Another one for the sparkies?

[travelrover]

Hi all

I installed a couple of Mud UK center consoles in my project 300Tdi a couple of years ago and changed all the lighting to green LEDs.

https://uploads.tapatalk-cdn.com/20220422/2496c896ab0b904e41d4ac84024837cd.jpg

As you can see they are VERY bloody bright. I went into the local Jaycar to buy a variable pot’ so I can dim them a bit. Anyway I asked the guy in the shop if he had something suitable for the job and he said yes he has dozens of them. I thought ok I’ll play your game, what would you recommend? This banter went on for a while and it turned out he needed me to provide the current draw for all the LEDs so he could recommend the correct pot. Well electricity and I have never really got on and I have no idea how to work this out! All the LEDs for the gauges came from Jaycar so maybe he should be telling me? I can have a look on the website of the switch supplier if they are still in business and get those.

But surely someone with greater knowledge than me could make an educated guess/guesstimate as to the correct ratings. I am looking for something that would go from full bright as per the photo to off in 1/2 or 1 turn of the dial or something in between.

Any ideas?

Cheers - Simon

[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

[travelrover]

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?

[trout1105]

I’ll see what’s on eBay! Is there anyway to cancel the RFI?
Turn the wireless off [biggrin][bigwhistle]

[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

[travelrover]

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!

[AK83]

I've been eyeing off one of these (https://www.ebay.com.au/itm/194988742408?hash=item2d663c1708:g:BsUAAOSwx8ZiXpy 5) 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.

[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 (https://www.ebay.com.au/itm/133978904441?_trkparms=ispr%3D1&hash=item1f31c3d779:g:r~YAAOSwW0lhzWhQ&amdata=enc%3AAQAGAAAA4ACiiYOv3Lsh5ZTgq2K7phLzw8R70 hwtoGIr8fmpTyuffKuy6v4R4bK6bO0z97zITKtT9MmD7Wukz7s 006%2F0DAq3ouyyYqLMQNIk8w47Dzh99wdm43%2FDhoNFB2RNN vYYT%2FOWAcF1TNAVluMTX60wqEcAbIrWNQlhvxgSCHOvSXLRv DnNdUeS%2F4zGLMyxiU5Yrgh5ZrDn7pIchlbxmrt1ag0IRt0t0 KDx0lbT49ee551Wy2MPxV3olpqwPCrE%2Fb%2FGJyk%2FABEQN N46HqBty86N%2BMwRdDK8d8kEHP2NoTnFr7xq%7Ctkp%3ABFBM sqiRxYxg)

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.

178424



So you could use one of these DIM12N - LED Dimmer, Rotary Potentiometer Controlled, Negative Output, PWM, 12V 24V, 10A Low Voltage (https://www.abeltronics.co.uk/products/led-dimmer-rotary-potentiometer-controlled-negative-output-pwm-12v-24v-10a-low-voltage/dim12n) 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.

[travelrover]

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 (https://www.ebay.com.au/itm/133978904441?_trkparms=ispr%3D1&hash=item1f31c3d779:g:r~YAAOSwW0lhzWhQ&amdata=enc%3AAQAGAAAA4ACiiYOv3Lsh5ZTgq2K7phLzw8R70 hwtoGIr8fmpTyuffKuy6v4R4bK6bO0z97zITKtT9MmD7Wukz7s 006%2F0DAq3ouyyYqLMQNIk8w47Dzh99wdm43%2FDhoNFB2RNN vYYT%2FOWAcF1TNAVluMTX60wqEcAbIrWNQlhvxgSCHOvSXLRv DnNdUeS%2F4zGLMyxiU5Yrgh5ZrDn7pIchlbxmrt1ag0IRt0t0 KDx0lbT49ee551Wy2MPxV3olpqwPCrE%2Fb%2FGJyk%2FABEQN N46HqBty86N%2BMwRdDK8d8kEHP2NoTnFr7xq%7Ctkp%3ABFBM sqiRxYxg)

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.

178424



So you could use one of these DIM12N - LED Dimmer, Rotary Potentiometer Controlled, Negative Output, PWM, 12V 24V, 10A Low Voltage (https://www.abeltronics.co.uk/products/led-dimmer-rotary-potentiometer-controlled-negative-output-pwm-12v-24v-10a-low-voltage/dim12n) 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

[slug_burner]

Sorry to go against the general advice provided by others.

You need to differentiate between LEDs and LED bulb replacements.

LEDs are diodes (light emitting diodes). Diodes have a turn on voltage, once the turn on voltage is achieved the current just goes through the roof if there is no current limiting resistor. The resistor determines how bright the led shines as it determines how much current flows through the LED. The only thing that is constant current is the drive current provided by an LED driver. So if you just have LEDs without a driver circuit then it is likely they have a current limiting resistor.

Most LED bulb replacements do have LED drivers. These are not just a LED, These are a circuit boards with multiple LED surface mount packages and control circuitry (LED driver). LED drivers are also used to allow the package work across multiple voltages eg, same bulb or strip works from 12-48 Volts or some other specified range. The things you may want to watch out for is the direction the LED packages are oriented in. There are bulb replacements that throw light out to the sides, some throw it out the end of the bulb and some try to emulated an incandescent bulb by throwing light out in as many directions as possible.

