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Basic Electronics » How much to switch a relay?

February 19, 2011
by Lusitania
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I'm working on a large robot project in college, and have some relays left over from the last design team.

The relays will be used to power some decent sized actuators. They worked last year, and will work for the actuators we have now, however I am unsure on what I will need to do to switch them.

The relays are 961A-1C-12DM. I also have a NI DAQ-6525, which is pretty much just 8 solid state relays. I "think" I can use the DAQ to cut off and on the large 12 volt battery to the relays to switch them. The 12 volt battery will also power some decent sized motors and the actuators.

So my question is, what do I need to switch those relays. I know it says it is 12 volts, but how many amps? Thanks much.

February 19, 2011
by mongo
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That relay is like the ones I use for fog lights and such. Good for 40 Amps at 12 V. The coil draws about 30 mA if I remember correctly. To drive the relay, use a transistor to amplify the current from the circuit.

February 19, 2011
by Lusitania
Lusitania's Avatar

It is definitely used in the automotive industry. When you say it draws 30 mA, you mean giving it 12V at 30 mA will switch it? How do you know this? I took a look at relays at RadioShack today, and had no clue how much.

You suggest using a transistor to amplify it, and I assume you mean from a 5V circuit. I wish I knew how to do that, but even more importantly, I don't think I have a circuit I could use in this way. Perhaps though, let me explain some more.

I am using LabVIEW to do all of the controlling. I have two DAQs I can use, one is the relay DAQ, the other has digital I/O, and analog I/O. I will be using the analog output to drive motors through a motor controller. The digital outputs I can use are 5V at 8.5 mA. Perhaps I can amplify this signal with a transistor, and cut out the relay DAQ all together.

I have little experience in this, and appreciate your help.

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