Homemade *bright* LED light setup

[Haku]

3mm LEDs arrived today, 10x red, 50x white. We're gonna need a bigger bag of white LEDs...

After doing some drilling today on the original reflector to actually determine how many 3mm LEDs I could comfortably embed into it I discovered I can get 60. Yes, 60, 6 rows of 10 holes drilled in the reflector won't adversely affect the structural strength of it and it will still partially work as a reflector:



You can see the test row of 5 holes on the right, then test row of 6 on the left and a partial grid in the center. It's going to be well over 3x the brightness of my present 17x 5mm LED setup which enables me to see along unlit paths/roads quite easily, I love cycling at night so things are going to be even more fun!

[Grandad]

Haku, Haku burning bright.

In the middle of the night.

Just watch out for Mr Plod.

Blinded by the sight of mod.

If he catches you just once,

He might bop you on your bonce.

[Merv]

Originally Posted by Haku

3mm LEDs arrived today, 10x red, 50x white. We're gonna need a bigger bag of white LEDs...

After doing some drilling today on the original reflector to actually determine how many 3mm LEDs I could comfortably embed into it I discovered I can get 60. Yes, 60, 6 rows of 10 holes drilled in the reflector won't adversely affect the structural strength of it and it will still partially work as a reflector:



You can see the test row of 5 holes on the right, then test row of 6 on the left and a partial grid in the center. It's going to be well over 3x the brightness of my present 17x 5mm LED setup which enables me to see along unlit paths/roads quite easily, I love cycling at night so things are going to be even more fun!

Hi Haku, Like your idea using Led's. I should include a fuse in one of the lines though as they can go short circuit, specially when driven hard! Another point worth knowing... The "Pound Shop" sell LED camping lights_ 24 very very bright led's in a circular plastic housing. All you need do is to carefully remove them from the PCB. That's what I call real value for money.

[Haku]

The reflectors I bought from sjscycles.co.uk arrived today, 2x Cateye front reflectors (only ordered one bracketed but both arrived bracketed) so I had a spare in case I screwed one up, and a Cateye back reflector which I only threw into the order because it was cheap and might have been good on my bike except for the mounting block on the back sticks out quite far and the setup I have for the back light/reflector (shown in the first post of this thread) is much thinner.

I managed to steal 15 mins on a milling/drilling machine today so:





Merv, the LEDs won't be directly powered from the bike battery's voltage but through a 5v regulator, then the LEDs will be powered in parallel sets of 3 with a current limiting resistor. The regulator will have a fuse between it and the bike battery so it'll blow if anything shorts, a rough estimate showed I'll need probably 1.5A at 5v to power all the LEDs.

[Haku]

Received the 33ohm resistors just before the weekend so I stuck 60 LEDs on a breadboard with 1 resistor per 3 in parallel and gave it 5v (all 60 LEDs with resistors took about 1.1A at 5v), the amount of light coming off them was brighter than an energy saving bulb that's rated at 60 watts light output! testing it outside in the dark it was somewhat unreal how clearly you could see everything. I ran them for about 36 hours straight and none of them flickered, dimmed or died, a few looked marginally dimmer than the rest but you can't expect cheap LEDs to manufacturered to a high standard.
Whilst the burn-in test was commencing I glued in the 60 LEDs, don't like working with superglue but it was the best type to stick them in with:



What doesn't show up in the images is how the reflector has gone a little 'milky white' because of the superglue, meaning it works even less as a reflector than before I glued the LEDs in but it's function now is to be a bike light in disguise so that's ok. I'm halfway through bending/cutting/soldering the 120 individual LED legs and should have them finished by tomorrow.
As well as gluing in the front light I set-to and did two duplicates of the back light you can see in the first post.

[john]

Originally Posted by Haku

Received the 33ohm resistors just before the weekend so I stuck 60 LEDs on a breadboard with 1 resistor per 3 in parallel and gave it 5v (all 60 LEDs with resistors took about 1.1A at 5v)

Isn't it better to put strings of LED's in series and use a resistor for each string rather that putting the LED's in parallel? That way you can ensure that each LED gets the same current.

