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Led display Digital Voltmeter question

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There are many 7 segment displays which will work. Compare the specs in the data sheet. You will come across two types. Common anode and common cathode. This is the most important difference. Choose the correct one. Also look at the other voltmeter project in the projects section. It uses a dual display. This is the MAN6710. These can usually be found for less than the price of two of the single seven segment displays. Both projects use the "Common Anode" type displays.

MP

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The discussion regarding the final corrections were in another area. This happens when someone starts a new topic instead of posting in the same thread.
I have merged that discussion into this one. Go back through the pages of this discussion and you will now find all of the information.

MP

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I have merged some of the old Digital Voltmeter conversations found in another area into this thread. Go back to page one and browse through the messages of this thread. You will find the answers to these questions in the past posts.

MP

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Will this schematic measure resistance?

Actually, what I am looking for is a schematic for an ohm meter that would measure 10k to 500k in 10k incraments and display it as 1-50, e.g. 10k-19.99k = 1, 20k-29.99=2....you know....

Anyway, if this schematic will not work, anyone have any ideas?

Thanks

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Hi,
i do have queries with regards to the LED display Digital Voltmeter. I am from a mechanical background and do not have much knowledge in electronic devices. I am currenlty trying to build a Led digital voltmeter. I would like to find out whether we have to programme the ICL7107 chip to display the voltage output or just need to buy the chip and connect according to the specifictions given in http://www.electronics-lab.com/projects/test/014/. Is the ICL7107 chip pre-programmed already? Thank you....

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Hello!

I would like to monitor the voltage from a sensor. The sensor produces 0 to 10 volts. I would like the display to show the voltage in relation to a scale of 1 to 2000.

eg.
0v = 0
2.5v = 500
5v = 1000
7.5v = 1500
10v = 2000

The digital voltmeter project can be modified to measure a voltage range of 0 to 20 volts by replacing R3 with 120 Kohm 1% res.

(Voltmeter project link)

http://www.electronics-lab.com/projects/test/014/index.html

Now if I took the voltage output ( 0 to 10v ) and put a voltage doubler there to make the sensor output 0 to 20v, and connected this to the input of the modified range voltmeter ( 0v to 20v),

Will the voltmeter display the range I want from the input voltage?

I guess I'd have to disconnect the decimal point LED in the display ( so 12.15v would read 1215 )

Will this do what I want?

Many thanks

ps. There is a long forum discussion about making the voltmeter

http://www.electronics-lab.com/forum/index.php?board=2;action=display;threadid=119;start=1;boardseen=1

This posed a few questions that I couldn't find the answer for. However, it was a long read (10 pages) so could somebody who's built the voltmeter answer :

How stable is the device? Somebody said as the voltmeter 'warms' up, the volt reading changes. Is this true? By how much? Could someone who's built this explain a bit more?

Will the voltmeter (when modified to 0 to 20v range) read to 2 decimal points (eg. 12.51 v ) ?

thanks

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Hai,
Can any one explain the function of pins27,28,29 on ICL7107.
Also I still didn't get clue why the pin7, which was said catode-A is shown linked to ground in the main schematic ???. Is it supposed to be pin5(cathode-dp) for required decimal pt.
Also How does the ref-hi(pin36) effects final mesurement. Can i ground it to have all my voltages(at VinHi) measured in reference to 0V.

thanks

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hi to everybody here
i am a new comer here with my 1st post, and i am really impressed to see the way you people are working for projects and discussing about them for the benefit of beginners like me.
i saw the LED display voltmeter and also browsed through the discussion about it, and i think its an ideal project for any beginner to start.

but i have some questions about it before its practical implementation (dont laugh if you find them too childish)
First Question:

for multi range, its recommened to use 0 ohm for 0-2 volts, 120 k ohm for 0-20, 12 k ohm for 0-200, and 1.2 k ohm for 0-2000.
i cant understand why no resistance for 2 volt, then suddenly increases 120 k for 20 V, then it gradually decrease for 200 and 200 V. I have always seen resistances increasing or decreasing in any multi range meter (current, voltage etc). but here it is showing different change ????

Second Question:

what about type of capacitors used? in diagram, they seem to be non polar but i want to confirm about their type. also voltage ratings of capacitors is not mentioned???

Third Question:

from the discription of circuit, it is clear that the IC 7107 is very delicate, what does it mean?? will the voltmeter be also very delicate that it may damage for a very small excessive voltage... So please make me clear about the tolerance level about which it can withstand.

thank you very much for reading all this stuff written by me...
waiting for a kind reply
bilal

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Some people recommend using IC for generating the -5V. But the best thing to do is to have a resistor divider across the -15 V which is available in all the voltage source to produce the -5V.

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Hi Shankar,
A resistor divider would waste a lot of power and wouldn't regulate the -5V very well.
A linear series voltage regulator IC is a voltage divider that hardly wastes anything and regulates the -5V extremely well. ;D

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I normally use an ICL7660 for a negative supply on mine, but the datasheet for the ICL7106 and 7107 shows how to use a CD4009 and some diodes to generate the negative voltage from the oscillator pins. This is probably the simplest. The negative side does not need much current.

MP

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I every body

I'm new here and i've read all the discussion forum, i'm shure it hellpe me doing my digital votlmeter.
I read that the IC 7107 can read capacitors to. Do any body try to do it??
i'de like to do one. Can any body hellpe me???

Thanks

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I was so fascinated that I decided to build the voltmeter on the breadbaord. It couldn't work correctly. It was just flshing. C6 and C7 are only on the components list and the PCB where are they on the schematic.

I am dissapointed cause I have probably messed up my ICL7107 IC

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