relations, e.g. between words and their meanings, which finally conveys the knowledge. For an example, one may know what an elephant is (Mati knowledge), but in absence of the word elephant, or other words describing it, or one’s inability to express it, one may not be able to convey it to others (absence of Shrut knowledge).

“In that case, all our current knowledge is Mati & Shrut knowledge”, said Yog, in a summarizing tone.

If you just consider the knowledge commonly observable through our sense organs & mind, in day to day life, then yes.

Why only day to day? Does knowledge of *all* observables, still not come under these two categories?

Before I answer that, I’d like to elaborate a bit on observables. By observables, we define anything having one or more of sound, colour/shape, smell, taste, touch. However, even within observables, there is a category, which literally cannot be observed using our sense organs, directly or even indirectly, which we would like to call the invisibles.

May not be observable today, but with evolution of science & technology, shouldn’t one day, we would be able to observe at least all the observables?

No. Even science has proved that there are limits of space & time, beyond which we may not be able to observe, even using any level of technology.

So, we cannot know about the so-called invisibles?

No. We just cannot observe using our sense organs and mind, but we can definitely know about them. And it is the knowledge of such observable invisibles, which doesn’t come under the purview of Mati & Shrut knowledge.

“Is that where the Awadhi knowledge comes into play?”, interrupted Upyog.

Exactly. Awadhi is the knowledge of observables, without using sense organs & mind, typically attained by deep meditation. However, it typically is bound by matter, space, time, properties.

“Any examples of invisibles?”, asked Sharīr.

Particles of speech, particles of thoughts, karma particles are all examples of invisibles.

What are these karma particles?

These are the particles restricting the complete knowledge of the soul.

“O! I see. So removing these we would get the complete knowledge and know everything”, spoke the still silent Jāti.


Please tell us how to remove them.

Yes Jāti, we’ll talk about them, but in separate sessions. Let’s complete our discussion on types of knowledge, today.

“What are these particles of speech and thoughts?”, continued Sharīr.

Our speaking and thinking also emits invisible particles. In fact, specialized knowledge of particles of thoughts is called Manh Paryav knowledge. Having this would enable one to know the thoughts of others.

Wooh! Mind reading.

And finally, Kewal knowledge is the complete knowledge of everthing – observable and non-observable, in all forms, in all spaces, in all times, of all properties.

“… which the soul already has. Just that these karma particles are the nuisances”, Jāti concluded as reminder.

Yes, let’s talk about them in our next session.

Next Class >>

PDF24    Send article as PDF   

Knowing the Knowledge

<< Previous Class

“Today, we’ll talk about knowledge, the very differentiator of our existence”, continued the professor after his invocation.

Still not convinced about knowing the non-observables, Jāti was really keen to know more about knowing.

Before getting into the details of knowledge, let’s try to understand, as who is the one who knows the knowledge. “What do you think, who is the knower?”, asked the prof pointing to Indriya.

“Eyes, I think, as what I see is what I know”, replied Indriya.

If eyes, then why not your other sense organs – ear, nose, tongue, skin – even they acquire their corresponding subjects of sound, smell, taste, and touch.

Ya ya, I think, all the sense organs are the knowers.

Anything else other than the five sense organs?

Hmmm. May be the sixth sense.

Let’s not get into that right away. But we’ll come to it.

Then, may be nothing else.

Okay. Then, with that do you mean that: if you do not see, you do not know; if you do not hear, you do not know; …

“No no professor. I think our mind is the one which knows, sense organs are just the via media, helping it to know”, interrupted Paryāpti.

Quite right, about the sense organs – they are not the actual knowers, they are just the means to acquire knowledge – and that also only some of the means.

Why only some of the means? Are there other means, as well?

Yes. Otherwise, it would mean that one would not know anything without using his sense organs. And then, what about a child, who is blind, deaf and dumb by birth – it shouldn’t be knowing anything other than taste, smell, and touch. But Helen Keller is a famous example pointing against this.

“Possibly, she got to know other stuff using her three sense organs”, quipped Prān.

Very unlikely. But then how does a new born know about crying, say when it is hungry? Or, how does it even know that it is hungry?

That’s basic instinct.

Exactly, that’s what my point is. Where does this basic instinct or basic knowledge come from?

