PIC to Relay

[Kalind]

Hey Master, i tried getting some info on triac's. Maybe you can send me a drawing/schematic using a triac and 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

[aratti]

Is a solid-state relay a better option?

Absolutly yes! they are a little more expensive but they are ready to use and very easy to use. Just connect pic output pin to the dc input of solid-state relay and load on the other side (See attached schematic)

Al.

[The Master]

I wasnt saying you should order from Rapid. They are my first choice though. Other electronics suppliers will have a page for relays too. I have been buying quite a few of their own components and i cant say ive had a single problem with any of them. When i need to use a new type of component i usually buy a few different versions that appear to do the same thing and test them. If by "78L05" you mean "7805 voltage regulator" then i have been using those for a long time now and theyve always been fine. Ive only had 1 or 2 beak but that was my fault for shorting it out and not realising till i touched them. I think one actually still works after burning my finger.

Heres a wikipedia page on triacs. Ill post back soon with a scematic and description. Also that page says the mains pins are A1 and A2 not A and B as i said before.

[paulbergsman]

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.