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best way to get HIGH signal without lower voltage or amp of the item? Answered

I would like some advice on getting a HIGH signal(that it has power to it and the signal is pulsed) from a fuel pump without lowering the voltage or amperage it receives. I am new and learning about electronics. However I thought about using a 2n2222 transistor for this. The voltage to the pump is 6-8volts. 

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user
lemonie (author)2011-05-15


Is this part of an engine, and if so what engine?

L

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user
danzar (author)lemonie2011-05-15

Yes its a part of an engine, Its a 1400cc motorcycle engine.

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user
lemonie (author)danzar2011-05-15


So you want to make a digital speedo/odometer that takes a signal from the crankshaft (via the fuel system)?
It usually helps these questions to explain what you're up to.

For signals you do not need to take much power out at all, the right resistor will do you fine.
I suggest that you ask steve about what to do with this if you are aiming for a digital speedo/odometer.

L

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user
steveastrouk (author)2011-05-15

You certainly wont' steal any power from a rev counter by taking an input from your pump !! Don't worry about it.

Steve

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seandogue (author)2011-05-15

A simple voltage divider can be used, if you know the maximum pulse height and want to drop it to something more in line with what you need.

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user
steveastrouk (author)2011-05-15

I don't understand the question- you want to know that the pump is running ?

Steve

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user
danzar (author)steveastrouk2011-05-15

Yes, I will explain in more detail. The fuel pump is driven by a pulse from the igniter to the coil. The pulse is going to be used to get the RPM's of the motor. The main concern of mine is, I don't want to lower the voltage or amperage that is delivered to the pump. Because I don't know the results on what that might cause to the pump.
So I would like to be able to read them pulses to the pump without changing the voltage or current going to it.
I really like learning about electronics, but I am one of the types that learn by working on things. So if you do want to help me with this item. Help me understand what I need to know.
Now I am just going off what I THINK i know. If i use a 1000k ohm resistor on the base of a transistor, would work (i think). the resistor limiting the amount of current and voltage from the pulsing 6-8v?

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