Pen arm working

Here’s a quick demo of the pen arm in action:

I’m pretty happy with how it’s working. Now I just need to get the drive train working. I think a few things are conspiring against it at the moment:

• Underpowered steppers - I’m intentionally using smaller steppers to keep the cost down, but powering these from 5V USB means they haven’t got much power. I’m going to use a 12V battery pack to get a bit more out of them.
• Drag from the USB cable - the only USB cable I have is pretty stiff so puts quite a lot of drag on the bot. I’ve got a bluetooth module I’m going to use which, in combination with the battery pack, should cut this out of the equation.
• Lack of grip on the wheels - I tried running an elastic band around the main wheel which did work a bit, but quickly slipped off and made things worse.
• Not 100% sure I’m driving the steppers correctly so I need to double check that too.

Now I just need to find the time to sit down and dig into it.