PIC18F2550 and problem with VDD

georgz · May 5, 2012

Hi, i'm using this uC and i'm dealing with a strange problem... I'm building a led globe and it's working great, i'm using 2 contacts for the VDD(5V) and VSS(GND) on a disk made of PCB. So there are wires which make the contacts on the disks' rails and my problem is that for a moment there must be a disconnection between the contacts and my uC does not restart itself. I must turn the power off and the on to start working again. There is a resistor on the MCLR pin. What might cause this problem??

wp100 · May 5, 2012

georgz said:
Hi, i'm using this uC and i'm dealing with a strange problem... I'm building a led globe and it's working great, i'm using 2 contacts for the VDD(5V) and VSS(GND) on a disk made of PCB. So there are wires which make the contacts on the disks' rails and my problem is that for a moment there must be a disconnection between the contacts and my uC does not restart itself. I must turn the power off and the on to start working again. There is a resistor on the MCLR pin. What might cause this problem??

Hi,

Your pcb disc contacts are always going to be electrically 'dirty', paricularly for a high speed micro needing a good supply

Lots of things could be done, but to keep it simple first try these two things

Put a large, 1000 or 2200 uf electrolytic cap across VDD and VSS so it holds the voltages for longer.

Fit a 100nf between Mclre and 0v, with the Pull up resistor of 10k, this should help Reset the Pic when power is restored.

If that fails perhaps try a rechargeable 4.5v battery connected to Vdd and the power source just feeding the batterys charger.

PIC18F2550 and problem with VDD

georgz

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wp100

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georgz

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PIC18F2550 and problem with VDD

georgz

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