SloBot – a reprieve

Well my experiments with SloBot today haven’t improved anything much. It really is no use unless I can solve the crashing issue – but I’ve already been through this and plastered capacitors all over the place. Chris mentioned back EMF – that’s taken care of by diodes on the Pololu Baby Orangutan B-328 boards, or is it…

Pololu Baby Orangutan B-328 Schematic

Pololu Baby Orangutan B-328 Schematic

(From theย Pololu Baby Orangutan B User’s Guide)

Well, apart from the two LEDs, I can’t see any diodes on there ๐Ÿ™

Another schoolboy error? Hmmm…

So, SloBot is crashing as I ramp up the motor speed. It’s not just when I turn it off. However, I don’t know exactly what happens when the speed increases and any change in magnetic field will generate EMF in neighbouring wires – that much is known.

It would seem sensible to chuck in some diodes and see if that helps matters – basic IN4001 power diodes will do and I have lots of those. Strangely, they were bought for this very purpose when I wanted to build my own H-bridge motor controller (a stupid idea with my then level of ability – it probably still would be).

I’m not entirely happy with all the wiring relating to motors and getting power from the batteries to the BabyO boards. I’d be happier with a chunkier and more secure ground connection as well. So, rather than heading for the scrappy, SloBot is going to get some more work done on it.

Here’s what we need for each motor:

Back EMF Suppression

Back EMF Suppression

The schematic is drawn with the excellent Upverter – only just started using it but finding it more natural than Eagle or DesignSpark. It runs in your browser and it’s free. Works for me.

Ok, so 4 diodes per motor, 16 in total. I can put those on some proto board in the bomb engine bay and tidy up the power and ground connections at the same time. The motor driver board can stay outside – there really isn’t that much room inside.

If this doesn’t work then SloBot is off to the robot scrapyard ๐Ÿ™‚

 

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