Power LED Backpack Lighting system

introPower LED Backpack Lighting system

There have been many LED instructables, so I will mainly focus on what's different about mine and leave you to fill in the details by reading elsewhere. I won't go into calculating resistor values, series vs. parallel, or things like that. Partially because I did this a while ago and don't remember some of the stuff.

First, the rationale: I don't want lights on my bike because they're theft magnets, are more fragile, and more cumbersome. I want a single battery pack that powers a tail light and one or two headlights, and I want to turn it all on or off with one switch. The backpack is the best way to go for me, since I also like to carry my lock in the backpack anyway and always have it with me.

I used two Luxeon Rebel Stars (145 lumens @ 700mA) for the headlights, and two Luxeon III red-orange side emitters for the tail light. I made a little 555 timer circuit (google it) and encased it in epoxy, and rigged up a switch so that the tail light is always blinking, but the headlights can blink or be solid. Due to my electronics half-assery, the headlights actually blink very slightly when "solid." You can't really tell when riding, though.

I went the resistor route instead of using a buckpuck, which I somewhat regret. A buckpuck is especially cool because you can later upgrade to a Li-ion battery pack (much more convenient to charge, and lighter) and it'll still work the same even though the input voltage is different. And it wastes less juice and thus produces less waste heat.

The switches I used are waterproof E-Switch 100AWSP1's, mouser part # 612-100A-A1422 / manuf. part # 100AWSP1T1B4M2RE.

A good place to go for 555 circuit:
http://www.instructables.com/id/EP8RPXKLVPEXCFLXNH/

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step 1Wiring

I thought it would be really cool to make all of the wiring really modular so that I could add/remove the blinky circuit or switches or lights or whatever down the line... but the sheer number of connectors needed ended up being ridiculous and I wouldn't do it that way again. It would be much cleaner and more robust to put the blinky circuit and the circuit to connect the battery/switches/blink all together in one little box, and then just plug the battery and lights and switches into the box.

I also used fairly heavy gauge speaker wire which made it a little more clunky than necessary.

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14 comments	Add Comment

Feb 18, 2010. 11:14 PMUOS says:

Cool idea, thanks!

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Sep 7, 2009. 11:16 AMH3xx says:

I'm surprised nobody's gone there yet but... BULLY BLINDERS!!! The gooneis were the first thin to come to mind...

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Jun 7, 2009. 2:17 PM

Udon says:

I like it. Clunky is good. I'm planning on building a backpack power/lights/charger/... thing, but I haven't thought of where everything would actually go. This instructable helps.

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Apr 18, 2009. 8:46 AMlavert31 says:

Hello, It's look neat and full light. about the star, did you use current regulator or just connect each star directly to the batteries? Etay

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Apr 15, 2008. 4:04 PMinsanityideas says:

Thanks for drawing attention to how simplified you can make the LED bike light... many people seem to fret endlessly about keeping water out or having huge heatsinks. didn't realise JB Weld was non-conducting. I have a question... did you find that the 555 timer was ok with switching two Luxeon LED's?? Thats quite a lot of current for a 555 to be passing and switching!! Or does it tend to act as a built in current limiter?

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Apr 15, 2008. 4:53 PMmackstann (author) says:

I linked the timer up with a transistor that could handle some huge amount like 60w. I don't remember where I saw how to do this but it's pretty simple. Basically, the high current goes through the transistor and the timer circuit just switches it on and off. You might also be able to use a relay for the same thing.

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Oct 24, 2008. 12:09 PMCalifflorida says:

Is the tail light daytime visible?

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Oct 24, 2008. 4:07 PMmackstann (author) says:

Yeah definitely. It's as bright or brighter than any other blinky I've seen. I haven't really done many side by side comparisons though.

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Aug 17, 2008. 1:10 AMbullet_proof says:

Does anyone have any more detail on how to do this? I've got a spare white luxeon and want to turn it into a forward-facing blinking light running at, say 500ma - but all the 555 chips I've found max out at 200ma. I've looked around but as I'm clueless with circuit design, I might have missed the configuration mackstann pointed out.

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Aug 17, 2008. 6:47 AMinsanityideas says:

I recently did this with a 555 timer, have not got round to doing a proper write up, but I can give you the quick answer. You need to connect a mosfet to the output of the 555 timer, and then use the mosfet to switch the LED on and off. The mosfet must be rated at a high enough current for your use (most are). Connect the source pin on the mosfet to the negative pin on the LED, the Drain pin on the mosfet to the negative rail for the circuit, and the gate pin of the mosfet to a 100K Ohm resistor which is connected to pin 3 on the 555 timer. You could also do this with a regular transistor, assuming you can find one that will switch 500ma or above. You don't need a heatsink on the mosfet, but you will need a way of limiting current through the LED, any of the circuits for controlling Luxon LED's will work.

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Apr 16, 2008. 3:23 PMinsanityideas says:

Yes I was planning to use a suitable transistor, was just checking to see if you had successfully bodged it without. I intend to use a decade counter IC (basically has 10 output pins and advances an "on" signal through each of them in turn in response to a timer pulse) to generate a custom flash pattern rather than just a regular on and off. Was thinking something like flash, flash, long pause, flash. Want to use a high speed time signal so its more of a strobe than a flasher, which would prevent the use of a relay.

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Aug 24, 2008. 3:25 PMcurlyfry562 says:

Sounds like you are using a 4017 decade counter. They are really simple to use, just google 4017 tutorials and you will find plenty of info. Good luck

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Aug 25, 2008. 7:00 AMinsanityideas says:

I was going to use a 4017 decade counter, but in the end used two 555 timers to create the effect I wanted. The first timer has a long on-off cycle which turns on the second timer which has a very quick on-off cycle. The output of the second 555 timer switches a MOSFET to turn on and off the LED's (as they exceed 200ma power draw). In retrospect this was much easier than messing around generating a time signal for the 4017 and then deciding on a pattern of on-off's, because I didn't require a specific flash pattern and the 555 timers allowed me to vary the duration of the "on" and "off" phase of the flash more precisely (using 4 variable resistors). The 4017 would be more suitable for people who want a particular 10 step flash pattern and less control over length of flash pulse (as this is always tied to the clock pulse). A 555 timer can be used to generate a timer input for the 4017. And your right the 4017 is easy to use... does exactly what it says it does!

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Aug 15, 2008. 4:32 PMcurlyfry562 says:

Cool idea with the backpack straps. I simply can't get over how efficent and bright the rebels are. By the way they have introduced the optics

http://www.ledsupply.com/db-opml-3-025.php

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