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You are here: Home / Meters and Testers / Digital Voltmeter Circuit Using IC L7107

Digital Voltmeter Circuit Using IC L7107

Last Updated on August 28, 2019 by Swagatam 54 Comments

The post explains a very simple digital panel type voltmeter circuit using a single IC L7107 and a few other ordinary components. The circuit is able to measure voltages right up to 2000 AC/DC V.

About the IC L7107

Making this simple digital panel voltmeter circuit is particularly easy due to the availability of the  A/D voltage processor chip in the form of IC L7107.

Thanks to Intersil for providing us with this wonderful little IC L7107 which can be easily configured into a wide range digital voltmeter circuit using a few number of common anode seven segment displays.

The IC 7107 is a versatile, low consumption 3 and 1/2 digit A/D converter IC which has in-built processors such as seven segment decoders, driver for displays, set reference levels and clock generators.

The IC not only works with ordinary CA seven segment displays but also with liquid crystal displays (LCDs) and has an in-built multiplexed back plane illuminator for the connected LCD module.

It ensures auto zero correction for inputs less than 10uV, a zero drift for inputs below 1uV/oC, bias current for inputs of maximum 10pA and cross over error of less than a single count.

The IC can be set with ranges as high as 2000 V AC/DC, and as low as 2mV, the later makes the IC very suitable for measuring low inputs from sensors like load cells, piezo transducers, strain gauges and similar bridged transducer networks.

In other words, the chip may be simply configured for making products like digital weighing scale, pressure meters, electronic strain gauge, vibration detector, shock alarms and many similar circuits.

Needless to say, the IC L7107 can be also rigged into a simple yet accurate panel digital voltmeter circuit, which is what we are presently interested in.

Circuit Operation

Referring to the circuit diagram below, the unit is a full fledged digital voltmeter circuit which can be used for measuring direct voltages right from zero to 199 volts.

The range can be appropriately widened or shortened simply by altering the value of the 1M resistor positioned in series with the input terminal. With 1M, the range gives a full scale of 199.99V, with 100K in place the range would become 19.99V full scale.

The circuit requires a dual +/-5V supply for operating, here the +5V may be strictly acquired from a standard 7805 IC regulator circuit, the -5V is automatically created by the IC 7660, and fed to pin#26 of the IC L7106.

The three 1N4148 diodes connected in series with the display supply line ensures optimal operating voltage to the displays for illuminating them with correct intensity, however for brighter illumination, the number of diodes may be experimented, as per personal preferences.

The 10K preset across pin#35/36 is used for calibrating the voltmeter correctly and must be set such that exactly 1V appears across pin#35/36. This will set up the circuit for displaying the measured magnitudes accurately as per the given specs, and datasheet of the IC.

Parts List

All resistors are 1/4 watt unless specified

  • 220 Ohm - 1
  • 10K = 1
  • 1M = 1
  • 47K = 1
  • 15K = 1
  • 100K = 1
  • preset/trimmer 10K = 1

Capacitors

  • 10nF Ceramic Disc = 1
  • 220nF Ceramic Disc = 1
  • 470nF Ceramic Disc = 1
  • 100nF or 0.1uF Ceramic Disc = 1
  • 100pF Ceramic Disc = 1
  • 10uF/25V Electrolytic = 2

Semiconductors

  • 1N4148 Diodes = 3
  • 7 Segment Displays MAN6910 or Equivalent = 2
  • IC L7106 = 1
  • IC 7660 = 1

Pinout details of IC L7106 for interfacing with a 3 and 1/2 digital LCD display.




Previous: 15V 10 Amp Voltage Regulator Circuit Using IC LM196
Next: Car Turn Signal Flasher Circuit with Lamp Malfunction Indicator

About Swagatam

I am an electronic engineer (dipIETE ), hobbyist, inventor, schematic/PCB designer, manufacturer. I am also the founder of the website: https://www.homemade-circuits.com/, where I love sharing my innovative circuit ideas and tutorials.
If you have any circuit related query, you may interact through comments, I'll be most happy to help!

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Comments

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  1. Search Related Posts for Commenting

  2. Ahmed lotfy says

    would it work if I use 4 single 7 segment display? I can’t find MAN6910 in my area

    Reply
    • Swagatam says

      if the pins are correctly matched then it might work

      Reply
  3. Davide Crescini says

    Hi Swagatam,

    I have 2 questions:
    1. Why i cannot leave a reply under this post “Transformerless AC Voltmeter Circuit Using Arduino”? It is a site bug?
    2. Still refering to “Transformerless AC Voltmeter Circuit Using Arduino” how much current it can handle? It can be used to measure home-devices like 2500W vacuum cleaner?

    Reply
    • Swagatam says

      Hi Davide, it is not a bug, the comment box is disabled since I am not an expert with Arduino and therefore cannot answer related questions.

