motor driver

By tlfong01 on May 12, 2021 • ( Leave a comment )

Motor Driver keeps dying/frying driving a worm gear motor

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I am looking for some consultation about controlling a24VDC worm gear moto. I have blown 4 h bridge motor drivers thus far and while I have been trying to keep my project price tag low I may need to step up in quality but I want to make sure something else may be going wrong. I am a ME by trade but I remembered a smidgen about inductive loads and back EMF wreaking havoc on components. I have been using the following: driver 1 and driver 2 to control the motor but they keep failing and at random times. This makes me suspect not my wiring but something else and possibly not protecting the components. My most recent board was working, next thing you know the ERR LED light is on and the manual says “ERR LED Indicator – Error LED Indicator, it will illuminate when fault detected in on board MOSFET driver.”

I would think a motor driver board would know it would be dealing with inductive loads and protect against this but maybe I am wrong. Do I need to spend more money on someting like the following?

Help a poor ME sticking his toe in the water of electronics!

Thanks in advance!mosfet motor h-bridge induction-motor ShareCiteEditFollowFlagasked 7 hours ago TheCodeNovice13355 bronze badges

1What is the frequency of the pwm? Generally I’d put a varistor (MOV) across the motor terminals as close to the motor as possible. Something like a 20mm 30V device. – Kartman 7 hours ago
@TheCodeNovice, Just now I skimmed the Pololu motor driver you are considering, to get a rough idea of your requirements: (1) Pololu G2 High-Power Motor Driver 24v13 (6.5V to 40V, cont 13 A without heat sink, no over-temperature, over current shut-off) pololu.com/product/2992. My first impression is that it is not newbie proof, because over temperature and over current can fry the driver! 🙂 – tlfong01 7 hours ago
1@Kartman my pwm frequency is 10kHz. Do you have a link of MOV so I know what I am looking for? – TheCodeNovice 7 hours ago
1@tlfong01, Would it over heat with out running the motor? I do not think that worm gear motor I am using will run close close to the rated 13A that is why I thought I could slide by without it. Do you know of a nice noob level h bridge brand I could use? – TheCodeNovice 6 hours ago
1Google MOV 20mm 30V – Kartman 6 hours ago
@TheCodeNovice, well, I did fry many gear motors (do’t ask me how many, but I do have spare gear heads, just in case! :)). One of the many reasons are (1) physically overloading, (2) gear stuck or crashed, (3) start current which might be many times of operating current (so Pololu suggests ways to avoid bad things happening, by using big cap near PSU, or slow slow starters). – tlfong01 6 hours ago
For motor newbies, I usually recommend the following Q&A: How to use motor drivers with H-bridge and PWM input, to control direction and speed of DC motors? – EESE, Asked 2020jul16, Viewed 1k times electronics.stackexchange.com/questions/510755/…. I usually newbies to start with plain, old, very power inefficient, stupid, L298N bipolar H-bridge, 4A driver, which has built in Schotty flyback diodes on board/module to protect back EMF. – tlfong01 6 hours ago
You can start messing around with the very popular yellowish, cheapy TT130 gear toy motor with operating current around 350mA, and stall current less than L298N’s max 4A (So it is very difficult for newbies to fry the driver!). After you have gained some experience and confidence, you can bravely go up using mid level MOSFET H-bridges, and perhaps catch up me, the motor driver ninja, with my BTN7971B, max 43A, with current control, current sensing etc etc. You can search “BTS7970”, “BTN7971B” for my related answers. Ah, I missed my locking down morning tea. Good luck and see you later. – tlfong01 6 hours ago
1@TheCodeNovice This is one of those times when I really tend to prefer BJTs. Not because BJTs are better. They aren’t. They are just different. But because it is harder to design MOSFETs for bullet-proof performance in motor bridges like this and if you are buying cheap products chances are you are also buying lower training and experience levels in designing them, too. I’m just a hobbyist and not a well-trained engineer, though. So I’m biased somewhat towards “easy to get right.” Take that into account. – jonk 6 hours ago
1@TheCodeNovice Aside from all the ways the MOSFET gate can acquire far too much charge with inductive motor loads — reversable moreso — MOSFETs also hate sudden junction temperature increases because of over-voltages across their internal body diodes. (Avalanche!) When the MOSFET is switched OFF the inductor’s reverse EMF passing through that MOSFET body diode heats it way past its limited junction temperature and boom. An external high power diode across the DS terminals can help. I guess I’m saying that design experience matters — especially with MOSFETs and inductors. – jonk 6 hours ago
1@tlfong01 if you want to convert this great info into an answer I will accept it. – TheCodeNovice 6 hours ago
1Do you have dead time when switching? – Gil 5 hours ago
@Gil, yes, that is my worry when I studied the OP’s two drivers he frird. His drivers use 4 discrete transistors to form a bridge (I am not sure if the module has hardware “break before make” mechanism so that one transistor switch off before the other switches on, otherwise there would be a “shoot through” current and fry something. The modern H-bridges have built in hardware shoot through through prevention. The two drivers the OP is using are either discontinued (for a reason) or seemingly old design. So I am recommending the newbie proof, L298N BJT NPN H-bridge, with built in flybacks. – tlfong01 5 hours ago
@TheCodeNovice, Thank you for your kindness. I am happy to write up an answer. Cheers. – tlfong01 2 hours ago

