voltage sensing switch design?

[E55AMG]

To preface, I dont have much knowledge in circuits, but I do have a good mechanical knowledge. Im interested in building a simple switch that can detect the output of my car's throttle position sensor as it rises from .1v or so at closed throttle up to 4.5v or so at full throttle. I'd like to use the switch to energize a relay for the nitrous system, as this would be a better setup that the micro switch that is currently attached to the side of the throttle body.
I know nothing of designing circuits, but if anyone can help I know I can etch a board and solder on the components correctly. Any help is largely appreciated. Thanks,

Jeff

 

[MikeMl]

Been discussed before. Here and
here

 

[E55AMG]

OK, I found your schematic, but I'm not that experienced with this stuff and dont know what all those values refer to. If I have the parts, I know I can build it, I just need a little assistance with what parts to buy. Thanks again,

Jeff

 

[MikeMl]

Assuming we are talking about this schematic, start by down loading a data sheet for an LM339. Note that it contains four voltage comparators; you will only be using one of them.

Note the pin numbers on the data sheet. As a minimum, you need five pins; Vcc-pin3, GND-pin12, In1(+)-pin5, In1(-)-pin4 and OUT1-pin2. You must ground all of the unused inputs (pins 6,7,8,9,10,11) and make no connection to all the unused outputs (pins 1,13,14).

Only other special part is the 8.2V Zener. Any 8.2V Zener will do. Here is a suitable one at DigiKey. You can get all the parts there. Here is a suitable LM339.

What else do you need?

Go to DigiKey