how long we have 2 wait to power up PIC aft shutting down it

[janetsmith2000@yahoo.com]

Hi,

When i turn the power supply off, I have to wait for 4 seconds before start turn on the power supply. I have set the PIN_A1 as a LED. and i monitor the feedback from PIC using rs232. If i turn it on straightly aft turn off, LED wont lit up, and no output to the screen. So I have to wait for 4 seconds. even 2 seconds wont work.

My question is, how to turn on shortly after turn off (4 seconds is taking too long)? if my set-up done wrongly? Do I have to change the NOMCLR to MCLR? change the capacitor? or change the resonator?

I am using PIC16f628A, using 8Mhz Resonator (3 pins). I use a ceramic capacitor (labeled as 104) at the vdd.

My configuration bit is

#fuses NOWDT,HS, NOBROWNOUT, NOMCLR, NOLVP

 

[Nigel Goodwin]

Reset on the PIC itself is so fast as to be instantaneous, what's slowing it down is your power supply. Setting brownout ON might improve things, but essentially your power supply need to turn OFF faster - presumably it includes large electrolytics and only a small load?.

 

[eblc1388]

Re: how long we have 2 wait to power up PIC aft shutting dow

When i turn the power supply off, I have to wait for 4 seconds before start turn on the power supply. I have set the PIN_A1 as a LED. and i monitor the feedback from PIC using rs232. If i turn it on straightly aft turn off, LED wont lit up, and no output to the screen. So I have to wait for 4 seconds. even 2 seconds wont work.

Do you know that the RS232 interface chip you are using need time to build up the charge on its four capacitors? If you turn ON the LED before using the RS232 USART function, you will find that the chip reset almost instantly.

Brownout protection has nothing to do in your case.

 

[evandude]

instead of turning your power supply on and off, try just plugging and unplugging it from the PIC board instead... that will eliminate the slow turn-on and turn-off of the power supply itself. I think you will find you can do it much faster that way :lol:

 

[janetsmith2000@yahoo.com]

Thanks for your reply, I will try out you guy's suggestions

I don't know if it is suitable to say thank you here because it will change the position of this post in the board

Thank you

 

[atferrari]

Perhaps this...

If all what you want to do is resetting your PIC at any time, without switching your supply off, just add a pushbutton with a NO switch between /MCLR and ground. :idea:

Just make sure /MCLR is connected to Vdd through a 10 K resistor. :!:

I use it in all my projects.