I had no problem getting my 3pi+ 32U4 bot running. I wrote a small sketch to have the bot run for a few inches and stop at a precise point. Everything was working fine and I was tuning some of the parameters (polling interval, rate of deceleration etc) when the unit suddenly wouldn’t power up any more. There are no hardware additions, just the stock robot from Pololu. I made my parameter changes, pushed the sketch to the robot and ran it a couple of times when it failed (power switch won’t work and blue led won’t light up). So the failure was not on a first run with a new sketch.
When I connect the bot to my macbook, the green leds light up fine, blue led underneath also lights up and I can transfer new sketches to the Arduino. I placed an audio chirp at the start of the sketch and that runs fine too. It’s just the auxiliary power circuitry won’t come on and the motors won’t turn without the power being on (power led doesn’t light up).
I’ve tried: a) resetting twice and reloading my sketch. No change b) removed the oled and tried - again no change. c) tried 3 different sets of tested batteries - no change.
How would I go about debugging this? I have a multimeter I can use. Could this be a hardware problem?
Thanks for any tips.
Hello.
With the robot not connected to USB, could you try turning the power switch to the ON position and measuring the voltage between ground (GND) and the following pins?
- VB (battery voltage after power switch)
2 VBAT (battery voltage after reverse-voltage protection circuitry)
- VREG (output of the 5V regulator)
- 5V (output of the power selection circuit)
Here is a diagram showing the location of those pins:
You can also find more information about each of them in the
“Power” section of the
Zumo 32U4 Robot’s user’s guide.
Brandon
Brandon
Thanks for the quick response. I have the 3pi+ bot with the circuit board that looks like this:
I don’t see any board markings or pinouts (in the diagram) labeled VB. What am I seeing are:
GND-VBAT 6.1
GND to PWRA - 4.6
Not sure if these are the numbers you’re looking for. I took the measurements from the lower right section of the board as in the attached photograph.
Kishore
GND to PWRB - 0.01
GND to 5V - 0.0
Sorry for the mix-up! It looks like you found the appropriate diagram.
If the 5V pin is measuring 0V when the robot is powered from the batteries (without the USB connected), then it is likely that the 5V regulator is damaged or not getting power. Can you check the voltage at the VSW pin (which is the voltage after the power switch that powers the regulator) as well as the voltage at the VM pin (which is the output of the regulator that powers the motors)? Both of these pins can be found at the front-left side of the robot:
Brandon
I’m seeing 0V for VM and 0.01 for VSW.
Kishore
Any suggestions for next steps?
Thx
Kishore
Could you post some pictures of the top-side of your 3pi+ robot?
Just to confirm, you can measure the expected battery voltage (~6V) at the VBAT pin (located at the bottom-right side of the robot), but even after pressing the power button, the voltage at the VSW pin stays near 0V?
Brandon
That’s correct. About 6V at VBAT, and 0.01V ar VSW even after pressing the power button. Picture of the board attached.
Thanks for the confirmation. At this point, there is probably not much more we can do without actually looking at the unit ourselves. Can you email us with your order information and a reference to this forum thread?
Brandon
I’ve done that. Thanks for your help.
In case it helps anyone else having a similar problem, here is what we found:
There was some corrosion on one of the batteries and corresponding battery contacts from what appeared to be leaked battery acid:
Even though the battery voltage was showing up at VBAT, it was interfering enough to prevent the robot from turning on. After cleaning up the battery contact and switching to fresh batteries, the robot is able to turn on and off normally again.
Brandon