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Topic: Help me to control this relay? (Read 3 times) previous topic - next topic

jangoforhire

I have some lights for my car that use these relays:


Front:


Back:



I am getting an Arduino Mega ADK in the next few days so I can control
my lights with an android app I am writing. But I can't figure out how I can get enough power to trip this relay. I am not to sure
what the coil voltage is...it trips on 12V from my car of course, and it also trips with a 9V battery. I have been unsuccessful so far
getting it to trip on anything coming from the Arduino though (I have a UNO currently). I am familiar with this diagram:



But I can't seem to quite figure it out...


Any help would be awesome, thanks!



Krodal

I googled it: http://translate.google.com/translate?sl=zh-CN&tl=en&js=n&prev=_t&layout=2&eotf=1&u=http%3A%2F%2Fhq-chn.cn%2FProductView.asp%3FID%3D186%26SortID%3D2&act=url

On the photo you see that it is for 14V. The number "-112DM" seems to indicate that it is for 12V.
This is a typical relay for in a car.
Can you measure the current through the coil at 12V? I doubt that a 2N2222 can handle this heavy relay.


Runaway Pancake


I am familiar with this diagram:
But I can't seem to quite figure it out...


What's the trouble?

[I thought you were getting some relay board for this deal.]  http://arduino.cc/forum/index.php/topic,103055.0.html
"Hello, I must be going..."
"You gotta fight -- for your right -- to party!"
Don't react - Read.
"Who is like unto the beast? who is able to make war with him?"

scottyjr

That simple circuit will work for your application. An Arduino cannot supply the current needed to energize this relay. The transistor can. It acts like a switch to complete the circuit to energize the relay. What switches the transistor off or on is the signal from the Arduino pin.

Relay power + would be power from the positive battery terminal and Relay power GND would be from your battery's negative terminal. This doesn't mean you have to run wires to the battery; it's just to say that the battery is the source of those two connections.

K1 (written horizontally) is the coil of your relay (pins 85 & 86). S1 & 01 of the K1 written vertically are the 'switch' that turn your lights on or off. S1 & 01 are connections 86a & 30 of your relay.

Diode D1 is necessary to prevent damage to the transistor when the relay goes from on to off.

The resistor in the circuit limits the current coming from the Arduino so as to not damage it.

The lower part of the diagram with all the GND connections is showing that the ground of the Arduino must be attached to the ground you are using to power the relay coil.

Basically this circuit is a s follows: The output from the Arduino turns on the transistor, the transistor turns on the relay, the relay turns on your lights. By the way, I believe this relay can be considered a 'small' relay since a similar relay's data sheet indicates it consumes 1.6 watts which would be around 130ma @ 12V which the 2N2222 can handle.. - Scotty

jangoforhire

#4
May 07, 2012, 05:15 pm Last Edit: May 07, 2012, 05:17 pm by jangoforhire Reason: 1

I googled it: http://translate.google.com/translate?sl=zh-CN&tl=en&js=n&prev=_t&layout=2&eotf=1&u=http%3A%2F%2Fhq-chn.cn%2FProductView.asp%3FID%3D186%26SortID%3D2&act=url

On the photo you see that it is for 14V. The number "-112DM" seems to indicate that it is for 12V.
This is a typical relay for in a car.
Can you measure the current through the coil at 12V? I doubt that a 2N2222 can handle this heavy relay.





I have tried to measure it using my DMM (set to the "20k" mode and placing the red probe on pin 86 of the relay, and the black probe on pin 85 of the relay). I get a reading of 0.08 which doesn't make sense to me. I thought it needed to be much higher than that?


Quote
What's the trouble?

[I thought you were getting some relay board for this deal.]  http://arduino.cc/forum/index.php/topic,103055.0.html


That was my original plan (thanks for the help with that by the way) but when I got the lights I want to control, they already came with these relays equipped. So I figured
why not just use the exiting ones instead of buying a new board.

Quote
That simple circuit will work for your application. An Arduino cannot supply the current needed to energize this relay. The transistor can. It acts like a switch to complete the circuit to energize the relay. What switches the transistor off or on is the signal from the Arduino pin.

Relay power + would be power from the positive battery terminal and Relay power GND would be from your battery's negative terminal. This doesn't mean you have to run wires to the battery; it's just to say that the battery is the source of those two connections.

K1 (written horizontally) is the coil of your relay (pins 85 & 86). S1 & 01 of the K1 written vertically are the 'switch' that turn your lights on or off. S1 & 01 are connections 86a & 30 of your relay.

Diode D1 is necessary to prevent damage to the transistor when the relay goes from on to off.

The resistor in the circuit limits the current coming from the Arduino so as to not damage it.

The lower part of the diagram with all the GND connections is showing that the ground of the Arduino must be attached to the ground you are using to power the relay coil.

Basically this circuit is a s follows: The output from the Arduino turns on the transistor, the transistor turns on the relay, the relay turns on your lights. By the way, I believe this relay can be considered a 'small' relay since a similar relay's data sheet indicates it consumes 1.6 watts which would be around 130ma @ 12V which the 2N2222 can handle.. - Scotty


Thanks for the explanation, I tried this was a 2N2222 earlier and I couldn't get it to work right. I tested the voltage coming off the transistor in my circuit and got around 5.5-6 volts. I am guessing I need a bit more than this so I am going to see if I can find a TIP102 transistor today and swap them out in my circuit.

Thanks for the help!

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