This is revision A of my cheap PIC programmer project.

Cheap PIC Programmer (Revision A)

Revision A Introduction

The revision A printed circuit board was sent out for fabrication in mid-February 1999. A number of problems were encountered and documented in the Notes section below.

Revision A Schematic

The revision A schematic is shown below:

Cheap PIC Programmer Schematic
The circuit works as follows.
A wall wart transformer provides 24VAC through power jack N1. The 24VAC goes through a power switch SW1, Fuse F1, and full wave diode rectifying bridge made of diodes D1 through D4. An electroylitic capacitor, C1, a variable voltage regulator, VR1, and a tantalum capacitor, C2, provide a 13 volt linear power supply. The output voltage of 13 volts is set by appropriate selection of resistor values R1 and R2. Please note that VR1 runs quite hot, so a heat sink is required. The electrolytic capacitor, C3, 5 volt voltage regulator, VR2 and tantalum capactior, C4, provide a 5 volt power supply. Resistor R5 and LED1 provide a power on indicator.
Signals from the controlling computer's parallel port interface come in on connector N2. The clock signal comes in on pin 1 (STROBE). The data comes in on pin 2 (DATA1). Pin 3 (DATA2) is used to control the tri-state output of buffer U1B. Pin 7 (DATA6) and pin 8 (DATA7) are used respectively control the application of Vss and Vpp to the chip. Resistor R10, transistor Q3, resistor R7, resistor R6 and transistor Q2 provide a 5 volt voltage follower. Resistor R8 and LED1 indicate when Vdd power is applied. Similarly, resistor R11, transistor Q4, resistor R4, resistor R3 and transistor Q1 provide a voltage follower for Vpp. Resistor R9 and LED2 indicate when Vpp power is applied.
Headers J1, J2, J3, J4, and J5 are used to route Vpp, Vdd, Vss, Clock and Data signals to the 40-pin ZIF chip N3. A shorting block is applied to each header to route the correct signal and voltage to the chip being programmed.

Revision A Printed Circuit Board

The revision A PIC programmer printed circuit board has been layed out. The following files are available:

PIC Programmer PCB Artwork Layer
This contains the artwork layer that specifies where the components are to be placed.
PIC Programmer PCB Back Layer
This is the back (solder) side of the board.
PIC Programmer PCB Front Layer
This is the front (component) side of the board.
PIC Programmer PCB Excellon Drill File
This is the drill file for the PCB in industry standard Excellon format.
PIC Programmer PCB RS-274X Back Layer
This is the industry standard RS-274X file that specifies the apertures and line placement for the back layer.
PIC Programmer PCB RS-274X Front Layer
This is the industry standard RS-274X file that specifies the apertures and line placement for the front layer.
PIC Programmer PCB Drill Size File
This is a short file that specifies the drill sizes for the Excellon drill file.
PIC Programmer PCB Parts List File
This is a the parts list file.
PIC Programmer PCB Size and Hole Counts
This is a short file that specifies the board size and hole count.

Revision A Notes

As I build each project, I type notes to myself immediately below. I consult these notes whenever I do another revision of the board:


Copyright (c) 1999 by Wayne Gramlich. All rights reserved.