Thread: Another one for the sparkies?

G'day Simon,

Unfortunately a variable pot is not the way to dim LED's. LED's are a constant current device. What you need is a PWM Led dimmer controller. Search Ebay and you will find lots of 12 volt PWM dimmers for around $10 each. These are designed for LED strips however, worth a try with your gauge LED's. Observe polarity!. (Unfortunately these PWM devices generate radio interference so something to check with the radio's in your vehicle.)

Let us know how you go.
Chris

Originally Posted by Busted Syncro

G'day Simon,

Unfortunately a variable pot is not the way to dim LED's. LED's are a constant current device. What you need is a PWM Led dimmer controller. Search Ebay and you will find lots of 12 volt PWM dimmers for around $10 each. These are designed for LED strips however, worth a try with your gauge LED's. Observe polarity!. (Unfortunately these PWM devices generate radio interference so something to check with the radio's in your vehicle.)

Let us know how you go.
Chris

Thanks Chris

I’ll see what’s on eBay! Is there anyway to cancel the RFI?

I’ll see what’s on eBay! Is there anyway to cancel the RFI?

Turn the wireless off

G'day Simon,

I see you are on VKS with receiver sensitivity < 1uV. RFI from LED PWM dimmers would be in a specific band of frequencies. The 12 volt input impedance to the dimmer is usually low so the main radiation will be from the output cable. Toroidal cores with this cable threaded thru to fill the toroidal will help. Also clamp on cores are also available. However, you may not have a problem in the frequencies you operate in because the current from the gauge LED's is small ( say < 30MA per LED.) so power level is also small. Also you probably have other switch mode type chargers (phone and GPS) fitted in the vehicle already.

For around $10 to $15 it's worth a try and see how it goes!.
Hope this helps.
Chris

Originally Posted by Busted Syncro

G'day Simon,

I see you are on VKS with receiver sensitivity < 1uV. RFI from LED PWM dimmers would be in a specific band of frequencies. The 12 volt input impedance to the dimmer is usually low so the main radiation will be from the output cable. Toroidal cores with this cable threaded thru to fill the toroidal will help. Also clamp on cores are also available. However, you may not have a problem in the frequencies you operate in because the current from the gauge LED's is small ( say < 30MA per LED.) so power level is also small. Also you probably have other switch mode type chargers (phone and GPS) fitted in the vehicle already.

For around $10 to $15 it's worth a try and see how it goes!.
Hope this helps.
Chris

Thanks Chris

Useful info! The HF is actually in my Td5 and not this one, well not at the moment anyway. There is an UHF. I seem to remember making toroidal coils at school a very long time ago!

I've been eyeing off one of these devices off ebay(and other places).

They come from the US and postage is horrendous from there .. for any product!
So too expensive for me at the moment.

But if Chris is right and they're maxing at 0.03 amps .. then one amp for all gauges and switches should be a good estimation of power consumption.

I've got two lines of thinking at the moment for my similar predicament.
A while ago I replaced all the instrument bulbs in the brothers D2 to LEDs. Around town the dash is perfect .. just a tad bright for dark hwy driving, but ok-ish.
The major problem is the HVAC unit.
Even around town it's 'IN YA FACE!!' bright .. on a dark hwy ... obnoxious is a close approximation on describing it's brightness. I'm too lazy to pull them out, and they are bright if needed on a bright sunny directly sun lit situation. But need major toning down for not in direct sunlight situations. The original bulbs were utterly useless in showing the display when direct sunlight was on it.
Anyhow!.. one of my solutions so far is to locate the cheapest LEDs, with a known not so bright design. I've bought and tried enough that I should have known! ..

My other idea is to use a Landrover part, not readily obtainable, but so far known to work.

Some Landrovers came with dimmable instrument systems. I can't remember all, but from memory US and Japan has them. Hard to get here.
Anyhow, I got one for my D1(which I converted all instrument bulbs to LEDs years ago) .. and I got a dimmer from overseas years ago too.
Some folks said it wouldn't work. I got mine at a price that was fair enough to give it a go. In a D1, it's plug and play(loom already had a spot for it) .. plugged in and BINGO! .. works a charm.
D1 doesn't use the D2 climate control tho .. so not the same issue. But the D1 is far nicer to drive on a dark road as I can dim the lights to very low levels.
I still have the issue of my 1Gauge led screen tho. Back when I got mine, it only came in a white on blue screen, and it's bright as hell. It dims with the park lights(ie dash light on) but on those dark roads. I still reckon "ust not enough" .. years back I asked the maker of the 1Gauge about it, he replied that I can change a resistor on the board to another value and will get more dimming.
Then found the device I linked too on ebay and thinking maybe that would be a better way to dim the 1Gauge screen. (been umming and ahhing on it for a few years .. so not an urgent issue).

