Electrical stuff..(long)... - Saab General Bulletin Board - Saabnet.com
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Electrical stuff..(long)...
Posted by KeithR (more from KeithR) on Sun, 1 Sep 2002 20:40:30
In Reply to: ot: voltage vs. resistance...(electricity boy?), kooch, Sun, 1 Sep 2002 17:35:32
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There is a difference between a variable resistor and a potentiometer. A variable resistor is used in line to drop voltage and /or limit current. A potentiometer is used to "divide" a voltage, with little to no current flowing in it.
Voltage does not "run" through a resistor, current does. The amount of voltage dropped across (lost) will depend entirerly on how much current is flowing through the resistor. Voltage=Current*Resistance
Sounds like you are wanting to send a reference voltage to the ecu. I'm guessing it will act to whatever voltage is presented to it but not use any current.I'm guessing you need a potentiometer more in the 1,000 to 5,000 ohm range. You hook one end to the 5 volts, the other to ground. The center lead, commonly called the wiper, will go from 5 volts at one end to 0 at the ground end of travel. This design, again, is used for a input that uses little to no actuall current, but just "feels" the voltage. The advantage of having both ends hooked to something (ground and 5 volts in this case) is that temperature changes will pretty much cancel out. A variable resitor will change its value based on temperature.
Clear as mud, right? If I knew the current draw of the ECU on that pin and a better idea of the aproxamate voltage I could help a little more.
posted by 166.102.15...
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