Re: Relays

[Bob MacFarland <emoto1@xxxxxxxxxxx>]

ABSDoug@xxxxxxxxxxxxxxx wrote:

>	Trying to learn more about relays. The part I don't understand; using small
>amounts of power to energies the switch with bigger amounts of power. Where
>do you pick up this smaller amount of power? I read how relays work and from
>what I read, all the power is coming from the same source; the battery.
>

The way the ones I have used work is that from the relay you have: wires 
to the on/off switch for the object being powered (aux lights, 
whatever), wires to the object being powered, wires to the battery, and 
what I'll call a "sensor" wire. I think the sensor wire is what you're 
asking about. The idea is you tap the sensor wire into any random 
circuit that will have power in it when the ignition is on. You might 
choose a headlight or tail light circuit or instrument light circuit, 
etc.  Anything that has constant power when the ignition is on, and no 
power when the ignition is off, is fine. The idea is that the relay uses 
power from the sensor wire to run an internal switch that decides if it 
is "ok" to send power to the object being powered. Assuming the object 
being powered's on/off switch is in the "on" position: Power from the 
sensor wire = ok to send power to the object. No power in the sensor 
wire = no power will be sent to the object. This feature prevents the 
mistake of leaving aux lights on to run down the battery after you shut 
off the engine and walk away. 

Does that answer the question?

- -- 
Bob
     Eventual Master of the Obvious
  R1200GS CB750F DoD EMOTO BMWMOA SOHC4
Proud walking jingle in the midnight sun

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