[Jeremy]

Yes, it's a lot better to use series strings. The plus points are that there's no need for a voltage regulator at all, the overall system efficiency will be higher and the LED brightness will be well-matched, with very little variation from one LED to the next.

Each white LED will drop around 3.5 volts or so, which means that around 8 LEDs can be used (with a single series resistor) on 36 volts (allowing for the lowest likely battery voltage), or 12 for a 48V system. The individual series strings, with series resistors, can be connected together in parallel.

For 60 LEDs on 36V, then maybe ten strings of six LEDs, with just ten series resistors, might be best. The current drawn would be around 300mA, for 30mA per LED.

Jeremy

[robertozm]

Originally Posted by Haku

Today I received the Adjustable Step Down Regulators, I'll only need one for this project but it's such a useful device I bought a spare, they can take up to 30v input so fine for 24-26v batteries but unfortunately no good for 36v battery setups. But the nice thing about using one of those DC-DC converters for your LED setup is you don't have to use your bike battery, you can easily use a 6 or 8 cell battery pack instead without having to re-calibrate the voltage going to the LEDs as the DC-DC converter outputs the same voltage for the LEDs no matter what the input - so long as it's higher than the voltage used for the LEDs plus 1.3v, so powering 3.4v LEDs you need a minium of 4.7v input.
Another good reason (besides simpler wiring for the LEDs) for using this DC-DC converter is that your lights will remain the same brightness when your bike's battery runs low, I ran mine completely flat recently to help cycle the individual cells inside (battery's running better now), my prototype front light setup remained bright even when the battery could hardly power the motor.

The small black box I'm using to house the switch and the DC-DC unit is from Maplins, part number N78BQ, it's not rated as waterproof but running it under the tap didn't show any leaks, I had to completely submerge it in water and shake/tap it before a couple of drops got in - so I'd say it will be fine for rainy conditions with a little extra care when making it. It will be mounted on the handlebars with the mounting that came off the reflector as my bike already has a reflector mount that goes on the forks.

The switch is also from Maplins, it's a Sub-Min Toggle E as I had it already but the A type is all that's needed, I'll be getting a waterproof cover for it when I can next get over to the store.

Hello Haku:
I am new in this forum as in electronics, so if I ask something really stupid do not be to surprise, since I have not a clue about electronics, BUT I am on an Ebike "experiment".
I have bought from goldenmotor the kit and also a battery of 36volt 15amp, and I would like to feed my lights from this battery.
I have been looking to the switching voltage regulator and the limit is 30volt, is any way I could solve this? May I used some of them in parallel or series?
If I buy from ULTIMASTORE - Energy Saving Lamps, LED'S, LED and put a few of them in parallel will it work?

As you can read I am completely lost, and any comments will help me a lot.
Thanks

[john]

Originally Posted by robertozm

If I buy from ULTIMASTORE - Energy Saving Lamps, LED'S, LED and put a few of them in parallel will it work?

As these are rated at 12V, you can simply put 3 of them in series and connect them directly to your 36V battery.

They will however dim a little as the battery runs down so you could do what I have done and put 2 in series with a regulator (LM317T - these only cost pennies).

BTW I now use MR16s from here eBay UK Shop - IT Global Solutions: Lighting, Radiator as I find them more directional and so give a better beem although they are more sensitive to voltage drop.

[robertozm]

Originally Posted by john

As these are rated at 12V, you can simply put 3 of them in series and connect them directly to your 36V battery.

They will however dim a little as the battery runs down so you could do what I have done and put 2 in series with a regulator (LM317T - these only cost pennies).

BTW I now use MR16s from here eBay UK Shop - IT Global Solutions: Lighting, Radiator as I find them more directional and so give a better beem although they are more sensitive to voltage drop.

John THANKSSSSSSSSSSS