Keep blowing stepper drivers - Page 1
Forum section: electronics / beginners

author: techninja80
author_rank: Regular Contributor
timestamp: August 17, 2021, 09:39:49 pm
content: Having trouble driving this motorhttps://www.openimpulse.com/blog/wp-content/uploads/wpsc/downloadables/42BYGHM809-Stepper-Motor-Datasheet.pdfWith these stepper motor driversDRV8825A4988Wired like this respectivelyhttps://www.makerguides.com/wp-content/uploads/2019/02/DRV8825-Arduino-stepper-motor-wiring-schematic-diagram-pinout_bb.jpgAnd like thishttps://lastminuteengineers.com/wp-content/uploads/arduino/Wiring-Nema-17-Stepper-Motor-to-A4988-driver-Arduino.pngIn both cases I had my power supply to CC of 1.7 amps. In both cases, the driver burns out at around 9V. The only thing that I think is very weird is that this motor says its Voltate is at 3V. Now, this is very strange because all other motors within the same torque rating are at 12+ volts. The drivers won't even turn it on unless it's above 5v. I know I am doing something wrong I assume it is something simple that can be solved and identified with good ole Ohms law, and math. But I am a newbie Any help will be much appreciated.

author: Unixon
author_rank: Frequent Contributor
timestamp: August 17, 2021, 10:30:10 pm
content: What driver boards are you using and what about their pinouts?

author: rstofer
author_rank: Super Contributor
timestamp: August 17, 2021, 10:35:12 pm
content: What is the current limit setting?The motor is rated 3V 1.7A but your driver without forced cooling is only good for 1A.There are some warnings here:https://www.pololu.com/product/1182There is also a video re: setting the current limit.Unless you plan to add forced cooling, don't set the current limit over 1A. This will give lousy performance on a motor rated 1.7A.QuoteThe voltage rating of the motor is of little concern. In fact, we want to drive it at several times nominal voltage in order to overcome the inductance and get faster rise time on the windings for higher rotational speeds. That's all fine and good but we can't overdrive the maximum current rating of either the driver or the motor, whichever is lower."Jones on Steppers"https://homepage.divms.uiowa.edu/~jones/step/My guess is that you are over driving the controller with the 1.7A and no forced cooling. Does it get hot before it blows?Running your power supply in CC mode is probably not helping. Pick a voltage, say 12V, and let the controller limit the current to 1A (without forced ooling). It will do a much better job.

author: janoc
author_rank: Super Contributor
timestamp: August 17, 2021, 10:44:27 pm
content: Quote from: techninja80 on August 17, 2021, 09:39:49 pmI would hazard a guess that you have a short circuit somewhere and/or are putting the motor voltage where it doesn't belong (e.g. a logic level pin).Concerning the voltage - ignore those 3V ratings. They are useless, that is a rating that says what is the max voltage you can use to not exceed the max current rating of the motor windings (and destroy them) when the motors are driven with DC.Which is completely irrelevant in practice because stepper motors are never driven like that - they wouldn't have any torque. All that it is good for is to tell you the resistance of the windings (divide the voltage by the max rated current), but that you can measure using a meter yourself.The driver drives them using short pulses of higher voltage, that limits the amount of energy that gets into the winding so that it doesn't overheat - on average the max rated current isn't exceeded even though the voltage is much higher than what is in the datasheet.How this works is well explained here:https://www.st.com/resource/en/application_note/cd00003774-stepper-motor-driving-stmicroelectronics.pdf

author: janoc
author_rank: Super Contributor
timestamp: August 17, 2021, 10:48:40 pm
content: Quote from: rstofer on August 17, 2021, 10:35:12 pmThat shouldn't blow even if he has the current set too high. Both those driver ICs have both overcurrent and thermal protection and will just shut down if they get too hot (a common problem in some 3D printers that use these).It would be helpful to see the actual setup instead of those silly Fritzing diagrams.

