5v sensor voltage source...

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01-09-2013, 05:25 PM

Speedtoys

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5v sensor voltage source...

Whats a clean way to provide a 5v source for aftermarket sensors under the hood of the car?

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01-09-2013, 05:40 PM

Jadz928

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Use a resistor.

From another website:

Quote:

One could use a 1k Ohm potentiometer to dial in required resistor value. (VERY IMPORTANT) Set the potentiometer to the HIGHEST value. (VERY IMPORTANT) Put the pot in series with the meter and the voltage source. Turn the potentiometer down very very slowly till the voltage across the voltmeter is at 5v. Turn off the circuit. Isolate the potentiometer and use an Ohm meter to determine the resistance (Ohms). Now use the resistor and confirm final voltage.

Does the AM sensor come with an predetermined resistor?

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01-09-2013, 06:04 PM

LT Texan

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Quote:

Originally Posted by Speedtoys

Whats a clean way to provide a 5v source for aftermarket sensors under the hood of the car?

how much current?

I'd use an LM317T voltage regulatory

circuit

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01-09-2013, 06:08 PM

dprantl

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I just took one of those cheap auto USB charger things, cracked it open and soldered my MAP sensor directly into it. USB output voltage is +5V. Looked a lot like this one.

Dan
'91 928GT S/C

475hp/460lb.ft

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01-09-2013, 06:14 PM

neilh

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Quote:

Originally Posted by Jadz928

Use a resistor.

From another website:

Does the AM sensor come with an predetermined resistor?

Resistor is only good if source voltage does not change. If you put a resistor of value X ohm in series with a load ( the AM sensor) of Y ohm, the voltage across the sensor is in the ratio Voltage * (X/Y). so if X and y are equal, the volts across Y is 1/2 the supply voltage. If the volts are 12, then thats 6v, if it goes up ( as in charging voltage) to 13.5, then its 6.75.
Use the LM317 ( from RadioShack) as suggested and it will always be 5V.

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01-09-2013, 06:17 PM

dr bob

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What Dan said. ^^^^

If you want to build a dedicated device, you can use a LM7805 regulator with a couple small caps and a heat sink to get exactly 5 Volts. Radio Shack parts for a few dollars. One Amp current capacity.