Instrument Illumination

Galwaylotus · May 26, 2012, 8:59pm

UAB807F:

Galwaylotus:

Make sure to get “superbright” LEDs and you need an in-line (series) resistor sized to the LED characteristics. I’ve done all indicators for my Mini as well as the illumination for the speedometer. I probably should have gone for a brighter LED for the illumination but it is readable and whiter than the normal bulbs. For my low oil pressure idiot light I bought a 10 mm flashing red LED which works well. The flashing LEDs have built in circuitry which obviates the need for a separate resistor. Good luck.

Hi there,

Any chance of posting a diagram and/or shopping list for us non-electrical numpties ? (being selfish it would be even better if it was a Maplin shopping list ) I’m quite happy soldering things together but know nothing about working out a circuit for LEDs and I quite like the idea of lower power consumption & presumably less heat generation.

Brian

Brian,

The bad news is that I did this a few years ago and cannot find my notes; however, the good news is that the LEDs came from Maplin and they just need a resistor in series to operate correctly. I think the Maplin catalog has some information on the proper resistance for each LED. I built a fibreglass instrument panel for my Mini and used LEDs for the relevant lights (directional indicators, main beam indicator, etc.) and to illuminate the speedo. The latter wasn’t as successful for the reasons mentioned on this forum but If I tried a bit harder I probably could have resolved that one too.

simonknee · May 26, 2012, 10:32pm

Have you seen the Christmas display festooned across the rear of most modern vehicles these days!!

Frank_Howard · May 26, 2012, 10:42pm

I started this thread with a straightforward, easy inexpensive fix to the instrument illumination problem. Call me old fashioned, but why do some people feel compelled to add on a complicated alternative solution that introduces a whole new set of problems?

ricarbo · May 27, 2012, 8:27pm

Using LED’s is not difficult. They drop 1.2 volts and draw about 20 milliamps (0.02 amps). so the calculation is (for one LED)

supply voltage minus 1.2 (let’s say 14.2 - 1.2 = 13).
then, using ohm’s law

13/0.02=650 ohm resistor - use nearest standard value of 680.

two led’s in series drop 2.4 volts, so
11.8/0.02 = 590 ohms - use nearest standard value of 610.

the important thing is not to put too much current through them. extra current blows them, but in practice they are just as bright with lower current, unless you go so low they completely fail to light. perhaps 4 milliamps. you can’t adjust the brightness by changing the resistor.
in practice, it’s ok to use a 1000 ohm resistor (1k) for 1 or 2 leds.

as they are ‘narrow angle’ light emission, you need to fiddle around to get the result you need, but once you’ve done it, they are extremely reliable and run cold, so don’t damage the paint inside the gauges.
you may not like the whiteness of the light, compared to the original lamps.

Richard

Sea_Ranch · May 27, 2012, 8:38pm

Excellent thread; glad the discussion has been renewed.

I’m wondering if part of the problem with the factory setup is the voltage regulation and lack of full voltage to the lights due to grounding or worn-out/improperly adjusted voltage regulator??

Just a thought . . .

Randy

Frank_Howard · May 27, 2012, 9:41pm

I had no idea that the incandescent lamps were damaging the paint inside the gauges. I’ll have to check mine to see how much damage I’ve caused.

UAB807F · May 28, 2012, 6:25am

Richard, thank you for the info, it’s all embarrassingly simple, logical and I really should have worked that out for myself. My only feeble excuse is that it’s been a long time since my Physics O level. I wasn’t thinking of instruments if I’m honest, I was wondering about the number plate lamps at the back.

Galwaylotus, thanks for the pointers as well. Maplins recently sent me a catalogue resembling the old telephone directory so again with some application I should make progress. (ironically, when Maplins send 4/5 page leaflets I tend to read the lot but with the magnum opus they sent last time I just put it in the shelf with the other references, never to be opened !)

simonknee · May 28, 2012, 8:57am

The “old fashioned” here are looking for cp-lighting.co.uk/10X28-12V-4W-330mA-MES

I found this by using the new-fangled google to search for “mes bulb 12V 4W”. If that is not quite the right style it looks like cp-lighting will have something that suits (no I have not used them but they are now bookmarked). Since google displays local suppliers perhaps the same search in your neck of the woods will pull something up a bit nearer than Surrey!