“That’s what I was talking about the sixth sense”, reinforced Indriya.

Yes. But, where does it come from? Isn’t it via something other than the five sense organs?

Possibly yes. Or, may be the mind has it already coded into it, and that’s how it knows it.

Okay. But how did it get encoded into the mind? Or, let’s first understand, what do you mean by mind?

“Mind means our brain, where it is already encoded through genes inherited from parents”, answered Paryāpti.

If it was genes alone, then why didn’t all the knowledge from parents pass along. Why does a kid needs to be taught all over again?

May be only some selected knowledge gets transferred through genes, the one we call basic instincts.

Then, where does the knowledge for intuition, creativity, out of the box thinking, etc come from? Are they basic instincts or not?

Possibly they are also basic instincts.

If they are the basic instincts transferred through genes, then why do they differ drastically even between twins?

“I think they are not basic instincts and their knowledge is rather acquired through our sense organs over time”, interrupted Indriya.

If this knowledge would have been acquired through mere sense organs, it should have been comparable in kids growing in the same environment with similar functional sense organs. But, we have examples of exceptional scientists, grown up among all other ordinary crowd in similar environments, but showing their extra-ordinary knowledge.

“Bottom line is that there must be some means other than the sense organs and the hereditary traits, from which the mind acquires knowledge”, concluded Prān.

And in the purview of science, it is impossible to explain those means. Say e.g. how did Einstein get the extra-ordinary insight into relativity? All kind of observational means would hit some or the other roadblock in answering this question. Then, there has to be something beyond science i.e. something non-observable to answer it. That’s where philosophy pitches in.

“This could be a strong reason to believe that non-observables do exist”, insisted Jāti.

Yes. In fact, the observable mind is just a front-end exhibitor of knowledge and not even the real knower. The real knower is the soul (आत्मा) – the back-end – deep within one self. And it has all the knowledge from time immemorial, so doesn’t need any means to acquire more.

If our soul knows it all, then why don’t we know all?

I just said, that the soul has the complete knowledge. That doesn’t mean that it knows it all, or in other words, it doesn’t mean that it is able to use it all, as well. Having something doesn’t mean that you’ll be able to use it.

So, is knowing, different from having knowledge?

Yes & No. Knowing is having, plus being able to use/apply that knowledge.

Ok, then I’ll rephrase my question. Even after the soul having the complete knowledge, why aren’t we able to know or use it all?

If we were just in our soul form, we would have known everything. But we (the souls) are bound and limited by all kind of worldly observable stuff, restricting our ability to exhibit, or even use our complete knowledge. And that’s why, unaware of that fact, we keep on trying to use various worldly means to keep on knowing more and more of just the observable stuff. Rather, if we are able to remove these worldly bounds and limitations, we’d attain the state of complete knowledge, where, we’d know about everything observable and non-observable.

“Wow! Then, please tell us how to remove these limitations?”, queried the impatient Jāti.

For that, we would first need to understand the various levels of knowledge and their limitations.

“Not now”, was the sigh from Jāti, as the bell rang again.

Next Class >>

PDF24    Send article as PDF   

Philosophy and Science

“Om Arham”, chanted the philosopher before starting his session.

“Why do you say this every time before starting your lecture?”, asked the curious Gati.

Both the words represent encompassing all sounds, thus representing everything. And so I start remembering everyone, as that is what philosophy is all about everyone and everything.

That’s quite of philosophy, but how does the two words encompass all sounds?

Both ॐ (Om) and अर्हम (Arham) sounds start with the first letter अ (a) and ends with the last letter म (m).

You mean letters of Indian languages, or Sanskrit?

Not only Sanskrit, but even its predecessor Prākrit – one of the oldest known languages. Both of them have the first letter as अ (a) and the last letter म (m) of their major alphabet set.

“Okay. But how can philosophy talk about everything, when even science is not yet able to do it?”, interrupted Jāti.

Let me ask you few questions. What is science?

Science is a study to know about the universe i.e. everything – using observations as the basis of that knowledge.

And how old has been this science around there?

It might have existed in some form or other, since long. But, based on what we have studied, there has been dedicated efforts to understand the universe only since these last few centuries.

