About Stepper Motors

_q12x_ · Oct 21, 2022

Actually there is another forum discussion until reaching this cct here. It was an entire evolution of it.
This cct is working ok but in certain parameters. It is limited to power and heat over the Tr's.
Is working fine in the 5V range for 2 of my stepper motors that I tested with it. But if Im bringing up the voltage, to 10V, I get 140dgrC on one Tr and about 60dgrC on a few others. At 5V, everything stays at a constant 50dgrC which I call it normal and safe.
One of the test motor is a Nema17 17HS4401. The other one is a scrapped stepper. Both work fine at 5V and even at 10V, no one was heating. Over 5V, especially at 10V, only the driver's Tr's were cooked to (almost)death. I stopped the power after smelling hot metal in the air.
I am also receiving a couple of L298N IC's. They are coming in the mail, not arrived yet. But I dont expect much difference from them, compared to what I have here. It would be nice to be better ! I hope so.
- My question:
- How to make this cct more powerful? To drive more power through the coils of the stepper motor? (and not blow up it's Tr's!)
I already have 2 answers to this question in my mind, but I dont want to influence your answer. I expect to be pleasantly surprised. Haha.

[ElectriciansForums.net] About Stepper Motors

Thank you !

_q12x_ · Oct 24, 2022

Nonono, all this Heavy math I did here is for (1 coil or motor) that I have brand new.
This is a very important math to be done! Is essential. I am not doing it every day. So thats my excuse not knowing it - not using it. I had to discover it myself from a movie I watched last night on youtube. And I didnt discover it, but I remember it, and I said aaaah, that thing... haha. And I quickly adapt it to my thing here.

marconi · Oct 24, 2022

Yes I understand your maths was for one coil. Mine was to give you a 'leg up' for the mosfet power to size the heat sink/radiator.

_q12x_ · Oct 24, 2022

marconi said:
Yes I understand your math was for one coil.

But I am driving 1 coil at a time, right? I dont need to *2 for both coils. Right?

marconi · Oct 24, 2022

_q12x_ said:
But I am driving 1 coil at a time, right? I dont need to *2 for both coils. Right?

Yes you are right.

marconi · Oct 24, 2022

https://www.farnell.com/datasheets/2303998.pdf

I had in mind last night the use of these opto-isolaters to control the mosfets.

_q12x_ · Oct 24, 2022

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 · Oct 24, 2022

_q12x_ said:
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_ · Oct 24, 2022

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 · Oct 24, 2022

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_ · Oct 24, 2022

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 · Oct 24, 2022

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

_q12x_ · Oct 24, 2022

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

My variable PSU is 30V @ 5A

marconi · Oct 25, 2022

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 · Oct 25, 2022

I will use the IRFZ44N like you.

_q12x_ · Oct 25, 2022

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?