About Stepper Motors

[_q12x_]

The problem is the very high power over the driving Transistor. That's the key for everything to work.
I did the Heavy math there. So you can do the easy stuff and make it work. Hahahaha.
----
Someone from the other forum, but also form UK, because I asked, told me this:

Notice that they can never get more than +5V, because they are being driven by the 4017 at 5V, regardless of how high your motor supply is. So their emitters only go to ~4.3V, and all the rest of the voltage is dropped across the transistor, causing them to heat up.

And my answer was this:
This is the theory I dont know at all ! This is the first time Im reading it ! Formidable.
So... a BJT transistor is voltage dependent? I never knew. I was having the impression that is behaving like a mechanical switch, also in the sense of letting whatever current and accepting whatever voltage on its C-E to drive higher voltage components/loads. Also in any Transistor datasheet is specified a maximum voltage over C-E, I was sure I got it right. Very curious !
For example:

Or maybe you know this thing in a context I dont know.
Try to understand me here- I really dont know what your logic is and Im trying to get it.
It has sense for the case you described. But also is weird from the datasheet point of view. I cant say I get it.
----
I want some light over this information here. Like I said, I believe what it said, but Im confused.
Try to explain.
Thank you.

 

[marconi]

The problem is the very high power over the driving Transistor. That's the key for everything to work.
I did the Heavy math there. So you can do the easy stuff and make it work. Hahahaha.
----
Someone from the other forum, but also form UK, because I asked, told me this:

And my answer was this:
This is the theory I dont know at all ! This is the first time Im reading it ! Formidable.
So... a BJT transistor is voltage dependent? I never knew. I was having the impression that is behaving like a mechanical switch, also in the sense of letting whatever current and accepting whatever voltage on its C-E to drive higher voltage components/loads. Also in any Transistor datasheet is specified a maximum voltage over C-E, I was sure I got it right. Very curious !
For example:
View attachment 102981
Or maybe you know this thing in a context I dont know.
Try to understand me here- I really dont know what your logic is and Im trying to get it.
It has sense for the case you described. But also is weird from the datasheet point of view. I cant say I get it.
----
I want some light over this information here. Like I said, I believe what it said, but Im confused.
Try to explain.
Thank you.

You know that a diode has a peak inverse voltage rating. Well a transistor, npn or pnp also has diode like junctions to form the collector, base and emitter on semiconductor substrate. Being diode like these junctions have ratings for reverse/inverse voltage to prevent so called avalanche breakdown and damage. Two reverse voltage ratings are specified Vcbo which refers to the cb junction with emitter unconnected ( Ie = 0) and Vceo which refers to the ce junction with the base unconnected (Ib = 0). In the forward biased direction the usual voltages associated with the space charge region apply between transistor junctions for base emitter and base collector which are 0.7V for silicon and 0.2V for germanium.
Have a look at these links:

Transistor terminal voltages - https://www.physics-and-radio-electronics.com/electronic-devices-and-circuits/transistors/bipolarjunctiontransistor/transistorterminalvoltages.html

What is Avalanche Breakdown? | Electrical4U - https://www.electrical4u.com/avalanche-breakdown/

 

[_q12x_]

I know all that basics. Your explanation didnt help. And is ok, dont worry.
Lets concentrate over the bigger problem.
- How to make a more powerful transistorized driver for a 1.7A motor coil? The answer might be using mosfets. Now is a question of how.

 

[marconi]

So you want me to design a driver for the transistors I select from those you have to pass 1.7A in wave mode to the 2 phase bipolar stepper 17HS4401 using the switching waveform produced by your circuit (CD4017)?

 

[_q12x_]

yes
Design from scratch or copy a circuit that is already made and tested in time.
Hopefully one that is not overheating anything, not the motors, not the Transistors or anything else. To run cool.

 

[marconi]

What is the maximum current your regulated bench power supply can deliver?