Exactly. Science, as we know of today, is a study based on observations. And if you define or assume, only what can be observed in the universe, as everything, then primarily science has been only few centuries old. But, if you accept even for a moment that there could be things, which can never be observed – you open up a whole new range of possibilities, which even science cannot talk about, as they cannot be observed.

You mean things beyond everything observable.


That’s absurd.

Why? There are so many things which you do not know and hence you have not observed. Does that mean, it doesn’t exist? I am just asking for a possibility of things non-observable by the five senses (touch, taste, smell, light, sound), directly or indirectly using any kind of instruments.

Okay. So, then what?

Nothing special. Just wanted to let you know that since time memorial, humans have believed in this possibility and have been studying and exploring on “everything”, which includes both observable and non-observable things. And, that study is what exactly called philosophy. Just that in the last few centuries, the focus have become more on the observable stuff, leading specifically to a branch of philosophy called science. And leaving the non-observables alone to philosophy, making us believe that philosophy is all but science.

So science is a branch of philosophy?!


And there are things beyond science – things which science can’t answer?!

Exactly yes. And going to roots, “All science is philosophy but all philosophy is not science”. In fact, science is just a very tiny fraction of the complete world of philosophy.

I don’t believe!

Yes because, we have been brought up only with the mindset that only what science says, exists. And that’s why, before I go further, I request you all, to at the least open up your mind for other possibilities. Otherwise, no point in discussing further. However, after we discuss, you still have the option to reject everything we discussed, if your conscience doesn’t accept it.

“That’s fine. But how do we proof that any non-observable thing exists?”, asked Kāy.

Note that, many theories even in science doesn’t have any proof, but we believe in them as no observations as yet contradicted with them. The day there is a contradiction, we would start looking out for another more fitting theories. Einstein’s theory did the same to Newton’s theory. So, in the same line, why can’t we believe in a theory of non-observables, at least till it finds any contradiction. FYI, towards the end of his life, even Einstein believed that there are things beyond science.

So, is there a theory about non-observables too?

Yes. Not just one, but many. Same as we have many in science. And they are not just about non-observables, but about everything both observables and non-observables. That’s why if we want to study and know about everything, we’d have to go beyond science and study these theories. But as these may not be tied to observations, they are referred to as philosophical theories, or simply philosophies. And that is what we study in a class like this.

“But before we get into any specific theory, I mean philosophy, just wanted to know, is there any possibility of knowing the non-observables?”, intervened the jolted Jāti.

That’s an apt question. Knowing is different from observing. And yes, we can know about the non-observables. In fact, knowing about them itself would be a proof of their existence.

But how do we know about them?

“For that, you have to continue attending these classes”, smiled the professor, as the bell rang.

Next Class >>    Send article as PDF   

Output Level Inversion using 555

This 24th article in the series of “Do It Yourself: Electronics”, does level inversion of a given input using IC 555.

<< Previous Article

By now, Pugs had tried two of the three operating modes of 555 – astable and monostable. How do you think, one can stop Pugs from trying the third one? So, here is his experiment to try the bistable mode, i.e. in which both high & low outputs are stable, meaning the circuit remains in the state it is in, unless triggered externally to go otherwise. A typical usage of this could be a NOT gate kind of level inversion by simply tying the input to both the trigger pin 2 and threshold pin 6.

Below is the schematic, and the breadboard connections made by Pugs with input from a pulled up switch:

Bistable (Level Inversion) using 555 (Schematic)

Bistable (Level Inversion) using 555 (Schematic)

Bistable (Level Inversion) using 555 (Breadboard)

Bistable (Level Inversion) using 555 (Breadboard)

This configuration is also referred as inverting Schmitt Trigger, and very useful in boosting fainting digital signals (though inverted) and removing noise. Putting two of such would make it non-inverting. But how does it boost or remove noise? Let’s assume Vcc = 5V. Say logic 1 (5V) signal is fainting to 4V. As it is still above 2/3 of Vcc (3.33V), the above circuitry will hit the threshold and output would be 0V (boosted logic 0). Similarly, if logic 0 (0V) is fainitng to 1V, still less than 1/3 of Vcc (1.67V), it would hit the trigger and output would be 5V (boosted logic 1). And in both cases, the output can be fed into another such circuitry to get the input boosted without inversion.