MES = Miniature Edison Screw
See: en.wikipedia.org/wiki/Edison_screw#Types

Simon

Higs · May 28, 2012, 10:42am

And even 6 watt ones here…

http://www.autoelectricsupplies.co.uk/product/499/category/92

So we have enough bulb types to set up a side by side test for brightness, whiteness, paint degredation(ess) etc…

I look forward to the fullsome report!

Richard

Frank_Howard · May 28, 2012, 2:41pm

Simon & Richard,

Good find! And as I said in my initial post, if you install the 4w bulbs in the smaller gauges and the 6w bulbs in the larger ones, the brightness will be close to the same for all 4 gauges. More importantly, all 4 gauges will be legible at night I know this first hand because I have yet to convert the bulbs in my Europa. There is a significant difference as I can read one set at night but not the other.

stugilmour · May 28, 2012, 8:35pm

Can someone with their dash out confirm the dimensions of the stock bulbs and the amount of clearance in the instruments, large and small? I think they are similar to the AES link above with 10 mm screw base, 11 mm round glass globe diameter, and 23 mm (0.906 inches) overall length. Note the 6 w bulbs are 14 mm globe diameter and might be difficult to fit?

Here are a couple of LED possibilities I found thru an MG forum that discusses this issue. Unfortunately they are a bit short on a ‘I used this exact part number and it worked great’ concluding post, although the last link comes close. There are a few positive remarks about the LBC Halogens as well. The second link below was pretty interesting comprehensive listing for all the side marker, reverse lights, etc.

mgexperience.net/phorum/read … sg-2038438

mgexperience.net/phorum/read … sg-1802512

mgexperience.net/phorum/read … sg-1812228

Some selected LED’s from the last link

This first one comes in various colours including warm white. It is billed as Bi-Polar, which might work with positive ground. I believe the T3-1/4 designation refers to the tubular glass diameter in eighths of an inch, which would be 13/32" or a nominal 10 mm. I think this diameter should fit in the small instruments and the warning lamp barrels. I believe the stock bulbs are G3.5, or a nominal 11 mm glass diameter. Although the bulb length is not stated, the pic looks promising with the flat face on the tubular glass.

eliteled.com/products/lightbulbs … dbulb.html

T3-1/4 (10mm) Miniature Screw (E10) Base LED Bulb:
? Patented ?pseudo filament? provides 360 degrees viewing angle
? Bi-Polar design, simple plug in, no need to worry about ?+? or ?-? direction
? 3-in-1 smd LED packaging - 3 LED dice inside each bulb
? Operates at 6 V, 12/14 V, or 24 V AC/DC
? Long Life span 100,000 hrs, No need to change light bulb any more
? Shock / Vibration resistant
? Available in White, Warm White, Blue, Green, Amber, and Red colors

Sale Price: $6.95 each in 12v

This second one comes in White only. Outside diameter and length might not fit in the small instruments or the warning light barrels.

ledlight.com/e10-screw-base- … -bulb.aspx

E10 Screw Base 5 5050 SMT LED Light Bulb
Product Code: 57567
Price: $8.99

E10 Screw Base 5 5050 SMT LED Light Bulb.
5 5050 3 chip LEDs.
Very nice product for E10 screw base applications.
12 Volt direct current.
Available in white only.
Approximate size is 1.15in x .45in. (29.2 mm x 11.4 mm)

Another pretty cool link. This supplier has a pretty complete listing of incandescent bulbs with dimensions. Plug in 12 volts and base E10 to get a complete listing. Looks like a lot of the higher wattage ones might be NLA.

donsbulbs.com/cgi-bin/r/t.pl

stugilmour · May 28, 2012, 8:50pm

Randy, were you thinking of the voltage stabilizer or perhaps the lame regulator on the stock generator?

Anyway, the instrument bulbs use Red / White wires from the panel switch, which is supplied from the side light switch (Red) at a full 12 v. Only the fuel gauge movement, the temp gauge movement (in the plus 2 electric type) and oil temp (if fitted) use the 10 v supply from the stabilizer.

Even with my completely new wiring, good grounds, and alternator the dash lights are really too dim to be practical, hence the desire to find something brighter. I checked my voltage at the bulbs when I put the dash in and it was good, so seems to be a ‘they are all like that’ deal.

