harrytr5 Posted January 29 Report Share Posted January 29 My dash gauge LEDS are green and too bright when I occasionally drive at night. I have bought two different electronic dimmers for LEDS and do not work. Before I waist any more money what is out there that works and easy to fit. I removed the rheostat years ago and fitted a clock in its place. All gauge lights are working as they should but need dimming. Nine LEDS in the gauges. Can you advise please. Regards Harry Quote Link to post Share on other sites
RobH Posted January 29 Report Share Posted January 29 (edited) Some more detail needed first Harry - What LEDs are they and how are they wired ? Are they just 12v replacements for the original bulbs using original wiring or is it a new wiring arrangement ? What dimmers did you try and how were they connected ? Some LED bulbs are not dimmable by just varying the voltage, and PWM dimmers may interfere with chips in the lamps - it might be worth asking the LED supplier about it. Edited January 29 by RobH Quote Link to post Share on other sites
RogerH Posted January 29 Report Share Posted January 29 Hi Harry Bob (LeBro) has published a very simple dimmer on here a number of times. Have a search and see what you think. Roger Quote Link to post Share on other sites
RogerH Posted January 29 Report Share Posted January 29 Hi Harry scab down ro the last post from Bob Quote Link to post Share on other sites
Lebro Posted January 29 Report Share Posted January 29 It certainly works with the LED bulbs I purchased, these I think: https://www.classiccarleds.co.uk/products/glb987-e10mes-5-smd-led-bulbs-dashboard-gauge-lighting potentiometer from ebay: https://www.ebay.co.uk/itm/391584895037 75R 2 W resistor also: https://www.ebay.co.uk/itm/161871446431?var=460853252103 Bob Quote Link to post Share on other sites
RogerH Posted January 30 Report Share Posted January 30 Hi Bob, it is such a simple circuit - elegant I think . Without realising it I use something very similar in my Logic Box dimmer Roger Quote Link to post Share on other sites
Andy Moltu Posted January 30 Report Share Posted January 30 Some LEDs are effectively on or off, so reducing the voltage will see little difference to brightness until they switch off. (Like most fluorescent lights.) Dimmers for these would effectively require very rapid on off switching to appear dimmed. (on for half the time gives the appearance of being half as bright (ish) if done at a high enough frequency. Otherwise you will need dimmable LEDs with a dimmer that works with the the range of voltage and current draw of your LEDs as Bob has detailed above. Quote Link to post Share on other sites
harrytr5 Posted January 30 Author Report Share Posted January 30 14 hours ago, Lebro said: It certainly works with the LED bulbs I purchased, these I think: https://www.classiccarleds.co.uk/products/glb987-e10mes-5-smd-led-bulbs-dashboard-gauge-lighting potentiometer from ebay: https://www.ebay.co.uk/itm/391584895037 75R 2 W resistor also: https://www.ebay.co.uk/itm/161871446431?var=460853252103 Bob Thanks Bob. I have the Red wire power on a bullet connector and the red whites on a bullet Separated at the mo. If I purchase the pot how is it wired to the circuit in simple terms please. Regards Harry Quote Link to post Share on other sites
DRD Posted January 30 Report Share Posted January 30 15 hours ago, Lebro said: It certainly works with the LED bulbs I purchased, these I think: https://www.classiccarleds.co.uk/products/glb987-e10mes-5-smd-led-bulbs-dashboard-gauge-lighting potentiometer from ebay: https://www.ebay.co.uk/itm/391584895037 75R 2 W resistor also: https://www.ebay.co.uk/itm/161871446431?var=460853252103 Bob Hi Bob - do you have any suggestions for a suitable housing to put it in? Cheers Darren Quote Link to post Share on other sites
Lebro Posted January 30 Report Share Posted January 30 The pot replaces the original switch on the dash, & the fixed resistor soldered, & attached ( glued) to the pot. Bob Quote Link to post Share on other sites
harrytr5 Posted February 3 Author Report Share Posted February 3 harrytr5 TR Register Members 2,248 posts Location:Hemel Hempstead Posted 8 minutes ago (edited) On 8/4/2022 at 12:08 AM, RobH said: You can use a dimmer like this https://www.amazon.co.uk/Controller-Adjustable-Voltage-Regulator-Control/dp/B07CG97HDL/ref=sr_1_43?crid=3UZJQW6BTUGMS&keywords=12v+dc+led+dimmer+module&qid=1659567621&sprefix=12v+dc+led+dimmer+module%2Caps%2C87&sr=8-43 If the thread on the potentiometer is too short for the panel you can replace it with one having a longer thread. (B100k): https://www.ebay.co.uk/itm/Long-Thread-0-25-6-3mm-Round-Shaft-Linear-Track-16mm-Guitar-Potentiometer/111359159274 Expand Tried this (controller-adjustable) and does not work.Perhaps wired up wrongly. LEDS from Classic Car Leds. As I do not drive so much when dark should I forget it as going round and round in ever decreasing circles. Could you make me one up Bob please and simple wiring diagram ?. Live feed(red) then feed to LED lights (red white trace) Then earth Regards Harry Edited 2 minutes ago by harrytr5 Quote Link to post Share on other sites
Steve-B Posted February 4 Report Share Posted February 4 I know purists may prefer green as originally that's what was supplied however I'm considering red for 2 reasons. First my car is red, and second, red is proven easier on the eyes in the dark than other colours. Anyone installed red dashboard lights from ClassicLEDs? Quote Link to post Share on other sites