The following video clip shows the immediate output level inversion. Specifically, observe that LED is off (low output) on switch released (i.e. high input) and LED is on (high output) on switch pressed (i.e. low input).


Interestingly, the bistable output can also be obtained using two separate switches, providing a possibility of using the setup in a system, controlled by switches. Here are two possible schematics for the same:

Bistable (Schmitt Trigger Circuit 1) using 555 (Schematic)

Bistable (Schmitt Trigger Circuit 1) using 555 (Schematic)

Bistable (Schmitt Trigger Circuit 2) using 555 (Schematic)

Bistable (Schmitt Trigger Circuit 2) using 555 (Schematic)

In both the above circuits, pressing switch SH will take the Vo output high, and pressing the switch SL will take the Vo output low. The only difference being as how is the Vo output brought low – in the first one using the trigger pin 6 and in the second one using the reset pin 4.    Send article as PDF   

Pulse Generation using 555

This 23rd article in the series of “Do It Yourself: Electronics”, generates a desired width pulse using IC 555.

<< Previous Article

After the square wave experiments, Pugs got more interested in understanding all the working modes of 555. His further studies revealed to him that 555 has basically three modes of operation:

  1. Astable – Both high & low outputs are unstable and keeps on oscillating to the other, i.e. high to low and low to high. So, also called oscillator. Examples include all the square wave generation, experimented till now, in the previous articles.
  2. Monostable – Exactly one (mono) of the outputs either high or low is a stable state. However, on an external trigger, it temporarily goes to the other unstable state, stays there for a predefined time and comes back to the stable state, on its own. This is what Pugs is planning to explore further by using a switch for the trigger. The pulse width of the unstable state is decided by the resistor and capacitor in the circuit. As it generates single (mono) pulse on trigger, it is also called monoshot configuration.
  3. Bistable – Both high & low outputs are stable, meaning the circuit remains in the state it is in, unless triggered externally to go otherwise. A typical usage of this could be a NOT gate kind of level inversion. Pugs plans to explore this in his next experimentation.

Now interestingly, the mono stability could be either in the low output or the high output. Correspondingly, the pulse would be high or low, and the trigger accordingly would be low or high. And for each of these the circuits are slightly different, especially from the perspective as to where the trigger is applied. Recall that voltage below 1/3 of Vcc on trigger pin 2 triggers output Vo pin 3 to high and voltage above 2/3 of Vcc on threshold pin 6 brings back output Vo pin 3 to low.

Below are the corresponding schematics, and the breadboard connections made by Pugs:

Monostable Low (High Pulse) using 555 (Schematic)

Monostable Low (High Pulse) using 555 (Schematic)

Monostable High (Low Pulse) using 555 (Schematic)

Monostable High (Low Pulse) using 555 (Schematic)

Monostable Low (High Pulse) using 555 (Breadboard)

Monostable Low (High Pulse) using 555 (Breadboard)

Monostable High (Low Pulse) using 555 (Breadboard)

Monostable High (Low Pulse) using 555 (Breadboard)

Observe that in either case, the trigger is being achieved on press of the switch. However, for triggering the high pulse (on Vo), Pugs needs to connect the pulled up switch output to trigger pin 2. And, for triggering the low pulse (on Vo), Pugs needs to connect the pulled down switch output to threshold pin 6. Also, note that in the first case, the final output Vo is brought back low by charging the capacitor connected to the threshold pin 6, to 2/3 of Vcc through R. And in the second case, the final output Vo is brought back high by discharging the capacitor connected to the trigger pin 2, to 1/3 of Vcc through R. And hence, in either case, the pulse width (time from trigger to restoration of stable state) would be decided by the following equation:
t_{pulse} = R * C * ln(3) … (6)
One may derive this, using the methodology similar to the one used in this previous article. So, it is left to the reader to derive the same.

Pugs tried the first (monostable at low output) experiment using two set of values: (1) R = 10KΩ, C = 100μF, (2) R = 10KΩ, C = 470μF. Using (6), the corresponding pulse widths are expected to be approximately 1 and 5 seconds.

And then he tried the second (monostable at high output) experiment using R = 10KΩ, C = 470μF. Using (6), the expected pulse width is approximately 5 seconds.

