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Can a relay also work the other way around, like high voltage circuit driving a low voltage circuit? If so, please provide me a link to such a product.

[Reply #1 on:]

Can a relay also work the other way around, like high voltage circuit driving a low voltage circuit? If so, please provide me a link to such a product.

Sure, it the coil voltage of the relay is rated for use with the 'high voltage circuit' value you are working with AND if that HV circuit can spare the extra current the relay coil will draw. The output contacts can be used with any voltage/current that is within the maximum voltage/current ratings for it's contacts.

Lefty

[Reply #2 on:]

My motiv is to detect if the circuit is in close or open state. The idea is to use the NC relay connected to the 220V and the drive the 5V to the Arduino when the current is flowing.

I did try to look for such relays with coil voltage 220v, but couldn't find. Please do provide me a link if you know one.

Thanks.

[Reply #3 on:]

Well they are certainly available from major electronics suppliers and even E-bay if you search around.

http://www.ebay.com/itm/JQX-13F2Z-AC-220V-Coil-10A-240VAC-28VDC-8-Pin-DPDT-General-Purpose-Relay-/300790758823?pt=LH_DefaultDomain_0&hash=item460886bda7

Lefty

[Reply #4 on:]

Thanks.

[Reply #5 on:]

Hi, Another often-used solution is a optoisolator chip driven from the 115/230V and it's output to Arduino.

There are a couple shown here: http://arduino-info.wikispaces.com/Popular-ICs

See: http://www.raspberrypi.org/phpBB3/viewtopic.php?f=45&t=9617 for an example. There are better circuits using a capacitor in the input circuit; I'll look.