Simple LC meter

LCmeter_5

 

This project is a simple LC meter based on PIC16F682A mcu.

Description

Here is another piece of laboratory equipment – LC meter. This type of meter, especially L meter is hard to find in cheap commercial multimeters.

Schematic of this one came from this web page:https://sites.google.com/site/vk3bhr/home/index2-html.

It uses PIC microcontroller 16F628A, and because I recently acquired a PIC programmer, I decided to test it with this project. Following the above link you will find the original schematic, PCB, source and HEX files for programing the microcontroller and detailed description.

Here is my adaptation of the schematic:

I removed the 7805 regulator, because I decided to use a 5V adapter from Sony mobile phone.

In the schematic, trimmer-potentiometer is 5k, but actually I put 10k, after consulting with the datasheet of the LCD module I bought. All three 10uF capacitors are tantalum and C7 – 100uF actually is 1000uF. Two 1000pF capacitors are styroflex 1% and inductor is 82uH. Total consumption (with back light) of the device is 30mA.

R11 limits the back light current and must be calculated according to the actual LCD module used.

I used the original PCB as a starting point and modified it to suit better to my components.

Here is the result:

The last two pictures shows LC meter in action. In the first of them, there is 1nF/1% capacitor and in the second – 22uH/10% inductor. The device is very sensitive – when I put the test leads there is 3-5 pF reading on display, but it is eliminated with the calibrating button.

Schematic

LC_meter_schematic

Photos

LCmeter_1

LCmeter_2

LCmeter_3

LCmeter_4

LCmeter_5

LCmeter_6

LCmeter_7

 

Update: 24 June 2012

One of my colleagues in a Bulgarian audio forum ask me to build him a copy of the LC meter, but this time with 9V battery power supply.  I made a new PCB with little rearrangement of the old one and adding a 78L05 voltage regulator.

I also added an automatic sleep mode, schematic of which I found here:http://www.marc.org.au/marc_proj_switch.html

The goal here was to make power consumption as low as possible. With increasing the value of R11 to 1.2kOhm which control the back light current, total current of the device was decreased to 11-12mA. Without back light at all the power consumption will be decreased even further, but the visibility suffers greatly.

After some tests, the value of the C10, which defines the ON time, was chosen to be 680nF. The ON time in this case is 10-11 min.  The MOSFET Q2 may be replaced with BS170, but bear in mind that the leads are in reverse order.

ON-OFF switch is momentary non lock type.

LC_meter_with_PS

Photos

LCmeter9V_1

LCmeter9V_2

LCmeter9V_3

LCmeter9V_4

PCB

Comments

  • Rana

    Where is the code or hex file for PIC 16F628A ???

    4 years ago
  • Electronics Lab

    You should find it on the original project link here: https://sites.google.com/site/vk3bhr/home/index2-html

    4 years ago
  • phong

    Where is the code or hex file for PIC 16F628A ???
    sent to hex file email adress : phongk8a1@gmail.com
    thank

    3 years ago
  • robin

    please provide the proteus file

    3 years ago
    • Electronics Lab

      Sorry, Proteus file isn’t available.

      3 years ago
  • JOHN WILSON

    I made the circuit in proteus and LCD shows calibrating…..(No change after that )

    3 years ago
    • Vinicius Andrades

      share the Project, please!

      3 years ago
    • Taha

      Could you send me the Proteus file please? Thanks in advance
      t90nassa@gmail.com

      3 years ago
  • İbrahim

    Hex code .,?? kiral96@hotmail.com upload

    3 years ago
    • Electronics Lab

      Hex code is added on the downloads section above.

      3 years ago
  • Javier Garcia Holgado

    Muchas gracias amigo. Espero que funcione. Te volveré a escribir si consigo terminarlo. Soy nuevo en esto de la electrónica. Un saludo.
    Thank you very much, my friend. Hope it works. I’ll write again if I can finish it. I am new in electronics. A greeting.

    2 years ago
  • Yevgheny

    This meter works good with capacitors. When I switch it to inductors it shows me ‘overrange’ . Then I insert inductor and it shows it’s inductance correctly. Something wrong with my device or this is correct behaviour ? Thanks

    2 years ago
    • admin

      It seems correct behavior to me. But it’s better to contact the author about it.

      2 years ago
  • Bittu

    is the hex file works same on other L c meter circuit ??

    2 years ago
    • admin

      You need to burn the specific .hex file to PIC mcu

      2 years ago
  • khoi

    The reed you use is replay? How many pin does it have? In Schematic I see It has 2 pins. But, anyway I has 4 pins in PCB, what’s wrong?

    2 years ago
    • admin

      The reed relay K1 controls switch K1, so actually it has 4 pins.

      2 years ago
  • Boo

    I need the code (maybe wirted .txt not .hex) Where I can find it?

    11 months ago
  • Sarath

    Sir is reed relay a solid state relay

    11 months ago
    • admin

      No, reed relay is a relay that uses magnetic field to control it’s state.

      10 months ago
  • Vinicius Andrades from Brazil

    I had success using a reed relay 5V, SIP 1A05 (Pan-Chang) from eBay.

    10 months ago
    • what did you do with two other relay legs

      10 months ago
      • admin

        You just have to connect the coil contacts and the Normal Open contacts. No other connections are needed.

        10 months ago
  • Alireza

    excuse me sir please help me, what is reed relay in this circuit ??? please say all of specification. thanks

    1 week ago

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