As in previous articles, Pugs tried observing the Vo output waveforms on the home-made PC oscilloscope, as created in his previous PC Oscilloscope article. But he observed nothing other than noise, except some change when he presses the switch. This reminded him that the home-made PC oscilloscope filters out low frequency (DC) voltages, and with such low frequency Vo, there would be nothing left to observe after filtering, except when there is some change on switch press. So, Pugs decided to rather use a multimeter. But, then got the idea of putting an LED instead, which is what is visible in the above circuitries.

And here are the three video clips of the LED blinkings observed in the three cases:

(1) 1 second high pulse (monostable low)


(2) 5 second high pulse (monostable low)


(3) 5 second low pulse (monostable high)


Observe the closeness of the pulse width timing (with a watch) from the above videos compared with the expected values.

Also note that during the low pulse (monostable high) experiment, Pugs is waiting for another 5+ seconds after the output Vo is high, before pressing the switch again. In fact, when he tried doing it without waiting, this is what he observed:


That’s weird – the pulse width also has reduced. But why is that? Possibly, because the capacitor is not charged back to the full, before the switch press and so it got discharged faster. That brings to the point, that derivation of equation 6 assumes that the capacitor is completely discharged in the first case (monostable low) and completely charged in the second case (monostable high), before the trigger. If not, the calculations would vary. Now, in the first case the capacitor gets immediately discharged as it is directly grounded through discharge pin 7. So, such scenario wouldn’t happen with that. However, in second case the charging is through resistors R & R1, so that would take its own time based on the RC value, which in the above case is 5+ seconds ((10 + 1)K * 470u). To avoid this, Pugs possibly would have to by-pass the big R in the charging cycle by putting a diode in parallel with R. If you believe it, go ahead and try it out.

Note: R1 has been taken small compared to R, exactly for reducing the RC effect. However, it cannot be made zero, as that would short the Vcc & GND (from discharge pin 7) when the low pulse is getting output on Vo.

Next Article >>

PDF24    Send article as PDF   

Symmetric Square Wave using 555

This 22nd article in the series of “Do It Yourself: Electronics”, finally generates a 50% duty cycle waveform using IC 555.

<< Previous Article

After failing to achieve 50% duty cycle square wave, or so called symmetric square wave, using his trivial circuitry, Pugs further explored. One clear observation was that the output pin 3 is the only pin which goes both high and low, correspondingly during the charging and discharging cycle. So, not using pin 3 means that there has to be two separate paths for charging and discharging the capacitor C, meaning two separate resistors R1 & R2 similar to the initial design as in the first 555 article.

So, Pugs restarted with the same initial design, where R2 was in discharging path and R1 + R2 in the charging path. Clearly, the problem is that R2 is also in the charging path, making it non-symmetrical. The thought of “Can R2 be removed just from the charging path?”, treaded Pugs into the short circuit and open circuit properties of diodes correspondingly in their forward and reverse biases. “Yes! Why not put a diode D1 in parallel with R2, such that D1 is short (aka forward bias) in charging cycle, and it is open (aka reverse bias) in discharging cycle?”, exclaimed Pugs. Thus, R2 would be by-passed in the charging cycle and used in the discharging cycle, exactly as desired. Here’s the modified circuit, which has just clicked:

Approximate Symmetric Square Wave using 555 (Schematic)

Approximate Symmetric Square Wave using 555 (Schematic)

Now the charging path has the resistor R1 & capacitor C, and the discharging path has the resistor R2 & capacitor C. So, we would get,
t_{on} = R1 * C * ln(2) … (4)
t_{off} = R2 * C * ln(2) … (5)

And if we put R1 = R2, we get a 50% duty cycle.

Live Demo

What do you think would Pugs wait for? Here’s his breadboard layout with two 4.7KΩ resistors (both of which closely measured 4.3KΩ on the multimeter), and a 1μF capacitor:

Approximate Symmetric Square Wave using 555 (Breadboard)

Approximate Symmetric Square Wave using 555 (Breadboard)

The audio jack is being used for observing the waveforms on the home-made PC oscilloscope, as created in his previous PC Oscilloscope article.

