Lights-Lumens, Lux, Watts, Candlepower...HELP!

[MikeL]

Thanks to this thread I got an Ixon IQ yesterday. Now that it is charged and dark I took it outside to see what it is like. Jaw dropping! I thought my halogen cateyes from a few years ago were bright, but this makes them look like christmas tree fairy lights.

If the blackburn mars 4 that should be arriving on Monday is half as good I'll be very pleased.

[bikefish]

Great thread -
Andrew - you wrote about the best LEDs - any examples of best and worst ?.
In Asia these alloy single LED torches usually come with a handlebar mount - starting from costing about 2 pounds (for the Tesco type) up to maybe 6 pounds for a magnifier lens (that focusses spot to flood) and has a "4core Cree" 3W on th e label.
The thing is the sellers will demo used ones which are real dim (and will sell em cheap too). So is this just poor quality control or do these LEDS fade in use ?

[Mike McGeever]

The AUK site has lots of good info about lighting.
They would wouldn't they, with all this long distance stuff.
And this being London- Edinburg-London year-max time 116.5 hours!
LTG Guru Francis Cooke sometimes does reviews in ARRIVEE the AUK in house magazine.

[insanityideas]

Have there been any significant improvements in cost/performance of the components in the last year ??
I didn't get round to building a front light last year - mainly due to the confusing number of options available.
Hopefully I can sit down a study my way through the maze during the long nights this winter.

I havn't felt the need to upgrade the LED's in my lights since I built them, as I finally got to the point where they were bright enough and practical enough for my needs, but I did have a look at LED's for a different project I was working on. There doesn't seem to be any "new" high power LED out there, although prices have gone down, so its easier to get the most efficient high power ones. Looking at commercial lights they seem to only be getting brighter by the use of more LED's. They all use Seoul Z-LED P4's or Luxeon 3w. http://www.dotlight.de have these at 7.95 Euro each which is a bit cheaper than they used to be.

My current bike light upgrade plans are replacing the simple flashing circuit with a microcontroler so I can get battery level information, greater efficiency and more consistent flash rate (moisture and temperature affect the circuit timings). I am also considering making a Li-ION battery pack, but that is still quite expensive and requires more care than standard AA rechargeables. Using a Li-ION battery pack would double power capacity and give a 2hr fast charge but needs careful construction to be safe. Right now I am making a battery test circuit just to see if my 2 year old 2500mah batteries really have that much capacity at 700ma discharge rate... the answer to that might make my mind up.

If you are considering a build your own I can recommend the relevant components to make your own variable output high efficiency constant current driver for the LED's that costs about £2 for parts from maplin as opposed to the £10-20 for a commercial driver. A good quality driver circuit is what makes lights work reliably, brightly and efficiently.

[Graham]

If you are considering a build your own I can recommend the relevant components to make your own variable output high efficiency constant current driver for the LED's that costs about £2 for parts from maplin as opposed to the £10-20 for a commercial driver. A good quality driver circuit is what makes lights work reliably, brightly and efficiently.

Thanks for the update - very useful.
A home made driver would be fun. Go on spill the beans . . . . in a descriptive and prescriptive way ( the only chance I have for it to make sense ).

Edit : I have just found the "How to make your own LED lighting" topic, from last year, and referenced to it in the "Too good to lose - Technical" section. Linked here also.

[kwackers]

If you are considering a build your own I can recommend the relevant components to make your own variable output high efficiency constant current driver for the LED's that costs about £2 for parts from maplin as opposed to the £10-20 for a commercial driver. A good quality driver circuit is what makes lights work reliably, brightly and efficiently.

Thanks for the update - very useful.
A home made driver would be fun. Go on spill the beans . . . . in a descriptive and prescriptive way ( the only chance I have for it to make sense ).

Edit : I have just found the "How to make your own LED lighting" topic, from last year, and referenced to it in the "Too good to lose - Technical" section. Linked here also.

A decent home made driver would use a microcontroller. There are several different one's that would work well, in the past I've done all the required stuff in one single 8 pin chip. This includes battery charging/checking, LED 'chopped' supply, various flash modes, PWM for brightness control, special flash mode for low battery (so it degrades gracefully).
Not all in the same box I should add, although it should be fairly trivial to bundle them all together.

Trouble with microcontroller code is it doesn't make for good reading being neither descriptive or prescriptive...

