Digital Volt Meter

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hindy123

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Hi all
Does anyone have a diagram for a digital volt meter to measure from
0v - 50v DC. The only thing is the unit must be powered by the same source it is measuring. If thats not possible I can live with a seperate 9v supply.
Its quite a few years since I did anything like this so if anyone has a project that includes a pcb layout that would be great.
many thanks
 
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The easiest way is using an ICL7107 (price ~US$ 1.30). It contains all necessary circuitry like A/D converter and display driver.

There are just a few external components necessary for the complete DVM circuit.

The basic voltage measuring range is 199.9mV. Using an appropriate voltage divider at its input the readout can be made from 0 to 99.9V

Boncuk
 
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Yes as Boncuk suggested its a good choice.

My friend made this circuit, worked fine & its reading speed also superb.Here is the complete circuit with PCB.Don't know what resolution to be adjust for the PCB.

REBER electronic
 
The ICL7107 needs a supply that is separate from what it measures.
It uses an LED display so it eats a battery in a few minutes.

Use an ICL7106 instead. It uses a low power LCD display so a little 9V battery will last a long time.
 
Yes making a hanheld portable device is a must.

I'll use high efficiency seven segment LED displays something like "HDSP - 7503"
 
Another reason to use a ICL7106 instead of a ICL7107 is that the ICL7107 gets so hot driving the LEDs that it's internal voltage reference starts to drift.
 
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audioguru said:
Use an ICL7106 instead. It uses a low power LCD display so a little 9V battery will last a long time.
Click to expand...

Thanks all for your input guys. It looks as if I might be able to manage that one, and looks as if it might do the job.

Audioguru will using ICL7106 instead of the ICL7107 alter the rest of the circuit at all?

I have just also noticed that on the circuit pics that there are components other than what the pcb has room for????
Does anyone have any idea what these are for ??

Thanks
Andy
 
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hindy123 said:
Thanks all for your input guys. It looks as if I might be able to manage that one, and looks as if it might do the job.

Audioguru will using ICL7106 instead of the ICL7107 alter the rest of the circuit at all?

Thanks
Andy
Click to expand...

hi Andy,

Compare the two circuits.
 

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ericgibbs said:
hi,
Also check the BP [back plane signal pin] to the LCD.
Click to expand...

Ok Eric, you lost me there, its a very, very long time since I did anything like this. I take it that where pin 21 goes to ground it needs to connected to the led's. if so where ? It looks as if it is for the minus sign ? what if I dont need the minus sign, can this be left as is?
 

hi,
No, the POL, 'polarity' is the minus sign.
On the LCD display, look at the dwg for your LCD, you will see BP pins as well as the segment pins.
They may be more than one BP pin on the LCD, they ALL must go to the BP pin of the 7106.

Another point to consider, if you are displaying 50.0Vdc, is the decimal point, these will also be indicated on the LCD dwg.

OK.?
 
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Hi Eric.
Got it now. Many thanks.
Fingers crossed that I get it all right, otherwise I will be buying a unit to do the job. Its been about 25 years since I did anything like this.
 
Interesting reading guys, will also help out with a few of my display projects, have been searching for a driver chip for a while, cheers,
 
For everybody interested in that chip: Intersil has published an application note with an autoranging circuit. Document name: AN046

It's contained in the list of datasheets searching for ICL7017 at http://www.datasheetarchive.com

Boncuk
 
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audioguru said:
The ICL7107 needs a supply that is separate from what it measures.
It uses an LED display so it eats a battery in a few minutes.

Use an ICL7106 instead. It uses a low power LCD display so a little 9V battery will last a long time.
Click to expand...

If you use it in bright environment an LC-Display is fine. I used it to make a micromanometer and reading in completely dark air channels requires an LED-display.

Using high efficiency LED-displays the current consumed by the display is below 100mA.

I also used the same power source for the pressure sensor circuit and the DVM circuit. Measuring current the power source must be separate from the circuit to measure.
 
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