Below is the waveform observed by Pugs, for the values of R1 = R2 = 4.3KΩ (measured), and C = 1μF:

R1 = 4.3K, R2 = 4.3K, C = 1u, D1

R1 = 4.3K, R2 = 4.3K, C = 1u, D1

From the above waveform, we approximately have t_on = 3.2ms and t_off = 3.0ms. Close enough to our expected value of 2.98ms (as per equation 4 or 5), but not really satisfactory as t_on and t_off are still not exactly same, even though R1 and R2 are closely equal.

In fact, t_on is slightly more, meaning the resistance in the charging path is more than just R1. O Yes! Our diode D1 is not an ideal diode, it would have some resistance in the forward bias as well, and that is what is getting added up in the charging path, causing this deviation. But how to avoid this? How about adding an equivalent diode D2 in the discharging path? That’s a cool idea, which looks like as shown below:

Symmetric Square Wave using 555 (Schematic)

Symmetric Square Wave using 555 (Schematic)

Pugs’ breadboard connections for the same are as follows:

Symmetric Square Wave using 555 (Breadboard)

Symmetric Square Wave using 555 (Breadboard)

Captured waveform as follows:

R1 = 4.3K, R2 = 4.3K, C = 1u, D1, D2

R1 = 4.3K, R2 = 4.3K, C = 1u, D1, D2

And, now we see that t_on and t_off both are approximately equal to 3.2ms.

To be more exact, one may use a pot in place of R2 & D2, and then adjust it to match it with resistance of R1 & D1 – more precisely by matching the off cycle to the on cycle.

Next Article >>

PDF24    Send article as PDF   

Trivial Square Wave using 555

This 21st article in the series of “Do It Yourself: Electronics”, tries generating a 50% duty cycle waveform using a non-conventional trivial circuit using IC 555.

<< Previous Article

On further observation, of the IC 555 behaviour, Pugs got a trivial idea of generating 50% duty cycle square wave using just one resistor and one capacitor as shown in figure below:

Trivial Square Wave using 555 (Schematic)

Trivial Square Wave using 555 (Schematic)

Note that, both the charging & discharging paths would have the same resistor R & capacitor C. So, putting in the equations (1) & (2) derived in the previous article, we would get,
t_{on} = t_{off} = R * C * ln(2) … (3),
thus giving a 50% duty cycle.

Live Demo

Excited by his idea, Pugs couldn’t wait but try out the same. So, he set the above circuitry on a breadboard as shown in the figure below:

WARNING: Do NOT put the pot to a value of zero, as that will overload the circuit. A safety workaround could be to put a fixed 1K resistor in series with the pot.

Trivial Square Wave using 555 (Breadboard)

Trivial Square Wave using 555 (Breadboard)

The audio jack is being used for observing the waveforms on the home-made PC oscilloscope, as created in his previous PC Oscilloscope article.

Then, for C as a 1μF capacitor, he adjusted R to different values to get different frequencies with 50% duty cycle. But, what’s this, none of them have a 50% duty cycle.

Below are some of the waveforms being observed by Pugs, for the values of R being adjusted to 1.5KΩ, 5KΩ, 10KΩ:

R = 1.5K

R = 1.5K

R = 5K

R = 5K

R = 7K

R = 7K

From the above waveforms, we approximately have the following t_on & t_off:
R = 1.5KΩ => t_on = 2.8ms, t_off = 1.1ms
R = 5KΩ => t_on = 8.9ms, t_off = 3.4ms
R = 7KΩ => t_on = 12.5ms, t_off = 4.8ms

Now, as per equation (3), for C = 1μF, and the above three R values, we should have got the following:
R = 1.5KΩ => t_on = t_off = 1.0ms
R = 5KΩ => t_on = t_off = 3.5ms
R = 7KΩ => t_on = t_off = 4.9ms

t_offs are pretty exact, but t_ons are really high. After quite a bit of analysis, Pugs realized that the peak Vo is not actually reaching Vcc. Debugging trick he used, was to replace the 1μF capacitor by a 100μF capacitor, thus reducing the frequency in Hz (eye observable), and then measuring the Vo using a multimeter. Aha! if the Vo doesn’t reach Vcc, then in the above circuit, we are not charging the capacitor using Vcc but this measured peak value of Vo. Mathematically, this changes our derivation for equation (1) in the previous article, though equation (2) remains the same. And hence, getting a correct t_off but incorrect t_on. Even conceptually, we can see that as Vo is less than Vcc, the capacitor would take more time to charge, and thus increasing the time (t_on), as observed in all the readings above.

