Fred H.
Well-known member
I was bored today (too hot to ride) so I went out the garage and made up some taillights for my new Givi out of some sample LEDs Lumex sent me.
(Full photo gallery here: https://www.pbase.com/fredharmon/giviv46 )
They worked out pretty nice. I used a Jumbo 5000mcd from Radio Shack (groan) for the tail lights, surrounded by two Lumex 3500 mcd on either side for the brake lights. The Lumex are actually much brighter and have a wider viewing angle than the Radio shack, which is why they are used for the brakes, as they would be way too bright for the tail lights. The larger Jumbo Radio shack makes a larger footprint of light at a less intensity so these were perfect for the tail lights.
I had to do some experimentation with an amp meter and different resistors and configurations to get the current within the spec for the LED's and adjust the brightness where I wanted them to be. I wired them in series in banks of four each as this reduced the necessary wattage for the resistor quite a bit. There is a good site for calculating resistors for LED's here if you ever need to do this:
https://metku.net/index.html?sect=view&...dcalc/index_eng
One thing you have to be careful of is not setting them to the max current/voltage drop spec, as that is not intended for steady operation. Read the spec sheet on the LED carefully and adjust the current for the normal steady state rating.
I used hot melt glue to position the LED's and bent the leads over the Givi lens assy, and solder tacked small wires on each one and then wired it up. I had to fuss with them several times to get them all aimed properly and in the same way so they weren't all off at different angles. Once I got them aimed and wired up, it all works great. I am surprised how intense these Lumex LED's are, so much so that I placed an order for more of them.
The LUMEX LED part number is SSL-LX5093SRC/E and you can order them from DigiKey for about 50 cents each. I used them in two banks of four in series with a 200 ohm resistor. You can't put all eight in series as they won't be bright enough, so you have to make two banks wired in parallel, and each bank should have it's own 200 ohm 1/4 watt or 1/2 watt resistor (1/2 watt is better).
The Radio shack Jumbo LED is Radio Shack part number 276-086. They were about $3 each (ouch!), though I suspect you could do some research on the LUMEX site and find the same thing for a lot less through DigiKey. I tried several resistor values to get the brightness/current draw I wanted (under 20mA) and finally settled on 330 ohms with 4 of these LED's in series. That gave me about 17mA. I could have reduced the resistor to about 250 ohms but that would have put the LED's near their max steady state rating of 20mA (the absolute max is 40mA). I may go back and reduce that 300 ohm rating to make them a bit brighter if they look washed out in sunlight. Another consideration is the contrast between brake and tail lights, and if you make the tail lights too bright, then you won't be able to see enough difference when the brake lights come on, so you have to compromise some on tail light brightness.
It really helps the rear visibility of the bike and works like a high mounted brake and tail light, getting the light up at more of an eye level with drivers.
Tail lights only
Tail and brake lights (Those Lumex LED's will burn holes in your retinas)
(Full photo gallery here: https://www.pbase.com/fredharmon/giviv46 )
They worked out pretty nice. I used a Jumbo 5000mcd from Radio Shack (groan) for the tail lights, surrounded by two Lumex 3500 mcd on either side for the brake lights. The Lumex are actually much brighter and have a wider viewing angle than the Radio shack, which is why they are used for the brakes, as they would be way too bright for the tail lights. The larger Jumbo Radio shack makes a larger footprint of light at a less intensity so these were perfect for the tail lights.
I had to do some experimentation with an amp meter and different resistors and configurations to get the current within the spec for the LED's and adjust the brightness where I wanted them to be. I wired them in series in banks of four each as this reduced the necessary wattage for the resistor quite a bit. There is a good site for calculating resistors for LED's here if you ever need to do this:
https://metku.net/index.html?sect=view&...dcalc/index_eng
One thing you have to be careful of is not setting them to the max current/voltage drop spec, as that is not intended for steady operation. Read the spec sheet on the LED carefully and adjust the current for the normal steady state rating.
I used hot melt glue to position the LED's and bent the leads over the Givi lens assy, and solder tacked small wires on each one and then wired it up. I had to fuss with them several times to get them all aimed properly and in the same way so they weren't all off at different angles. Once I got them aimed and wired up, it all works great. I am surprised how intense these Lumex LED's are, so much so that I placed an order for more of them.
The LUMEX LED part number is SSL-LX5093SRC/E and you can order them from DigiKey for about 50 cents each. I used them in two banks of four in series with a 200 ohm resistor. You can't put all eight in series as they won't be bright enough, so you have to make two banks wired in parallel, and each bank should have it's own 200 ohm 1/4 watt or 1/2 watt resistor (1/2 watt is better).
The Radio shack Jumbo LED is Radio Shack part number 276-086. They were about $3 each (ouch!), though I suspect you could do some research on the LUMEX site and find the same thing for a lot less through DigiKey. I tried several resistor values to get the brightness/current draw I wanted (under 20mA) and finally settled on 330 ohms with 4 of these LED's in series. That gave me about 17mA. I could have reduced the resistor to about 250 ohms but that would have put the LED's near their max steady state rating of 20mA (the absolute max is 40mA). I may go back and reduce that 300 ohm rating to make them a bit brighter if they look washed out in sunlight. Another consideration is the contrast between brake and tail lights, and if you make the tail lights too bright, then you won't be able to see enough difference when the brake lights come on, so you have to compromise some on tail light brightness.
It really helps the rear visibility of the bike and works like a high mounted brake and tail light, getting the light up at more of an eye level with drivers.
Tail lights only
Tail and brake lights (Those Lumex LED's will burn holes in your retinas)
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