Pic programmer

 Download the schematic (PDF)

This circuit is based on the original Tait programmer. We made a few changes in order to support recent PIC micro controllers:

• The PGM pin is pulled to ground to ensure that it's at low logic level during programming and LVP mode is not entered (Ref. 1). LVP is enabled by default on brand new PICs like the 16F628A; erasing the chip also re-enables LVP. Noise spikes may cause unpredictable results during programming, if they couple into the PGM input (Ref. 2). A pull down resistor is a simple and cheap fix.

• Selectable Vpp: you can choose the programming voltage amongst three values  with a dip-switch. Modern micro controllers generate the programming voltage internally and the requirement of 13.4 V is now obsolete (it's only necessary to ensure backwards compatibility with old micro controllers). The voltage applied to the MCLR pin must be less than 13.5 V (maximum absolute rating) for recent devices; choosing 12.7 V allows some headroom. 
  Select Vpp before powering the programmer.

SW2-A	SW2-B	V pp » V hi
o	o	13.4 V
c	o	12.7 V
x	c	12.0 V
o = open; c = closed; x = don't care

The programmer requires an external power supply of 18 V DC typically (two 9 V batteries in series, for example). The supply voltage for the 7406 IC and the micro controller is regulated by the 7805.

We recommend the 7406 or the 7407, with high voltage open collector outputs. Both inverting and non-inverting buffers can be used with one distinction: the software must be initialized by selecting the type of the buffers.  

If the circuit is powered by batteries, a switch helps extending their lifetime.

The software can give enough information on the process and no addidional LEDs are used in this circuit.

Programmed devices: PIC16F84A, PIC16F88, PIC16F628, PIC16F628A, PIC16F690, PIC12F629, PIC12F675, PIC12F508, PIC12F683.

Check the data sheets and the memory programming specifications of other PIC micro controllers before programming them with this circuit.

List of parts (v1.3.4)

Part	Value	Part	Value
D1	1N4001/7	U2	LM7805
D2, D3	1N4148	U3	SN7406
LED1	green LED	Q1, Q2	BC307 (BC556, BC557)
R1, R5, R6	4700 ohms	J1	DB25F connector
R2	1500 ohms	C1	100 m F - 50 V cap.
R3, R4, R10, R11	10k ohms	C3, C6	10 m F - 25 V cap.
R8	3300 ohms	C2, C4, C5	10 nF ceramic cap.
R9	15k ohms	sockets	DIP8, DIP18
R12, R13	47k ohms	SW1	switch
U1	LM7812	SW2	dip-switch

Device	Configuration	V pp
PIC16F84A	oscillator: XT	13.4 V
PIC16F88	oscillator: XT, HS	12.7 / 13.4 V		disable the LVP fuse
	INTOSC (MCLR disabled)	12.7 / 13.4 V
PIC16F628 PIC16F628A	oscillator: XT, HS	12.7 / 13.4 V		disable the LVP fuse
	INTOSC (MCLR disabled)	12.7 / 13.4 V
PIC12F508	INTOSC (MCLR disabled)	12 / 12.7 V  (*)		calibration value!
PIC12F629 PIC12F675	XT, INTOSC (MCLR disabled)	12 / 12.7 V (*)		calibration value!
PIC12F683	INTOSC (MCLR disabled)	12 / 12.7 V (*)		WinPIC800, PICPGM Programmer
PIC16F690 (**)	HS	12 / 12.7 V (*)		WinPIC800, PICPGM Programmer
PIC16F887 (***)	HS	12 V		PICPGM Programmer

(*) Voltage applied to the MCLR pin must be less than 13.5 V (maximum absolute rating).

(**) The PIC16F690 can be inserted in the DIP8 socket.

(***) The Vdd pins of the PIC16F887 have been connected directly to 5 V (output of the 7805 regulator).

IC-Prog setup

DL4YHF's PIC Programmer setup

PIGPgm Programmer setup 

Hardware Check

The Hardware Check (or Interface Test and similar) function allows you to toggle the programming signals and check the voltages with a digital multimeter, before you start using the programmer.

PIC12F629/675, PIC12F508/9, PIC12F683	PIC10F200 (not tested)
	-
PIC16F690	-

Data sheets

• SN7406 (SN7407)
• BC307, BC557
• 7812, 7805
• PIC micro controllers: Microchip

Links

• IC-Prog
• DL4YHF's PIC programmer
• WinPIC800
• PICPgm Programmer

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