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Low Cost/Current 3-28vDC supply from 120/240v.

L

logjam

Jan 1, 1970
0
I want to switch 120/240vAC in a project with a panel mounted toggle
switch. I do not want any electric shock hazard from touching the
switch terminals.

I've looked at the solid state relays like the D2W202F triac based
relay.

http://www.crydom.com/userResources/productFamilies/7/crydom_d2w.pdf

They list a typical current of 3ma to turn on the relay with 5vDC. I
don't know how much the current will change with 28v being used to
switch the relay.

What I was thinking about was a bridge connected directly to 120/240vAC
and then a 5.1v zener diode/resistor regulator. Probably at the output
of this small circuit board would be an additional resistor to limit
the current at 5v to 10ma?

So from quick math it seems like this solution would waste around
2.5-3W at 240vAC all the time?

Are there any other solutions any of you could think of that would be
better than this?

For safety, I was imaging an input fuse of .1A and using maybe 3-4
zeners. They are cheap enough. If something were to go wrong the fuse
should blow first.

Thanks,
Grant
 
H

Homer J Simpson

Jan 1, 1970
0
I want to switch 120/240vAC in a project with a panel mounted toggle
switch. I do not want any electric shock hazard from touching the
switch terminals.

Shrink wrap them.
 
L

logjam

Jan 1, 1970
0
Homer said:
Shrink wrap them.

I've thought some more about it and I think I will do nothing. I will
just run let the kit builder make their own choices. Including a PCB
and parts dealing with AC and any shocks will be my fault.

The kit currently has the panel mount switch soldered to a PCB (comming
through the panel). The instructions are to put electrical tape over
the 2 1" traces and switch terminals.

Grant
 
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