      Current is never relevant to voltmeters. The current can be any value as long as the voltage is within the maximum specified range of the meter. Similarly it can handle any wattage as long as the volt is within the specified max range

      Reply
  4. Hedi says

    Hi. As always good explanation and good project. Meanwhile i have some questions :
    – By setting Vref = 1v The max vinput is then set to 2v . Isn’t it?
    – The voltage divider across pins 30 and 31 is here for setting the range of the voltmeter. Then is it correct that removing the 1M resistor will allow to have a range of 2v (equal to the max vinput) ?
    – In case of a range of 2v what is the resolution (accuracy) in mv ?

    Thanks again.

    Reply
    • Swagatam says

      Hi, sorry I don’t remember the working and the specifications of the IC, it was written a long time ago.

      I think the datasheet of the IC will have the answers.

      Reply
  5. LamNH says

    Dear Sir,
    IC 7106 is desisgned to drive LCD display (meanwhile 7107 is for 7seg LED display). In ur circuit, I wonder if the IC could supply current eanough for 7 seg LED display? The circuit is only work with dual supply voltage or it could works with single voltage?
    Thanks and best regards,
    LamNH

    Reply
    • Swagatam says

      Dear Lam, the circuit will work if connected exactly as suggested in the diagram.

      Reply
      • Lam NH says

        The title is “Digital Voltmeter Circuit Using IC L7107” but the circuit showing IC 7106. Is that corect? Pls confirm. Thanks!

        Reply
        • Swagatam says

          Both have similar features except the digital display, so you can use any one of them depending on the display.

          Reply
  6. Mark says

    Thank you for doing this kind of website. I love it. One problem however, a seperate bom would be awesome. I am old and kinda blind. Hard to see the values of the components. I think they are capacitors, but the “n” is throwing me off. Please enlighten me. Thank you kindly sir.

    Reply
    • Swagatam says

      Thanks very much for liking my website! I have added the parts list for your reference!
      “n” means nano, or nanoFarad (nF) for the designated capacitors.

      Reply
  7. Alwin says

    hello sir
    I wanna measure 0.001v – 5v, which ic is good for this (analog to digital converter ), Is this possible to measure this voltage range

    Reply
    • Swagatam says

      hello alwin, digital will be obviously better….yes it is possible to measure this range with any good quality DMM

      Reply
  8. dada neamul says

    sir
    You Use Two 7 Segment display. If I Want To Use One 7
    Segment Display ..! What Should I do…… Sir I using A Variable DC Power Supply Unit But I Have No ckt Diagram for Digital Volt Display.

    Reply
    • Swagatam says

      Dada, I don't think a single display would be possible with this IC, because the IC is specifically designed to drive a 3.5 digit display

      Reply
    • dada neamul says

      thanks for your compliment.

      Reply
  9. Shreyansh Likhar says

    can i interface it with any microcontroller(8051 or AVR)?

    Reply
    • Swagatam says

      yes, you can do it…

      Reply
  10. Nitin Sarda says

    Sir,

    I have a digital voltmeter which measure the 24 volt dc.

    When it was new then voltage was measuring ok. But after 2 months, voltage reading fluacting in display. I mean it show 25,32,47 volt etc.

    How to stop the wrongly fluction on display??

    Reply
    • Swagatam says

      Nitin, if it has a selector switch then the problem could be in the switch, just move it rapidly up/down and then check the response….loose prod connectors could also be an issue, so you can check it as well.

      if these are OK, then your meter is surely malfunctioning.

      Reply
  11. Bradley Nelson says

    Sorry if this comment posted more than once. I've had a hard time submitting it.

    I'm wondering if this circuit could output the voltage reading to an Arduino instead of the LEDs? I'd like an Arduino to be able to read voltage and store the value as a variable in a program.

    Will this meet that need?

    Reply
    • Swagatam says

      I am sorry I have no idea how this circuit may be configured with an Arduino…

      Reply
  12. Bhaskar Srivastava says

    Can this Circuit can be used to measure AC house hold Supply. ??

    Reply
    • Swagatam says

      yes, after appropriately rectifying and calculating the input resistors

      Reply
  13. frank rebosura says

    Sir it is directly connected to the AC output voltage of the generator set to measure its output voltage or it is only used to measure DC voltage?

    Reply
    • Swagatam says

      convert AC to DC and then the 10K preset across pin#35/36 could be used for calibrating the voltmeter correctly and must be set such that exactly 1V appears across pin#35/36. This will set up the circuit for displaying the fed magnitudes accurately.

      Reply
  14. style says

    Thanks for reply sir. Why its called 3 and half digital display ..

    Reply
  15. style says

    Hello Sir
    Thanks for reply. can u tell me the address in mumbai.
    regards

    Reply
    • Swagatam says

      you can many good shops in lamington road (grant road)

      Reply
  16. sinu sivadas says

    Hello Sir
    Is this IC is available in India particularly in Bangalore and what is its cost

    Regards

    Reply
    • Swagatam says

      Hello sinu, it's available in Mumbai, I am not sure about other states or Bangalore

      Reply
  17. vishwas poojary k says

    what is the indian price of that ic?

