Momentary break?

Is there such a thing as a momentary break circuit? I've been racking my brains to try and figure how to do this, this is what the circuit needs to do: When the ignition goes from high to low, current needs to break for a small amount of time (half sec, one sec, somewhere around there). Otherwise, when the ignition is high or low, current needs to flow. Thats it, just need to break the current for a split second to trigger a close on a motorised device but leave the device supplied for operation at all times. Anyone know how I can achieve this easily please? Thanks a lot for any help

Hi Jeff, thanks for the reply... im a bit puzzled how that would work, that just breaks continuity when the starter is activated? (meaning my device will sense the break and operate when I crank the ignition) Im looking for the opposite effect, I want to break continuity momentarily when I stop the car and remove the ignition key, but, still have it supplied with power if I want to operate it with the keys out yeah? The supply current to the device must be continuous no matter whether the starter/ign is high or low, I just need to find a way to drop the line momentarily when I turn off the car engine with the key. Does that make more sense?

You may have to install a toggle switch and do it manually. Let me think about this for a bit.Jeff

Velocity Custom Home Theater

Mobile Audio/Video Specialist

Morden, Manitoba CANADA

its a tricky one huh? Further information - the device operates itself when it senses the ignition going low, just I want to make the line go live again straight after its gone low, but without switching the ignition back on- thats the point of operation that I need to create somehow. thanks for looking at it

no idea anyone? Jeff?

A simple one off the top of my head... The circuit break timing depends on the value of c1. Hope it helps.

Hi satkunas - interesting but how does that make the ignition line live again after switching? Correct me if im wrong, that looks like it just pauses for t seconds after switching on the ignition? I think its going to take 2 coupled together somehow- perhaps that is the other half? To refresh, I have an ignition switch in the on position, power is flowing at that time- I want to turn off the key (cutting power) and have the line drop for half a second or so, THEN have the line switch back to live without switching the ignition on again. Somehow. I dont want a drop when the ignition key goes in again however the system needs to reset somehow for the next key removal. I have constant + available (as well as IGN) I was thinking that perhaps use the ignition to trigger a drop on the constant +, or, if theres a way of triggering the constant on again after ignition supply goes off, I dont mind, either way will work, its < 2w device. I wish it could be solved with one relay but I dont think thats possible is it?

Right - what about this? This is what I think should happen. Can anyone please check this and make constructive comments please? When IGN is hot, constant flows through relay 1 to the device. When IGN goes low, constant switches to NC (87a) and output is sent to relay 2 via a 2200uf cap, which delays the coil by about a second? Once C1 is charged, relay 2 constant is switched to output. When IGN is returned to hot, both output lines are temporarily hot but R1 bleeds off C1 and closes the link to relay 2? So, overall operation is that when the ignition key is taken out, the output line drops to 0 for half a second then flips high again. When the ignition key is returned to the car, output stays high but resets itself ready for the next cycle. Questions are: Will C1 (2200uf 63V) be ok being hot all the time the car is parked 24/7? Will having constant hot through relay 1 and 2 for a short while when switching the igniton back on give me any problems? Do i need a clamp diode on relay 1? its a direct feed from car battery via a 10A fuse and ignition switch, no delicate circuitry. Thanks in advance to anyone that can understand the diagram enough to help :)

Anyone please?