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1 Answer

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Question

The OP has so far fried four motor drivers. He wishes to know what went wrong, and how to avoid frying more motor drivers.

Answer

Part A – Analysis of the the OP’s motor and motor drivers

We will first study his motor and motor drivers, and then guess what went wrong.

Uxcell JFC63R Gear Motor (Appendix A)My first impression is that it is a very powerful motor. I usually first look at the motor shaft. The shaft is 10mm diameter, which is for very powerful motors. The power is 80W, an of course is very powerful. This implies big current is need to drive this motor, and that the back EMF, which is proportional to the square of the motor current, is huge, and needs a powerful and fast Schottky flyback diode to absorb the motor’s inductive energy, when the motor current is switched off.Another implication is that even with light load, the motor might not move, and the stall current would be many times of the operating current, and the motor driver might easily get fried, if there is no over current and over temperature protection.

Cryton 80W, 13A Motor Drive MD13S (Appendix B)The Cryton MD13S looks OK, except it can only handle max 13A continuously. As mentioned earlier, this motor stall current may exceed 13A, this overheating the driver and fry it.

Niyito 170W, 110A Motor Driver (Appendix C)The current rating looks OK. However, there is heat sink used, which might be problematic, if there is no temperature protection.

Part B – Suggestion to the OP and other motor newbies

The OP appears to have thrown himself at the deep end of the swimming pool. I would suggest to start learning at the shallow end, ie cheapy motor drivers and motors such as L298N H-bridge motor driver, and TT130 toy motor.

The good thing is that the basic principles of H-bridge drivers are almost identical, no matter current rating. In other words, almost all knowledge and skills can directly transfer when switching to industrial/professional grade stuff.

So, after gaining experience and confidence, he can then try high end motor drivers such as BTN7971B (45V, 50A), and not so powerful (therefore not so easily fried! :)) motors such as JGB37-520 (12V, 350mA), as described in this motor newbie tutorial.

References

(1) Uxcell DC24V 80W 100RPM 8NM 10mm Reversible Worm Gear Motor High Torque Speed Reducing Electric Gearbox Motor-JCF63R – Amazon

(2) Cytron 13A DC Motor Driver MD13S – Amazon

(3) Noyito 170W 2-Channel 3.3V/5V Logic input PWM H-bridge Motor Drive Module – Amazon

(4) Pololu G2 High-Power Motor Driver 24v13 – Pololu

(5) How to use motor drivers with H-bridge and PWM input, to control direction and speed of DC motors?

(6) What is back EMF? EESE, Asked 2021apr27, Viewed 714 times

(7) BTS7960/BTN7971B Motor Driver Q&A 1/2

(8) BTS7960/BTN7971B Motor Driver Q&A 2/2

Appendices

Appendix A – Uxcell Motor

(1) Uxcell DC24V 80W 100RPM 8NM 10mm Reversible Worm Gear Motor High Torque Speed Reducing Electric Gearbox Motor-JCF63R – Amazon