purchasing Mosfets

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tumbleweed

Well-Known Member

Most Helpful Member

• Feb 7, 2022

• #21

Are you trying to program with external power or power via the pickit?
Does it program if you have the ON-OFF switch in the OFF position and set the pickit to supply power?

Double check the PCB footprint for the mosfet. The pin numbers on the schematic are correct, but that doesn't mean the PCB matches.

 

MrDEB

Well-Known Member

• Feb 7, 2022

• #22

No external power, just the Pickit2.
Am contemplating adding external power or removing the mosfet and finish up writing code and testing. Then reinsert ti mosfet and hopefully it will work (after connecting 6v battery)

 

MrDEB

Well-Known Member

• Feb 7, 2022

• #23

will double check the foot print.
Tried switching theswitch off (not sure if I did)?

 

MrDEB

Well-Known Member

• Feb 7, 2022

• #24

checked footprint and seems good. Tried switching the ON/OFF to off and still the pickit2 won't communicate.

 

Nigel Goodwin

Super Moderator

Most Helpful Member

• Feb 7, 2022

• #25

What failure message does the PK2 give?. With the switch in the OFF position the FET should make no difference to the operation as it's not connected to anything.

However, the PK2 can supply very little current, the PK3 a little more, and the PK4 can supply considerably more - the PK2/3 often won't work if there's an LCD module attached. Usually using a PK4 solves the problem - or unplug the LCD if it's pluggable.

 

T

tumbleweed

Well-Known Member

Most Helpful Member

• Feb 7, 2022

• #26

Tried switching the ON/OFF to off and still the pickit2 won't communicate.

Click to expand...

And you say it worked on this board before you soldered on the fet?
If the switch is off that makes no sense... the only load with MCLR asserted should be the uC, so the current shouldn't be a problem.

Try setting the PK2 voltage a little lower, like 4.75V or so.

 

MrDEB

Well-Known Member

• Feb 7, 2022

• #27

thats what I thought, if switch is off it basically disconnects the mosfet.
will do futher investigation.

 

MrDEB

Well-Known Member

• Feb 7, 2022

• #28

I assembled a second board w/o the mosfet and it works.
next step is remove the mosfet.

 

MrDEB

Well-Known Member

• Feb 10, 2022

• #29

UPDATE I removed the mosfet and still get a vcc error.
Futher probing with meter planned

 

MrDEB

Well-Known Member

• Feb 11, 2022

• #30

found a small problem. I made the mistake of using my new hot air gun to install the through hole switches and a small solder ball found its way to the Vcc and Grd.
Cleaned the issue up and now I get no voltage error but the pickit2 won't reconize the chip.
Futher meter probing.