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| LED dimmers [message #303668] |
Sat, 16 July 2016 17:24  |
Keith V
Messages: 2337
Registered: March 2008
Location: Mounds View,MN
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hey there LED fans.
I bought some really nice, like as good as hoped, better than expected LED ceiling lights.
They are good looking and bright... too bright.
http://r.ebay.com/H905Pk
No problem, they are dimmable, so I go gets a dimmer from Super bright LEDs.
Single color dimmer with RF remote, $5.88!
https://www.superbrightleds.com/moreinfo/wireless/ldrf-8a-12-24-volt-dc-led-dimmer-rf-remote/64/367/
Great, being me, I open the control box to see if it has a common ground and... drum roll... it has a common high side and it switches the low side!
Well Dang, all my lights are high side switched.
So before I go and fish a new ground, does anyone know of a low cost high side dimmer for LEDs?
Thanks GMCrs
Keith Vasilakes
Mounds View. MN
75 ex Royale GMC
ask me about MicroLevel
Cell, 763-732-3419
My427v8@hotmail.com
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| Re: LED dimmers [message #303676 is a reply to message #303668] |
Sat, 16 July 2016 20:24  |
Joe Weir
Messages: 769
Registered: February 2013
Location: Columbia, SC
Karma: 7
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Will this work?
https://www.amazon.com/gp/product/B01C4BFH7I/ref=oh_aui_detailpage_o03_s00?ie=UTF8&psc=1
https://www.amazon.com/gp/product/B01C4BFH7I/ref=oh_aui_detailpage_o03_s00?ie=UTF8&psc=1
I used it on LED strips. Touch, on. Touch, off. touch-hold, dims.
76 Birchaven - "Wicked Mistress" - New engine, trans, alum radiator, brakes, Sully airbags, fuel lines, seats, adult beverage center... those Coachmen guys were really thinking about us second hand owners by including that beverage center...
Columbia, SC.
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| Re: LED dimmers [message #303681 is a reply to message #303668] |
Sat, 16 July 2016 22:19 |
Bullitthead
Messages: 1411
Registered: November 2013
Karma: 5
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Senior Member |
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I got those dimmers from superbright too, Keith. Just use it to interrupt the ground side of the LED unless you have the kind of LEDs that are integrated into the bayonet base. If you cannot isolate the ground side from the chassis ground it becomes much more expensive, as the PWM dimmer for the positive side does not seem to be around for less than $40 last time I looked. I got to the point of looking in my books from college to design my own circuit, but life intervened and the project got sidelined. I really need one for my LED dash and gauge lights, and the gauges are common-grounded inside the sealed unit, so I cannot get to the LED and disconnect the ground side. I also am reluctant to try and isolate all the instrument lights that I put the 194 LED bulbs in. If I find one for the right price I'll PM you.
Terry Kelpien
ASE Master Technician
73 Glacier 260
Smithfield, Va.
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| Re: LED dimmers [message #303691 is a reply to message #303687] |
Sun, 17 July 2016 10:08 |
Keith V
Messages: 2337
Registered: March 2008
Location: Mounds View,MN
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I think it will be easier, cheaper and better to just fish a new ground wire.
How hard could that be ha ha ha ha
Keith Vasilakes
Mounds View. MN
75 ex Royale GMC
ask me about MicroLevel
Cell, 763-732-3419
My427v8@hotmail.com
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| Re: LED dimmers [message #303706 is a reply to message #303668] |
Sun, 17 July 2016 15:16 |
A Hamilto
Messages: 4508
Registered: April 2011
Karma: 39
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Senior Member |
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Keith V wrote on Sat, 16 July 2016 17:24hey there LED fans.
I bought some really nice, like as good as hoped, better than expected LED ceiling lights.
They are good looking and bright... too bright.
http://r.ebay.com/H905Pk
No problem, they are dimmable, so I go gets a dimmer from Super bright LEDs.
Single color dimmer with RF remote, $5.88!
https://www.superbrightleds.com/moreinfo/wireless/ldrf-8a-12-24-volt-dc-led-dimmer-rf-remote/64/367/
Great, being me, I open the control box to see if it has a common ground and... drum roll... it has a common high side and it switches the low side!
Well Dang, all my lights are high side switched.
So before I go and fish a new ground, does anyone know of a low cost high side dimmer for LEDs?
Thanks GMCrs If I am an electronic component, all I see is voltage from the input side to the output side, and current in between.