author: rstofer
author_rank: Super Contributor
timestamp: August 17, 2021, 11:27:21 pm
content: Quote from: janoc on August 17, 2021, 10:48:40 pmOverheating is indeed a part of the controller design. Maybe it isn't overcurrent but unless I had current within specs, I wouldn't count it as working.I'm also wondering about the CC power supply mode and whether there is any oscillation in the power input. There is a warning about certain capacitors on the board and transients. Apparently, power glitches can destroy the chip. The warnings are worth understanding.I would put the power supply in regulated voltage mode, set the current at a couple of amps (so the current limit doesn't operate) and then set the chip current limit as given in the video (which I haven't watched).

author: techninja80
author_rank: Regular Contributor
timestamp: August 18, 2021, 01:13:10 am
content: Thanks the diagrams are way better. I have giant jumpers on the breadboard, so it would be a jumble of wires in the end. I just measured the resistance on the paired wires on the motor to see if the motor was defective. Both read 1.8 ohms. I compared it with another motor brand new. Both identical.I took the build apart as I don't have any more drivers. I have 4 more being delivered tomorrow. I will put a pic of the build, before I run it.

author: techninja80
author_rank: Regular Contributor
timestamp: August 18, 2021, 01:15:23 am
content: Quote from: rstofer on August 17, 2021, 11:27:21 pmI will give it a try.

author: janoc
author_rank: Super Contributor
timestamp: August 18, 2021, 07:57:53 am
content: Quote from: techninja80 on August 18, 2021, 01:13:10 amThe point of showing what you have connected where is that you may think you have connected it as in the diagram but in reality you may have connected +12V into one of the logic lines and now are blowing the chips up as soon as the voltage rises above a certain level.The CC mode of the PSU could be, indeed, a problem - there are very often short current spikes as the device switches, which could trigger the current limit (is the PSU CC mode indication flashing/turning on?) and confuse the driver. That would cause oscillation and the chip destroys itself.

author: reed
author_rank: Contributor
timestamp: August 18, 2021, 01:14:12 pm
content: In my limited experience...If the power supply still has charge (or on even) and I tweak a wire then it'll probably blow the driver board! Simple as that, having blown a few I am now very careful and not had any more issues whilst experimenting.I believe it's to do with the capacitors on the driver board, I forget what it's called, but they are sensitive to spikes and inrush currents. I'm sure someone else can explain this better.

author: rstofer
author_rank: Super Contributor
timestamp: August 18, 2021, 04:45:07 pm
content: According to the web page, long jumper wires are not your friend.https://www.pololu.com/product/1182-- see WarningsI would be looking for a different driver. There is a larger version that includes reverse power protection and can also provide 5V and 3.3V power for the uC.https://www.pololu.com/product/1183

author: reed
author_rank: Contributor
timestamp: August 18, 2021, 05:25:18 pm
content: I moved onto TB6600 for my Nema 23 sized motors, but they will work for lower current too

author: techninja80
author_rank: Regular Contributor
timestamp: August 19, 2021, 02:41:24 am
content: Quote from: techninja80 on August 18, 2021, 01:15:23 amHere it is set up with a different motor that requires fewer amps. currently working I will swap out the motor with the desired motor that runs at 1.7A. We will see if this burns out. Here are pics of the build as requested. Wish me, luck folks. My bottle opening robot of seniors and the bottle opening challenged depends on it LOL.

author: janoc
author_rank: Super Contributor
timestamp: August 19, 2021, 08:57:46 am
content: Those loose connections with the jumper wires and breadboard are really really not your friends.See this comment on Pololulu's website that rstofer mentioned?QuoteLoose wires with intermittent contact are a good way to blow things up.Quote from: techninja80 on August 19, 2021, 02:41:24 amThat should not make any difference, the current is limited by your driver's current limit setting and not by the motor. The bigger motor may not have enough torque at the same setting but that's all.However, you may want to look at your power supply. Again, Pololulu:QuoteYou have neither and have connected the supply and everything using long wires - the extra inductance will make the current spikes even worse. That could easily lead to problems.