JohnC Posted March 17 Report Share Posted March 17 On 2/5/2024 at 1:43 AM, Steve-B said: I know purists may prefer green as originally that's what was supplied however I'm considering red for 2 reasons. First my car is red, and second, red is proven easier on the eyes in the dark than other colours. Anyone installed red dashboard lights from ClassicLEDs? Yes. They work fine but you'll need a dimmer as they are very bright. I made one per Bob's design above and it works a treat. BTW I don't know what market had green dash lights. Both my large dials have blue diffusers. Not that they did much; the original lights were always a dim yellowish glow! Cheers, John Quote Link to post Share on other sites
CarreyRT Posted March 20 Report Share Posted March 20 On 1/30/2024 at 6:20 AM, Lebro said: It certainly works with the LED bulbs I purchased, these I think: https://www.classiccarleds.co.uk/products/glb987-e10mes-5-smd-led-bulbs-dashboard-gauge-lighting potentiometer from ebay: https://www.ebay.co.uk/itm/391584895037 75R 2 W resistor also: https://www.ebay.co.uk/itm/161871446431?var=460853252103 Bob Good info there, Bob! I'll see if we use that as well. Thank you Quote Link to post Share on other sites
harrytr5 Posted March 20 Author Report Share Posted March 20 This has all been sorted on an earlier post thanks to Bob Ledbro. Regards Harry Quote Link to post Share on other sites
Tom B Posted March 21 Report Share Posted March 21 I posted this in the TR6 forum some time ago. The “proper” way to dim an LED is to switch it on and off very quickly. This is completely standard practice. The technique is called Pulse Width Modulation (PWM). I used a PWM unit from Abeltronics, but there are many types available. It is quite easy to replace the Rheostat with a simple potentiometer (this controls the “on” and “off” of the PWM unit). Fitting the knob on the potentiometer is a bit of a fiddle but the PWM unit just goes into the line that feeds the LEDs. You can see the connections in the photo below. The potentiometer controls the brightness. Note that this unit will work with filament bulbs (or a mixture of the two) as well. Regards Tom Quote Link to post Share on other sites
Lebro Posted March 21 Report Share Posted March 21 Overkill ! Bob Quote Link to post Share on other sites
RobH Posted March 21 Report Share Posted March 21 (edited) 46 minutes ago, Tom B said: The “proper” way to dim an LED is to switch it on and off very quickly. This is completely standard practice. The technique is called Pulse Width Modulation (PWM). PWM is one way to do it if the LED lamp is a simple one with no internal brightness- control chip but is by no means the only way. Current control is just as 'proper' since luminous intensity is almost linear with current. A series resistor is considerably cheaper than a PWM controller. (I would agree with Bob that using a 10Amp PWM unit on LEDs drawing a few mA is certainly overkill ) PWM has its own drawbacks. The fact an LED has instantaneous response means there can be problems with 'strobing' of moving objects if the PWM frequency is too low. Sometimes this is noticeable when you just move your eyes - things can momentarily appear to flicker. (I was in a restaurant not long ago where the tables were lit by dimmed LED spotlamps. As people moved cutlery while eating, the LED lighting gave a most disconcerting flicker effect from the reflections. If the lamps had been old-fashioned halogen you wouldn't have seen it because of the thermal lag in the filaments. ) Edited March 21 by RobH Quote Link to post Share on other sites
Tom B Posted March 21 Report Share Posted March 21 Sure, the unit is oversized but didn't cost that much (as I said, others are available), has screw connectors, so is trivial to implement. Just remove the connectors from the back of the rheostat, extend them to the unit and screw them in. The lights in your house are controlled using this type unit. Never come across strobing as an issue - as far as I can remember the unit I used operates at 240Hz. Anyway, whichever method - getting rid of that rheostat can only be a good thing... Regards Quote Link to post Share on other sites
Spit_2.5PI Posted March 22 Report Share Posted March 22 (edited) 21 hours ago, RobH said: PWM has its own drawbacks. The fact an LED has instantaneous response means there can be problems with 'strobing' of moving objects if the PWM frequency is too low. Sometimes this is noticeable when you just move your eyes - things can momentarily appear to flicker. Yes, some early car LED tail lights used to do this. I remember one - I think it was a model of Peugeot - was particularly bad in my eyes. Scanning the road the tail lights would appear to flicker quite badly. I'm not sure that 240Hz would be fast enough to eliminate this - only one way to find out. ** But then, I can see the flicker of an olde fashioned (CRT) television out of the corner of my eyes. Cheers, Richard ** Experiment done. I can't replicate the "eye movement strobe" effect at 100Hz, so 240Hz should be good. Edited March 22 by Spit_2.5PI Quote Link to post Share on other sites
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