    Reply
    • Swagatam says

      no idea, sorry

      Reply
  18. currentviews says

    Sir,
    Its really excellent Project Post. i liked it too much, already i bought every parts . here i did not get ICL7106. but i got ICL7107 they told me its similiar like ICL7106 , i need to know how can i connected it with 7 segment display, is it like ur instruction numbering, basically i considering number 1 pin from left side and continuously from right. like IC pinout perhaps its not right way about pin connect among IC and 7 segment display. please i need to know about 7segment display pin setup configuration ..

    Reply
    • Swagatam says

      thanks currentviews,

      the best place to get the information is to look in its datasheet.

      Please type "datasheet" with the "part number" or simply "7-segment display datasheet" in Google search…… you will get a comprehensive info regarding the same.

      Reply
  19. Tanmay Deshmukh says

    And sir where should the preset to be connected?

    Reply
    • Swagatam says

      Hello Tanmay,

      pin36 is connected to the slider arm of the preset.

      The preset has three pins, the center pin will go to pin36 and the other two pins will connect with pin35 and the 15k resistor…..

      Reply
  20. Tanmay Deshmukh says

    Hello sir,
    As am a very beginner, confusion is How is the pin 36 of ic 7106 connected, i think is in between two resistors given.is it ?

    Reply
  21. Saroj Panda says

    it showing only a point in the second display nothing else

    Reply
    • Swagatam says

      did your apply any input voltage?

      Reply
  22. farkhana says

    Hi there,

    I have made using same IC. However, my input is 4-20mA and the output is indicator that shows -30 to120.
    Is it possible to show -30 on 7-segment?
    Do you have any idea how to do that?
    Many thanks for your help.

    Reply
    • Swagatam says

      Hi, There should be a way definitely, however I have no idea how to do it.

      Reply
  23. Abu-Hafss says

    Hi Swagatam

    Is it possible to convert/modify a digital AC voltmeter to use as a DC voltmeter?
    AC voltmeters are cheap and easily available in various sizes.

    Reply
    • Swagatam says

      Hi Abu-Hafss,

      I am not sure how to make an RMS detector, without this it would be impossible to convert AC meter into DC.

      Reply
  24. Subhramanyam says

    I am expecting your reply soon sir!!!!!!

    Reply
  25. Subhramanyam says

    It is ok sir. But i have a small doubt.
    Eventhough i am caliberating this circuit with a known frequency signal, will it be same for another signal having a different frequency but having the same peak to peak voltage of the known one since it is not functioning as a frequency to voltage converter, otherwords saying the circuit functions only as a voltage finder. If anything wrong i have said, please correct me Sir

    And also tell me is it possible to adjust the reading to 50 when 50 Hz is fed ( i think only the voltage equivallent will be shown)

    Reply
    • Swagatam says

      Subhramanyam , the above circuit is a voltmeter not a frequency meter, so you cannot feed frequency directly to this circuit, as mentioned in the above comment and as per your previous comment under the "simple frequency meter" article, you will have to integrate the frequency meter circuit output with the as above circuit to get a digital reading….I think this is what you had asked in your first comment, right?

      Reply
    • Swagatam says

      ..the frequency meter circuit using IC 555 can read right from 10Hz to 10kHz comfortably, so 50Hz won't be an issue.

      Reply
  26. Subhramanyam says

    How can i use this circuit to measure frequenc SIR?
    Directly feding the input signal into the voltage measuring terminals'???
    I have 4 no.s of 7 segment single LCD displays ( each having 10 legs ) with me. Can they be used? How to wire them?

    Reply
    • Swagatam says

      yes connect the frequency meter output to the shown points and adjust the 10k preset for calibrating it with the known frequency value.

      You will have refer to the datasheet of the displays online and identify the pinouts and then integrate with the above circuit.

      Reply
  27. Abu-Hafss says

    Hi Swagatam

    I am bit confused for the connections of ICL7106 to a 3.5-digit LCD (H1331C).

    a) Where to connect pin 19 (AB4) of the IC?
    b) Where to connect pin 20 (POL) of the IC?
    c) Where to connect pin 21 (BP) of the IC?

    d) What is pin 8 (DP3) of the LCD for and where to connect?
    e) What is pin 12 (DP2) of the LCD for and where to connect?
    f) What is pin 16 (DP3) of the LCD for and where to connect?
    g) Where to connect pin 1 (COM) and pin 40 (COM1) of the LCD?

    Reply
  28. Swagatam says

    You can refer to the datasheet of the IC and check if this option is enabled in it.

    Reply
  29. Swagatam says

    don't use a pot, instead use a preset, it's more firm and will keep the setting intact, if possible glue it after the setting is done.

    Reply


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