Here's the basic setup:
I have a dimmer switch that is a Variable Resistor (VR). When the VR is in "clicked/full brightness" position (meaning that the lights are at full brightness), 0.77 volts or less is outputted from the VR. When the VR is not in "clicked/full brightness" position (meaning that the lights are dimmed), 1.4 volts or more is outputted from the VR. Basically I need a comparitor circuit (and a relay to invert voltages) that will take 0.77 volts or less and activate a 12 volt circuit. If the VR outputs 1.2 volts or more, then the 12 volt circuit is not activated.
VD = Voltage Dimmer
VO = Voltage Out
When VD <= 0.77, VO = +12v
When VD > 0.77, VO = No Connection
Can someone help me design this circuit? Any help would be appreciated.
What are you trying to accomplish with this? There might be another way to do it. The way you want to go about it would be pretty hard to get it to do what you want.
The dimmer output should be negative. You must have tested the wire referenced to ground instead of referenced to the parking light. But anyways...
A transistor turns on typically at about 0.6-0.7 volts. Since the minimal voltage you got is 0.77, you will need to make a voltage divider so that less than 0.6 volts is at the base of the transistor. Given that, you can use a NPN transistor that will output a negative signal which you can use a relay to invert that signal to a positive or turn on a PNP transistor to supply +12volts. I would draw one but i'm tired tonight.
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Karl
Pacific Accessory Corporation
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