author: dmills
author_rank: Super Contributor
timestamp: August 19, 2021, 10:05:11 am
content: Second the comment about decoupling, especially if trying to do a high current motor drive on bloody plugin breadboard (awful stuff, shudder).100nF ceramic and a 10uF electrolytic or so across the logic supply right next to the driver on short leads, AND a 100nF + 100uF electrolytic across the motor supply close to the driver would be about my minimum on a motor board.I would also look at your grounding, in particular do the motor and logic current loops share a ground at any point?Looking at the pinout on that board you should be able to get the decoupling caps on the breadboard with no issues.For things like motor driver boards where spikey glitchy mess is a thing, I usually add 330R resistors in series with the control pins, this has no effect on logic levels, but limits the currents that can flow when it all goes sideways, and makes the logic side considerably more robust.

author: techninja80
author_rank: Regular Contributor
timestamp: August 19, 2021, 03:49:20 pm
content: WOW!!! I am blown away by all the help I am getting. First of all thanks to all that have replied. Here is the results of last night.So I had the lower motor working which I showed the pictures of. The next thing I did was try to set the current limit on the IC by checking the AMP draw on the motor with the breaks on full. Here is what I discovered which I believe lead to the two previous burn out. The pot used the change the current limit is very speratic. When I turn it will change from decreasing to increasing even going in the same direction of turning the pot. Previously I was not aware of this and attempted to increase the limit with the motor running watching the amp draw from my power supply.I have a question for you very smart folks. Can someone explain this phenomenon I encountered. My voltmeter was in series with one of the coils of the motor while I was adjusting the current limit on the IC. The voltmeter read 1.6 amp on the motor, however, my Powersupply only reported about 600Ma draw. I know the motor was getting the power from the supply. How can there be two different readings?{EDIT} I would like to add I was able to get the 1.7A motor to run, without blowing up the IC. Like I said I was watching the PS amp reading while adjusting the POT on the IC. This was wrong because the PS was not reporting the correct AMP the IC was putting out. I just got my first Oscilliscope yesterday, so I was wondering if there is a test I can do to help me figure why the PS was reporting the wrong amp draw.

author: rstofer
author_rank: Super Contributor
timestamp: August 19, 2021, 05:37:03 pm
content: Neither of your current readings are likely to represent winding current. The pulse width is too narrow, while stepping, for most meters, including the PSU, to measure accurately.That's why the process is to measure the voltage at the Vref pad and adjust the resistor using a formula provided in the datasheet and also at the web site and likely on the video. The driver knows how to measure the narrow pulses and can limit the current in accordance with the formula.Try the video, it may work out. I still haven't watched it...ETAOK, I watched it...There is a reason that the steady state current will only be about 70% of the nominal value and it has to do with microstepping. But the motor needs to be stationary, you still can't get a good reading of the step pulses unless you use a scope on the Vref pin.EVERYTHING is explained in the video!https://youtu.be/89BHS9hfSUk

author: janoc
author_rank: Super Contributor
timestamp: August 20, 2021, 10:02:12 am
content: Quote from: techninja80 on August 19, 2021, 03:49:20 pmEasy - the pulses are too narrow, the PSU meter basically reads an average value. Ever used PWM to produce "analog" voltage output? It is exactly the same thing. You would need an oscilloscope and measure the current using a fast current probe or a shunt in series with the supply line.The voltmeter - not sure how you are measuring it. If you are measuring the voltage on the reference pin, as described in the documentation, that's the correct way how to get the set current of the driver.If you are measuring current directly in series with one of the motor windings that will give you a completely wrong value because the pulses are again too narrow for the bandwidth of the meter and they are far from sinusoidal. Again, you would need an oscilloscope to measure the current accurately.

author: jmelson
author_rank: Super Contributor
timestamp: August 20, 2021, 05:24:04 pm
content: On the CRAMPS board, which uses these type stepper drivers, I have a 100 uF 35 V aluminum electrolytic cap across the motor power supply (pin 16 to pin 9).This is highly recommended, and I can't see anything like that on your breadboard.Jon