Back to Latest DIY_____

Some of the printers I'd been taking apart contained DC motors instead of the steppers I was mainly after. Hewlett Packard ones and anything intended for high resolution or photo printing tend to use DC motors along with an optical fringe band or disc position sensor so as to get a better resolution than can be obtained with steppers. I decided I ought to do something with them, and one day I got an Epson 300 photo grade printer which contained a printhead drive belt long enough to fit over a small spare bicycle wheel (when you build pedal generators you tend to get front wheels left over). I found a spare bit of front fork to mount the wheel using a coachbolt as a spindle and jigged it up on a piece of scrap metal for a base. The belt and motor from the printer looked as if they'd fit. I made a mounting plate for the motor and welded it to a bit of tube. Some brackets for a pivot were made up and then welded to the base. The motor was fitted and the setup tested with a small light bulb.
In any project involving putting together bits of recycled stuff there's at least one stage where it looks as if it's all gone wrong, and I'd just hit that stage. I hadn't noticed before but the teeth on the motor gear (and the belt that came with it) were actually slightly angled, and the load of the light bulb pushed the belt sideways against the end washer nearest the motor and it fell off  taking the belt with it. One answer might have been to reverse the rotation direction or turn the motor mounting around. The first option might have made it more acceptable to the proportion of the population (including me) that are left handed, and the second one would have meant re-doing the whole thing in mirror image.
The solution I found was to rummage around in the box of motors, getting this one which had straight teeth and a solid rim at one end of the gear. The gear was a tight push fit on the spindle so it was easily reversed to put the rim on the motor side. Of course, this motor was a different size so the mount was modified and welded back together.
The generator worked well with the new motor and a small spring from the printer to tension the belt. The fact that the belt still had angled teeth didn't seem to matter at all and it would easily run small light bulbs without slipping. In any case the generator was only meant to produce a couple of Watts and the motor which probably originally ran on 24V had a winding resistance of about four Ohms.
A handle was quickly fabricated from bits of folding pushchair (one of the most useful things you can get off the rubbish tip) and braced to the wheel hub using a bit of printer rod. The whole thing was given a coat of paint and fixed to an offcut of chipboard as a base with a recycled christmas tree light as an output indicator. Final modifications were a pair of output sockets and a Schottky diode (from the printers power supply) in series to prevent reverse polarity if it was turned the wrong way.