[TR] Converting TR6 rheostat to LED use

John Innis jdinnis at gmail.com
Thu Feb 22 06:49:18 MST 2018


I LM317 is a voltage regulator.  You CAN use it as you describe, basically
with a series resistor to sink the excess voltage and therefore indirectly
adjust drive current.  But I find this approach to have a very poor dimming
curve.  The PWM dimming solution gives you a much better control,
especially at the dim end of the curve.  The other issue with the LM317 is
that it is not very efficient.  All the gains you get from going to LEDs
are essentially going to be lost as heat from the regulator.

On Wed, Feb 21, 2018 at 4:50 PM, Paul Tegler <ptegler at verizon.net> wrote:

> Randal corrected my 'incomplete' response (tnx)
> see below
>
> all my LBC's have LED's in the dash
> since they draw much less current than normal bulbs all you need is a
> simple LM317 regulator,
> one 5K pot and one 240 ohm resistor
>
> It will be 'warn to the touch, but no more than the old bulbs would be warm
>
> look up the spec sheet for am LM317. truly dirt simple...doesn't need and
> diodes or caps
>
> ptegler
>
> Paul Tegler ptegler at verizon.net www.teglerizer.com
>
>
> On 2/21/2018 12:35 PM, Randall wrote:
>
>> One note of caution.  Read the instructions that come with a PWM dimmer
>>> carefully.  Some require that the LED's connected to them are NOT
>>>
>> grounded.
>>
>>> This can be a real pain the butt for LBC's where everything is metal and
>>> all the metal is grounded.
>>>
>> Which is exactly why I would say the one you linked to is Not Suitable.
>>
>> As usual, Amazon won't tell you little things like whether you can use it
>> or
>> not; but the information is on the seller's web site:
>>
>> "As with pretty much all dimmer switches, the ground side is switched
>> rather
>> than the positive side. So you must hookup the output ground wire to your
>> LEDs."
>>
>> https://www.oznium.com/led-dimmer-knob
>>
>> -- Randall
>>
>>
>> ** triumphs at autox.team.net **
>>
>> Donate: http://www.team.net/donate.html
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>>
>>
>
> ** triumphs at autox.team.net **
>
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>



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