Power problems

[mackrackit]

BTW, the transformer is standard adjustable DC adaptor so it aleady has diode bridge inside.

What is the voltage out of the transformer?
May not be high enough.
What is the 7805 voltage when circuit is on (LCD)

[menta]

transformer output without load is ~16V.
7805 output is 4.95 while its on.

I have another circuit usining the same parts, with one change, I use the PIC Kit2 demo board with 16f887 which works ok.
When I use its 5V power for the second circuit I get the same results.

[gringobomba14]

Menta, 4.95V is good. Whats the current rating on the transformer? I can see maybe over an amp of current straight off without studying the schematic for longer than a few minutes. Perhaps there is just not enough current to power the LCD? Failing that, what is the current rating for your 7805? Depending on the package they're good for between 250mA and about 500mA. Try putting 2 in parallel (If the tranny has an output of greater than 1500mA)

[skimask]

In that schematic, I don't see anything connected to MCLR. If MCLR is floating, or worse grounded, the program might not get the chance to start.
Try adding a +5v line to the MCLR pin on the '887 and see what happens.
The program may already have the MCLR pin configured as an I/O, but we won't know without seeing the actual program itself.

Also, are you using an 887 or 877A? Because there is no 887A...

[menta]

Yes, its 16f877A, my mistake.
I tried connecting the MCLR pin to the +5v but it didn't help.
It also didn't help using 2x 7805.
Its very strange because I have another circuit just exact to this one but using a 887 on a demo board.
BTW, if I use the programmer voltage output (just + and - ) and connect them to the circuit its also working ok.

[gringobomba14]

You don't have enough current. Can't be anything else then. Do you have a multimeter? whats the current drain on the circuit?

[skimask]

Yes, its 16f877A, my mistake.
I tried connecting the MCLR pin to the +5v but it didn't help.
It also didn't help using 2x 7805.
Its very strange because I have another circuit just exact to this one but using a 887 on a demo board.
BTW, if I use the programmer voltage output (just + and - ) and connect them to the circuit its also working ok.

Are you using the same program between the 887 on the demo board and the 877A in the circuit? If so, it won't work.

[menta]

The program is working when I use the programmer as power supply.
I of course compiled the program differently for each controller.
I have multimeter, What is the best way to check the current ?
serially to the + ?