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555 timer woes

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ghostman11

Well-Known Member
i have been trying for the last couple of days to get a circuit to work and i am having no luck, what i want to do is the following.

i have 4 pc's that control k190 tempretue units thru the serial ports on the pc's (theese units will be replaced eventualy), they work great except we get alot of power outs around here that normally only last 3-5 mins. The problem i have is i then have to go turn the pc's back on so the units function, if it happens dureing the night then i loes incubators full of eggs :(. my idea is simple.....if i have a 555 monostable circuit that is connected to a 12v psu then when the power cuts out and comes back on i want it to send a pulse to eigther transistors (prefered) or relays that are connected to the on switches on the pc's in effect shorted them every time the power comes back on thereby turning the pc's back on automactically :D.
i managed to figure i would need the 55 in monostable mode and i only need a single pulse each time of a second any more than 4 seconds and the pc will shut off (bios setting). i have attached my attempt of the circuite can any one point out where i am messing up please.
 

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  • pc switch.png
    pc switch.png
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... what? you want this to pulse once every second? or are you trying to get a delayed start up? WHAT ARE YOU DOING MAN!!!
 

ghostman11

Well-Known Member
i have a psu thats always on...when we get a power cut (happens alot here) i want a circuit that will send a single one second pulse when the psu comes back on so i can auto start the pc's back up..
 

ghostman11

Well-Known Member
base resistors noted :D :D i will go figure out what size i need.......... i might be a while :D
 
Last edited:

Hayato

Member
Inside the BIOS setup there is an option, to keep the power down and to auto power up on ac power loss.
 

ghostman11

Well-Known Member
ok thanks...the pc's are old all they do is control the thermostat units there isnt an option for auto power up :(
 

smanches

New Member
Why not just get a UPS for when the power goes out?
 

ghostman11

Well-Known Member
i looked into a ups but discounted it for many reasons, i just thought a nice simple 555 circuit would do it without taking up space and needing batterys looked after etc plus on occasion we have power outs in excess of an hour so a ups wouldnt help much in that case.
 
Last edited:

ghostman11

Well-Known Member
thanks i will try it out. i couldnt figure out how to have it trigger just once when the power came back on
 
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