Hello I have made a power supply and I want to put on the digital panel meter that I have. The problem is that the meter cannot measure the same voltage that it is being powered by. Or even a voltage form the same supply. I can power it with a separate source such as a 9 v battery and it works fine but I don't want batteries in my power supply. Does anyone have any ides how to isolate the think or how to change it so that it can measure form the same source that powers it. Or does anyone know of a small digital panel meter that can measure it own voltage that is cheap like under 20 dollars.
thanks

 

well, if u still heve the meter....
does the power suply have some ac current? and then the ac is rectified and regulatend and so on...?
if u have ac, try to use a capacitor, a diode to form an auxiliary suply, considering that the VM doesnt consume much.....
if it does, try to use 2 larger capacitors and a full wawe rectifier....

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I don't think the supply suggested by bogdanfirst will provide the isolation you require...
There are DC-DC converters that can do what you want ...
http://www.tracopower.com/products/index.htm - look for the TMA/TME range, I have used these things before, they are good

http://www.cdpoweronline.com/product...egory.asp?ID=1 is an alternative (same idea)

Power supply can't get any easier 8)

Radiospares in the UK sell both ( http://rswww.com ) at around £6

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i had buit a power suply and used some voltmeter like you said....and i used something like i said, but because it was an old type of VM, it used around 100mA(it had 4 digit display with leds), so i used a full recifing bridge, and 2 capacitors, not just one......and it worked...maybe u have some other type of VM?
anyway u could use thae same kinf of idea to generata symetrical voltages from a single suply....

 

hi, i would like to know if someone here , can provide me some links to pages where contain info about galvos , i pretend to build something similar,or at least try it, so any info will be really appreciated.
thanks !

 

ELIEZER19_GT, you can post your own topic, you don't have to post a reply and ask for something else. Anyway, here are some sites that might be of some help.

http://www.star-laser.com/Starlaser/...stargrafis.htm

http://www.navactiva.com/?dir=http:/...dad.asp?id=778

http://es.xgoogle.org/details?channe...te&network=251

http://www.fedit.es/FEDIT/entidades/detalle.asp?id=87

I didn't try any, so I hope they are of any help

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If Your VM chip is 7107 You can apply a simmetrical + - 5V supply.This method enabled make common GND.See datasheet on Intersil-Harris site.