high-low switch for strip light LEDS (12volt)

Thread Starter

revdr.biko

Joined Dec 16, 2019
14
so i thought it would be easy but i'm confused.

i have a sail boat and enjoy customizing basically every aspect of it.
the boat came with a poorly rigged high-low switch for the incandescent bulbs in the head. it is actually a high-low 'fan' toggle with a resistor on one side and it has little to no effect on the led strip lights.

i thought: good idea (full lights vs night lights), now lets rig up some LED strip lights to do the same. (not a full range dimmer, but a high or low rocker switch)
"it'll be easy ", i said.... (famous last words)

i bought a on-off-on rocker switch (I 0 II) and a controllable dimmer (see attached images)
but i am trying to figure out how to wire the whole thing up so it works with out reversing the polarity on the controllable dimmer .

so before i wire things up and smoke the controllable dimmer i though i'd ask for some help.

thanks

'Senior Noob'
 

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dendad

Joined Feb 20, 2016
3,939
You are better off to not reduce the voltage as LEDs are current devices.
Look for a PWM (Pulse Width Modulation) controller so the LEDs still run at the required current, just the duty cycle is changed. Then you will get good controllable dimming.
But what you have may work ok. Maybe include a diode, 1N4007, with Anode on the reg out, Cathode to reg input to ensure the reg IC is powered when fed from the output. It may not need it.
 
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Thread Starter

revdr.biko

Joined Dec 16, 2019
14
But what you have may work ok. Maybe include a diode, 1N4007, with Anode on the reg out, Cathode to reg input to ensure the reg IC is powered when fed from the output. It may not need it.
thanks.!
not exactly sure about diode recommended placement. reg out is?? reg in? reg IC?

i was thinking that if the switch was set to 'low' the power would go through the step-down buck and that's clear. no other route.
however if the switch is high, could the power go backward through the step-down buck ? (reverse polarity would smoke the thing i'm guessing)

i'm guessing that's what your diode suggestion is about, i just not sure where. i'd guess in-line between the positive output of the step-down buck and the load, but i'm not sure.

plus i've already bough this stuff... next time i look into Pulse Width Modulation .
 

Audioguru again

Joined Oct 21, 2019
3,860
Get rid of the voltage converter and replace it with a resistor calculated with simple math to reduce the current which reduces the brightness of LEDs.
 

kaindub

Joined Oct 28, 2019
92
Reducing the volts by a resistor or regulator causes the LEDS to loose colour rendering. As someone already mentioned younger a PWM dimmer to regulate the light intensity
 
You may be able to buy a suitable power supply of the type specified - for LED applications, constant current, which is the best way to go, for less than a lot of dinking around on your part. Just make sure you have figured how much current you will need for the max driving power you may need, then add a reasonable overhead rating to keep the supply under max output wattage rating. Amazing how cheap really good, already built supplies are these days. Dendad is right in the information provided.
 

col_panek

Joined Oct 30, 2015
12
Something I've done is to run the 12V through a couple diodes to get the voltage drop down to the right level. If you have a few diodes, try them in series. Diodes are pretty cheap and small, drop around 0.6 volts each. Wire it right across the output terminals of your switch, the anode pointing to the "low" setting, and run the "high" terminal to your lights. Presto, 12V or 10.5V.

I've used PWM dimmer modules for my kitchen under-counter lights. They're about $4 from China, and smoothly adjust the power output.
 

Thread Starter

revdr.biko

Joined Dec 16, 2019
14
thanks everyone.
the PWM is definetly the way to go (next time, these are simple soft-white strips)
Resistors are the worst. least amount of ctrl & most amount of heat. (it's what the boat came with orig and needs removed)

i just wanted to make sure the two positive leads did not cause reverse polarity (backwards) through the dimmer when 'full' was selected. this would also be a concern for the PWM too.
 
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