Post by thread:[EE] soft power switch

Hi all, I am working on PIC project where the whole system is powered by battery. I am trying to add soft power switch , ( push it to on, push it again to off) . I found lot of solutions using relays, but i am looking for transistor based solution. Anybody implemented this before ? Thanks in advance. regards, palani

> Hi all, > I am working on PIC project where the whole system > is powered by battery. I am trying to add soft power > switch , ( push it to on, push it again to off) . > > I found lot of solutions using relays, but i am looking for > transistor based solution. Anybody implemented this > before ? Thanks in advance. > > regards, > palani How about having the PIC sleep and wake on the power switch being activated? Or, if the PIC supports two oscillators, drop down to a very low speed (32kHz) to drop power consumption, then go back to high speed when "turning the unit on." Harold -- FCC Rules Updated Daily at http://www.hallikainen.com - Advertising opportunities available!

palam.c wrote: > Hi all, > I am working on PIC project where the whole system > is powered by battery. I am trying to add soft power > switch , ( push it to on, push it again to off) . > > I found lot of solutions using relays, but i am looking for > transistor based solution. Anybody implemented this > before ? Thanks in advance. > > regards, > palani > Yes. The easiest way is to do this is to use an external CMOS device, such as CD4001. This chip draws no measurable power whatever. The CD4001 always has power, and the PIC VCC is provided by one or more of the CD4001 gate outputs. The CD4001 is cross-wired to generate a flop-flop. The switch is designed so that by pressing the switch, the flip-flop supplies power to the PIC, by forcing the CD4001 to turn "ON". The PIC also senses the switch using an input pin. so that later it will act on it to turn the supply off later. The PIC does its thing, then will sense the switch being pressed again for OFF. The PIC notes the press, then waits a second after the switch has been released (to ansure that the switch won't be pressed again), then the PIC pulses an OUTPUT high through a CAP (0.005uF will do, if the resistor to GND on the CD4001 is high in value). The pulse thru the cap will cause the CD4001 flip-flop to toggle off. That's it. If you have rouble following me, I can dig out the schematic. . --Bob

> Hi all, > I am working on PIC project where the whole system > is powered by battery. I am trying to add soft power > switch , ( push it to on, push it again to off) . > > I found lot of solutions using relays, but i am looking for > transistor based solution. Anybody implemented this > before ? Thanks in advance. > > regards, > palani > -- You may find this page useful http://www.romanblack.com/self_swi.htm ~Kevin

palam.c wrote: >Hi all, >I am working on PIC project where the whole system >is powered by battery. I am trying to add soft power >switch , ( push it to on, push it again to off) . > >I found lot of solutions using relays, but i am looking for >transistor based solution. Anybody implemented this >before ? Thanks in advance. > >regards, >palani > > Palani, Something like this? http://ww1.microchip.com/downloads/en/DeviceDoc/40040b.pdf tip # 11 Bill

On Friday 23 June 2006 02:35, William Bross wrote: > palam.c wrote: > >Hi all, > >I am working on PIC project where the whole system > >is powered by battery. I am trying to add soft power > >switch , ( push it to on, push it again to off) . > > > >I found lot of solutions using relays, but i am looking for > >transistor based solution. Anybody implemented this > >before ? Thanks in advance. > > > >regards, > >palani > > Palani, > Something like this? > ww1.microchip.com/downloads/en/DeviceDoc/40040b.pdf > tip # 11 > > Bill Thanks for all replies. I am planning to go with microchip's solution. I don't have previous experience with FETs. I need to select a FET for a power switch, can i get the list of popular (or) general purpose FETs . Is there any website containing list of commonly used (or) popular electronic devices ? regards, palani