On this realization, Pugs approximated the measured value of maximum Vo to 3.65V, i.e. 3.65/5 of Vcc instead of Vcc in deriving the equation (1) of the previous article, getting the following relation:
2/3 * V_{cc} = 3.65/5 * V_{cc} * (1 - e^{\frac{-t_{on}}{R*C}}) + 1/3 * V_{cc} * e^{\frac{-t_{on}}{R*C}},
which on simplifying gives:
t_{on} = R * C * ln(6.2632) = R * C * 1.8347

Putting in the values, gave t_on values amazingly close to the observed values, thus again verifying the theory.


Also from the 555 IC datasheet, Pugs found that there is always some expected drop on the peak Vo from the supply voltage Vcc, and the peak Vo in most cases would be less than Vcc – thus rendering all our standard calculations of t_on futile. In fact, if we put the actual value of peak Vo in our calculations, we would get the results as observed. But getting the actual value of Vo is non-trivial and non-standard. Moreover, even if we do that somehow, we are not going to get our desired 50% duty cycle.

Thus, moral of the story is that, in general, Vo should not be used to generate the trigger voltages, as practically it may not be reaching Vcc, as in the case above. And, Pugs would have to find out some other way to achieve 50% duty cycle.

Next Article >>    Send article as PDF   

Square Wave using 555

This 20th article in the series of “Do It Yourself: Electronics”, explains the basic working of IC 555 and generating a square wave using it.

<< Previous Article

Playing with raw electronics (without any microcontroller), further boosted the confidence of Pugs to dive into non-microcontroller electronics. This time he decided to explore the ever popular IC 555, loosely also known as the timer IC.

555 Functionality

555 is basically an 8-pin IC, with pin 1 for GND, pin 8 for Vcc, and pin 3 for Vo – the output voltage, which goes either high (Vcc) or low (GND), based on the other pins.

Vo goes high if the trigger pin 2 senses voltage less than 1/3 of Vcc. Vo goes low if the threshold pin 6 senses voltage greater than 2/3 of Vcc.

Pin 5 can be used as a control voltage always fixed to 2/3 of Vcc. Putting reset pin 4 low any time makes Vo go immediately low. So, if not in use it is recommended to be tied to Vcc.

Discharge pin 7 becomes GND when pin 6 senses voltage greater than 2/3 of Vcc and becomes tristate (open) when pin 2 senses voltage less than 1/3 of Vcc. In other words, discharge pin 7 becomes GND when Vo goes low and becomes open when Vo goes high.

Generating a Square Wave

Given this background, one of the common uses of the 555 IC is to generate a square wave of any particular frequency and duty cycle (on pin 3), by varying some analog voltage between GND and Vcc (on pins 2 and 6), more precisely between 1/3 Vcc and 2/3 Vcc, both inclusive. And this analog voltage is typically achieved by charging / discharging a capacitor through one or more resistors. Thus, the time constants given by τ = RC, R being the resistance, and C being the capacitance in the corresponding charging & discharging paths, controlling the corresponding on & off cycle of the square wave.

Let’s consider the following circuit with R1 as a variable resistance (pot) between 0-10KΩ, and R2 as fixed resistance of 4.7KΩ, and C as a 1μF capacitor.

Square Wave using 555 (Schematic)

Square Wave using 555 (Schematic)

In the on cycle (when Vo (pin 3) is high), pin 7 would be open. Pins 2 & 6 can be assumed tristate. Hence, then C is getting charged towards Vcc through R = R1 + R2.

In the off cycle (when Vo (pin 3) is low), pin 7 would be GND. Pins 2 & 6 can be assumed tristate. Hence, then C is getting discharged towards GND (pin 7) through R = R2.

Moreover, note that in the on cycle as soon as capacitor voltage reaches 2/3 Vcc, Vo (pin 3) becomes low, and pin 7 becomes GND, i.e. off cycle starts.

And, in the off cycle as soon as capacitor voltage drops to 1/3 Vcc, Vo (pin 3) becomes high, and pin 7 becomes tristate, i.e. on cycle starts.

