This should provide the necessary constant +12v constant supply, but releasing the relay once it is latched will require the removal of the constant +12v input from relay #1. If this is wired to a circuit in the vehicle that has power only while the ignition is on, the circuit will reset every time the key is turned off.
posted
I also have another diagram that requires the use of three relays and two diodes to latch and release the entire assembly with either (+) positive or negative (-) pulses. If you need it let me know.
posted
mabeita, is there some practical appilcation for that type of circuit. What could it be used for. sounds cool.bagged89's web page
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posted
Go to you local Volvo dealer and ask for the head ligth relay for an 240, those relays have the function you want and the dealer should be able too tell you how to use it.
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quote:Originally posted by Mabeita: I also have another diagram that requires the use of three relays and two diodes to latch and release the entire assembly with either (+) positive or negative (-) pulses. If you need it let me know.
Later
Send me this at cwsmith@dsmtalk.com or post it here...i'm interested in knowing.
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posted
There are two variations of this design, each of the variations requires the use of either negative (-) or positive (+) pulses which can be provided by an alarm's door lock outputs, various detection devices, or just plain old manually activated switches. The design requires the use of two relays and a standard 1n4001 diode, to perform the actual latch, the third relay is optional and is used in the event that the latched output polarity needs to be reversed or a higher current capacity is required.
Be forewarned that the latched assembly has a current draw of approximately 130ma, if you require the use of a third relay the load will double. This current estimate is only the draw created by the latching relays, and does not include the current required by the device(s) that you are supplying power to.
Variation One: Negative (-) pulses used to provide a constant ground.
Relay #1:
87 Open
87a +12v constant (fused 1a)
30 to pin 86 on relay #2
85 (-) negative pulse to release latch
86 +12v constant (fused 1a)
Relay #2:
87 Ground
87a Open
30 Constant ground output
85 (-) negative pulse to initiate latch
86 to pin 30 on relay #1
Diode:
Cathode: pin 30 on relay #2
Anode: pin 85 on relay #2
Variation Two: Positive (+) pulses used to provide a constant +12v output.
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