Quote Originally Posted by Kalind View Post
Could you people tell me what's the difference between a solid-state relay and a normal relay. Is a solid-state relay a better option? Thanks again guys and girls
NEVER USE CMOS/TTL LOGIC TO DIRECTLY DRIVE A.C. INDUCTIVE LOADS.

Let me repeat that:

NEVER USE CMOS/TTL LOGIC TO DIRECTLY DRIVE A.C. INDUCTIVE LOADS.

The only safe way to control an A.C. inductive load is with a light beam.

To hammer home my point, consider DIRECTLY controlling a window air-conditioner with signals from you deluxe "game-machine" PC's parallel printer-port's CMOS/TTL signals. Will it work? Maybe. But, for how long.
Do you want to gamble with your rather expensive PC? I don't think so.


I suggest the following:

Use an optocouple between your PIC's output pin and the relay coil.
This provides a light-beam barrier between your PIC and the inductive A.C. world.

It will cost a lot more, but you could use a solid state relay, [SSR]. The SSR has an optocouple input, which controls a solid state driver circuit.

SSRs get hot. That's why the base is a big slab of metal.
SSRs come in two varieties. One for A.C. circuits. One for D.C. circuits.
The rated voltage is the maximum safe operating voltage.
SSRs rated at 120v D.C. work very well in 24v applications.