And the above sequence keeps on repeating, thus giving a square wave on Vo (pin 3), with on time t_on controlled by charging through R1 + R2 and off time t_off controlled by discharging through R2.

From RC circuit analysis, we have that voltage Vc across a capacitor C, getting charged through resistance R, at time t is given by:
V_c = V_s * (1 - e^{\frac{-t}{R*C}}) + V_i * e^{\frac{-t}{R*C}},
where Vs is supply voltage (Vcc in our case), Vi is the initial voltage on the capacitor.

So, t_on could be obtained from the fact that it starts with inital voltage Vi = 1/3 Vcc, and ends when Vc = 2/3 Vcc, being charged by Vs = Vcc through R = R1 + R2. That is,
2/3 * V_{cc} = V_{cc} * (1 - e^{\frac{-t_{on}}{R*C}}) + 1/3 * V_{cc} * e^{\frac{-t_{on}}{R*C}},
which on simplifying gives:
t_{on} = R * C * ln(2) = (R1 + R2) * C * 0.6931 … (1)

Similarly, from RC circuit analysis, we have that voltage Vc across a capacitor C, getting discharged through resistance R, at time t is given by:
V_c = V_i * e^{\frac{-t}{R*C}},
where Vi is the initial voltage on the capacitor.

So, t_off could be obtained from the fact that it starts with initial voltage Vi = 2/3 Vcc, and ends when Vc = 1/3 Vcc, being discharged through R = R2. That is,
1/3 * V_{cc} = 2/3 * V_{cc} * e^{\frac{-t_{off}}{R*C}},
which on simplifying gives:
t_{off} = R * C * ln(2) = R2 * C * 0.6931 … (2)

Live Demo

Pugs doesn’t get a punch unless he sees the theory working in practice. That’s where, he sets up the above circuitry on a breadboard as shown in the figure below:

WARNING: Do NOT put the pot to a value of zero, as that will short Vcc & GND, and may blow off the circuit. A safety workaround could be to put a fixed 1K resistor in series with the pot.

Square Wave using 555 (Breadboard)

Square Wave using 555 (Breadboard)

The audio jack is being used for observing the waveforms on the home-made PC oscilloscope, as created in his previous PC Oscilloscope article.

Below are the three waveforms Pugs observed for the values of R1 being adjusted to 1.28KΩ, 4.2KΩ, 8.6KΩ:

R1 = 1.28K, R2 = 4.3K

R1 = 1.28K, R2 = 4.3K

R1 = 4.15K, R2 = 4.3K

R1 = 4.15K, R2 = 4.3K

R1 = 8.60K, R2 = 4.3K

R1 = 8.60K, R2 = 4.3K

From the waveforms, Pugs approximately have the following t_on & t_off:
R1 = 1.28KΩ => t_on = 3.8ms, t_off = 3.0ms
R1 = 4.15KΩ => t_on = 6.0ms, t_off = 3.0ms
R1 = 8.60KΩ => t_on = 9.0ms, t_off = 3.0ms

Now, as per equations (1) & (2), for C = 1μF, R2 = 4.7K, and the above three R1 values, we should have got the following:
R1 = 1.28KΩ => t_on = 4.1ms, t_off = 3.3ms
R1 = 4.15KΩ => t_on = 6.1ms, t_off = 3.3ms
R1 = 8.60KΩ => t_on = 9.2ms, t_off = 3.3ms

Pretty close, but the t_off not really satisfactory. That triggered Pugs to take out his multimeter and check the resistance of the fixed resistor R2, he used. Ow! that actually measured 4.3K. Recomputing using R2 = 4.3K, gave values amazingly close to the observed values.


Thus by appropriately choosing the R1, R2, and C values one should be able to get a square wave of a desired frequency given by 1 / (t_on + t_off) and duty cycle given by t_on / (t_on + t_off). Obviously, the frequency would have a practical upper limit dictated by the 555 IC, though it is typically in MHz. What about duty cycle? Note that as per relations (1) & (2), t_on will be always greater than t_off. Thus, duty cycle would be always greater than 0.5.

So, what if we need duty cycle less than 0.5, or at least equal to 0.5, where t_on = t_off. This is what Pugs is working out on. Watch out for the next article.

Next Article >>    Send article as PDF