Upgrading Instrument to LEDs

[pschuyler]

I have decided to replace the indicator lamps with LEDs, mine are dim and two are burnt out.







Here is the full article if your interested.

http://schuylerbeemer.blogspot.com/2...g-on-tach.html

[kstoo]

You are my hero. I have wanted some help with this for a long time.

[criminaldesign]

i like that. and after i just replaced the bulbs.

[toooldtocare]

Nice idea.. Question about the alternator though, I thought it was also tied to the charging circuit, that if it burned out the alternator would not output voltage because the field current flows through it? Did you check to see that it is still charging? Your write up stated that it is the only tied to a failure, so you had to watch it.

Next time my bulbs let loose, I am going to do this upgrade, thanks.

[pschuyler]

What I meant in the writeup is the bulb can fail and you have no warning that the charging system is not working. Sine these LEDs have such long life I'm not too worried about it failing, but I will check that the alternator is still charging upon usage. I kept all the old bulbs in the tool tray in case of emergency, minus the burned out ones.

Thanks for the reply.

[toooldtocare]

Here is why I question the LED in the charging circuit. LEDs consume very little power and I think act as other diodes, that is only allow current to flow in one direction.

According to the Haynes manual, ÔÇ£The charging system consists of a 12-volt three-phase alternator which has a rotor fixed to the front of the crankshaft, rotating within a stator screwed to the crankcase. The rotor is not permanently magnetized, energizing current being supplied by the charge warning lamp circuit via two brushes bearing on slip rings.ÔÇØ

If a small amount of current does not flow through the bulb (not enough to light it) to energize the rotor, the alternator may not put out current. It is easy to test, just put a voltmeter on the battery when the engine is off, then running. Of course, the voltage when running will be much higher, 13.5 to 14.5 volts is normal.

Thanks for experimenting with this.

[kstoo]

Choices:

• Don't replace the incandescent bulb.
• Replace it with an LED and add the resistor.

Snobum article
If you think that the charging light design is weird, my first bike, a Gilera 124, was designed so that you could not start it if the taillight or brake bulb was burned out.

[toooldtocare]

Snobum article[/URL]
If you think that the charging light design is weird, my first bike, a Gilera 124, was designed so that you could not start it if the taillight or brake bulb was burned out.[/FONT][/QUOTE]

So was my first bike, 64 Ducati Mark IV Scrambler. Had a toggle switch on the tail light, and another one on the headlight. Purpose, to by pass the filament in the bulb (which acted as the ballast resistor) to send mag power to the plugs. If the engine quit, flip the switch and try a restart.. Sold the bike because it quit often.

[pschuyler]

I appreciate the feedback on the Generator Light, looks like I have two options, bypass it with a resistor, Motorad Electrik actually sells this device, or go back to an incandescent bulb.



The bypass circuit is $3.50 , and the bulb .99, so either option is not going to brake the bank. Thanks for all the replies.

Here is the link for the bypass, or you can make your own from Radio Shack parts.

http://www.motoelekt.com/genlightacc.htm

[toooldtocare]

The nice things about LEDs, they seldom fail. What causes them to fail is too much forward current, and if their internal current limit resistor is correct, that is almost never. Thus, I like the idea of using LEDs like you used.

My bike (78 R100RS) has the voltmeter, so the warning light is meanless. But, the bike is also 32 years old and things are not like they used to be. Thirty-two year old bulbs and wiring are not the most reliable, so I think I will add the 330 ohm bypass when I do my LED mod.

Question is, I know you must put it in parallel with the LED, but where is the best place. Let us know how you do yours. I know Motorad Electrik probably tell you the best place when you buy it. This is so simple I will make my own.

Thanks,

[20774]

Question is, I know you must put it in parallel with the LED, but where is the best place.

kstoo provided the link to Snowbum's article which discusses the placement of the resistor.

http://www.bmwmoa.org/forum/showpost...04&postcount=7

[toooldtocare]

kstoo provided the link to Snowbum's article which discusses the placement of the resistor.

http://www.bmwmoa.org/forum/showpost...04&postcount=7

Sorry, missed that, thanks.

[mymindsok]

Soooo....

If you use the bypass, does that mean that you get no warning light is the rotor fails or will the LED light up as does the stock incandescent bulb?

If the LED lights up, I"M IN!!

[20774]

The way I understand it is that it works the other way. If the incandescent bulb fails, you'll still get charging. It would seem that in the case of the LED, you might actually need the resistor mod in order to compensate for the lack of proper resistance that the stock bulbs offers.

But if the rotor fails, then there should be a differenial voltage on either side of the bulb (or LED) and it should light.

[amiles]

The nice things about LEDs, they seldom fail. What causes them to fail is too much forward current, and if their internal current limit resistor is correct, that is almost never. Thus, I like the idea of using LEDs like you used.

My bike (78 R100RS) has the voltmeter, so the warning light is meanless. But, the bike is also 32 years old and things are not like they used to be. Thirty-two year old bulbs and wiring are not the most reliable, so I think I will add the 330 ohm bypass when I do my LED mod.

Question is, I know you must put it in parallel with the LED, but where is the best place. Let us know how you do yours. I know Motorad Electrik probably tell you the best place when you buy it. This is so simple I will make my own.

Thanks,

The warning light for the alternator is not meanless or meaningless. If the filament fails you will not have charging until it is replaced, of course your meter will tell you this as well. The resistor will provide charging weather or not the filament is functional.