pic burner - not enough voltage

[OrganGrinder]

hi

i have completed making a pic burner on a stripboard following the schematics on the page.  the only deviation was that i replaced the  2.2k trimport with a 2k trimpot (2.2k was not immediately available)

now when i am testing (before placing the chips) i get a maximum voltage across j2 of 9.5 volts.

could this be because of the trimpot i used, if so i assume i would need to go to a 5k trimpot, is this ok?

if something else may cause the problem, can i have some suggestions.

btw, the 5v sections are working fine, same with the power led and i am running off 2 9v batteries.

thanks

OrganGrinder

[OrganGrinder]

hi again

i have replaced the 2k trimpot with a 5k, and also have bypassed the bridge rectifier (i am using a pair of 9v batteries).  the results - now j2 reads 10 volts, still short of the 12.5 i need.

i have also played around with disconnecting d1 and/or r1 but either does not have any effect.

i don't think i connected the regulator backwards (switched input and adjuster/ground) but then i don't know what the results of that would be if i did.  btw i connected the 5v resulator correctly - it outputs 5v as expected.

just for your info, i can turn j2 down to around 0.5 volts and the power led turns off when j2 is around 5 volts (but that was expected considering the schematic).

any advice would greatly be appreciated.

OrganGrinder

[OrganGrinder]

hi again

looks like i did have the lm317 on backwards afterall.

now the initial test for the pic burner works (i can get 15 volts if i wanted). 

I have it set to 12.5  +/- 0.02 volts, so i think i am in business for now.

just realised i forgot to attach the printer port to the board, but thats another story

for anyone who hasn't guessed already, this is my very first electronics project (i do not count the stuff i did in highschool nearly 20yrs ago, didn't even use solder then)

well i got this done by the DIY code, i did it myself.  a few more mistakes like this and i will be an expert.

see ya all

OrganGrinder

[stryd_one]

a few more mistakes like this and i will be an expert.

;D That is a classic! That should be your sig hehehehe

[audiocommander]

I had also voltage-problems when using two batteries, but then I remembered, I once measured much more voltage from a cheap power supply than expected; so I tested all my supplies and got lucky with the second one! Although it says max 12V I can measure 18V!!!

(The cheapest one from Reichelt btw).

So, before going out and buying an expensive 15V power supply, it might be worth testing the ones already lying around. The PicBurner went very well without batties ;)

[OrganGrinder]

hi all

after fixing the original problem for this topic, i have come across a few more.

when testing the board with p18, i found the voltage at mclr was around half the 12.5 volts it was supposed to be.  i worked over what i did wrong, and guess what?  it seemed just like the original voltage problem i had before, so i turned the bc337 around and it worked perfectly from then on.

but that wasn't the end of by problems...  turns out that i had swapped the yellow and red leds, that shouldn't have been too much concern, but they didn't work when testing Vcc and Vpp, turns out i had placed then in backwards, which i have fixed now.

after all that, the board tests correctly and i have programmed all my pics with no problems (after slowing the io transfer a little).

now i am waiting to recieve the pcbs i have ordered from smashtv and hopefully not make these mistakes again.  being a newb is hard work, fixing the mistakes you should have not done in the first place (especially after trying to avoid these specific mistake).

cya

OrganGrinder

[stryd_one]

Nice one! Stick with it mate, you're making progress -And hey, your experiences can help others now that you've put them on the board :)

Good luck!