How to split an electric current.

[Null Pointer X]

I need to siphon off 1.5-2v from a power source that produces anywhere between 2.2-2.5v, but is constantly changing. are there any parts that could help me, or have I touched on a near-impossible task?

 

[MikeMl]

What do you mean "siphon Off"? A regulator drops the difference between the unregulated power source and a load you want a fixed voltage across. Look up "series regulator" like an LM317.

 

[Null Pointer X]

I mean, 1.5 will go down one wire, and the rest will go down another wire

if Vt=2.3,



v1\ /v2
---|vt

v1 should equal about 2.5 or 1.7,
v2 should be vt-v1, or about .6v.

 

[colin55]

Put a 470R resistor on the positive line. On the end of the resistor connect 3 diodes in series with anode to the resistor with the other end of the diodes to the 0v line. Across the three diodes will be 1.8v, and it wont change.

 

[Null Pointer X]

Thanks for your help, Mike and Colin.

 

[crutschow]

Put a 470R resistor on the positive line. On the end of the resistor connect 3 diodes in series with anode to the resistor with the other end of the diodes to the 0v line. Across the three diodes will be 1.8v, and it wont change.

Not exactly. It will change with temperature about -6mV/C and also some with load.

If you want better stability than that, use a voltage regulator such as the LM317 that Mike suggested.

 

[colin55]

How are you going to get an LM317 to work on 2.5v???? At 3v in, it provides 10mA output.

 

[crutschow]

How are you going to get an LM317 to work on 2.5v???? At 3v in, it provides 10mA output.

You are right, of course. I didn't take a close look at the voltages. He would need a low dropout regulator.