Cheers!

ricarbo · May 28, 2012, 9:50pm

I typed up a long (for me) reply, but it doesn’t seem to have appeared. perhaps it will later. In short, the manual lists the correct panel lamp as a 987 (2.4 watt. E10 or MES base, 10mm thread, 11mm globe and 23mm length). Richard (Higs) link to better car lighting shows a led substitute, that looks great, made for the job.
I think higher wattage incandescents would be potentially unsafe. the circuit needs a fuse, if you ask me.
Richard

Sea_Ranch · May 29, 2012, 5:40am

Again I say, awesome thread and info.

Thanks for the clarification, Stu. Yes, I was thinking of the voltage stabilizer and I thought it fed the dash lights (didn’t look at my schematic to see ). I’m sure you’re right; my dash lights are very dim, too.

Higs · May 29, 2012, 6:26am

Another link for uk owners:

http://www.rapidonline.com/Electronic-Components/12v-Warm-White-LED-Bulb-1960mcd-100-41-0842#techSpecs

I think this is close to ideal (happy to be corrected) - 12v, warm white, wide viewing angle, negative earth.

I did notice from the three MG links above two interesting things:

(Thread 2) They soon descend into squabbles about what car/year certain features were introduced (we are not alone!)
There was interest in colours other than white for their instruments (any takers here to be first to suggest another colour for an Elan…?)

Richard

gherlt · May 29, 2012, 8:36am

regarding the bulb from rapidonline I would like to highlight the indicated power rating:
240mW, as a guidance I use a factor of 8 to 10 to calculate the equivalent “old” power rating,
which in this case would give 2.4 W. Not much more than the old 2W bulb.

I did try once a 200mW LED (not sure of the angle, though) and it was as bad than the old one.

gherlt · May 29, 2012, 8:42am

We need something like this:
ledlight.com/e10-screw-base- … light.aspx
ledlight.com/e10-screw-base- … -bulb.aspx
ledlight-ledbulb.com/html/Au … s/237.html

They have 0.4W rating, this could be a 50% increase …

ricarbo · May 29, 2012, 9:40am

Frank, I think you need to be very wary of fitting larger incandescent lamps, because of the heat they produce. Look at thishttp.doc (19.5 KB). ok, it’s about MG’s, but our wiring is similar, that circuit has no fuse and the car is fibreglass, so the fire hazard is worse. I don’t think extra heat is very kind to the electronics in the tacho, or the 50 year old plastic, either. An inline fuse looks well worth it’s small cost.
Richard

oldelanman · May 29, 2012, 3:10pm

On the small instruments (at least the oil pressure gauge which is the only one I can easily get to) only around 4mm of the bulb intrudes into the instrument case itself, the majority - including the filament - remains inside the mounting tube. This could be why the illumination is ineffective. In the oil pressure gauge there is not sufficient clearance for the bulb to intrude further because the bourdon tube runs very close - can’t say if this applies to the fuel gauge as well. Maybe a 360 deg LED is not necessary in this application as the sidefacing elements would be inside the tube anyway.

Frank_Howard · May 29, 2012, 4:07pm

Richard,

I watched the video. There is nothing in the video that indicates that the wiring meltdown was caused by fitting a larger incandescent lamp. As a matter of fact, Twist said that the meltdown was caused by a dead short in one of the bulb holders. Twist made no mention of larger bulbs being used in the MGA. Did a larger bulb cause the holder to short? How could it if larger bulbs were not being used? Obviously, something else caused the bulb holder to short out.

You say that you don’t think extra heat is very kind to the electronics in the tach. What do you base this on? Have you installed larger bulbs in you car and witnessed any failures? I suspect that this is simply your opinion.

I have actually installed 4w and 6w bulbs in my car and I have found that the larger bulbs have absolutely no effect on any of the instruments except for the fact that I can see them now. I’ve had the larger bulbs in for 6 years and I have taken my car on extensive trips, sometimes at night. No problems. My recommendations are based on actual real life use. They are not based on my opinion.

I even added a new Smiths ammeter to my car. Rather than being constructed of metal, the can is now made of plastic. The ammeter came from the factory with a 4w bulb and the bulb holder is plastic as well! Do you honestly believe that Smiths is currently putting out instruments that are fire hazards?

As far as fuses are concerned, I ditched the 2-fuse box years ago and replaced it with a 16-fuse box. My dashboard light, parking light, side marker light, tail light circuit is protected by a 10 amp fuse. It has never blown.

There may be legitimate reasons for installing LEDs but reduced heat is not one of them.