Lighting Wiring

[THerman]

emjay has it. If you had your circuit built I would bet that when you turned one switch on both lighted switches lit up. This is not necessarily bad. You could keep your circuit and be able tell where the backup lights were getting power from.



ie. Both cab switches are off, but are lighted: lets you know the bed switch was left on. It would also make an in cab indicator of the backup lights being on. (obvious when dark, but not so during the day)



Just something to keep in mind. I would probably make the dash mounted switch lighted, and not put the extra diodes in. Then your cab switch is also your indicator.



Just something to think about.



Give 5 engineers a problem, come up with 15 solutions... .

:-{}





Tod

 

[R-N-R]

Tod, thank you for the input! I thought about all switches lighting when one was turned on and agree that it would be a good thing. But I'm still missing the basic concept here. And, after adding in the second switch, I tried building the circuit on the bench (truck bench... sort of) with the additional diode and discovered that the switches will still pass negative (one switch off) and positive (other switch on).



Thanks Again,

Bill

 

[THerman]

Bill explain again where each switch will be and what you hope to do. If you want to be able to turn on the lights at one location and then turn them off at another switch, a completely different wiring scheme will be needed.



Tod

 

[emjay]

How Many Diodes Does It Takes To Get AMPED?

With any of the switches turned off, the lamp on the switch is shorted out (unlit) and no current flows through the switch to ground because the diode is reverse-biased. The model that you have is infinitely expandable. Only the switch that is turned on will have a lit indicator, which is handy for determining which switch or switches are active.

 

[R-N-R]

Hi Tod, that last repeat post was a "refresh" mistake so I deleted it.



One switch in the cab, one in the bed, and the factory reverse lights "acting" as a switch. I did not anticipate being able to switch the aux lights on/off from any location, more so I just want to be able to turn them on & off from any single location.



Emjay,

What does reverse bias (diode) mean? How will it prevent the ground coming out of the "off" switch from meeting the current" coming out of the "on" switch.



Bill

 

[THerman]

Originally posted by Rock-N-Rammer

Tod, thank you for the input! I thought about all switches lighting when one was turned on and agree that it would be a good thing. But I'm still missing the basic concept here. And, after adding in the second switch, I tried building the circuit on the bench (truck bench... sort of) with the additional diode and discovered that the switches will still pass negative (one switch off) and positive (other switch on).



Thanks Again,

Bill

Bill, are you talking about a logic system here? ie both switches need to be on for lights to be on?



As I see it, emjay's set up will work perfectly provided the diodes are wired in the right direction



Tod

 

[THerman]

a reverse biased diode has a positive voltage applied to the negative side (trying to flow backwards) (the side with the | on it)



need to stick with positive flow... . from battery to ground.



Tod





aol chat todherman

 

[R-N-R]

Tod,



No, no logic involved (perhaps that is my problem )



One switch at a time is used.



What I'm stuck on is how to prevent both negative (sw #1 = off) and positive (sw #2 = on) from meeting.



Is the short occurring from the positive feeding "back through" the switch? If this is the condition, I can understand how a diode will prevent the problem. I have been thinking that the problem is occurring between the switches and the relay.



Bill

 

[THerman]

Bill, I finally understand your problem.



The diodes emjay drew in are needed to prevent your problem. They act like check valves and will prevent this.



Tod

 

[THerman]

The way to view the diagram is that current only flows from the pos + terminal of the battery to chassis ground. It can only flow through the diode in the direction of the arrow (can't go backwards)



Hope this helps.



Tod

 

[R-N-R]

Well guys, I'm going back to faith here .



I understand that ground does not flow, it is however present.

I understand that positive voltage does flow, ie: current.



What I do not understand is...



sw1 "off" thus providing ground through the load lead to the common load terminal of the connection box

and

sw2 "on" thus flowing voltage (current) through the load lead to the common load terminal of the connection box



How will the diode will stop the voltage from meeting ground at the common load terminal of the connection box.



I do understand that the diode will prevent the voltage from entering the "off" switch.



Does the short occur when the voltage reaches the screw in the frame (so to speak). If so, then I understand how the diode will prevent the short.



Or does the short occur when the voltage reaches the ground "presence". With this scenario, I do not understand how the diode will prevent the short.



You guys certainly will have forgotten way more than I will ever know about electrical engineering. Therefore, (this is where the faith comes in) I will listen, pick up new diodes, and build the circuit as described and expect it to work .



Thank you for all of your patience and assistance!

Bill

 

[emjay]

THerman's right!

Ok, this is the last picture I'm drawing because this is too much fun. In the illustration below, one switch is off and its common terminal is connected to ground through the switch. The other switch is on, and the common terminal is connected to +12 through it. The arrows illustrate the current flow. Notice that the current cannot flow back through the top diode, because it is reverse-biased, meaning the cathode is more positive than the anode. The opposite must be true for any current to flow through the diode, minus the forward voltage of the diode (typically 0. 7 volts).

 

[R-N-R]

Well, it works like a dream!



Thanks again to Joe, Johnny, Jim, Mike, and Tod!!



I used a diode on each switch, including the trans reverse light wire. Everything is wired into a 7 post wire connection box. I also added a pilot light in the dash panel (cubby plate) to indicate when the rear aux backup light switch is activated. The dash panel is key on pwr, the bed panel is constant hot.



So now I have :

Aux backup lights that can be switched from either the cab or bed and also work in conjunction with the factory reverse lights.



A 12v cap light that can be switched from either the bed or the cab.



I am also prepped to add aux backup lights to the rear end of trailer which will work in conjunction with the reverse lights and are switchable from the cab as well.



Next up will be a momentary push button switch to flash my running lights and a 3 pos rotary for the EZ



Thanks again for everybody's help!!

Bill

 

[THerman]

Great work! Glad to hear you got it done.



Tod