12C671 - GP3 problem

[malc-c]

Hi, I have attached the schematic

Comments:

1) - There are no smoothing capacitors either side of the regulator - what are you using to provide the 12v supply. If it's simply a bridge rectifier off a transformer then the supply will need smootthing.

2) - I assume the diodes are LEDS ? If so then you would be better off putting them in series with the resistors rather than in parallel.

3) - If they are not LEDS, then try removing them from the circuit, there may be some reverse bias or something causing the current to flow and possibly short out the supply ?

As Dave has mentioned - It does sound as if you are constantly resetting the chip before it configures itself.

[aratti]

With reference to your schematic, I am sure you have mistaken in drawing it, while the hardware is correctly wired, otherwise you will short the 12 Volts as soon as you connect it to the circuit. ( see the snap posted and compare it with your circuit)

As far as the code is concerned, I would place a delay below the label send

send:
PAUSE 10
if gpio.1=0 then
serout ToTx,N2400,["G0"]
Low ToTx
pause 10
endif

Al.

[malc-c]

With reference to your schematic, I am sure you have mistaken in drawing it, while the hardware is correctly wired, otherwise you will short the 12 Volts as soon as you connect it to the circuit. ( see the snap posted and compare it with your circuit)

how did I miss that ! I was just getting confused with all the diodes !

Mind you I guess it was just a miss-print, otherwise there would of been a nice bang when he powered it up for the first time

[Bruce]

Have you tried this with _PWRTE_OFF..?

[financecatalyst]

Aratti, your eye for detail is good. I made mistake in drawing it. Thanks for correcting it. I tried with a pause of 50mS before going to label send, but it didn't worked.

Malcom, Mackrackit, thanks for pointing out the smoothing capacitors and resetting problem.

I tried the smoothing capacitors at in & out of 78L05. At one configuration of 47uF at input & 22uF at output, everything works fine with one particular 12V battery I have but does not work when I change the battery. That particular battery had a voltage of 12.96V, I changed it, the other battery had 12.16V. I tried many times with with 12.96V, it works fine all the time but not when I change the battery. I tried different values of capacitors and the results were very strange, at few other configurations of the capacitors, it even affected other pins as well. All these trial were done with 12.96V battery.

After seeing these results, I believe the problem is related to correct configuration of capacitors. Any comments?

I would like to ask two things:
1) Is there any formula or way to find out the correct capacitor values at in & out of 78L05?

2) Is there any way around the resetting problem of GP3, I would like to try it as well to see if that is the root cause of this problem?

Bruce, thanks for the reply, I will try with _PWRTE_OFF and update this thread.

Thanks everyone for trying to help.

[aratti]

1) Is there any formula or way to find out the correct capacitor values at in & out of 78L05?

No! Simple rule of thumb. place 220 nF at the input and 100 nF at the output, the closest possible to the regulator terminal.

Al.

[mackrackit]

If the _PWRTE_OFF idea does not work then I think you know the problem is in resetting as you mentioned if the chip has continuous power it works.

So you could add something to the GPIO.3 button to power the chip first, before the actual button is pressed. No magic but more circuits.

[financecatalyst]

I tried with 220nF at input & 100nF at output of 78L05. Changed the config a little to try this code on 12F635 which I happen to have quiet a lot. This way I can save few 12C671. The circuit remains the same.

_PWRTE_ON or OFF is not making any difference.

The problem is stuck on GP4 now. GP 0,1,2,3 are working fine.

[Archangel]

Hello F.C.
What voltage do you read on GP.3 when the switch is pressed? I ask because it is an input with schmitt Trigger input, perhaps the voltage is not low enough to switch it.