12v multi circuit inout. Need help with component choice! one way diode, P mosfet, pn junction or whatever

Thread Starter

bacoman

Joined Jan 23, 2024
3
Hey, newbie here, I have a relatively simple problem that after hours of reading seem to be easily accomplished in multiple ways, but i keep getting caught up in the different aspects and choices available. I will post issue at hand, please let me know what component you would use to solve the problem. I am a small engine mechanic not en engineer, just trying to determine the proper long term solution.

I have a set of 9 led lights on a mechanical relay triggered by dome light circuit, so when i unlock my truck the 9 puddle lets come on and turn off once i start the vehicle. I want to isolate one of those lights and be able to turn it on or off when driving. the switch i will use a switch pros switch panel. Basically a panel with multiple switches that puts out power through a solid state relay. power could be on 1 circuit or the other sometimes both. Basically i need a or set of proper "one way diode" or something similar that can allow me to join the 2 power input wires to that one light input without traveling back and lighting up the other lights or back feeding the solid state relay switch. This is a low draw 12v led light, but not sure how voltage drop would effect it. Is it best to use a diode, p mosfet switch, PN junction or something different. Thank you so much for your time!
 

Thread Starter

bacoman

Joined Jan 23, 2024
3
Hey, newbie here, I have a relatively simple problem that after hours of reading seem to be easily accomplished in multiple ways, but i keep getting caught up in the different aspects and choices available. I will post issue at hand, please let me know what component you would use to solve the problem. I am a small engine mechanic not en engineer, just trying to determine the proper long term solution.

I have a set of 9 led lights on a mechanical relay triggered by dome light circuit, so when i unlock my truck the 9 puddle lets come on and turn off once i start the vehicle. I want to isolate one of those lights and be able to turn it on or off when driving. the switch i will use a switch pros switch panel. Basically a panel with multiple switches that puts out power through a solid state relay. power could be on 1 circuit or the other sometimes both. Basically i need a or set of proper "one way diode" or something similar that can allow me to join the 2 power input wires to that one light input without traveling back and lighting up the other lights or back feeding the solid state relay switch. This is a low draw 12v led light, but not sure how voltage drop would effect it. Is it best to use a diode, p mosfet switch, PN junction or something different. Thank you so much for your time!
led strips have 18 white smd5050. will only need .5 amp or less to work, just want to not backfeed when other circuit is on
 

MisterBill2

Joined Jan 23, 2018
18,519
Certainly two diodes will be the way to go. This is based on the guess that the LEDs are all 12 volt devices made for operating on a 12 volt automotive system. It is also based on the guess that each one draws less than half an amp, which is a reasonable guess.
The installation will require two diodes, type 1N4001, or equivalent types (rated one amp 50 peak reverse volts), or better. Each diode will be in series, between the power source and that one LED, with the "arrow" on the diode pointing toward the LED. The big deal hard part is connecting the diodes and not letting any of the connections accidentally short circuit to anything else..Not that terribly hard, but rather important.
 
Last edited:

ThePanMan

Joined Mar 13, 2020
793
Welcome to AAC.

There are two possible ways your dome lights are lit: 1) they could get 12V when they are supposed to be on. 2) they could be constantly powered with 12V and only when they're supposed to come on they get grounded. Before you proceed you need to determine which way they are powered.

1) Interrupted power.
2) Interrupted ground.

1) Power comes on to light the lights.
2) Ground is applied to lights that are always powered. Without ground they don't light.
 

Thread Starter

bacoman

Joined Jan 23, 2024
3
Certainly two diodes will be the way to go. This is based on the guess that the LEDs are all 12 volt devices made for operating on a 12 volt automotive system. It is also based on the guess that each one draws less than half an amp, which is a reasonable guess.
The installation will require two diodes, type 1N4001, or equivalent types (rated one amp 50 peak reverse volts), or better. Each diode will be in series, between the power source and that one LED, with the "arrow" on the diode pointing toward the LED. The big deal hard part is connecting the diodes and not letting any of the connections accidentally short circuit to anything else..Not that terribly hard, but rather important.

This seems like a reasonable task. Although in series was shocking to me. I would have figured parallel, one for each power source after the switch before they join to the light.
 
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