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

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Rana

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

phong

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

robin

please provide the proteus file

JOHN WILSON

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

Vinicius Andrades

share the Project, please!

Taha

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

İbrahim

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

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.

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

Bittu

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

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?

Boo

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

Sarath

Sir is reed relay a solid state relay

Vinicius Andrades from Brazil

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

what did you do with two other relay legs

Alireza

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

Mohsen

hi friend please say me about reed relay in this project.why use it.? can another thing replace it.?

Anonymous

can we use 82uh resistor like inductor ?

Anonymous

no you can’t use a resistor in place of an inductor. You can use an inductor of 82uH that may look like a resistor from the outside.

Hakan

sorry for my English. i tried to say can we use 82uh inductor looks like a resistor.
as i understand from your reply i can use it right?
thank you very much

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