Dimming Instrument illumination

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wiltsathome
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Dimming Instrument illumination

Has anyone with a late model Caterham with LED illuminated instruments found a way of dimming them using a PWM rheostat or potentiometer? 
I find the brightness of the instruments blinding at night and would prefer to dim them rather than simply putting an on/off switch into the circuit
Look forward to your possible solutions

Jonathan Kay
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With LEDs the most common current (!) fix is sticking a sticker in the way. Some people use a bit of sticky tape but you can buy purpose-built stickers!

Recent discussion.

Jonathan

(David White's solution)

Roger Ford
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Is the problem with the instrument illumination in general, or the brightness of warning lights (most obviously the high beam light)?

And if it's the general illumination, do the instruments only light up when the vehicle lights are on, or are they always illuminated?

If they're only on with the lights, then it would seem worth experimenting with a PWM on the lighting-circuit feed to the instruments. Whether it would work on not would depend on whether the LEDs are fed directly (or through a simple voltage reducer), or whether they have on-board drivers.

If it's the high beam, that's going to be fed from the general power circuit, so I can't see anything being possible without dismantling the whole instrument.

Jonathan Kay
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"Is the problem with the instrument illumination in general, or the brightness of warning lights (most obviously the high beam light)?"

Ah... I assumed it was the warning lights. Good question.

Jonathan

wiltsathome
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Cheers guys, the problem is the white light background lighting to the instruments that on my 2016 car are like Blackpool, dazzling forward vision and reflecting so badly in the side screens that the mirrors are useless. Happily, my high beam light isn't too bad (better than my previous 2006 car)

The easy solution is to put a switch into the red/white feed off the back of the light switch, the snag with this is that you cut all illumination to both instruments and the switch indicators. Next option is to take each feed to each instrument into one switch and leave the switch illumination intact. But the ideal fix is to find a way of dimming the lights to switches and instruments with something like an old fashioned rheostat but I know some LEDs won't work with a normal voltage reducing rheostat.  
I'm therefore looking to see if anyone has found a good way of achieving the latter solution 

 

Wilt

Jonathan Kay
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I've got the factory wiring diagram if anyone would like a copy.

Jonathan

wiltsathome
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That would be most handy Jonathan, if it for a 420r would it be possible to email on wiltsathome@hotmail.com please?

Wilt

Jonathan Kay
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Wilco

Jonathan

Roger Ford
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I'm therefore looking to see if anyone has found a good way of achieving the latter solution 

I think you might be blazing the trail here. First thing I'd try would be to add something like this into the lighting circuit 12v-24v mini dimmer controller, but I strongly suspect that will just reduce the voltage. Might work, very unlikely (IMO) to damage anything and it's dirt cheap (not sure about postage). If not, you'll need to go PWM. There are loads of DIY PWM dimmer circuits on the web, but few ready-built ones. It looks like this PWM motor controller might do the job, even though it's designed for something completely different.

Of course for this to work, you're going to need to isolate the lighting feed to instruments and switches, you don't want to be PWM-dimming your headlights or tail lights.

Look like an interesting winter project, but my 2014 310R doesn't suffer from the same issue - otherwise I'd give it a try.

Roger Ford
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Just one more comment, often reducing the voltage to LEDs will have no effect until you reach a certain level, then it will start dropping. So, for example, if you have 3.5v LEDs and a 12v feed, the driver circuit will reduce the supply voltage to 3.5v for output, and won't care if you give it 15v or 8v. However once you get below, say, 5v, it won't be able to sustain the 3.5v output and the output will drop. That assumes the driver is using a constant voltage output, if it's constant current it probably wouldn't work the same way.

I don't suppose you have a bench power supply? If you did you could remove one of the instruments and see the effect of reducing voltage from 12v down to, say, 1.5v and see if the instruments eventually dim, or whether the lighting just suddenly switches off at a certain level.

SM25T
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As owner of a 2002 car, we can only dream of being able to illuminate instruments to that level !!