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This hobby servo hack will add shaft position feedback by tapping into the servo's own internal potentiometer. The only parts that need are wire and a little bit of solder, making this hack practically free. Common electronics workshop tools are required, so if you're minimally set-up and already have a servo, it should take you less than an hour to make the modification and run the test code.
I thought of this after building projects with servos and getting frustrated by the fact that after restart, the servo would zoom around if it wasn't already at the first coded position. There are code samples below (arduino) that map the servo's range to the feedback with minimal offset.
As with any hack, you assume some risk of wrecking your servo motor, so use a cheap one!
Discussion topics include: Collision Detection. Gestural Keyframing. Software Increase of Torque. Haptic Control.... (uuh, fill in the blank folks!)
Parts and tools needed to complete this mod:
> Arduino (or other microcontroller) and it's attendant parts.
> Hobby servo (Featured: HITEC-322HD)
> Stranded wire (Should be smaller than 20 gauge. I use 24g)
> Set of small screwdrivers.
> Wire snips
> Wire strippers
> Soldering iron and solder.
> A few resistors (1K, 4.7K, 3.3K, 2.2K, or similar)
> Small knife