For those interested I'd recommend a good trawl through the various technical reference docs available by their manufacturers. (I use PIC's - Microchips website has lots of useful resources which are well worth a read.)

[insanityideas]

I use the ST Microelectronics L200C adjustable voltage and current regulator. As I said you can buy this through maplin, I am sure there are other regulators from different chip manufacturers that work exactly the same if you have trouble finding this model. Use the Programmable current regulator circuit in the technical data sheet, you will require two small ceramic capacitors and 1 resistor, the resistor allows you to set the desired current. It is a switching regulator so its very efficient, and it has built in overheat, overcurrent etc protection so its very hard to destroy. The formula for the resistor value is: output current in A = 0.45/value of resistor.

All the info and datasheet: http://www.maplin.co.uk/Module.aspx?ModuleNo=8064

As mentioned by kwackers you can do things with microcontrollers, but for just controlling current to an LED it would be overkill and requires more components. With the L200C you can get several different brightnesses by using a switch to change the value of the control resistor. The L200 can also be used in conjunction with a PWM to control brightness, just set it to the maximum power and then turn it on and off with a suitable transistor to achieve PWM.

[Graham]

Sorry, I'm still stumbling about with this one and it is all pretty basic (probably).

Which is the most suitable L200C package - pentawatt or LC-3 ? Does it matter ??

What type of board would I mount it on ? Clip-in or solder ?

What type of switch would be suitable to give variable resistance equivalent to OFF, LOW, MED, HIGH

PS. I will be using a 13.2V Lumicycle NiMh battery pack, so that's driving 3 *P4s.

[Kirst]

Cycle forum yacf tested out a variety of lights last year by mounting them on a bike in a member's garage and testing them out against a wall. It's worth popping over to yacf and looking for the thread.

[andrew_s]

Sorry, I'm still stumbling about with this one and it is all pretty basic (probably).
Which is the most suitable L200C package - pentawatt or LC-3 ? Does it matter ??
What type of board would I mount it on ? Clip-in or solder ?
What type of switch would be suitable to give variable resistance equivalent to OFF, LOW, MED, HIGH
PS. I will be using a 13.2V Lumicycle NiMh battery pack, so that's driving 3 *P4s.

Unless you want to build the driver for entertainment or experience, I'd suggest just buying a driver. If you factor in your time, money wasted on buying the wrong parts, or inadvertently blowing them up, it's cheaper.
Look at Cutter in Australia for decent drivers, or Dealextreme has loads of small & cheap ones.

[andrew_s]

Great thread -
Andrew - you wrote about the best LEDs - any examples of best and worst ?.
In Asia these alloy single LED torches usually come with a handlebar mount - starting from costing about 2 pounds (for the Tesco type) up to maybe 6 pounds for a magnifier lens (that focusses spot to flood) and has a "4core Cree" 3W on th e label.
The thing is the sellers will demo used ones which are real dim (and will sell em cheap too). So is this just poor quality control or do these LEDS fade in use ?

The LEDs to look at are :
Seoul P4 - about 240 lumen off 1A @ 3.5V
Seoul P7 - This is 4 of the P4s in one - 900 lumen, I think the 4 dies are arranged serial (1A @ 14V), but it could be parallel.
Cree XR-E - about 240 lumen off 1A @ 3.5V
Cree MC-E - 4 of the XR-E in one - 900 lumen. The 4 dies can be set up parallel or serial (or 2S2P).
Cree XP-G - up to around 350 lumen off 1A @ 3.3V. This is too new to have appeared in off the shelf products yet.

Maximum output is dependent on the LED not getting too hot. This is more difficult for the P7 or MC-E, so you don't generally get more than 700 lumen from them, regardless of claims.

The cheap torches are also available over the internet from dealextreme or kaidomain. The dimming LEDs will be because of shoddy design and construction. There will be no good thermal connection between the LED and the lamp body, so the LED will overheat and thus go dim. If you get one, it's probably a good idea to take it apart and make sure that there is some thermal grease and that the LED is reasonably tightly pressed against something that would allow cooling.

[rogerzilla]

The figures are usually lies. You need to see beam photographs at a constant exposure setting in order to judge.

FWIW, a Shimano DH-3N72 dynamo hub and a B&M Cyo ("60 lux" version) are pretty unbeatable for the money - much less than £100 if you go to Roseversand.de, who seem to have a sale on. They will, however, send you giant catalogues in German for the rest of your natural life and beyond.

