OT:Switching line voltages

[Martin Czech]

:::Hi I know its OT but I was hoping someone might 
:::help:
:::
:::How can I switch a line voltage (110V60Hz) with 
:::a small controll voltage.  
:::
:::At first I thought RELAY, but I don't want to 
:::have to use a transformer or AC controll signal 
:::(it does have to be ac right?).
:::
:::Can this be done with power transistors?
:::
:::Basically, How do they switch those digital pl
:::uggin timers?
:::
:::Thanks in advance for your help?

ONLY FOR PEOPLE WHO KNOW WHAT THEY ARE DOING!

(Last time somebody fried his multimeter when misinterpreting some advise).

Bipolar transistors and mosfet can do this today, but it requires
engineering skill to prevent the circuit from blowing up. I wouldn't
claim that I would get such a circuit running in the first try. SCR/Triac
circuits are quite robust, why not use such a device? I guess these
timers use a SCR, because of simplicity and low losses / heat.
There are semiconductor "relais" on the market, GTOs I guess.

Anyway:

BE CAREFULL TO ISOLATE THE SIGNAL PATH FROM MAINS.  OTHERWISE IT MIGHT
KILL YOU OR SOMEBODY ELSE. TRANSFORMERS, OPTOCOUPLERS.

You see, a safe circuit isn't that easy, a mechanical relay with 5V
or 12V DC steering coil seems the easiest and safest to me...


m.c.