Interesting Remote Control Circuit

[tranceracer]

I found this AC remote device at a local store and picked one up thinking I could mod it to run only on DC (batteries) to eventually control my rig remotely w/ out wires.  I figured that has a step-down transformer and a diodes and caps for the DC to feed the receiver ckt.

When I opened it up, the ckt doesn't have a step down transformer!  Does anyone know how they are stepping down the voltage from 120V down to I presume 9V to 12V DC to operate the relay and ICs?

I'm wondering if this may be a better way to step down voltages with the help of a voltage regulator than to use a xformer? It would make for a much smaller footprint for an AC/DC converter.









Does anyone think this may be a plausable alternative to a transformer? 
It'd be interesting to hear any opinions on the Pros and Cons.

[R.G.]

It's a great alternative - except you'd get electrocuted. 

The circuitry is not line-isolated. They just poorly rectify the AC power line to get a minimal amount of power for the controller and receiver to run on. I can't tell from the photos, but I suspect the relay's coil is 120Vac rated as well.

There are lots of ways to step down voltage other than transformers - but none of them isolate you from the AC power line, and the threat of sudden death.

[tranceracer]

Thanks RG!
Very interesting!

The relay is rated at:

10A 30VDC
10A 250VAC
15A 125VAC

COIL: 12V DC

Since the coil is rated at 12V DC then I guess they are stepping down the voltage to 12V.

[R.G.]

Yes, either stepping down to 12V or current limiting to the right value. You can current limit with a capacitor and not waste any power in the step down like you would in a resistor. Or it may be a small step down regulator, even if that's more expensive.