DIY Winder Help

[mcgruff]

I've pulled the motor out of a cordless screwdriver to use in a home-made winder and I need some help with the electronics.

Unloaded, it spins far too quickly for my home-made counter (using the calculator trick). I need to wind the pickup at about 200rpm or less or the counter can't keep up. That might be a little on the slow side for some but 25mins per coil is OK for me since I only wind once a month or so.

If I want to add a speed control, is this as simple as simply sticking a variable resistor in series with the motor or is it more complicated than that?

I've been messing around with some old guitar pots and so far the only thing I've learned is that this is a great way to burn out guitar pots.... Does anyone have any idea what sort of current rating I'll need? The motor is powered by a 4V battery.

[David King]

Mcgruff,

You need to figure out what the wattage is. W = V * A, You know the Voltage (4V). Now you need to measure the amp draw of the motor running under a slight load with a multimeter.
You can skip all that and buy a 500 ohm, 10W wire wound pot or better yet, get a PWM kit off ebay for $8.

[mcgruff]

Thanks for the tip I didn't know about PWM kits. That sounds ideal - I'll look into that.

Dropping the voltage to 1.5V helps to slow it down. I also found a 50R 5W rheostat which didn't cost much and looks promising. Unloaded, it needs fine adjustments under 10R to get into the speed range I'm looking for so it's tricky to control. I'm hoping that will sort itself out once it's pushing against a normal load. I can always put a resistor in parallel to get more useable adjustment out of the rheostat.

I need to figure out how to attach a bobbin holder to the axle. It ends with a little 5x5mm cog but I don't have any attachments for that. Should be able to figure something out.

So far it's been really easy to put together. The whole thing, including a calculator for a counter, comes in at under £10 for a pocket-sized, battery powered winder you could take anywhere.