Author Topic: Flashing LED Lights for Bicycle  (Read 7488 times)

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Offline WooferHound

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Flashing LED Lights for Bicycle
« on: May 13, 2018, 08:01:32 am »
The severe cold this last winter froze the engine in my van and I have converted completely over to bicycles to get around town for awhile. Am using a 50 year old Schwinn 10-speed as my main bike and just rebuilt an 18-speed Roadmaster as a backup bike for the occasional flat tire. Pedaling about 2.5 miles downtown to work which only takes me almost 15 minutes. While I am riding I have plenty of time to dream up improvements to make the ride safer and more comfortable. I would really like flashing LED lights all over the bike powered by the spinning wheels.

So the current idea is to attach a magnet to the spokes of the rear tire, then mount a coil on the frame where the magnet passes. This would flash the lights once everytime the tire rotates. Tried to make a test setup last night and it did not work as well as I thought it would.

The coil was a factory air-core choke with about 150 turns of very fine wire, maybe 26 gauge, and measures 1.6mh, it is about the diameter of a dime and 1/4 inch thick. The LED was a 2 volt red soldered directly to the choke without any resistor.
I started out with a magnet the size of a Quarter,  passing it by the coil  by-hand as fast as I could without any light produced. Then tried a 1 inch stack of magnets about the diameter of a nickle and still could not produce light. So I tried to use an 8 inch stack of 2x2x1/2 magnets leftover from building my small Wind Generator and produced some barely noticeable strobing  made from the fastest movement.

I really thought this would be enough to flash some LED lights.
What would be the best way to make this work ?
Was also thinking about using a Bridge Rectifier with it's voltage drop to extend the length of the flash and would probably need some kind of current limiting because of traveling at different speeds.
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Offline Wolvenar

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Re: Flashing LED Lights for Bicycle
« Reply #1 on: May 13, 2018, 08:45:46 am »
I get the DIY aspect, but with the cost of these super bright high visibility safety lights anymore, it's just easier and cheaper to grab a rechargeable super bright one online or from Walmart. ..

But, if you are still going to DIY.. I would rectify the output, add a cap to hold the charge for a tad longer on time of the LEDs.
Then add a proper resister and zener diode to limit the maximum voltage so it is predictable, use identical LED(s) in parallel if more than one and add the proper resistance to limit the current.

This is all with the assumptions you can get enough power from that setup, and that you want the LED to flash on for a short time only at the occasions it can source the power each time the magnet(s) come around from the wheel.
Trying to make power from alternative energy any which way I can.
Just to abuse what I make. (and run this site)

Offline noneyabussiness

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Re: Flashing LED Lights for Bicycle
« Reply #2 on: May 13, 2018, 12:50:30 pm »
Maybe try a non-polarized capacitor parallel with led.. but im with wolvenar , i doubt you will get enough juice...

Offline MadScientist267

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Re: Flashing LED Lights for Bicycle
« Reply #3 on: May 14, 2018, 01:48:06 am »
The coil is the main killer.

Air core has the least concentrated flux... You could stack those magnets until you're blue in the face, it's gonna be a diminishing ROI if the magnetic circuit isn't tight enough.

Achieving that isn't quite what it appears by simply "flipping an axial PMA inside out" with 1 magnet and 1 air coil (or even one on each side).

In an axial PMA, the flux is tightly controlled by the discs and magnets themselves, causing it to "beam across" the gap, which significantly offsets the inefficiency of the air core. In a situation like the bike, the flux is dilute and "flairs" out as it leaves the poles... maybe "aimlessly" is a decent word. Closing it up (look at the brakes for an immediate visual on my kneejerk thoughts) will help tremendously.

That's also an awful physically small coil. You're cutting the turns with a much larger diameter "slice of flux" than the coil, which just further dilutes it's potency and with that kind of difference in diameter, probably is even causing self-canceling effects. An air core coil doesn't have any means of directing the flux thru the center so it cuts more efficiently, so this won't work.

One more thought comes to mind for when it's on the bike... the rim, being steel, is going to also steal some of the flux and short it out... difficult to work around since you can't put a pair on either side even to gain a useful pole out of them, because of the brakes.

This is one of those "what works in the classroom needs performance tweaks before it's useful in the real world" deals. If you were looking to read RPM, I'd say you're on a reasonable path, sorta... Any kind of real power, no.  :-\

Steve
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Offline Pete

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Re: Flashing LED Lights for Bicycle
« Reply #4 on: May 14, 2018, 07:16:31 pm »
Hi Woof, a lot of small engines have a charging coil on them to charge their starting battery if they are electric start. You could get one of those coils and use it to run the LED,s. It does seem that a small rechargeable commercial light would be easier, but then easier is not so much fun is it.
You could also just try getting a piece of steel and winding your own  core on it. You are only looking for low current and low voltage after all.

