I'm wanting to build an intelligent speed control circuit for a 240v fan motor, using a PIC microcontroller. I'm looking for a suitable SSR (Solid state relay) to drive the fan, based on 5V control signals from the PIC.

Based on various temperature readings, I want to turn the fan on/off under PIC control. Having proportional 'dimmer' control would be really nice, because I can soft-start the fan, and also run the fan at low speeds when full power is not required, giving more efficient and quieter operation. However, if this is too expensive, or if it requires more than a single screw-in component on the 240V side, I'll settle for on/off control.

The fan is just a basic 240V extraction fan, so probably a 20W motor, or something like that. Not a huge motor, but maybe I still need an SSR specifically made to handle inductive load?

Also, I want a basic screw terminal setup for the 240V side, because I really don't want to muck around with making my own circuit boards or soldering on the 240V side.

I looked on RS and Element14 (farnell), but I was just overwhelmed by many very expensive options, and I really don't know what to choose.

Can anyone recommend any suitable SSR devices, or suggest what criteria to look for, beyond the basics of voltages and current ratings?

 

Using a SSR will give you full on/off control, i.e. no phase angle control as a 'Dimmer' circuit is.
So you would probably need to modify an off the shelf dimmer for digital to analogue control, or make something such as in the Fairchild App note AN-3006 for zero cross over detection switching etc.
For straight SSR's look for the Opto22 line, they make many configurations and types.
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Max.