Good Day All.

Upto now whenever I have needed to switch mains powered items on and off I have always used SPST or DPST relays.

I now need to be able to switch a mains unit on and off via a microcontrollor, the problem is that it can't be a mechanical switch like a standard relay due to the risk of sparks, as the room with this unit does at times have flammable liquids and gases.

The liquids and gases are unliky to get close to the unit in question, but I want to limit any meny risks as possible.

The mains powered unit is 240volt 75watt.

Could you please advice.

Thanks for your time.

Best Regards.

 

Try a solid sate relay

 

Here is the Wikipedia article on SSR's - http://en.wikipedia.org/wiki/Solid_state_relay

75 watts is a fairly small load, so finding one to handle your equipment should be easy.

 

Thank you for your replys.

I am just reading the wikipedia link.

As I have never used SSR's before are they just wired in like a standard would be, or does it need extra circuit.

How meny amps is 75watts at 240vac?

Best Regards.

 

Depending on the input configuration it may or may not need a current limiting resistor for the input's LED. If the input is spec'd as "3-32VDC", it already has a built in resistor. If the input is spec'd as a voltage drop and a minimum and maximum current, you will need to add the appropriate resistor in series. Unlike (most) DC electromechanical relays the input has a polarity. Also, if you are switching an inductive load like a motor, the output rating should be at least twice the maximum current rating of the motor. And maximum ratings with heavy loads only apply when heavily heat-sinked. But, for your load a 1A rating should be fine.

Ken

 

Thank you for your reply.

I am looking at a Carlo Gavazzi "RP1A23D3" Datasheet: http://www.gavazzionline.com/pdf/rp1a48d5.pdf

Will this do the job ok?

Thanks again for your time.

 

Should work fine.

Ken

 

as the room with this unit does at times have flammable liquids and gases.

You best be checking with your local electrical code as they most certainly will have regulation that affects your need.