Why would it matter where I am in the circuit?
In the picture below, isn't the voltage across C and D and the current through PWM the same in both cases? How does PWM know where it resides relative to the battery and ground? In my mind it doesn't. When PWM has the duty cycle at 0%, the voltage across the other load is 0 (as well as the current), so the voltage across PWM is 12V. When PWM has the duty cycle at 100%, the voltage across the other load is 12V and the voltage across PWM is 0. Current is what it is. Voltages for duty cycles in between 0% and 100% are what they are.
Numbers remain the same for both circuits. PWM doesn't know if it is high side switched or low side switched.
Wired in the switch position so that the current goes through it the right direction it seems to me like it would work.
If it doesn't/can't work, could someone that understands draw me a simple picture so I can understand, please?
[Updated on: Wed, 17 August 2016 17:27] Report message to a moderator |
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| Re: LED dimmers [message #303717 is a reply to message #303706] |
Sun, 17 July 2016 16:50 |
Keith V
Messages: 2337
Registered: March 2008
Location: Mounds View,MN
Karma: 0
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not into drawing pictures, but yours are basically backwards.
I'd like to know how you are powering these circuit on the top, looks like magic to me since the PWM is on LEDs will be dropping all the voltage and the PWM will be at zero V. When the PWM is off it does have 12v but it cant draw any power since those Light emitting diodes aren't conducting
The bottom circuit is also pretty magical, you have a circuit that can run on zero power. When the PWM is ON, there is ( hopefully ) very little voltage drop across the device, and when the PWM is on, there is ( again hopefully ) 100% voltage drop across the device.
Both these scenarios leave no power to run the PWM
The problem with your drawing is it doesn't show the control circuit or where it gets it's power.
The dimmer has 2 inputs and 2 outputs, 1 positive, one negative.
I opened the box and the positive line goes straight through, while the ground side has the PWM driver in the way.
So the controller absolutely does know where it is in the circuit, it is switching the ground side.
The pwm driver is on the low side, meaning on the ground wire, I'm sure there are many reasons to do it this way, but Id bet it's mostly cost as you don't need a boost circuit to turn on the high side switch.
( FETs need the gate to be 2-5 volts above the source voltage to turn on, transistors need less, like .6-.7v )
Keith Vasilakes
Mounds View. MN
75 ex Royale GMC
ask me about MicroLevel
Cell, 763-732-3419
My427v8@hotmail.com
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| Re: LED dimmers [message #303726 is a reply to message #303721] |
Sun, 17 July 2016 20:35 |
Bullitthead
Messages: 1411
Registered: November 2013
Karma: 5
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The power to the load powers the PWM CIRCUITRY. It is not a discreet electronic component and needs power and ground to function. The PWM circuit varies the conduction time of the negative lead coming from the load. In fact, the power lead coming out of the PWM does not have to continue on to the load, and does not even have to be connected to anything. The load can be powered separately as long as the ground of both power sources is common. The PWM circuit can still impose a waveform on the negative return line from the load, no matter where the load gets its power from.
Terry Kelpien
ASE Master Technician
73 Glacier 260
Smithfield, Va.
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| Re: [GMCnet] LED dimmers [message #303756 is a reply to message #303726] |
Mon, 18 July 2016 09:49 |
Keith V
Messages: 2337
Registered: March 2008
Location: Mounds View,MN
Karma: 0
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Senior Member |
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So I finally hooked the dang thing up, it's dead. Sheesh.
Now I have to go through the return process and wait.
And I agree with Terry about the system power, it's merely a convenience to have it pass through, there is no need to connect the leds to the output power.
>
> The power to the load powers the PWM CIRCUITRY. It is not a discreet electronic component and needs power and ground to function. The PWM circuit
> varies the conduction time of the negative lead coming from the load. In fact, the power lead coming out of the PWM does not have to continue on to
> the load, and does not even have to be connected to anything. The load can be powered separately as long as the ground of both power sources is
> common. The PWM circuit can still impose a waveform on the negative return line from the load, no matter where the load gets its power from.
> --
> Terry Kelpien
>
> ASE Master Technician
>
> 73 Glacier 260
>
> Smithfield, Va.
>
>
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Keith Vasilakes
Mounds View. MN
75 ex Royale GMC
ask me about MicroLevel
Cell, 763-732-3419
My427v8@hotmail.com
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