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!
- 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 12 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 12 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 12 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 12 hours ago
- 1Google MOV 20mm 30V – Kartman 12 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 12 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 11 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 11 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 11 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 11 hours ago
- 1@tlfong01 if you want to convert this great info into an answer I will accept it. – TheCodeNovice 11 hours ago
- 1Do you have dead time when switching? – Gil 11 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 11 hours ago
- @TheCodeNovice, Thank you for your kindness. I am happy to write up an answer. Cheers. – tlfong01 8 hours ago
The OP has so far fried four motor drivers. He wishes to know what went wrong, and how to avoid frying more motor drivers.
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.
Appendix A – Uxcell Motor
Appendix B – Cytron Motor Driver
Appendix C – Noyito Motor Driver
Appendix D – Old BTS7970/BTN7971B testing images for the OP’s reference
- BTN7971b module
- BTN7971B wiring
- BTN7971B testing 1/2
- BTN7971B testing 2/2
BTS7960 PWM Test
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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…TheCodeNovice1931Thank you for this well researched answer. One quick one question…. If I am forced to use this motor for my application what would be a suitable noobie driver or what can I put across the motor to give me some buffer. I was looking at the BTN7971B and modules that came up appear to be all 12VDC rated and not suitable for this motor. I think what killed me this go round is I used the manual control buttons which go at 100% duty cycle and back to 0%. My application wont ever do that but I would like some robustness in the electronics anyway. tlfong015917Just a quick reply. (1) BTN7971B is 45V, 44A max. See Ref 9 in my answer.Another quick reply. (1) I always use 12VDC for my all Micky Mouse toy projects using DC motor. For my other projects using bipolar stepper motors, I use 12V to 48V PSU. (2) For DC motor drivers such as L298N and BTS7960/BTN7971B, it is perfectly normal to use 5V, 0V to enable/disable motor operation. If you use PWM signal, that is 100% duty cycle 5V, 0% duty cycle 0V, and between 0% and 100% for speed control. It is completely safe to use any duty cycle values.You might like to read Ref 11 for a review of 80W DC motors. You motor without the gear box is very likely size 775, 24V, 8000 rpm. I have litttle experience in 775 motors. I only play with smaller 12V, 370 motors. But I do have a couple of 12V 775 gear and no gear motors. Perhaps I can search my junk box for them and try to compare with your 24V 775 motors. BTW, you might like to get one or two 775 no gear motor for experiments. Usually you won’t fry no gear motor that easily. It is only geared at low ratio and slow but powerful models that can fry easily.I only played with the old BTS7960 motor driver a couple of weeks ago. I have not yet thoroughly tested the BTN7971B. Perhaps I can try that later, for your reference, but no guarantee at all. I am now reading my old posts (Ref 7, 8) and copy and paste some images to refresh my memory. Please feel free to ask me any newbie questions.I have uploaded some images of my old BTS7960 and BTN7971B tests in Appendix A, Section 1, 2. You might note that in the first photo of the real module wiring, I am using both polyfuse and slow blow fuse to protect my PSU and motor driver module from over current.And in Appendix D Section 2, (a) You use 24V instead of 12V, (b) You use plain jumper wire by hand DC 5V and DC 0V to enable and disable the motor driver operation. (If using PWM, 0% will disable module, 100% will drive motor full speed, and between 0% and 100% for adjusting speed.)And you might like to watch video of Ref 12 to learn how to find you motor’s no load, load, and stall current. Cheers.