looking for some sort of one shot relay

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Thunderchild

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I'm looking for some sort of latch relay whereby it just takes a pulse to switch it on and another to switch it off (or a reverse polarity pulse), it needs to be as compact as an automotive relay and work on 12 V
 
20+ basically i need an automotive relay replacement that latches as opposed to only being on when there is current
 
Thunderchild said:
20+ basically i need an automotive relay replacement that latches as opposed to only being on when there is current
Click to expand...

i was just doing a search and cant seem to find anything practical... have you thought about using a IC and transistor to keep the relay latched? there are plenty of IC's that will stay on with one single pulse and the same for turning it off...
 
I'm also looking at VERY low power consumption in order to produce very little heat as i'm putting it in a rather confined space, currently the automotive relay is 3 watts, so baring using very low RDSon mosfets I need some sort of mechanically latch thing, I had thought maybe I could build something with a motor so it screws and unscrews to open and close a switch but that may become bulky and I'm not equipped to make it really
 

you could make a PCB with the IC and transistor and relay mounted to it... the IC and transistor wouldnt draw alot of current (depending on the relays coil resistance) say less than 250mA total! i needed the same sort of thing as what you are doing and i used a 30A relay(PCB mount type relay) and it used about 75mA to activate the coil in the relay! i know its a bit of stuffing around! BUT its cheap and compact and will do the job well...
 
yes well I have no problem using a transistor to drive the relay but 3 W of heat from the coil is too much for me as my case has a 10C/W temp coeficient, thats why I want it to latch so it is not on all the time and does not make much heat
 
Thunderchild said:
yes well I have no problem using a transistor to drive the relay but 3 W of heat from the coil is too much for me as my case has a 10C/W temp coeficient, thats why I want it to latch so it is not on all the time and does not make much heat
Click to expand...
hi TC,
Tell us what the project is and why/how, like to help.
All you have told is what we can and can't have or do.
 
Well its a power control box for a car and the "relay" must handle the full current going into the system from the dynamo, it will not need to operate quickly hence the idea of the motorised switch
 
Thunderchild said:
Well its a power control box for a car and the "relay" must handle the full current going into the system from the dynamo, it will not need to operate quickly hence the idea of the motorised switch
Click to expand...

same setup as i mentioned before, but replace the "relay" with a solenoid? (create your own relay) sorry!!! forgot you didnt want current flowing all the time for the "switching"!
 
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Thunderchild said:
Well its a power control box for a car and the "relay" must handle the full current going into the system from the dynamo, it will not need to operate quickly hence the idea of the motorised switch
Click to expand...

hi,
These micro switches will handle the current, for possible use with a electromechanical operation
When you say 'pulse' operated is that a electrical pulse or what.?
Your Search Results | Farnell United Kingdom
 
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by pulse i mean a 12 V power supply switched on for as long as necessary to operate but obviously not non stop like a relay, it will be MCU controlled so I can meet most requirements, I haven't looked at the specs of those switched but they look rather large, i have the space of 1 or two automotive relays, maybe i need to find a suitable motor mechanism like... oh what: a servo ! how stupid of me not to think of the obvious ! a servo can easily push a switch, now I just need to figure out how to control one from an MCU
 
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hi,
I wouldn't say they were large, 1inch by about 3/8inch, switching 25A.
 
hm thats not a bad size (I'm decorating so maybe not paying enough attention to this) coupled with a servo, but of course if I had a servo like the ones in RC planes i could build a switch onto it.
 
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that looks very interesting Ron, of course I'm also not looking to break the bank to buy one, I think the thing is they are so seldom used that they tend to have a higher price which i have found before of much lrger units that were not suitable but did the job
 
Right suddenly i can find these on RS and Farnell, but most are 16 A, however I was wondering. As I'm only going to open and close the relay when about 1 amp is passing (there is specific circuitry making this "decision") would I get away with 20 A passing but not being switched
 
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