Switch PIC16F877 ON/OFF

[koossa]

Thank you Melanie, I will try that!!!

[koossa]

Hi Melanie,

I'm not that good with electronics and have asked someone else if it would work if I use a signal Diode such as 1N4148?
This is what he Said:
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No it wouldn't work, because the MAX1672 digital inputs need 0.4V VIL(max), and your signal diode would make the pin over 0.8V.
Even if you use a Schottly diode like the panasonic MA793 or a germanium diode (0.2V to 0.3V) this would still make the VIL too high, and would leave a very narrow noise margin. At cold temperatures the circuit might not turn ON.

The (2) 2K resistors make a VIL of less than 70mV, guaranteeing the turn ON. And the PIC has no sweat driving the resistors loads.
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Is he correct with his comments?

[Melanie]

You've shot yourself in the foot with the way you've designed your circuit. Just try it with a silicon diode, and if it's not reliable, use a germanium one. I've not looked at the product Datasheets but offered a potential solution on your circuit, it's up to you to go impliment and play. If you want to experiment at extremes, you've got a fridge, you've got an oven. Go test. Geeze, there's no guarantees in this world apart from death and taxes.

[koossa]

Hi Melanie

Thank you for your reply!

You've shot yourself in the foot with the way you've designed your circuit.

What is a better way to design it, I can still make changes to my design?

[mister_e]

Probably i don't understand the whole thing as it's suppose but here's what i suggest.

remove the diode and blah blah. Use only your keyboard.

You just want to monitor the ON switch right???

This switch is attach between RB.3 and RB.4 right???

NOW what about...

' define and blah blah 
'
'
HIGH MAXPIN
LOW PORTB.3
OPTION_REG.7=0 'enable internal Pull-UP
While PORTB.4 : WEND ' wait untill ON button is pressed
LOW MAXPIN

This should work

[koossa]

Hi Steve,

I'm not sure if I understand you correctly.

The MAXPIN is HIGH by Default, which keep the Power to the PIC Off.
If I press the ON Button, it pulls the MAXPIN to LOW and the circuit will switch on.
The First Line of your Code, "HIGH MAXPIN" Would then switch the Power to the PIC Off?