Contact-less tachometer based on PIC16F628A uC

Check out my new tachometer project based on PIC16F628A microcontroller. It uses an infrared sensor module to sense the rotation speed of a shaft or disc. The range of measurement is 0-9999 RPM. The full details on hardware and software is available.

0-20V Digital Voltmeter (DVM) using PIC12F683

After finishing the serial LCD project, it is time to do some cool projects using PIC12F683. Now we can have a nice LCD display with PIC12F683. This project shows how to make a digital voltmeter of range 0-20V using PIC12F683. Enjoy!

Background
You cannot feed 20V  directly to a PIC I/O pin, you need a resistor divider network that converts 0-20V range into 0-5V. The figure below shows how it will be achieved.

At any instant, the voltage Va will be 1/4th of the input voltage, Vin. So, for maximum input voltage of 20V, the Va will be 5V. A 5.1V Zener diode in the figure is to prevent Va to rise above 5.1V if the input voltage goes much above 20V. This will protect the microcontroller port. The analog voltage Va is read through AN0 port and is converted to 10-bit digital number (0-1023) by PIC12F683.