The PWM light dimmers are used for their efficiency, less heat build up if you turn the LED on and off and control the brightness by controlling the ration of on to off period. LED in general are more efficient at turning current into photons (light) A current limiting resistor is always burning energy turning power into heat. So PWM dimmers are more efficient as they don’t build up as much heat they can be made in small packages as smaller or no heat sinks are required.

So if you have a single led with a current limiting resistor a potentiometer will work. If you have LED bulb replacements then they will be constant current devices and a PWM dimmer will be required.

[BradC]

Most (no, pretty much all) "led replacement" bulbs are one or more leds with series resistors. They can be dimmed just the same way a traditional incandescent filament is dimmed by reducing the voltage, and traditionally in a car that was done by a rheostat (a variable resistor). Slightly more modern cars used something a bit more clever (like a variable linear regulator), and it's only really quite recently that PWM became common.

No need to over-complicate it. Connect the LEDs up to the existing dash dimmer, add another one or use some other form of rheostat. No PWM, no RFI, no hassle.
Yes, if you go to Jaycar you'll need to know the current consumption to ensure they give you a wirewound pot with the correct approximate value and power rating. You can measure this with a multi-meter in series with the lamps.

[travelrover]

Most (no, pretty much all) "led replacement" bulbs are one or more leds with series resistors. They can be dimmed just the same way a traditional incandescent filament is dimmed by reducing the voltage, and traditionally in a car that was done by a rheostat (a variable resistor). Slightly more modern cars used something a bit more clever (like a variable linear regulator), and it's only really quite recently that PWM became common.

No need to over-complicate it. Connect the LEDs up to the existing dash dimmer, add another one or use some other form of rheostat. No PWM, no RFI, no hassle.
Yes, if you go to Jaycar you'll need to know the current consumption to ensure they give you a wirewound pot with the correct approximate value and power rating. You can measure this with a multi-meter in series with the lamps.

Thanks BradC

Unfortunately there is no existing dimmer of perhaps I wouldn’t have this challenge.

Maybe I need to pull the dash apart and put a multimeter across as you say.

[BradC]

You need to get in series with one of the supplies to the LEDs and measure the current.

Are the LEDs currently on all the time or switched with the head/dash lights?

Let's do a worked example based on 6 gauges and an estimated maximum LED current of 20mA (pretty typical).
6 x 20mA = 120mA.

So flat out, those LEDs are going to draw 120mA. As you drop the voltage, the current will also fall in a non-linear manner, but for the sake of the exercise, let's go with half brightness, half voltage.

So we assume at half brightness, we'll want half voltage (6V) and the LEDs are going to draw 60mA. You need to drop 6V at 60mA so you'll want a 100 Ohm resistor which is going to dissipate ~360mW.

You'll want a >=3W wirewound pot. Something like : R2156A - Taiwan Alpha 100R Lin D Shaft 24mm Single 3W Wire-wound Pot - Altronics (https://www.altronics.com.au/p/r2156a-100r-lin-d-shaft-24mm-single-3w-wire-wound-pot/)Although ideally you'd probably want more like 250 Ohm to dim them to almost nothing.

The reason for the 3W pot is to do with the current handling of the element. The power rating of a pot is for the entire element, so the closer the wiper is to the start the lower the power it can handle. Easiest way to work that out is to calculate the current the entire element can handle and not exceed that. Power = the square of the current multiplied by the resistance (P=I2R).

For a 3W 100 Ohm pot that is the square root of 3W/100 Ohm (173mA). A 1W pot would only be able to handle 100mA, so when you just crack the knob to "slightly less bright" you've already exceeded the element power handling and it will eventually experience a "life limiting event" and release the magic smoke. Once you get down into carbon trace pots (which barring one useless exception are all Jaycar stock) then you'll cook the element in short order.

If you can get a current measurement for a group of LEDs, it's easy to work out the entire load. If you don't have a decent meter with a good low current resolution, put a 100Ohm 1W resistor in series with the LEDs and measure the voltage drop. Current can be calculated from that I=V/R.

You can always play with fixed resistors until you get a brightness that you're happy with and work from there.

[travelrover]

You need to get in series with one of the supplies to the LEDs and measure the current.

Are the LEDs currently on all the time or switched with the head/dash lights?

Let's do a worked example based on 6 gauges and an estimated maximum LED current of 20mA (pretty typical).
6 x 20mA = 120mA.

So flat out, those LEDs are going to draw 120mA. As you drop the voltage, the current will also fall in a non-linear manner, but for the sake of the exercise, let's go with half brightness, half voltage.

So we assume at half brightness, we'll want half voltage (6V) and the LEDs are going to draw 60mA. You need to drop 6V at 60mA so you'll want a 100 Ohm resistor which is going to dissipate ~360mW.

You'll want a >=3W wirewound pot. Something like : R2156A - Taiwan Alpha 100R Lin D Shaft 24mm Single 3W Wire-wound Pot - Altronics (https://www.altronics.com.au/p/r2156a-100r-lin-d-shaft-24mm-single-3w-wire-wound-pot/)Although ideally you'd probably want more like 250 Ohm to dim them to almost nothing.

