Using microcontrollers you can design many interesting and useful electronic projects . This electronic project circuit is based on PIC16C622 microcontroller ( manufactured by Microchip ) . This PIC project is a simple resistance and capacitance “Pic Meter” which can measure resistance in the range 1W to 999W and capacitance from 1 nF to 999 nF.
This PIC METER uses a variation of the single-slope integrating converter.
All measured data are transmitted to a PC which displays the value measured.
This Pic Meter project is powered directly from the RS-232 serial port ,the RTS and DTR lines from the serial port output 3V to 11V to the PIC METER. The diodes D2 and D3 prevent any damage to the PC’s serial port.
Resistor R10 is used to current limit the Zener diode, D4. D4 is used to regulate the RTS and DTR voltage to 5.6V. Capacitors C3 and C4 provide power supply filtering to the Zener diode and the PIC16C622. Using this type of powering source for the PIC Meter will not damage the RS232 port , because this project has an very low current consumption of 7mA.
S1switch is used to select either a resistor or capacitor measurement. RB5 of the PIC16C622 is used to detect what type of component is being measured.
Resistor measurements that are started without any component connected to the measuring terminals will cause an error. Capacitor measurements without a component connected to the measuring terminals will give a result of 0 pF.
Switch S2 is used to initiate a measurement. The switch is connected to RB6 of the PIC16C622 and the
PORTB wake-up on change interrupt is used to detect a key press.
The charge time of the unknown RC network is measured using Timer0 , measured value is multiplied by the known value of resistance or capacitance and stored in an accumulator. Then the charge time of the known RC network is measured. The accumulator is divided by the known RC network charge time to give the value of resistance or capacitance of the unknown component.
This software and project was designed by Rodger Richey from Microchip Technology Inc.
You can download the software for this project from the Microchip website or following this link .Pic meter pic16c22 source code