Current in one direction only...diode??

[DMWWEngr]

I'm working on "designing" a circuit for my car. I want to splice a wire in to an existing circuit to make the lights flash when I want them too.

Imagine you have wires heading to your lights (in a car), I want to splice a wire in so that I can turn the lights on with the flip of a "switch". Yet NO current will run down my "splice" wire when the the "switch" is NOT used and the lights are turned on using the factory system. (Flashing lights for keyless system)

Currently it is set-up with relays but this is very cumbersome and I would like to install something smaller!!

I believe a diode can be used for this but I'm not sure how to design it?? Anything else that can be used??

Voltage=12v
Two bulbs per circuit = 5 Watts/bulb

TIA!!

 

[morizabal]

Why not hook up your switch in parallel with the existing factory switch, or mechanism that triggers the flashing lights.

 

[DMWWEngr]

I can't do that.....

My "switch" is a signal receiver that sends a signal out to turn the lights on. Therefore there is no input lead to the switch, only the output lead (that I want to control the current flow in).

Thanks for the suggestion though!

 

[xnuke]

How about using your signal output to drive a relay? You could put the relay's N.O. contact in parallel with the factory switch, and it will close when the relay coil is energized.

 

[DMWWEngr]

Good point.

I will look into that possibility. Although the whole purpose of this is to remove the relays (or at least one) to save space. As it is now it is VERY tight.

I will look into this possibilty. Thanks.

 

[dydt]

i don't know exactly how you want it wired but answering your question about the diode....maybe you have a point..

yes diode can be wired as forward or reverse bias..when it is forward biased current will flow to the load ( in your case a lamp ) and if reverse biased no current will flow ..

since negative of battery is the chassis ground, connect the cathode of the diode positive source and the anode of the diode back to the lamp...this arrangement WON"T turn your light on...then you can tie a SPST switch across this diode which will give you control of the lamp theoretically this should work.....you may want to give it a shot...


dydt

 

[DMWWEngr]

I have an OEM lamp circuit. It is power source, a factory switch, and the bulbs. I'm splicing in a second switched power source bewteen the "factory switch" and the bulbs in the existing circuit....simply adding a wire into the "side" of the circuit. I want current to flow from the second power source to the bulbs (not concerned about "current" flowing to the "factory switch&quot. However, I do not want current to flow from the existing circuit to the "spliced" second power source (when the factory switch is turned on).

Here's a bad drawing of the splice:
(I only want current to flow "downwards"....NOT upwards!!)

(Splice)
!
!
!
!
!
-------o------------------ (Existing Circuit)


I believe that a diode can be used for this purpose but I'm not sure how it should be oriented.

My questions:
1) First off, will a diode work for this??
2) If so, how do I orient the cathode and anode (which one goes towards the power source...upwards)??
3) How do I calculate which size of diode I need to use??

If a diode won't work for this purpose is there anything else that will?? The above questions would also apply.

Sorry for the confusion. I should have "drawn" this to begin with.

TIA!!

 

[jarvis]

Yes, the it sounds like the diode should work if it is as simple as your diagram.

If the power source is positive, then the anode goes toward the positive power source and the cathode goes to the load.

Make sure the diode can handle the current, you don't want to start a fire.

Good luck

 

[DMWWEngr]

That's really all that I needed to know!! I (hope) I can figure the current!!

Thanks to everyone for there help!!