Anomolies with LED Lamps, & Indicators

[Teflon-Mike]

Well, Don't know if any-one has discovered this, BUT!

Decided to fit LED bulbs to Snowie's 125 Super-Dream to lower the battery drain and free up some power for Heated-Grips, better lighting and a few other accessories.

Commonly known that fitting LED indicators or indicator bulbs, that the flasher unit has to be changed as the lower load of LED's effects the flash-rate of conventional electro-mech flasher units.

We needed a new flasher unit anyway, as the one we took off was full of water. But, looking for a replacement, I discovered that a lot of 'LED' flasher units are simply re-tuned electro-mech units, just like the normal tungsten bulb ones.

This means that they suffer the same load dependent flash-rate problem. So, if you fit a tungsten bulb when an LED goes, they flash slow, just like fitting an LED with one tund for tungsten makes it flash fast.

We got an electronic flasher unit, becouse these are timed by a chrystal and a bit of smart electronics, and provided you get one thats rated high enough, will flash at a fixed rate no matter whether you have a Tungsten bulbs, LED bulbs or a mix of both.

But, we also got LED instrument bulbs for the dash-back-light and idiot lights. With Tungsten bulbs, each one draws almost as much current as the Stop-Lamp or side-light, and with five of them, switching to LEDs suggested a saving of about 15W, on thier own.

First of all, on the Super-Dream they are peanut bulbs, and can be fitted two ways round in the holder. With filiment bulbs this is not a problem, as they'll work both ways, but LED's are directional, so it was a bit of a faff pulling the bulbs, fitting the LED's, then checking the orientation, then checking which hole they go back into.

Now, up to this point all seemed well, but for some curiouse reason, the left hand indiactors were a bit 'dim'.... so I tried sorting out bad earth connections. This eventually entailed completely rewiring each indiactor and adding a seperate earth strap.

THEN I discovered that the tell-tale didn't light up with the right hand indicators, then all FOUR indicators started lighting up with the left hand indicators!

Wiring was traced back to the switch, resulting in the horn switch shorting & going off down my lug-ole at close range!

Eventually, With ALL wires buzzed out, and checked, all was as it should be, BUT, all four indicators, and the tell-tale lit up indicating left, but only the right indicators and no tell tale lit up indicating right!

Tracing the tell-tale wiring revealed the problem.

The Tell-Tale has NO earth!

It has two wires, one to each terminal of the tell-tale bulb. One is connected to the left indicators in parallel, one to the right, also in parallel.

With tungsten filliment bulbs, when you indicate left, puts volts on the left hand terminal, current flow through the bulb, and earth through the right hand indicator bulbs.... when you indicate right, puts volts on the right hand terminal, current flows from right to left and earths through the left hand indicators.

Current draw is small, and the voltage drop accross the bulb large enough that the 'off' side indicators that the bulb is earthing through, dont light up.

Until you fit LED bulbs!

And two things happen. First, the LED is directional, so only allows current to flow in one direction, so the tell-tale only lights up when you indicate left or right, but not both.

Second, the voltage drop is negligible, so theres still enough volts to light the LED bulbs on the 'off' side, and you get hazard warning lamps, instead of indicators!

Removing the tell-tale from the circuit got the indicators working as they should.

But no tell-tale. So I had the ingeniouse idea of wiring them into the common feed from the flasher unit. Unfortunately..... result continiousely flashing tell-tale! BACK to the drawing board.

I have come to the conclusion that I need a couple of diodes. One on each tap into the left and right indicator cicuits, pointing at one end of the indicator tell-tale, the other end redirected to a common earth, in order that current can flow from either indicator circuit to the tell-tale, but NOT through the other indicator circuit.

As schematics:-

Original Indicator Wiring
https://i178.photobucket.com/albums/w269/teflons-torque/Little%20Dreams/inds_1.jpg~original

LED Indicator Wiring
https://i178.photobucket.com/albums/w269/teflons-torque/Little%20Dreams/inds_2.jpg~original

A Trip to Maplin beckons!
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My Webby'Tef's-tQ, loads of stuff about my bikes, my Land-Rovers, and the stuff I do with them!
Current Bikes:'Honda VF1000F' ;'CB750F2N' ;'CB125TD ( 6 3 of em!)'; 'Montesa Cota 248'. Learner FAQ's:= 'U want to Ride a Motorbike! Where Do U start?'

[el_oso]

can you not simply use an LED for the dashboard light? i am however not sure if the filter on the dashboard will let through the wavelengths of light needed to get the colour on the dash.
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Duke 390
Previous: '05 XR125L | '96 XJ600S Diversion |'05 Suzuki GSXR1000 | '05 Honda CBR125-R | '97 YZF 600R Thundercat | '11 Honda CBR250
Car: Jeep Wrangler 4.0L

[Rogerborg]

Yup, you're correct about the diodes. I had to do the same trick when I replaced dual tell tales with a single one.

[Teflon-Mike]

[stinkwheel]

An anomoly I have pointed out to numerous people who then don't listen.

However, one of them came up with a simple and elegant solution. You need two LEDs for the tell-tale, one wired in each direction.

You can buy loose LEDs off ebay, ready wired up with a resistor and flying leads to run on 12V for very little money.

Either solder them directly into the wiring loom or, if you're feeling fancy, break the glass off an old bulb, solder the LEDs to the terminals therein and fill it with epoxy.

Similar to ebay item: 350228638603

EDIT: Picture added.
https://www.bikechatforums.com/download.php?id=75872
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“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[el_oso]

[stinkwheel]

[BradKlein]