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DRV8801 Problem – Help Needed


#1

I am trying to use the DRV8801 motor-controller to control the motor in an open-source project (HO locomotive). I need help. The controller is not behaving as I expected. I have one on a breadboard in a simple test setup. The general test setup is pictured here:
{removed hard to see pictures}
The primary problem (with PWM to ~5 volts and BREAK to GND) is the applied ~12 volts on VMM is being limited to about ~5 volts, and the board will quickly over heat. I first tested the board by gradually increasing VMM and it was doing basically the same thing. I have tested with both the ~12 volt motor and the ~12 volt resistor-LED.

Thank You!
Bob


DRV8801 PWM voltage
#2

Hello.

It looks like your pictures cannot be viewed without creating an account for the site you linked to; could you try hosting them on our forum or attaching them to your next post? Can you explain what you mean when you say that your 12V input is being limited to about 5V? Where are you measuring the 5V? How quickly does it overheat? What are the specs of your motor, and how much current do you expect it to draw? Have you measured the current draw (or monitored the current sense pin) to try to see how much current is being pulled?

-Brandon


#3

[quote=“RT_Coker”]I am trying to use the DRV8801 motor-controller to control the motor in an open-source project (HO locomotive). I need help. The controller is not behaving as I expected. I have one on a breadboard in a simple test setup.
The primary problem (with PWM to ~5 volts and BREAK to GND) is the applied ~12 volts on VMM is being limited to about ~5 volts, and the board will quickly over heat. I first tested the board by gradually increasing VMM and it was doing basically the same thing. I have tested with both the ~12 volt motor and the ~12 volt resistor-LED.

Thank You!
Bob[/quote]
Thanks!!!
Now with pictures you can see.
Bob





#4

[quote=“BrandonM”]Hello.

It looks like your pictures cannot be viewed without creating an account for the site you linked to; could you try hosting them on our forum or attaching them to your next post? Can you explain what you mean when you say that your 12V input is being limited to about 5V? Where are you measuring the 5V? How quickly does it overheat? What are the specs of your motor, and how much current do you expect it to draw? Have you measured the current draw (or monitored the current sense pin) to try to see how much current is being pulled?

-Brandon[/quote]
I can set the DC train-controller voltage to +12 volts when disconnected, turn all power off, connect it to the circuit, and turn power on with the meter on VMM, and the meter only shows about ~3.5 volts, and the DRV8801 gets hot real-fast.
The motor draws 0.3 amps when directly connected to the +12 volts. Don’t have the specs on it. The maximum current expected is less than 1.5 amps (a stalled HO locomotive).
I have not tried monitoring the current sense pin.
Thanks!!!
Bob


#5

Has your DRV8801 motor driver carrier ever worked for you? From your description, it sounds like there is a short somewhere in your setup. I also noticed that there is a “direction” switch on the supply you are using for VMM. Have you verified that the voltage is not being applied backwards? Our DRV8801 carrier does not have any built-in reverse-voltage protections, so if VMM was ever applied backwards, the board might already be damaged.

Also, it is hard to tell from your pictures, but it looks like a few of your header pins (in particular the VDD and OUT+ pins) might not be soldered. If this is the case, I recommend making sure that all of your header pins are soldered in and making a good electrical connection.

-Brandon


#6

I have a DRV8801 connected in the circuit that I am working on and the one in the breadboard. Neither has ever worked for me, and both are displaying the same symptoms. I have a third DRV8801 that is unused.

I have checked for shorts on the DRV8801 and cannot find any, except between the two GRD connections. The resistance between the various other pins is about what I would expect given the circuit description. I have checked the voltages the breadboard circuit is supplying to the DRV8801 and they are all as expected.

I have been very careful about not supplying a reverse voltage to VBB, but this is still a remote possibility.

I have check and re-solder VMM & OUT+. The circuit is too small for me to accurately verify the solder connections.

The breadboard is still behaving as described earlier.

If you can give me a copy of the test setup and procedure for the DRV8801, I will try it with my remaining DRV8801.
Thank You!
Bob


#7

If you are going to try testing your unused one, I would suggest keeping your setup as simple as you can and testing it without a load. We do not have a wiring diagram for this kind of setup, but you should be able to use a 3.3V to 6.5V source for VDD and use jumpers to connect this voltage to the DIR and PWM pins as well. Also, Could you try using a different supply for your motor power (preferably a simple battery pack or benchtop supply)? If your supply voltage is not dropping anymore in this setup, could you measure the voltage of the OUT+ and OUT- pins to make sure you are getting an output?

-Brandon


#8

I am going to use my last unused (still in the package) DRV8801 in my test setup as you suggest.
Bob


#9

Brandon,
Much Thanks!

My last DRV8801 in the test setup works! I should have breadboard tested everything before trying to put the locomotive configuration together!

I have created a group called “Open-Source-Bluetooth-Train-Control” whose purpose is to encourage, promote, and develop Open-Source-Bluetooth-Train-Control. If you (individual or organization) are interested in possibly being a contributor, you can check it out here: trainboard.com/grapevine/gro … roupid=125
And here: trainboard.com/grapevine/blo … 5-RT_Coker
Bob


#10

I am glad you got it working; thank you for letting us know. If you do not know what damaged the other boards, and you plan on moving the working board to your other configuration, I recommend doing it slowly and in steps. That way, if something goes wrong, you should have an idea where to start troubleshooting. Also, thank you for sharing those links; it looks like a neat project.

-Brandon


#11

I have blown another DRV8801. But now I at least know when it is happening. It happens on the initial power-on surge with the PWN-on and a motor load on the output. Even though the DRV8801 VMM is from a full-ware-rectifier, I suspect that the power-on surge is creating some sort of reverse-voltage that is destroying the DRV8801. The power-on-surge will be unavoidable in normal use of the DRV8801 in the HO locomotive. The input to the full-wave-rectifier is not AC it is a switched DC (looks like a square-wave AC).

Any simple suggestions to fix this (or other ideas about the cause of this problem) from anybody will be appreciated.
Thanks!
Bob


#12

I am not sure if this will help your problem, but if you think a voltage spike is causing the problem, you might read our “Understanding Destructive LC Voltage Spikes” application note (particularly the “Limiting the Magnitude of the LC Spikes” section). You might also consider looking into using TVS or Zener diodes or other voltage suppression measures.

-Brandon