LED upgrades on Motorcycle

[JohnD]

I am in the process of changing the tail lights on my motorcycle for LEDs. It's something i've been thinking about for sometime now. i haven't any experience with electronics but am willing to give it a go. I bought myself 40 ultra bright clear LED and 10 resistors. The guy who sold me the LEDs said i should wire them in a series of 4! Does this sound like the best approach to take? What are the advantages of wiring them in series as opposed to parallel?
I originally intended the LEDs to be the stop lights on the motorcycle but recently noticed on a car that the stop lights and running lights appeared to be the same! Does this sound plausible? I would like to use the same LEDs for both purposes, is there a way, perhaps use different resistors for the stop lights to increase the intensity of light!!! Sorry now i'm babbling. Any advice would be appreciated. Thank you.

 

[Boncuk]

LEDs on motorbyce

Hi JohnD,

assuming the LEDs are red you can connect as many as 6 LEDs in series. The advantage of series connection is: only one current limiting resistor for six LEDs (single LEDs require one current limiting resistor)

Further assuming a forward voltage of 1.8V per LED the total forward voltage for six LEDs will be 10.8V (6 X 1.8). Another assumption is 13.8V from the generator if the engine is running. So there are 3V left to "kill".

Depending on the forward current of the LEDs you must calculate the current limiting resistor as follows: R=UBat (13.8) - UF (forward voltage 10.8)/forward current. E.g. forward current is 20mA, the resistor has to have a value of 150 Ohm (13.8V-10.8V/0.02A). The power across the resistor also has to be considered: P(Watt)=UXI, P=3X0.02 = 0.06W or 60mW. A standard resistor can carry a load of 250mW. So this type will do for your purpose.

To dim the rear light to see the difference between normal rear lights and brake light just increase the resistor to 240 Ohm and use full brightness for the brake light (150 Ohm).

Theoretically you could use 7 LEDs in series, but with no generator active chances are bad to see any LED.

Kind regards

Hans

 

[JohnD]

Hans thankyou very much for the information. now that i know i can use the same LEDs for the running lights and brake light, which is fantastic news, i now have another problem. If i have my running light on and i apply the stop lights i now have 2 reistors being applied to the LEDs (The running light resistor and the brake light resistor). Could this cause problems or do i have to compensate for this and make allowances for the running lights resistor. Would a relay work? Preferably i'd like to keep this as simple as possible

Thanks again

John

 

[fingaz]

Hi John,

Try looking at the schematic here : https://www.redcircuits.com/Page85.htm

This is probably the most simple way to do what you want.

Hope it helps.

 

[k7elp60]

Hi John,
If it were me I would try to replace the existing incandescant bulbs with LED replacements. Here is a website that might help.
http://www.superbrightleds.com/carbulb-notes.htm
Ned

 

[audioguru]

Many LEDs have a viewing angle that is too narrow to be used on a motor vehicle. Other LEDs are too dim or have the wrong value current-limiting resistor that makes them too dim.

That is why it is illegal to change the lights on a motor vehicle in Canada.

 

[Hero999]

Hans thankyou very much for the information. now that i know i can use the same LEDs for the running lights and brake light, which is fantastic news, i now have another problem. If i have my running light on and i apply the stop lights i now have 2 reistors being applied to the LEDs (The running light resistor and the brake light resistor). Could this cause problems or do i have to compensate for this and make allowances for the running lights resistor. Would a relay work? Preferably i'd like to keep this as simple as possible

Thanks again

John

The problem is, they won't light when the battery voltage drops below 11.4V (assuming 1.9V per LED) and most lead acids are rated to discharge to about 10V.

Using four in series seems sensible to me - I wouldn't go over five tops.

 

[JohnD]

Thanks for all the advice guys.
Fingaz i'm going to use the schematic on your link. I havent the experience to construct my own circuit and though yours looks pretty complicated at least it should work.
By the way which part of Derbyshire are you from? I lived just outside Derby for 3 years. A very beautiful part of the country.

 

[k7elp60]

Many LEDs have a viewing angle that is too narrow to be used on a motor vehicle. Other LEDs are too dim or have the wrong value current-limiting resistor that makes them too dim.

I agree with you. Here in the USA a lot of things are going to LED's Most intersection lights now are a big array of LED's and replacements for a lot of auto bulbs are availible.
My self I have not found any LED's to use in place of regular incandescent bulbs for reading.

 

[fingaz]

By the way which part of Derbyshire are you from? I lived just outside Derby for 3 years. A very beautiful part of the country.

I live near Ripley. yeah, it's a nice place to live. I can think of much worse places I could be

I used to live on the Sussex Downs, another great part of the country to live in.

Glad the schematic helped anyway. If you have any problems with it, post on here and someone will surely help you out.

 

[Nigel Goodwin]

I live near Ripley. yeah, it's a nice place to live. I can think of much worse places I could be

As you're down Ripley, do you know where 'Lumb Farm' is?, I've got to take my wife there tonight

 

[fingaz]

As you're down Ripley, do you know where 'Lumb Farm' is?, I've got to take my wife there tonight

Yeah, I know it. Been there a couple of times. It's not far out of ripley, heading towards denby. . .

 

[Nigel Goodwin]

Yeah, I know it. Been there a couple of times. It's not far out of ripley, heading towards denby. . .

Been there, just got back - found it no problem - thanks.