 

[_q12x_]

What is the maximum current your regulated bench power supply can deliver?

My variable PSU is 30V @ 5A

 

[marconi]

Good morning. I may be a few days starting because I am overdue to deliver on a promise to my wife to install an outside light to cover the far end of the garden so that we can see our Jack Russell when she goes out at night. I am accompanying my wife on an outpatient appointment and this weekend we are away. Thus, next week I will begin.

I have in mind using optocouplers like the ones I mentioned earlier to make the transition between the 5V logic waveforms and the high side transistors. MOSFETs and perhaps some changes to your waveform generator. I have found the NEMA motor and will buy one.

 

[marconi]

I will use the IRFZ44N like you.

 

[_q12x_]

I made this movie last night and is completely unrelated to what we are doing here. Im braging with it and show it off. You can actually see on the table this project we are working right now with the H-bridge and the motors, but I push them away to make room for the new one. Is good to watch a technical video while you are away with your troubles. Especially when you are waiting for something and starts to be boring. See how much I care for you?

 

[marconi]

I am waiting with my wife at addenbrookes hospital Cambridge. The hospital is very large. Not had chance to watch your last video.

https://en.m.wikipedia.org/wiki/Addenbrooke's_Hospital

A question- what do you intend to use the nema17 stepper motor for? Knowing what for would provide me with some (extra) motivation to get started.

 

[_q12x_]

I am waiting with my wife at addenbrookes hospital Cambridge. The hospital is very large. Not had chance to watch your last video.

You will, when you will be bored out of your ears. Waiting in hospital, I know that story, I actually waited for days at some point in my life. I hope is not something serious, but a routine check, right? I wish you and your wife good luck. Good luck from Romania is a precious thing, you get it very rarely in your life. So use it well.
The motor eh? Haha. Well... not really-really a plan per say... but I do have something in mind. Its a very simple thing, but we will get there. Trust me. For now, I want a very serious and stable and reliable stepper motor driver/controller. That is capable (most importantly) to drive at full potential these motors ! Not like my dinky driver that is able to spin them but not really put them to serious work. You get the idea.
Another important thing is accessibility ! We, humans, in these modern days, we got used to already made boards that are performing very well, no doubt about that. But it should be correct to have the proper circuits to build those well performing boards they sell so expensive as well. Dont you think? I very much do. So from that aspect of things, I am very ----ed off and I want to correct it. I want a (very) good performant cct for driving these motors, available, online, on internet, and not hunt for help. That's important ! In my mind. I hope I transmitted to you the same feeling I have. And you should transmit it as well further.

 

[marconi]

I doubt my circuit will be the acme of what is possible. To do that requires considerable testing and real life trials to discover and fix problems which may at first be hidden. That is why in my view some of the best technology is often years old. But my breadboard may work reasonably well as a technology demonstrator which with your patience you can perfect.

 

[_q12x_]

Not acme as you say. Good enough is good for me. You know me.
My only concern is to work at a certain randament or in other words at a certain values I put it to work.
Simple.

 

[marconi]

Stepper and mosfets arrived. And I thought I would do some reading up since the last time I made any circuitry for stepper motors was 40 years ago at college:

https://www.ti.com/lit/ml/slua618a/slua618a.pdf?ts=1666798524312

If you dip into this reference you will see there is more to a good driver circuit than at first blush*. Maybe too mathematical for you but the text is reasonably understandable.

*
at first blush

phrase of blush

1. at the first glimpse or impression.
   "his next decision was at first blush disconcerting"

 

[_q12x_]

WOW- it must cost you a small fortune.
I have a success ! With the mosfets !
I managed to install a primary external PSU of 12V to drive all the gates and the voltage regulator and the logic circuit.
And a secondary PSU, my variable PSU that I can monitor the Amps and Volts on the motor itself.
Here is what I tried:

The 4wire NEMA17 - the new one, worked excellent at the lowest fv to the highest. I didnt reach 5V, but up to it, like 4.5, 4.8V. But the amperage was considerable high, at 1A, 1,2, 1.5. I keep it running most of the time somewhere at 300mA-to-600mA.
Some of the Tr were hot and some were Very-Hot.