[rgc_911]

It is a switching regulator so its very efficient

It (L200C) isn't - its an adjustable linear regulator - it drops 2v between input and output making it pretty useless for AA powered applications.

You need a boost driver - even my £8 Tesco torch has one, producing 3.3V from 2 NiMH AAs in series (2.4v input).

The Zetex chips are way better but you'd be better off buying the buckpuck or similar (or a P7 torch from Dealextreme and have done with it)

[insanityideas]

It is a switching regulator so its very efficient

It (L200C) isn't - its an adjustable linear regulator - it drops 2v between input and output making it pretty useless for AA powered applications.

You need a boost driver - even my £8 Tesco torch has one, producing 3.3V from 2 NiMH AAs in series (2.4v input).

The Zetex chips are way better but you'd be better off buying the buckpuck or similar (or a P7 torch from Dealextreme and have done with it)

Yep I got that one very wrong. After writing it I thought I might have been wrong, took a little while to get round to checking which I have now done and agree that it is just a linear regulator, all be it one that is very easy to use. In the interests of being useful to make up for being wrong I will explain the difference for other readers, feel free to correct further errors:

This is in relation to how regulators effect LED's:

• A Linear regulator uses a transistor in a way that makes it work like a variable resistor. The regulator adjusts the amount of resistance the transistor provides in order to achieve the desired effect. In the case of the L200C we would set it to achieve a particular current flow and it would adjust resistance and therefore the voltage supplied to the LED to achieve this. Because it is just a series resistor any excess voltage absorbed by the linear regulator is converted to heat. From an efficiency perspective the circuit consumes the same number of Amps regardless of the voltage, as long as it is sufficiently high to power the circuit. This means that when you measure the power consumption in Watts the circuit consumes more power the higher the voltage is, but without putting out more light. In a battery operated system this means that having extra batteries to create a higher voltage wastes the power in the extra batteries.
• A switching regulator uses a transistor and an inductor. The transistor is turned on and off very rapidly to control the voltage supplied to the inductor which behaves a bit like a transformer allowing the regulator to vary the voltage it outputs. Changing the on and off timings will change the voltage generated by the regulator. A 'BUCK' regulator will reduce the supply voltage to a lower output voltage and a 'BOOST' regulator will increase the output voltage to a level higher than the input voltage. A 'BUCK/BOOST' regulator will do both functions depending on the difference between output and input voltage. If a switching regulator is in BUCK mode the current flowing (AMPS) at its input will be lower than current flowing at its output, and vice versa in BOOST mode. Therefore the power consumption for the complete circuit including the LED will remain broadly similar regardless of the voltage supplied to the regulator.

A switching regulator is therefore better because it is less wasteful of energy and allows more variety of battery options. However it is not always the best choice of component, it is more complex than a linear regulator and depending on circumstances may not be more efficient. In a system where the input voltage is similar to the output voltage the regulator needs to waste very little energy as heat, making it the best choice. However in a system where the battery voltage may start out much higher than the output voltage of the regulator, or may actually go lower than the output voltage of the regulator as the battery drains a switching regulator of some form would be best.

In my current light setup a linear regulator is "good enough", however I am starting to plan an upgrade project for my lights that will consist of a new battery pack and new electronics, this will include a switching regulator for improved efficiency. I have used the lights for 2 years and decided that while I only need them a little brighter, my biggest need is actually better battery life. The new battery pack will provide most of the battery life improvements, but using a switching regulator will give a little more life and stop the lights dimming as the pack becomes almost entirely discharged. I also want to add a battery gauge, and a slightly less annoying flash pattern as apparently some drivers find it "too much", or "too bright".

Anyway, thanks for the correction, hope my explanation wasn't too messy, and apologies to the internet for spreading miss-information.

[rgc_911]

no worries and glad you weren't offended - it's rare that I can contribute so definitely on this forum

The main advantage I have seen of the pucks is that you can parallel them up for more current (well some of them)

Been looking at the various self build options but gave up and ordered a P7 torch from Dealextreme.com.

I think that the commercial offerings are way overpriced and am running 2 Tesco 3w Cree torches (£8 each)and a Halfords LED lamp and it is seriously good up to 25 mph on unlit roads. Unfortunately I have a 35 mph downhill which has been 'interesting' lately hence my interest in light upgrades and DIYing them.

let us know how your upgrade works out

cheers
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