Perhaps a comparator or differential amplifier configured for negative voltages. I'll have to think some more....
When stationary, do you have the motor freewheeling?
OR
Locked rotor?
In other words when the motor is stationary do you have any MOSFETs switched ON?
Thanks.. Tom.. 
Hi, @myksj
Can you please post a copy of your circuit, a picture of a hand drawn circuit in jpg, png?
Hand drawn and photographed is perfectly acceptable.
Please include ALL hardware, power supplies, component names and pin labels.
That is a wire connected diagram, not a net listed PCB diagram.
You need to show signal and power flow, also D, S and G designators not 1, 2, 3.
Sorry but a properly drawn schematic makes troubleshooting so much easier, and you/we are in troubleshooting mode.
Thanks.. Tom..
@DaveX
Thanks for the advice.
Let’s try reducing the ‘time constant’ resistance value.
So far, fortunately, the 'FET' has not died due to electrical driving. Your time constant seems to be correct. I will correct it. Thanks.
@JCA34F
I didn't check the current when I forced it to turn.
(When applying external force to turn the motor, on the PCB)
- It felt like it was dead because the internal pressure was high.
- It was certain that the components were hot.
@jremington
As you said, I think I'm still lacking. I'll study hard. Thank you for your answer.
@JohnRob
Thank you for your reply.
@TomGeorge Thank you for your reply.
After searching, I found the answer I wanted. (Link)
https://www.ti.com/lit/ab/slla527a/slla527a.pdf?ts=1724333465065&ref_url=https%253A%252F%252Fwww.google.co.kr%252F -
(Before) When the H bridge was stopped, all the switches of the MOSFETs were closed.
- Through the link above, I learned that ‘Protection Back EMF’ can be prevented through ‘motor driver’s braking mode’.
- And, I learned that when the H bridge is in use, the voltage should be detected and processed in real time.
- I looked it up because it was a concept I didn't know before.
(Before posting this article, I didn't know about 'Protection Back EMF'.)
Do you mean ALL of the MOSFETs were conducting?
Tom..
That is a problem. If you rotate the motor too fast yon can generate a voltage higher than the battery voltage. Current will then flow through the diodes. You will then exceed the current rating of the diodes. They will burn out and then the MOSFETs.
Your idea with the relay will certainly solve that problem.
nonsense
Thanks for your reply.
First of all, I don't know much about mechanism design. The mechanism structure is shown in the picture, and the height is controlled from 0 to 30m.
- In principle, the position should be controlled through electricity.
- And, when manually controlling the mechanism, it is specified that the motor wiring should be removed and processed.
- However, the user does not follow the manual, and manually raises and lowers the mechanism using an 'electric drill' while connecting the motor wiring. This causes death.
https://www.ti.com/lit/ab/slla527a/slla527a.pdf?ts=1724333465065&ref_url=https%253A%252F%252Fwww.google.co.kr%252F 2 - The above is a case similar to mine. It seems.
(Before posting this) I didn't know about 'braking mode' like in the picture (FIG1) of post #46.
As a result,
-
the diode died due to the internal voltage, causing a short circuit,
-
the MOSFET died due to the short circuit? I assume.
-
When stopped, it seems that it can be solved through 'braking mode' or 'relay switching mode'.
-
According to my research,
While driving, the battery voltage can increase 2-4 times due to 'Back EMF Overvoltage'. This At times, it is said that the voltage should be checked in real time and processed with a discharge resistor.
A motor can be a generator. The "back EMF Overvoltage" is just the plain electricity generated by operating the motor as a generator. Depending on the speed, it could be significantly more than 2-4X the battery voltage.
For your operators, it might be best to add a switch to disconnect the motor labeled something like "FREEWHEEL - BRAKE/CONTROLS" so they can flip it to FREEWHEEL and disconnect the motor from the electronics when they want to drive the motor with the drill. It will move faster and easier with the motor/generator completely disconected (and not attached to a resistor.)
Thank you for your answer.
I have a question because I don't know.
- In terms of small signal analysis, shouldn't the resistor be considered as two 10K resistors in parallel?
- How is '87nF' calculated?
- For example, C(total) = C(gs) + C(gd)
the rotor can be disconnected from main shaft electromechanically. there are decoupler units that raise friction when powered, i've seen such in some printer.
@DaveX
Thanks for your answer.
You are right.
However, users do not follow the manual.
They tell you to remove the motor wire from the PCB when operating manually, but some people do not follow the manual.
Mechanically, the motor itself has an electronic brake, but they remove it and use it.
So, this part should be done in the circuit.
What about your relay solution?
post #12
Method:
- When stopped, 'floating' the wiring through the relay.
- When running, 'connecting' it through the relay.
So problem solved
@kolaha
I don't know much about the mechanism, so I don't know.
However, when the mechanism is raised, the current that goes into the motor is as follows.
- 0~5m: about 5A
- 5~10m: about 7.5A
- 10~15m: about 10A
- 15~20m: about 12.5A
- 20~30m: about ~20A
I don't know much about the mechanism, but they said that the gear(?) changes depending on the section, and the current goes in a lot accordingly.
My question has been resolved. Thank you.
If the 'time constant calculation' is correct as you said, it may have been lucky and not died.
And, the actual operation is
Once a day, and the operation time is about 100 seconds.
It seems that there was no problem when driving electrically because of the short operation.
- Day 1: 30m (after a week) / - Day 8: 0m, withdrawal
(In reality, I don't use it even once a day.)
As you pointed out,
- I think I need to reduce the resistance value.
- I think I need to increase the PWM frequency.
Thank you.
I was certain I got it from the datasheet for your MOSFET:
... but I cant find that number now. Sorry. I might be completely wrong about the timing. You should be able to get the right numbers from the "Gate Charge".