Pete

Offline WooferHound

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Re: Flashing LED Lights for Bicycle
« Reply #5 on: May 18, 2018, 10:36:49 am »
I guess I had forgotten how hard it is to make useful power.
Now i am thinking I need to try and make a small magnetic circuit with 2 magnets and a U shaped piece of metal to carry the flux between them and through the coil.
Already starting to worry that the magnets will unbalance the tire. Want to avoid any iron cores so no energy is taken away from the rolling bike.
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Offline WooferHound

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Re: Flashing LED Lights for Bicycle
« Reply #6 on: September 25, 2018, 08:09:51 am »
I have a lot of time to think about it while riding the bike and I believe the solution isn't magnets & coils. It would be so easy to make Solar Bike Lighting. I might even have everything I need here already. Might want to get a battery specific to the purpose. Could start with a Solar Yard Light and work from there.
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Offline hiker1

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Re: Flashing LED Lights for Bicycle
« Reply #7 on: September 26, 2018, 11:03:12 am »
Stopped in a my local Home Depot..they had large hooded solar yard lites for a buck eighty...took one home ..let it charge all day...nice bright flood lite..burned all night...thought about hooking to bike as well....😜
just do it

Offline hiker1

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Re: Flashing LED Lights for Bicycle
« Reply #8 on: September 26, 2018, 11:08:12 am »
Should have grabed a few more..end of season sale..ILE buzz back ...pick up a few more..?
just do it

Offline WooferHound

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Re: Flashing LED Lights for Bicycle
« Reply #9 on: September 28, 2018, 08:59:20 am »
Stopped in a my local Home Depot..they had large hooded solar yard lites for a buck eighty...took one home ..let it charge all day...nice bright flood lite..burned all night...thought about hooking to bike as well....😜

That is too cool, almost perfect to add directly to the bike.

7761-0
I am going to make my Bike Lights from this Solar Garden Accent Lighting unit. In this picture I have pried the unit apart and you can see both the front and the back. Also disassembled a computer battery pack and got six 18650 Lithium batteries that are rated 3.6 volts at 2600 mah. The one in the picture has been running a Red & White LED for 12 hours.

The plan is to cut out the AA battery holders to make room to glue in the larger Lithium battery. The Solar panel measured 4.75 volts in full Sun so I should be able to put a diode inline so the battery will charge up to 4 volts. There will be a toggle switch on the handlebars to control it. There will be 10 LEDs total: 2 white facing forward,  2 white facing the road over both tires, and 4 red in a square pattern facing the rear. Fairly Tricked Out and very visible.
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Offline hiker1

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Re: Flashing LED Lights for Bicycle
« Reply #10 on: September 28, 2018, 05:35:05 pm »
Nice...post a few pics when mounted..the lights were sold out when I went back...dang...I new I should  have picked out a few more...thought maybe they were defective..at such a low price...😜 haven't built any gens in awhile...have a few ideas about another bike gen...never ends..😜
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Offline WooferHound

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Re: Flashing LED Lights for Bicycle
« Reply #11 on: October 02, 2018, 04:56:36 pm »
This project is coming along, mostly testing right now.

Open Circuit, the panel measures 4.75 volts at .125 ma.
Hooked the Solar Panel to a 1N4007 diode then to a 18650 Lithium battery.
Target charging for a lithium battery is 3.9 - 4.1 volts.
My battery was getting up to 3.5 volts. Was wanting more than that so I fished around and found a Schottky diode with a smaller voltage drop. Soldered that on there today and placed it back out in the Sun today to see if it bumps the voltage up a coupla points. As soon as I see how high the voltage gets with the Low Loss diode, I will do the calculations and order the LED-resistors for for this project and plenty more.

Have also cutout the backpanel for the battery. I already have all the Wire, LEDs, power switch and other stuff to put it all together. Current plans are to have 12 LEDs running totaling 240ma.
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Offline rossw

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Re: Flashing LED Lights for Bicycle
« Reply #12 on: October 02, 2018, 05:18:19 pm »
Woof, I don't wish to pick on you ... but cripes, can you check your work??

Firstly. you can't have a current flow into an open circuit.
Next, 0.125mA seems waaaay too low. Certainly too low to be any practical use.
If your LEDs are drawing 240mA, it would take you 80 WEEKS of uninterrupted full sun to charge your battery up enough for 1 HOUR of operation, at 0.125mA. And over that timeframe, the self-discharge would eat most of it up anyway.

1N4007 or even schottky diodes at those voltages are hideously inefficient. A tiny P-channel mosfet off ebay will cost you less than a 1N4007 diode, and when wired as an "ideal diode" will have virtually no voltage drop in this application.

Offline kurt

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Re: Flashing LED Lights for Bicycle
« Reply #13 on: October 02, 2018, 06:08:19 pm »
those batteries from the laptop pack are lithium cobalt batteries they really do not like being charged by anything other than chargers specifically designed for them and they have a tendency to get angry and explode and spit fire that will not go out when abused google lipo fire there are allot of videos of it. i would suggest spending a couple bucks and buying a few batteries of a safer chemistry to play with

might i suggest a couple of those aa size lifepo4 cells with built in over voltage and over discharge protection  be much safer
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Offline frackers

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Re: Flashing LED Lights for Bicycle
« Reply #14 on: October 02, 2018, 06:26:01 pm »
I'd recommend one of these between the solar cell and the lithium cell
https://www.aliexpress.com/item/5V-1A-Micro-USB-18650-Lithium-Li-Ion-Battery-Charging-Protection-Board-Charger-Module/32809897126.html
Its what I used on my weather station and apart from 1 week in the middle of winter has provided 24/7 charge from a 1w 6v panel for over a year now.
Almost the same price as a diode!!

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