But it got me thinking about using the already proven LR device too.
I haven't yet installed my other ones in the D2 to see how much it dims the HVAC(this is the urgent one to sort out) .. I usually drive it with HVAC off at night .. it's so bright.

Going by Chris's comments, it must be that the LR dimmer(available for both the D1 and the D2) may be PWM devices. I haven't opened one up to see tho.
I recently also got one out of a Rangie(late model) from the wreckers too) .. RR's seem to be more common in wreckers nowadays(strange) .. which came to Aus with these dimmers. They are very much the same, other than the way they mount inside the dash.

I don't know what you plan to end up doing, but at some point I'll test the dimmers on some LEDs I have, to see how easy it is to dim them down, and by how much.

But to answer your question(again) .. I reckon you're running about 1 amp total with the setup in your photo.

The other thing I did a while back was to test the current draw on some T5 and T10 LEDs I used for various jobs(park lights and interiors and stuff). Where the incadescent drew near 1 amp(I think 0.7a) .. IIRC, the LED versions drew 0.1a by comparison.
Note that these were the wedge type (T5 and T10) used for a lot more brightness than a small dial gauge needs. So for small gauge globes like you'd be using... I reckon the 0.03a value would be about right.

Hi Simon,
For the gauge lights you could use one of these or something similar.
30A 12V-12V Metal LED Switch Dimmer Controller Manual Operation for Strip Light | eBay

However on your On-Off rocker switches, the voltage that runs the LED also delivers voltage to your load so the above wouldn't cope with your carling switches.

Screenshot 2022-04-26 154517.png



So you could use one of these DIM12N - LED Dimmer, Rotary Potentiometer Controlled, Negative Output, PWM, 12V 24V, 10A Low Voltage or find similar for a reasonable price.


I agree with the previous post about not using a pot to dim LED's but it will work to a certain extent.
If you want to have a 'crack' at it I'd suggest starting with a 1K or 2K pot and as many watts as your willing to pay for and throw away. 5 watts will kill it and probably 1 watt should do the job easily, most pots are 1/4 watt. I couldn't get any specs on the LED power off the interweb thingy.
Edit - typical stated currents for LEDs are 10mA so if you have 12 LEDs at 10mA that's 0.12A at 12V is 1.44 watts

The Pot will need to go on the negative side of the switch LEDs as per the above, however you will find that the LEDs will not dim consistently because all of them will have a load resistor built in and they will be slightly different and ohms laws states etc etc. Also as you vary the load on the pot (ie turn things on and off) the voltage on the remaining LEDs will change slightly and the LEDs will change in brightness (maybe only slightly). There is a work around but it's not neat.

Boaties live and die on cabin light brightness and on the water at night I am completely obsessed with it, so there is a bit of info many of those forums.


Cheers Glen.

Originally Posted by Dorian

Hi Simon,
For the gauge lights you could use one of these or something similar.
30A 12V-12V Metal LED Switch Dimmer Controller Manual Operation for Strip Light | eBay

However on your On-Off rocker switches, the voltage that runs the LED also delivers voltage to your load so the above wouldn't cope with your carling switches.

Screenshot 2022-04-26 154517.png



So you could use one of these DIM12N - LED Dimmer, Rotary Potentiometer Controlled, Negative Output, PWM, 12V 24V, 10A Low Voltage or find similar for a reasonable price.


I agree with the previous post about not using a pot to dim LED's but it will work to a certain extent.
If you want to have a 'crack' at it I'd suggest starting with a 1K or 2K pot and as many watts as your willing to pay for and throw away. 5 watts will kill it and probably 1 watt should do the job easily, most pots are 1/4 watt. I couldn't get any specs on the LED power off the interweb thingy.
Edit - typical stated currents for LEDs are 10mA so if you have 12 LEDs at 10mA that's 0.12A at 12V is 1.44 watts

The Pot will need to go on the negative side of the switch LEDs as per the above, however you will find that the LEDs will not dim consistently because all of them will have a load resistor built in and they will be slightly different and ohms laws states etc etc. Also as you vary the load on the pot (ie turn things on and off) the voltage on the remaining LEDs will change slightly and the LEDs will change in brightness (maybe only slightly). There is a work around but it's not neat.

Boaties live and die on cabin light brightness and on the water at night I am completely obsessed with it, so there is a bit of info many of those forums.


Cheers Glen.

Hi Glen

I appreciate the detailed guidance. I’ll read it again and work out how I could apply to my set up.

Thanks again

Simon