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Author Topic: Relay connection question-SPDT type  (Read 569 times)

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DH

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Relay connection question-SPDT type
« on: January 31, 2014, 12:16:58 PM »
I cant find a good diagram to explain this, but I'll give it a shot.
An SPDT relay has 5 terminals, and is normally open, correct?
Terminals 85 and 86 (for the coil), terminal 30 INPUT (common) and terminals 87 and 87a are the OUTPUT switched terminals.
My question is this: On most relayed circuits I've seen, INPUT terminal 30 is
almost always connected to 12v continuous, and the 87 and 87a
are OUTPUT terminals on the load side(?) of the relay. Will the relay function the same if the wiring were reversed? I.E. terminals 87
and 87a were used as INPUT power sources, with terminal 30  as an OUTPUT on the load side (the load being the horn)?
Does this make sense? I'll try to find a diagram .....THANKS!


Edit: like on the relay shown..
« Last Edit: January 31, 2014, 12:24:57 PM by DH »
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Offline 74750k4

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Re: Relay connection question-SPDT type
« Reply #1 on: January 31, 2014, 12:28:06 PM »
« Last Edit: January 31, 2014, 12:39:29 PM by 74750k4 »
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Offline Destruckto440

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Re: Relay connection question-SPDT type
« Reply #2 on: January 31, 2014, 12:39:56 PM »
Not sure why you'd need to do that but it wouldn't matter which way the power flows though the contacts on the relay. There are no diodes restricting flow in any one direction. Could you explain what you're trying to do? What do you need two different voltage sources for?
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Offline dave500

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Re: Relay connection question-SPDT type
« Reply #3 on: January 31, 2014, 01:18:49 PM »
make sure its not a change over relay,87A is connected to 30 when the relay is off,then when the relay is activated 87A becomes disconnected and 87 gets hooked to 30,you can use relays "backwards"ok,they have a standard design for when inserting into a socket type connector,if your using fly leads not in a gang plug you can hook them to suit yourself.

some relays have diodes to prevent back feeding though!be sure you dont have one of those.
« Last Edit: January 31, 2014, 01:22:35 PM by dave500 »
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DH

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Re: Relay connection question-SPDT type
« Reply #4 on: January 31, 2014, 05:28:15 PM »
Using 2 relays. Integrating the bikes horn into aftermarket alarm
system. Using the alarm module to trigger relays simultaineously.
When alarm is activated, first relay switches power to horn ckt.
and second relay switches groundpath for horn, bypassing the horn button.   1 relay installed(backwards) on positive side of horn ckt.
and 1 relay installed conventionally on ground side of ckt. Wired so
that horn is isolated from alarm system when alarm is inactive.
Clear as mud? ;D  Thanks folks. the responses were helpful .
Apologies, as this is related to something I posted a while ago.
Yes I did search.I know better..
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