TMH-260 Turbo

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Al Nejati
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Re: TMH-260 Turbo

Post by Al Nejati » Sun May 09, 2021 12:59 am

I have several questions but the most important observation is that you may need diodes from each motor phase to 40 V, as in the attached schematic for a unipolar stepper driver.

Without that, you'd be getting inductive voltage spikes every time a mosfet turns off. These spikes can very easily kill the mosfets. The zener/avalanche diodes (D1-D4) probably aren't doing anything to protect the mosfets from these spikes:
1. They probably lack the ability to actually carry the amount of current required here (up to 7-8 A spikes, or 1-2 A continuous)
2. Their breakdown voltage (120v) is higher than what the transistors can tolerate anyway.
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Gustavo Cervantes
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Re: TMH-260 Turbo

Post by Gustavo Cervantes » Sun May 09, 2021 2:40 am

Not sure why i wrote IRF530, Im actually using IRF630's,
When i started working on this controller i actually was using Flyback diodes instead of Zeners to disipate the energy, however i noticed that the common wire was heating up, which stopped after switching to the zeners, the ones im using are 1N5381B
On the board i forgot to ad a few resistors and the gate protection zener, i bodged them on this last effort.
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Al Nejati
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Re: TMH-260 Turbo

Post by Al Nejati » Sun May 09, 2021 3:30 am

COM wire overheating is due to the following reason. Each motor winding acts like a transformer. Whenever a half-winding is on, the other half-winding has opposite voltage across it, and now because there's a diode across it too, the transformer is effectively shorted. Current grows through the motor winding without bound.

The solution to this is to instead have the flyback diodes go from the transistor drain to 2*V_supply (80V), rather than 40 V. It's hard to explain this briefly in words, it's best to see this in action in the circuitjs app: https://tinyurl.com/yg3y5ue7
(The transformer is simulating one of the two motor windings; the 20 ohm resistor is simulating the 'load' on the motor).

The switch is set to '80V', if you instead flip it to 40V you can see the current build-up effect occurring.

If the supply doesn't have 80V output, you can 'simulate' it by having a capacitor with a 80V zener, like follows: https://tinyurl.com/yje82yck

The 100 ohm resistor is just arbitrarily chosen; I actually don't know the right value to use here. It would have to be calculated based on allowable voltage drop and dissipation.

Al Nejati
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Re: TMH-260 Turbo

Post by Al Nejati » Sun May 09, 2021 3:34 am

That circuit will both properly snub the voltage spikes and dampen the current spikes through the components.

Gustavo Cervantes
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Re: TMH-260 Turbo

Post by Gustavo Cervantes » Sun May 09, 2021 3:52 am

Well thats seems familiar, thats the topology of a switch mode power supply, to be honest the zener diode idea i took from another guy, seems to work for him, not sure why my implementation is giving me problems.
I will do some measurements and report back.
Thank you Al for your input on this

Al Nejati
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Re: TMH-260 Turbo

Post by Al Nejati » Sun May 09, 2021 3:54 am

No problem!

Actually I have a question for you: how did you drive the hall effect sensors to get that scope output?

Gustavo Cervantes
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Re: TMH-260 Turbo

Post by Gustavo Cervantes » Sun May 09, 2021 4:05 am

Since it was like 2 years ago, im not too sure on the details, i just remember probing with a voltmeter to find the windings, once i isolated those i just took the remaining cables and started aplying 5v and ground to a bundle of 3 with a current limited source until i got a signal out.
And its not a scope it's the serial ploter from the arduino IDE, I did not have a scope then so I had to get creative.

Al Nejati
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Re: TMH-260 Turbo

Post by Al Nejati » Mon May 10, 2021 1:23 am

Chris Giles wrote:
Tue May 22, 2018 8:42 pm
Hi Gustavo,

it looks like you figured it out, but in case it's any help note that the pinout of the motor's connector and its internal circuit are shown on p9 of the user manual for the TCP380 controller (you will find PDF via Google). I don't know what those two components with a Theta symbol by them are. Maybe the resistor shown from pin P to N is a thermistor.

I can also see the service manual for the TCP310. It uses IR3525A PWM controller ICs. I wouldn't fancy trying to replicate a controller from scratch but I wonder that a generic motor controller board could be adapted using the knowledge from the manuals. How did you get on?

Regards
Chris
The components with theta symbol are the thermistors (PTC type). The resistor from P to N is a feedback resistor.

Al Nejati
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Re: TMH-260 Turbo

Post by Al Nejati » Mon May 10, 2021 2:53 am

Also I think I figured out how to properly drive the hall sensors.

As can be seen in the pdf that Chris posted, the hall sensors are series-connected. They are probably intended to be driven with constant current. Based on the manual for the TPH062, I tried a constant current supply of 20 mA, with F being the negative side and G being the positive side of the current supply. Then, the first hall sensor H1 develops either a positive or negative voltage between L and H, and the second sensor H2 will develop a voltage between J and K.

Gustavo Cervantes
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Re: TMH-260 Turbo

Post by Gustavo Cervantes » Mon May 10, 2021 3:44 am

Ok it seems that I misunderstood your last question, at the moment I'm driving the hall sensors with 5v directly, the the output gets compared by the lm2903 to a fixed voltage set via a 10 turn preset that's how I'm getting a 0 or 1 from them,
that's what I feed to the decoder down the line.
I knew there was something else going on there, to be honest I was wondering how the Hall's were connected, but since this seemed to work well enough for my purposes I decided to carry on as is.

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