Faulty Bee Bot Junior School educational robot

[Clive Carrington]

Been asked to fix some faulty Bee Bots by my local Junior School. These are simple programmable robots from here:

TTS Bee-Bot Programmable Floor Robot Single

A perfect starting point for teaching control, directional language and programming.

www.tts-group.co.uk

The Bee Bot is programmed with a series of commands by pressing buttons for Forward, Backwards, Turn Left, Turn Right and then pressing the execute button. The battery is well charged and I've tried swapping with a known working Bee Bot. Three of these Bots will only run through three commands before resetting itself. I've tried running them lifted up so that there is no movement and it still stops after about 8s. Not sure this is, therefore, a poor connection.

I've found this unofficial service manual, but this fault condition is not covered.

TTS Bee-Bot Unofficial Service Manual

The TTS Bee-Bot Programmable Floor Robot is an educational desktop robot geared towards teaching children simple programming concepts. The robot replays a sequence of movement steps (Forward, Back, Turn Left 90°, Turn Right 90°) which are programmed using buttons on its back. The robot provides...

hackaday.io

Has anyone else tried to fix one of these? Any ideas welcome.

 

[danadak]

You might check the two electrolytic caps, are they bulging at all ? Thats
a sign they are failing.

I noticed in manual the soldering on the boards looks pretty crappy, you might
inspect with a magnifying glass for any poor connection.

These 4 connections in manual, notice how lower right lead seems not to have
solder wicked fully around it......

These do not look great either :

Google "good solder pcb connections" and look at images found in your browser.
PCB Flux helps a lot.

Regards, Dana.

 

[ahsrabrifat]

Measure the battery voltage under load. If it drops significantly, the Bee-Bot may be resetting due to a low-power condition. Clean the battery terminals and contacts inside the Bee-Bot.

 

[Clive Carrington]

Dana. Thak-you for your thoughts. I checked the Caps and they are fine. When initially reading the service manual I thought I'd be replacing those charger PCBs given their poor quality, but the ones I have are much better quality, so perhaps they've changed their supplier. The batteries all charge and then hold their charge for several days afterwards. The main PCB also looks in good condition. too.

Ahsrabrifat, Thank-you. I've checked the battery voltage under load for both a working and a non-working Bees and both exhibit the same small change in voltage, but only dropping by 100mV or so when the Bee is moving.
The fault still exists when I hold the Bee off the ground when there is less load.
I tried swapping a batteries with a good Bee, but the fault stayed with the Bee, not the battery, so I'm reasonably confident it's not the battery.

I'm baffled by what could be resetting the device after roughly 8s. It's unlikely to be a bad connection, otherwise the timing would be more random. I'm next going to look for a voltage regulator and see if there's any drop on the regulated side. It's handy to have both working and non-working Bees to compare, though!

Thank-you again for your thoughts.
Regards, Clive