mains voltage sensing
mains voltage sensing
(OP)
I'm designing a piece of equipment that has two AC powered servo drives. I have a power switch that cycles the mains power (110-240 VAC), with an LED inside. The LED isn't wired directly to the switch because the switch is designed for 120VAC 60 Hz or 240VAC 50 Hz. I am attempting to avoid bringing the mains onto a PCB (for regulatory reasons) just so I can sense them and drive an LED.
Is there a simple way to monitor the mains voltage with galvanic isolation so I can illuminate my LED when the mains switch is closed?
I thought about a current monitor, but that will give a false reading if the fuse is blown.
I could add a transformer, but that seems like overkill.
No, there are no signals that I can tap from the servo drive to power my LED.
Are there any simple mains sensors available?
Thanks,
John D
Is there a simple way to monitor the mains voltage with galvanic isolation so I can illuminate my LED when the mains switch is closed?
I thought about a current monitor, but that will give a false reading if the fuse is blown.
I could add a transformer, but that seems like overkill.
No, there are no signals that I can tap from the servo drive to power my LED.
Are there any simple mains sensors available?
Thanks,
John D





RE: mains voltage sensing
David Castor
www.cvoes.com
RE: mains voltage sensing
RE: mains voltage sensing
RE: mains voltage sensing
The usual solution is a combination of a capacitor, resistor and perhaps a diode. Problem is, these components might need to be installed on a PCB. So you're back to where you don't want to be.
It might be (far) simpler to use a stand-alone panel mounted indicator light and ignore the troublesome LED in the switch.
RE: mains voltage sensing
TTFN
FAQ731-376: Eng-Tips.com Forum Policies
RE: mains voltage sensing
I don't understand that at all. A self powered GO-O GO current relay could be a viable option. This device has a current transformer with a one inch hole and a set of dry contacts. Usually rated at 10A pull in, looping the power wire to your device 10 times gets that down to 1A. Hold in is much lower so if the device has an inrush current required amps is lower. This would detect a blown fuse.
RE: mains voltage sensing
How about an old-fashioned Neon indicator? (I believe that's the right name, English is not my native language. But you know, the amber ones that you see on stoves etc.)
Benta.
RE: mains voltage sensing
----------------------------------
If we learn from our mistakes I'm getting a great education!
RE: mains voltage sensing
What I have done in my own house is wire up an outlet to the switched AC circuit, and then plugged in a surplus AC Adapter to provide a low voltage signal. The pump in my septic tank is wired up such that the switched hot is brought back into the basement. I've got a 12VDC electromagnetic counter that tracks the pump cycles. For a one-off project, this approach might be the 2nd simplest.
RE: mains voltage sensing
http://www.crmagnetics.com/2550.pdf
Ed
RE: mains voltage sensing
I'm stuck with LED in the power switch for consistency with our other products (that all have internal power supplies so normally this is a no-brainer). After working all day through transformer, power supply, AC relay, and neon designs I realized each servo driver has an unused RS-232 port on it. I'll tap enough current out of that to drive a transistor and power my LED! Innovation at its slowest...
Thanks for all your help everyone!
John D
RE: mains voltage sensing
Keith Cress
kcress - http://www.flaminsystems.com
RE: mains voltage sensing
John D