4-20mA output

J

jlhooper

New Member
Hi all
I would like to convert a voltage input to a current output.
eg 0-5v to 4-20mA.
I can do the "adc input part" of it OK.
But I'm not up to speed with the output.
I believe it is done with PWM.
Rather than certain fixed output values I would
like a "continual real time" output.
Grateful for any help thanx.
Jeff
 
J

jlhooper

New Member
I'm guessing the output load would be fixed,
as it would be feeding into a reader/processor type arrangement.
What that load is, I'm unsure of at moment.
What I'm trying to achieve is :
4-20 in, / do some maths on it /, then re output this as 4-20.
The reader will only cope with 4-20 input.
I just guessed that for picaxe to first read 4-20, it would have to be
read as a voltage. (I don't have a problem with that part, "250 ohm resistor trick").
Jeff
 
S

SgtB

Member
How about a digital pot and a voltage referance? Pardon my ignorance if this is a bad idea.
 
B

boriz

Senior Member
More detail about your app would be useful. But in the mean time, Google ‘current mirror’ and possibly ‘tutorial’. It uses one transistor to program the current in another. You will find current mirrors all over the place. Inside op-amps for example.
 
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