It is really quite a simple circuit and its main objective is to provide ICSP connections to your pic microcontroller.
Here is the pcb version (click to enlarge):
PIC Programmer Circuit diagram
Disclaimer : If you build this circuit you must double check each connection to the parallel port cable to avoid damage to your computer. This includes checking for shorts between each pin at the parallel port on your circuit. For initial testing it is best if you use a spare (old computer). Building this project is your own responsibility and I can not be held responsible for any damage to your computer.
- Transmission line termination - lets it work over a long cable.
- LM317 voltage regulator to get 11.6 volts and protect the circuit
- Power supply steering diode (stops you reverse connecting the supply).
- Changed LM340-5 to 3pin 100mA LM78L05.
- ICSP connector.
- An LED to show that power is applied.
- Changed 74LS244 to 74HCT244 because I had one handy!
- Standard 10k resistors instead of 2k - just easier if they are all the same.
Transmission line termination
Power supply regulators
Vo = 1.25 * (1+R2/R1)
5V power supply
- The 5V regulator should be designed for the target board i.e. heatsinking etc.
- You could get more noise into your circuit.