Led display Digital Voltmeter question

[benz1]

I am building the same circuit as discussed earliers. I want to attach the meter to a supply and measure the same supply. I find its not possible as the ground and the common is not same.

I am attaching the circuit to a 12V supply using a 5V regulater. then monitor the same 12 V supply. How can I do this? Thank you for your help.

 

[MP1]

Benz, you cannot power any digital voltmeter from the supply you are measuring. You have to provide an unchanging supply voltage to the meter. There are a few ways to do this. Primarily, you will want to pull the supply off the secondary side of the transformer somewhere and not from the variable output. You can do this in many cases by just adding another regulator, etc.

MP

 

[Kasamiko]

I just finished mine on a breadboard..but when I powered it, The digits that was displayed was NOT zeroes but random numbers if I try to adjust the trimmer but only the leftmost digit display "1" I check my display segment by connecting PIN# 37 to +5V and all are ok..
Did I missed something.. ???

Rhonn

 

[ante1]

Hi Rhonn,

Do you know if the schematic you have used is updated, there have been some issues and a couple of errors if I remember correctly?

Ante :

 

[Kasamiko]

Hi Ante, can you point me to the tested and working schematic for this project. I got a lot a ICL7107 sample chip from Maxim and Intersil and I'm planning to build a regulated power supply with digital readout for voltage and current respectively..
Maybe this circuit will do the job.
http://www.electronics-lab.com/projects/power/032/index.html
Regards.


Rhonn

 

[Kasamiko]

I have found this this updated and corrected schematics..
But want to clear this out.. Based on the two posted schematics, is PIN #30 connected to PIN #32 and 35 or what??
Thanks again..

Rhonn

 

[ante1]

Rhonn,

Yes, the REF LO and IN LO shall be connected to COM.

Ante :

 

[Saint1]

stuee,

Yes, this circuit can measure current if you like. You need a shunt for this.

Ante :

Ante,

What would the circuit look like and what value shunt resistor would be needed to enable the meter to measure 30 vdc and 3 Amps

Greg

 

[ante1]

Greg,
Welcome to this community.
I assume you are using an analogue meter since you want a 0

 

[audioguru2]

Greg,
If you are building our "0-30V, 0.002-3A Power Supply", instead of adding a current meter with shunt in series with the load, which spoils the voltage regulation, why not monitor the voltage across its R7, which is already in series with the load and is outside the voltage-regulation loop. R7 will be the meter's shunt, and you just need to divide the voltage across it by 4.7 to get a 3A range.

 

[ante1]

audioguru,

Greg asked

 

[Saint1]

Greg,
Welcome to this community.
I assume you are using an analogue meter since you want a 0

 

[ante1]

Sorry, I believed it was a mistake curse I don

 

[Saint1]

Hi Guy's

Sorry. I am causing all sorts of confusion here. To clarify....This digital volt meter is a great idea. I will build my own 0-30vdc variable supply at 3 amps. very similar to what you have on your site. However instead of using analogue meters. I would like to build this digital voltmeter into it. I would also like some detailed guidance from you knowlegable gentleman as to how to change the digital meter into a digital ammeter.

Your assistance would be greatly appreciated.



Greg

 

[MP1]

This has already been answered here on the site. You just need to search. It was either in the digital voltmeter discussion or it was in the 0-30 Volt Power Supply discussions. I recall seeing a diagram posted to use the digital voltmeter for both volts and amps.
If you cannot find it, let us know.

MP

 

[Saint1]

I have found all the info on your site.

Thankyou Gents

 

[niceride]

Hi guys, just registered, have a couple of stupid questions. i am software guy not an electronics major so go easy on me. i would like to use this project to measure voltage of a car battery.

that is, i am looking for something that i can position on top of the battery with double sided tape and connect to the + and - and have it display the voltage. this way i can pop the hood and see at a glance what the voltage is.

will this project be able to do that? what kind of mods do i need to do for it to accept +12v input? are there ready made gadgets that are available cheaply that will do what i am looking for?

thanks for help in advance...

 

[MP1]

How will you power it? You should use a different power supply to power the circuit. The device you are measuring will be your power source.

MP

 

[dlugolinski]

I am looking to do the same project as nice ride....couldn't you just use the same battery that you are measuring with a regulator circuit regulated at 5 volts?

also i need to know how to get the 0-20 volt display scale...
what resistors and capacitances are needed????

thanks

 

[GPG1]

ICL7107 Power Supplies
From the data sheet:
The ICL7107 is designed to work from