Arduino and Relay Both in DC power

Hi!

I have a need to operate an item that uses 12VDC @ 10amps intermittently. The intermittently would be defined by a timer for the on/off period and the duration of the off. Sounds like a pretty good job for a microcontroller such as the Arduino.

So on to the questions...

I need to buy a relay with a 12V @ 10amps rating on one of the throws. The other throw should be able to be triggered or untriggered based on the load the arduino can drive to it. I need to find this load, so I buy the right part.

The questions are:

Anyone driven a 12VDC relay with an arduino? Which part is recommended?

What is the maximum safest load I could drive from an arduino pin in volatage and amperage? This will define the relay that I buy and the wire grade that I use.

Can the Arduino be run on DC power for this application?

Appreciate any insights anyone can offer, I hope to finish my project very quickly after hearing back and will post to the other thread about the outcome.

Regards, s_g

Hi.

Anyone driven a 12VDC relay with an arduino? Which part is recommended?

Many will fit, the most important point being that it can handle the power your device uses.

What is the maximum safest load I could drive from an arduino pin in volatage and amperage? This will define the relay that I buy and the wire grade that I use.

The Arduino's specs on this matter are here http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1212879467/5#5 . For more complete information on electric characteristics, refer to the Atmega168 datasheet

So, 40mA from an IO pin, 200mA from/to VCC/GND pins. So 200mA for your relay, with a transistor.

Can the Arduino be run on DC power for this application?

What do you mean ? On the same power source than your device ? The only risk is that the high power consumption when the device starts resets the board. Looking at mine, there seems to be a few capacitors, so if they're here to prevent this, you should be safe.

Did you try googling this?

http://www.google.ca/search?q=relay+arduino

There are literally hundreds of diagrams out there on how to drive a relay, and even one in the Arduino playground that explains how to do it with Arduino. Lots of results as well for Arduino & Relay , as in above link.

D

Wow! Thank you for the ultimate in fast replies, I can see why your sig says needing sleep ;)

Based on 40mA on a pin and 200mA on the VCC, may I know whether I can have the arduino regulate the Vcc from 0 to 200mA itself based on some code that keeps a timer? If not, then I will be stuck driving the GPIO pin high and low from 0 to 40mA. This might also be a workable option, just have to research based on ideas from here.

As for the 2nd point, I don't need the arduino driven from the same DC supply as the other device it is driving. I just need it to be receptive to DC power on its own and would actually prefer that, so I don't need to do much with voltage and amperage regulation. This should keep it simple and the most complex part will be driving the relay to on/off.

Wow! Thank you for the ultimate in fast replies, I can see why your sig says needing sleep ;)

Burned fingers is the real reason. You know these stupid Antex soldering irons with a little protective cap, that makes the work easier, because you can put your finger close to the iron part but not touching it ? well, sometimes you believe it's here, and it's not. OMFG.

Based on 40mA on a pin and 200mA on the VCC, may I know whether I can have the arduino regulate the Vcc from 0 to 200mA itself based on some code that keeps a timer? If not, then I will be stuck driving the GPIO pin high and low from 0 to 40mA. This might also be a workable option, just have to research based on ideas from here.

You can't regulate Vcc. You can use a NPN transistor as a switch to relay power from the VCC to the relay. As Daniel2 suggested, try googling. Best URL of the world : http://www.allaboutcircuits.com/

As for the 2nd point, I don't need the arduino driven from the same DC supply as the other device it is driving. I just need it to be receptive to DC power on its own and would actually prefer that, so I don't need to do much with voltage and amperage regulation. This should keep it simple and the most complex part will be driving the relay to on/off.

Sorry, I don't get this point. Either you're not clear enough, or it's just my English. What do you mean "I just need it to be receptive to DC power on its own and would actually prefer that, so I don't need to do much with voltage and amperage regulation." ?

The Arduino has a power plug with a power regulator which allows it to be powered through an AC>DC converter. Voltage range certainly is in the documentation.