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PIC16F877A charging problem

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smiles

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pic16f877a simulation

I write program for PIC in MPLAB, test simulation in Proteus, all compiling and simulation is okey.
Before load the program for PIC (.hex file) I test voltage's value of all pins.
After load program to PIC, I see that which pins have high value voltage is unchanged, which pin has low voltage have the new value greater than before a little (before: 0.7V then after : 1.03V) and no pins change value from high to low or vice versa.
I check and see that the program is loaded successfully to PIC, but seem that it is mostly like before ???
Could you tell me what problem with it ???
Thanks so much !!!
 

Hi! Here is my circuit in Orcad
**broken link removed**
Here is simulation in Proteus
**broken link removed**

Added after 1 hours 36 minutes:

when I verify my .hex file it says "error verifying address 0x000000 verified 2805 read 3fff"
in this case, when I continue to "Program all" to charge for PIC, does it accept ?
I am using winPic800 (GTP-USB programmer)
When I plug my GTP-USB by cable adaptador USB, I measure the voltage in between Vpp and GND of ICSP connector, it is about 7.86V ???

Added after 33 minutes:

TRISA, TRISB to determine which pin of PORTA, PORTB is output or input, I did it in my Assembly code ?
 

I think I found a problem on the GTP-USB circuit, that is in Voltage multiplier, as you see in this image **broken link removed**, it says it output two 13.5VDC but when I measure, it just output 7.7V and 9.4V. Check the circuit I see that the parameters of components is correct, the circuit is right connecting, RA0-RA3 output 2.2V.
Any ideas about this ?
Thanks !!!
 

The reading on RA0-RA3 is about right if you are using a DC voltmeter.

Have you put any load on the 13.5V?
If possible disconnect the load and do a measurement again. This should give you a 13.5-13.8 V result.
 

    S

    smiles

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As you see in the picture, the load is 2K2 resistor, diode and it continue to go to Vpp pin, the next load is my PIC16F877A.
I also check the real circuit again, found that 2k2 resistor and diode is wrong connection, repair and it make the voltage to Vpp is lower than before :D
I simulate that voltage multiplier circuit in Proteus, found that it depend on the pulses from these RA pins, but don't think problem is in PIC18F2550, how can I check that PIC still working ???
 

If you have a scope, please take a look of the wave output from PIC18F2550.
 

Yes, I took a look on ocsilloscope, find that RA0 to RA3 still output pulses, measure at the output of voltage multiplier, still get the same value like before :cry:

Added after 3 minutes:

So the reason back to the voltage multiplier, maybe I have to check diode, capacitor again ?
 

Please Check the phase of RA0 and RA1 on the scope. (same to RA2 and RA3 signal).

pictures of both signal-pairs would help a lot.

If you bring RA0 and RA1 on the same screen, they should always be at different phase at any time. Othwewise, please fix this issue first.

To quickly identify whether it is the voltage-boost circuit issue, could you please take out two 2.2k resistor, and find wha't the voltage on both 13.5V output point?
Funny N.
 

    S

    smiles

    Points: 2
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Yeah !!! after disconnect the 2k2 resistor, the voltage raise up to 13.7V :D
Could you explain me why, caused of when I test simulation, seem that problem is not at this resistor ?
RA0 (RA2) has the frequency greater than RA1(RA3) two times, I lost the second channel probe :(
So ... the GTP-USB circuit image is wrong ??? Can't believe ???
 

This just proves the PIC18F2550 voltage-boost-circuit working.

Without more detail, it is hard to tell which part of the circuit after the 2.2K resistor got issue(s).

The problem is not the 2.2K resistor.

Sounds to me, somehow, there is either a heavy load or some kind of short-circuit after the 2.2K resistor.
Funny N.
 

yeah, their circuit's image is certainly right.
I think the problem is at ULN2003A, like in this image
 

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