That said I've still had time to play in the workshop and I've got some projects to write-up that I think people may be interested in.
This last week I've been consumed with stepper motors. Well to be specific, trying to find some that are fairly small, powerful and cheap which is proving a challenge.
Ebay is awash right now with 5v steppers that are geared - model number is 28BYJ-48 rated at 5v.
I ordered several but I probably should have grabbed just the one first to experiment with.
Now they are nice steppers for the money. However they have a built in gear box that reduces the speed and means their maximum output speed is very limited. The gear box does mean they have a fair amount of torque though.
However, they weren't a complete waste. Each motor was supplied with a little driver board. Now I don't use stepper motors often, and I've always opted for dedicated driver chips for them. However these driver boards are simply based around a ULN2003 Darlington driver chip. Each IC's contain seven Darlington drivers, rated at around 500ma and up to 50v. They even have the suppression diodes built in and are perfect for driving low current small steppers, motors, bulbs and relays.
It's one of those "why didn't I think of that" type of situations. You simply drive the IC from your CPU, and with four output lines you can drive the stepper in either direction and run in different stepping modes, all for peanuts. These IC's (or one of the many alternate variants) are usually easy to get hold of, and in the case of the ULN2003, you get three spare driver channels for other things as a bonus. I think there is an 8-channel variant which would be useful for a robot with two steppers.
So, whilst it turned unto a useful exercise after all it doesn't solve my current problem.
One solution that I've tried previously is using a modified radio modellers servo motor.
You open the servo and make a change (usually simple) to allow the shaft continuous 360 degree rotation.
However, whilst usually having masses of torque, servo's are rather large, expensive and quite noisy.
There are some micro servos available but they are tricky to modify for full 360 degree rotation.
So, back to searching Ebay.