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control an alarm with the U3

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#1 dc21

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Posted 17 January 2013 - 01:22 PM

I have a Grote alarm http://www.grote.com...ct_number=73040. It is 12V @ 0.4 amps. I would like to turn it off and on with the U3. I have a 12V 1 amp transformer for power.

Can I use a Bosch relay http://www.parts-exp...tnumber=330-070 that I can get from my local Napa store?

Do I need a Crydom DC60S3 http://ca.mouser.com...alkey558-DC60S3 ?

The Crydom datasheet said to use a diode for DC inductive loads as shown in the attachment. Is this needed with the Grote alarm?

I am using the U3 with a DB15 and a VB6 program to monitor shaft speeds in a seed cleaning plant. It has been working great for about a year now. Excellent product!!

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#2 LabJack Support

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Posted 17 January 2013 - 02:21 PM

I have a 12V 1 amp transformer for power.

I assume you mean that you have some sort of AC/DC or DC/DC supply to provide 12VDC power, such as a wall-wart. I ask because technically a transformer just works with AC, so if you are just feeding 120VAC through a step-down transformer you would get AC out.

The Bosch relay is for 12V control, so you would need a 12V power supply and an LJTick-RelayDriver to use that.

The Crydom relay you can control directly from the U3:


I don't know whether that alarm presents an inductive load, but the flyback diode is a good idea to keep your system from producing excessive EMI and to improve overall system reliability. See if Grote or Crydom have an opinion and can recommend a diode. Short of that, just look for a big beefy standard diode.


Digikey has zillions to choose from, but here is a 200V 30A diode:


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