Hi guys,
I have been making a 555 timer to act as a 'delay on break' eg when the 12v trigger is cut the output is fired to provide 12v for a period of very roughly 0-60 seconds, adjustable. It will be powered by 12v car supply, so un-smooth 12-15v dc. The 'trigger' or 'switched' line is also car 12v, from a switch in the car. I need the output to stay switched on for a while after I switch the switch off and I think this circuit may do it easier and smaller than a 555. Am I right?
FYI the load on the output is about 2a (5a would be better) at 12v from a solonoid coil. It will need a 'hard' off, eg it needs full supply voltage to operate and when switched off it can't 'ramp' down it has to have the suply cut, or a gradually lowering voltage could hold the solonoid open an unpredictable amount of time.
Please see attached and give comment, also on the choice of transistor as I don't know, and if or not I need to have the transisotr switching a relay or if I can use some sort of power transistor.
Thanks, Greg.
I have been making a 555 timer to act as a 'delay on break' eg when the 12v trigger is cut the output is fired to provide 12v for a period of very roughly 0-60 seconds, adjustable. It will be powered by 12v car supply, so un-smooth 12-15v dc. The 'trigger' or 'switched' line is also car 12v, from a switch in the car. I need the output to stay switched on for a while after I switch the switch off and I think this circuit may do it easier and smaller than a 555. Am I right?
FYI the load on the output is about 2a (5a would be better) at 12v from a solonoid coil. It will need a 'hard' off, eg it needs full supply voltage to operate and when switched off it can't 'ramp' down it has to have the suply cut, or a gradually lowering voltage could hold the solonoid open an unpredictable amount of time.
Please see attached and give comment, also on the choice of transistor as I don't know, and if or not I need to have the transisotr switching a relay or if I can use some sort of power transistor.
Thanks, Greg.
Attachments
-
54 KB Views: 142