I am very happy that nothing burned out.
Well... in my first try I actually forget a link wire in the breadboard and that got extremely hot and the plastic got in thick smoke and I thought it was a Tr. But the Tr was fine. Haha. But that was the only incident and at relatively low power.
No motors , no Tr and no important components were damaged.
The Voltage regulator started to heat up quite high with a heat sink on it. BIGGER is BETTER was always my motto. Haha. But that can wait.
The only failure I have so far, with this current circuit that I just tested, is the second 4wire scrapped motor. It only trembled and never rotated. I switched its connection wires a lot and the motor could NOT start rotating. Only vibrating. I noticed the new NEMA17 was trembling until 4V but after 4V started rotating. So, I increased the Amps and Volts for the scrapped one, I reached 5.5V but at a very high Amp of ~2A, so I dialed down for safety. The Tr's got extremly hot at that point. I did all this experimentation as quickly as I could, in a couple of seconds, no more than 10s per high level of power. Usually I keep everything working at a very safe temperature and power of 300mA and somewhere at 2V. At this level Ican see trembling in the motors and also no heat on the Mosfets or the VoltageRegulator.
Like the BJT version, this mosfet version has the Voltage dependent to the Amps. But is a lot better because is not limited like the BJT was. I couldnt reach 1A with the BJT. If I remember right. At 600mA everything was starting to get extremely hot. So usually if I remember right I was keeping at 300mA or less. Back then the scrapped motor worked perfectly for the tiniest impulses. But now.....????
Now that I have 2 functional circuits, its a stage completed at this point.
I will try to build the BJT that give me the best results, as a stand alone board. As weak as it was, it did served very well for testing the motors. This more powerful mosfet circuit.... hmmm, I will come to it when I will finish the BJT one. If the scrapped motor worked with this mosfet circuit, I would have been very happy. So far im only 50% happy.

 

[_q12x_]

comments from the other forum:
I only look at the top Transistors. All the bottom ones are drive at 5V ! So 4 mosfets in the lower side. Hmmm. I didnt notice it. But it worked like that, haha.
Someone noticed 2 of the mosfets are still working at 5V, and I looked more closely and 4 of them , the bottom ones, are at 5V but I notice after all the thing worked as described. Hahaha
It worked fine....

 

[marconi]

Good morning. I have been studying your latest driver circuit, the one with some mosfets circled in red. I think you have made a wiring error between the cd4017 and the two H bridges. If you think of each of each H bridge as being made up of diagonal pairs of mosfets ie \ and /, then for wave switching the pairs are switched on as in my attachment to #7.

The sequence, looking at my #7 table is 1, 4, 2, 3, 1, 4, 2, 3, 1……..where these numbers refer to the pairs of Q transistors read left to right 1, 2, 3, 4.

Your pairs of diagonal transistor are being switched 1, 3, 2, 4, 1, 3, 2, 4, 1…….

If you study your diagrams at #1 and #36 in the way the 4017 is connected to the two H bridges you should see what I mean.

 

[_q12x_]

Thank you for your last comment.
My friend mister @marconi ... check this out, what I received today !

The far right IC that almost has no marking left on it is the one from you. I notice mine are bigger. I didnt realized it when I buy them. Eh...
Cool, yes ?

 

[marconi]

Thank you for your last comment.
My friend mister @marconi ... check this out, what I received today !
View attachment 103229View attachment 103231
The far right IC that almost has no marking left on it is the one from you. I notice mine are bigger. I didnt realized it when I buy them. Eh...
Cool, yes ?

Your chips At28c64 have 64k of memory whereas the At28c16 I sent you had 16k. Otherwise they have the same technology inside. There are two more pins for the address on yours A11 and A12.