The reason for the 3W pot is to do with the current handling of the element. The power rating of a pot is for the entire element, so the closer the wiper is to the start the lower the power it can handle. Easiest way to work that out is to calculate the current the entire element can handle and not exceed that. Power = the square of the current multiplied by the resistance (P=I2R).

For a 3W 100 Ohm pot that is the square root of 3W/100 Ohm (173mA). A 1W pot would only be able to handle 100mA, so when you just crack the knob to "slightly less bright" you've already exceeded the element power handling and it will eventually experience a "life limiting event" and release the magic smoke. Once you get down into carbon trace pots (which barring one useless exception are all Jaycar stock) then you'll cook the element in short order.

If you can get a current measurement for a group of LEDs, it's easy to work out the entire load. If you don't have a decent meter with a good low current resolution, put a 100Ohm 1W resistor in series with the LEDs and measure the voltage drop. Current can be calculated from that I=V/R.

You can always play with fixed resistors until you get a brightness that you're happy with and work from there.

Thanks BradC

I won’t pretend that I understand half of that. Yes they are wired via the head/dash lights. From memory they are all on the same relay.
I would be happy with between a 1/3 - 1/2 less brightness. It’s ok during the day but at night is just too much. Im off to the auto sparkie for other things this morning so will discuss with him.

Thanks again.

[trout1105]

Thanks BradC

I won’t pretend that I understand half of that. Yes they are wired via the head/dash lights. From memory they are all on the same relay.
I would be happy with between a 1/3 - 1/2 less brightness. It’s ok during the day but at night is just too much. Im off to the auto sparkie for other things this morning so will discuss with him.

Thanks again.

See if you can get your auto sparkie to retro fit a rheostat (dimmer) for you[thumbsupbig]

[travelrover]

See if you can get your auto sparkie to retro fit a rheostat (dimmer) for you[thumbsupbig]

He said, hmmm a good question! We did discuss rheostats. Anyway it’s booked in for some other work in a couple of weeks and he will have another look then.

[Busted Syncro]

G'day Simon,
Out of interest and research I purchased a PWM dimmer on Ebay for $8.68 post free. (See attached photo.). It arrived today and pulled it apart to see what technology is used. The design is a low frequency PWM using a 555 IC timer. It will not generate RFI. The circuit design, PWM's the negative supply lead to the LED's. This means it will control the LED's in the Carlin switches as well because the input and output positive leads in the dimmer are connected together on the circuit board. However, the dimmer will only control 12 volt LED's from a 12 volt supply. (Caution. If you use 24 volts supply you must use 24 volt LED's.)

I made up a test rig after re soldering 2 dodgy joints on circuit board and it controlled a 12 volt gauge LED from Off to Full brightness. (The standby current is 15mA without a LED on the output.)
This information is only for the dimmer in the photo and a search on Ebay will find it.

Happy Days!
Hope this helps
Chris178530

[travelrover]

G'day Simon,
Out of interest and research I purchased a PWM dimmer on Ebay for $8.68 post free. (See attached photo.). It arrived today and pulled it apart to see what technology is used. The design is a low frequency PWM using a 555 IC timer. It will not generate RFI. The circuit design, PWM"s the negative supply lead to the LED's. This means it will control the LED's in the Carlin switches as well because the input and output positive leads in the dimmer are connected together on the circuit board. However, the dimmer will only control 12 volt LED's from a 12 volt supply. (Caution. If you use 24 volts supply you must use 24 volt LED's.)

I made up a test rig after re soldering 2 dodgy joints on circuit board and it controlled a 12 volt gauge LED from Off to Full brightness. (The standby current is 15mA without a LED on the output.)
This information is only for the dimmer in the photo and a search on Ebay will find it.

Happy Day!
Hope this helps
Chris178530

Brilliant

Thanks Chris! All 12 volts here, I’ll track it down

[Busted Syncro]

CAUTION. The negative leads from the gauges and switch LED's must go directly to the dimmer output negative terminal. NOT thru the vehicle earth or body system. Also the existing positive lead that comes from the side light/headlight vehicle switch to your LED lights can stay connected however you need to connect a wire to the INPUT positive terminal on the dimmer from this side light/headlight switch. (Reason. The dimmer input positive terminal and output positive terminal are connected together on the circuit board.)
This means you don't have to pull cables out and will make install easier.

NOTE: the dimmer NEGATIVE INPUT terminal goes to battery negative/ vehicle negative.

Hope this makes sense.

Chris

[travelrover]

CAUTION. The negative leads from the gauges and switch LED's must go directly to the dimmer output negative terminal. NOT thru the vehicle earth or body system. Also the positive lead that comes from the side light/headlight vehicle switch to your LED lights can stay connected however you need to connect a wire to the INPUT positive terminal on the dimmer from this side light/headlight switch. (Reason. The dimmer input positive terminal and output positive terminal are connected together on the circuit board.)
This means you don't have to pull cables out and will make install easier.

Hope this makes sense.

Chris

ThanksChris