ThunderBorg Power Issue Diagnosis and Repair

Submitted by JonnyAlpha on Fri, 04/30/2021 - 14:54

Forums:

Hi,

I am having some power issues with my MosterBorg based Robot, this seems to have happened after a bit of a misshap with a workbench involving a collision and a drop whilst I was carry it. The damage sustained was to the robot, but the robot now only boots to the rainbow splash screen and reboots again over and over.
The multi colour LED cycles through various colours when the power is switched on and settles on yellow.

If I disconnect the battery and power the Pi from a Pi PSU the Pi boots up fine and the multi colour LED is red.

History:
The robot has been working fine for a few years, and more recently, I have been making some modifications ready for PiWars at Home 2021.
I have been running the robot on a 14.4v LiPo with a BattBorg to power the UltraBorg.
Rather than mount the ThunderBorg onto the Pi using its built in Header I have flipped it and am using 6 x Dupont connectors, this has been working fine for a few months.

More recently I desoldered the 9v Battery Connector to aid securing the ThunderBorg on top of the Pi (I am sure I checked and the Pi worked after this mod.

Although the Pi boots up fine maybe the way it gets powered from the GPIO is damaged?
Maybe the ThunderBorg battery supply method has been damaged?

14.4v LiPo is showing 15.6v

What would be the best method of troubleshooting this to identify the issue?

Your help and assistance would be greatly appreciated, especially as the deadline for PiWars is looming :-(

Bill

Images: 

JonnyAlpha

Fri, 04/30/2021 - 19:54

Found this post with some info on testing the regulator and bypassing it with a Batt Borg (which I have - no idea when I bought it?).
http://forum.piborg.org/node/2727
Might help me diagnose the power problems.

JonnyAlpha

Sat, 05/01/2021 - 11:00

Well I carried out the tests in the forum post linked above and on the ThunderBorg built in 5v Regulator I was getting 15v from the battery terminal and 4.9v from the 5v terminal.
However the Pi still keeps rebooting when on batter power alone?
So I need to test the 5v supply to the Raspberry Pi?

JonnyAlpha

Sat, 05/01/2021 - 11:40

So I disconnected everything and tried powering the Pi using a spare BattBorg only and a 6 pack of AA Batteries, the Pi booted up fine. prior to this I tried another 14.4. 4S Lipo and the ThunderBorg but had the same restarting issue. So I know the powering the Pi from the Pi GPIO is fine.

piborg's picture

piborg

Sat, 05/01/2021 - 13:52

This is an unusual problem, you have done all the right things trying to diagnose the cause :)

Given the results of your checks I think the problem has to be with the ThunderBorg itself. I have two theories what the problem might be:

  1. The regulator is failing to provide enough power under load.
    This would mean that the 4.9V it is supplying drops considerably when the Pi tries to draw more current from the 5V rail. Since it does this during boot-up it could explain the problem.
  2. The connection between the regulator output and the 5V GPIO pin is damaged.
    In this case the ThunderBorg would be making a poor connection between power and the Pi. This could mean that the supply to the Pi is intermittent, or simply high-resistance.

If #1 is the problem then the solution would be to replace the regulator. Unfortunately this may prove difficult as the pins are soldered before the ThunderBorg Lid is attached to the ThunderBorg, making access difficult.

If #2 is the problem then it may be something like a cracked solder joint to one of the 5V related pins (repairable), or it might be a damaged track on the PCB itself (not repairable). You could try visually inspecting the ThunderBorg and see if you can spot any cracks, bad solder connections, et cetera.

Another option in both cases would be to connect the spare BattBorg to the battery screw terminals on the ThunderBorg and then connect its output to the daisy-chain connector on the ThunderBorg to work-around the fault.

JonnyAlpha

Sat, 05/01/2021 - 16:40

Well it turned out to be the connecting cables between the Raspberry Pi and the ThunderBorg, all is OK now.

piborg's picture

piborg

Sun, 05/02/2021 - 09:45

That's good news. Glad to hear you found the problem and it was something easy to solve :)

I will make a note that the connection cables for the 5V can cause this kind of problem in case someone else has the same trouble in future.

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