The Triumph Dolomite Club - Discussion Forum

Hi all,
I’ve just fitted a set of green LED lights into my instruments. They’re a little too bright ! Has anybody fitted a dimmer switch ?
Thanks, Richard

It depends on what LED's you have fitted and whether or not they have a built in driver circuit. Many good quality ones have a built in constant current circuit. This keeps the brightness the same even if the voltage varies. So a "simple" dimmer will not work.

However, It may be possible to use a PWM (pulse width modulation) circuit to turn the LEDs on and off at a fast rate which will reduce the perceived brightness.Again it depends on what LEDs you have and any inbuilt circuit that is driving them.


If you can let us know what LEDs you have then I might be able to help further.

Roger

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1975 Sprint Man O/D in Honeysuckle Yellow
1971 Stag Auto White

Too many cars, too little time!

Hi Roger,

I asked the vendor and they replied...


Hi Richard,

We don't stock a solid state dimmer but if your rheostat is in good condition with a voltage range down to 9 volts you should find these dim. They start lighting at 9v and reach full brightness at 11v. They will react quicker than incandescent lamps though.

Kind regards
Classic Car LEDs Ltd

Does that shed some light on the matter ?

I got this set which gave me the right bulbs for a Dolomite...

https://www.ebay.co.uk/itm/184367572556

Thanks, Richard

I fitted some of those self adhesive green flexible LED strips round the instruments in my Elan and they were too bright. I put a resistance in the supply to cut the voltage to about 10 volts and they were fine then. In fact, thinking about it, I probably used an electronic voltage stabiliser, the sort that is used in classic cars for some of the gauges. They output 10 volts steady.

_________________
Mike
(1969 MGB GTV8, 1977 Dolomite 1850HL, 1971 MGB roadster now all three on the road)

Just put a resister in-line on each lamp. Pennies!

_________________
Sprintless for the first time in 35+ years. ... Still Sprintless.

Engines, Gearboxes, Overdrives etc. rebuilt. PM me.


1997 TVR Chimaera 450

Richard,

This was what I had in mind: -

https://www.ebay.co.uk/itm/Lucas-3R-Rhe ... Swy5Bau616

Expensive and you also need the knob but they are only a few pounds.

Glen.

They wont dim LEDs

Dave

Not without a resistor in parallel with the LEDs, which might have to be small and high wattage, and so negate the low power advantages of the LEDs.

But if it's not powering too many LEDs, what would be the problem with a standard pot as a potential divider with a padding resistor between it's low end and earth, so the bottom of the pot is near the threshold voltage of the LEDs. Might need a bit of experimentation with different values, but the pots are like 99p each on ebay.

If there are too many LEDs to drive through a normal pot, then it probably does need a current amplifier between the pot and the LEDs. One of the PWM voltage converter / small DC motor controllers looks like a good choice.

Graham

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The 16v Slant 4 engine is more fun than the 3.5 V8, because you mostly drive it on the upslope of the torque curve.

Factory 1977 TR7 Sprint FHC VVC 697S (Now all of, but still needs putting together)
B&Y 73 Dolomite Sprint UVB 274M (kids!)
1970 Maroon 13/60 Herald Convertable (wife's fun car).