Creating Power Supply with LCD

[hugoender]

Hello,

I would like to make one of the simple variable power supplies based off the LM317 (or similar) voltage regulator. While the circuit for this is trivial, I would also like to have an LCD screen (or even a seven segment LED) display the voltage and current. Any suggestions on how to go about accomplishing this?

It seems to me that this might be a complex project but you guys seem to come up with simple solutions to complex problems all the time so I am posting this here to see what feedback I can get from you.

Oh and btw, I would not require much voltage nor current from this supply. It would be 1.5V-12V and up to 2amps (could be 1.5A... doesn't really matter since this is just for hobby circuit making).

Thank you for your input.

 

[Hero999]

What about just using an LCD voltmeter module?

Or just buying an ultracheap DVM and using its guts?

 

[Mikebits]

I like option 2. I have snagged cheapo DVM's for as low as 5 bucks.
Harbor Freight Tools - Quality Tools at the Lowest Prices

 

[Hero999]

That's the sort I'm talking about.

You'll probably need a separate supply for the meter though, use a LM7808 or LM317 set from 7V to 9.6V

 

[Mikebits]

You could always go old fashion analog meter movements.
Jameco Electronics Test, Tools & Supplies: VELLEMAN INC.: AVM6015
These might be easier to mount in a box.

 

[crutschow]

I like option 2. I have snagged cheapo DVM's for as low as 5 bucks.
Harbor Freight Tools - Quality Tools at the Lowest Prices

Sometimes they have them on sale for $2-3.

Of course if you want to display both voltage and current at the same time you'll need two of them.

 

[crutschow]

You'll probably need a separate supply for the meter though, use a LM7808 or LM317 set from 7V to 9.6V

The supply may have to be isolated. You can determine this by using the voltmeter to measure its own battery voltage. If one terminal doesn't measure 9V and the other 0V then the battery is floating and you must isolate the meter supply from the one your are measuring. For example, on a voltmeter I have, the battery terminals measure about +5V and -4V, indicating a floating battery.

You could use a small 6.3VAC filament transformer to generate an isolated supply. Depending upon the actual open circuit voltage of the transformer, a half-wave or bridge rectifier should generate about 9V. You may not even need a regulator.

 

[crutschow]

You could use a small 6.3VAC filament transformer to generate an isolated supply. Depending upon the actual open circuit voltage of the transformer, a half-wave or bridge rectifier should generate about 9V. You may not even need a regulator.

The won't let me edit my own post to I have to do another.

You could also use a 9V wall-wort for an isolated supply.

 

[Clyd3]

epemag the electronics magazine had a nice power supply quite like what you're after in one of their issues, using PICs and alike...