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Any inexpensive LED dimmer circuit for devices with diode for dimming?

Any inexpensive LED dimmer circuit for devices with diode for dimming?


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Old 09-21-22, 05:20 AM
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Any inexpensive LED dimmer circuit for devices with diode for dimming?

I've run into this a couple times recently when replacing incandescent bulbs with LEDs.

The fixture has a diode inline to give a dimmer level than full brightness. That works for incadescent but not LEDs.

Anyone know of a simple, small, circuit that would take the place of the diode for the same effect? I'd envision maybe a small dial to adjust desired brightness 1 time, then put the circuit out of the way.

I put in LEDs in our GE range hood. the light switch has full and night light settings on the 3 position swtich (on, off, night light).

They just put a diode in the circuit for the nightlight. (I cut off the shrink tubing for the picture : )

At this point, I'll just cut out the diode and join the wire together. Then either position is on (on, off, on).

I'd like to keep the night light if possible.

recommendations?


 
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Old 09-21-22, 05:33 AM
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The trouble is that LED's don't use a simple method for dimming. There are two basic methods. The analog way they voltage fed to the LED is varied. The LED interprets different voltages as a signal for how bright to power the LED. The more common (these days) way is by pulse width modulation (PWM) where the light flickers on and off very quickly depending on how bright or dim you want the LED. The more time the LED spends "on" the human eye perceives it as brighter.

In your case I'd do some simple tests before hacking your vent hood. I'd get an LED light bulb and try reducing the AC voltage going to the bulb. This test is important to also see if your LED will respond to varying voltage or if it needs PWM for dimming. This can be done with a transformer, voltage regulator or resistor. A resistor is possibly the simplest and cheapest. If using a resistor you will need to properly size it according to the wattage of the bulb you use. The resistor will get hot during use so you need a big enough one to handle the load and you need to mount it somewhere it doesn't pose a fire hazard.
 
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Old 09-21-22, 08:49 AM
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@pilot dane

As always, Thanks!

I was hoping to get a link to something to buy : ) finding a resistor, correct wattage, etc that can do that. I'll never pull that off.

I found this... doesn't work with 120v LEDs (I know - the LED doesn't see 120v inside the bulb).

https://www.oznium.com/switches/mini-led-dimmer-knob

I'm hoping there's what's in a lutron wall dimmer that is just the circuit board and a small potentiometer or similar to set and forget the dimming level.

 
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Old 09-21-22, 09:16 AM
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There really is not an easy way to dim 120v LED bulbs. The dimmer board in LED dimmers is fairly involved. It doesn't vary voltage.... it pulses it. Pretty hard to duplicate in a small package.
 
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Old 09-21-22, 09:35 AM
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I have an Eaton TAL06P2 dimmer switch (not a smart switch) the works with all types of bulbs. It has dimming level and minimum dimming features that allow you to set and forget. The thumbwheels are behind the switch plate. It works for either single pole or 3-way switching.
 
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Old 09-21-22, 11:01 AM
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I'm not familiar with dimming LEDs with reduced voltage. All I'm familiar with is drivers using 10V dimming. Can anyone explain how it's done or point me to where I can learn more?
 
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Old 09-22-22, 06:21 AM
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Thanks everyone!

@Pilot Dane - I'd like to take apart a newer dimmer switch to see what IS in there / how large it is. Partly for curiosity, partly to see if I can get the board out to use in these situations.

I know I took apart a 20 year old dimmer switch when I replaced LEDs in the ceiling. Heat sink, big transistor looking thing (3 leads, metal on top to bolt to the heat sink, etc).

Just thought - if you have a 100w incadescent and old style dimmer set for night light / low light output.... how much power does it use? Same as full bright? 100w? just most of it in in the heat sink? but a 100w bulb gets hot. so I guess it's not got 90w in the heat sink. Burn the wall : ) ??!!
 
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Old 09-22-22, 08:09 AM
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I am sorry, I should not have mentioned variable voltage dimming since bulbs are generally no longer available. I used to work in electronics assembly and consulted on a project for one of the earliest dimmable LED bulbs. They relied on a minimum voltage to provide enough voltage to power the light. The voltage was interpreted as a command for brightness. It worked sorta OK within reason but had fundamental problems and technology left it in the dust.
 
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