voltage sensing relay?

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sitinduk

Member - Posts: 9

Joined: August 06, 2003

Posted: April 28, 2004 at 11:45 PM / IP Logged

Hi, is it possible to set up a relay that will activate only at a certain voltage? For instance, say terminal 86 is connected to ground, and 85 is connected to a wire that varies from 0.5V to 4.8V. I only want the relay to activate its circuit when 85 sees 4.8V.

xetmes

Silver - Posts: 586

Joined: May 18, 2003

Posted: April 29, 2004 at 5:47 AM / IP Logged

You could use electronics to scale the voltage, or use an analog to digital conversion, but with just a relay it may be tricky or unreliable.Can I ask what the purpose is?

sitinduk

Member - Posts: 9

Joined: August 06, 2003

Posted: April 29, 2004 at 8:37 AM / IP Logged

I was going to make a switch for a custom nitrous oxide setup. I wanted the nitrous and fuel solenoids to open only at wide open throttle. The throttle position sensor varies its voltage from 0.5V at closed throttle to 4.8V at WOT. They make mechanical switches for this purpose, but I wanted to go with something electric.

xetmes

Silver - Posts: 586

Joined: May 18, 2003

Posted: April 29, 2004 at 6:25 PM / IP Logged

hmm is this just a DC voltage? I dont know enough about the TPS...

If it is just DC:

You could use a differential type amplifier like an opamp and compare the value to a reference voltage and detect when the difference is 0V.

Or you could use a programmable controller and use analog to digital conversion and compare it in the digital world, that would be my preferred choice.

sitinduk

Member - Posts: 9

Joined: August 06, 2003

Posted: April 29, 2004 at 9:42 PM / IP Logged

The TPS is just DC. I'll have to look into a programmable controller.

Thanks for your help.

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voltage sensing relay?

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