Schematic & layout for an updated JDM2 PIC Programmer. Includes clock & data filter, Vpp voltage divider for modern PIC microcontrollers (eg USB PIC 18F2455/4455).
This programmer uses 6 common components. Though the link says ’16F84(a)’ only, I used it for the more modern (and cheaper) 16F628(a) processors without problems. This programmer has served me extremely well, but it is limited to (less than) 18 pin PICs with a programming Vpp of 13 volts.
The circuit is based on the JDM2 programmer (http://jdm.homepage.dk/newpic.htm ), with two enhancements: clock and data line filtering & selectable programming voltage.