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Motor Speed Control (part 3)

2.3 – Motor Speed Control (part 3 – thinking about heat)


The triac is going to need a way to cool off during continuous use. You could buy a standard heatsink from Maplin or similar or make your own. As my triac is rated at 26amps I am not too worried about it- but something to lick the heat away is needed.

I used a section of aluminium channelling (same as used on the lathe bed) bolted together with a bit of old heatsink rescued from a discarded computer PSU, with a bit of flattened copper pipe.

As far as I know copper is better at conducting the heat, and aluminium at radiating it to the surrounding atmosphere. Hence the copper helps disperse the heat throughout the sink and the aluminium radiates it off.

Whatever you find to use, cut your metal to a sensible size with a hacksaw , or similar (if you only have a junior hacksaw make or buy a full size one or you will waste a lot of time). Drill your holes, then, clean and polish all joining surfaces. The cleaner and flatter the meeting surfaces the better the heat will transfer. If you have some, apply thermal paste before bolting up the assembly.

The triac needs something to dissipate heat