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.
For more detail: Simple PIC LC meter