Triple Cree Dyno Power w/ high/low beams and stand light

[sfCyclotourist]

Just finished the construction of my new triple Cree dyno-powered bike light, with remote switch box, stand light, and hi/low beam...

The full set of photos is here.

 

[Steve K]

Just finished the construction of my new triple Cree dyno-powered bike light, with remote switch box, stand light, and hi/low beam...

The full set of photos is here.

hi Jim,

hey, I need to see a schematic! Did you just use the toggle switch to control how many leds are powered? And what did you use to implement the standlight? Just put the supercap in parallel with one led? Not very exciting, from an electronics standpoint, but if it works, it works.

As far as whether it is worth doing, it depends on whether it exceeds the capabilities of commercially available lights. The commercial lights do a better job of putting the light on the road, but do they do a good job with the standlight?

regards,
Steve K.
(still trying to find time to build up my own fancy-schmancy standlight circuit)

 

[unterhausen]

nice bag, too bad there is a 2 1/2 year waiting list

 

[sfCyclotourist]

hi Jim,

hey, I need to see a schematic! Did you just use the toggle switch to control how many leds are powered? And what did you use to implement the standlight? Just put the supercap in parallel with one led? Not very exciting, from an electronics standpoint, but if it works, it works.

As far as whether it is worth doing, it depends on whether it exceeds the capabilities of commercially available lights. The commercial lights do a better job of putting the light on the road, but do they do a good job with the standlight?

regards,
Steve K.
(still trying to find time to build up my own fancy-schmancy standlight circuit)

Hi Steve,

I basically borrowed your 4x Cree light design that you posted to the iBOB list about a while back.

The only significant change I made to your circuit was to just use a single LED in the "low beam" mode, with a 1F/5.5V memory-backup supercap wired in parallel. I got this idea from the thread on stand lights.

The toggle switch is a DPDT on/off/on which I use to switch between 1 LED or 3 LEDs, by shorting out/bypassing 2 of them. I'm using the other pole in the switch to switch the current from the hub before it reaches the Schottky bridge, but that's redundant. (In my ignorance, I thought it might be worthwhile to not have the current pumping through the bridge needlessly -- I don't know if there's any potential for leakage through the diodes?).

The standlight works better than I expected, the LED stays lit for a good 3-4 minutes, although after a minute or two is very dim. I've seen the standlight on the Edelux in action, and it is much better overall -- brighter and longer-lasting. The Cyo is similar in comparison.

My goal with this light was to have multiple LEDs for good brightness at speed, but then to be also able to switch back to a single LED for slow-speed climbing or off-road riding. Since there's no smoothing cap, I get some flicker at very low walking speeds, but that mostly goes away at 4-5 mph. At those very low speeds, the SON28 hub doesn't produce enough voltage to pump current through all 3 LEDs, but it lights up a single LED well enough.

Curiously, spinning the front wheel by hand, it seems that there's more resistance/drag when the light is running in 1x mode than in 3x mode -- the wheel doesn't spin as freely when powering 1 LED vs. 3. Although things seem to work fine, I'm worried that I might have a partial short somewhere. Any other ideas?

 

[sfCyclotourist]

nice bag, too bad there is a 2 1/2 year waiting list

Thanks. I tested the prototype and gave feedback to Zugster, and in return I got bumped to the start of the build queue. It's worth the wait IMHO.

 

[Steve K]

Hi Steve,

I basically borrowed your 4x Cree light design that you posted to the iBOB list about a while back.

The only significant change I made to your circuit was to just use a single LED in the "low beam" mode, with a 1F/5.5V memory-backup supercap wired in parallel. I got this idea from the thread on stand lights.

When I went back and looked at the comments on the photos, I saw the reference to my iBob e-mail. Boy, I was surprised that the tinypic URLs still work!
The use of a manual switch for the hi/lo beams is pretty basic, but certainly suitable to those who aren't used to building up circuit, and the reliability is very good. Plus, you've maintained the option of converting to a 4 led arrangement, in case you feel the need for a little more light. It's good to have some flexibility.

The toggle switch is a DPDT on/off/on which I use to switch between 1 LED or 3 LEDs, by shorting out/bypassing 2 of them. I'm using the other pole in the switch to switch the current from the hub before it reaches the Schottky bridge, but that's redundant. (In my ignorance, I thought it might be worthwhile to not have the current pumping through the bridge needlessly -- I don't know if there's any potential for leakage through the diodes?).

Can you explain what you mean by "switch the current from the hub"? If you are wiring the switch in series with the dynamo and bridge rectifier, such that current is interrupted, and no current flows, then that's a good thing. It does require that the switch be rated for 100 volts, though.

If you are using the switch to short out all of the leds, which is the same as shorting the dynamo, then you are adding unnecessary drag. It doesn't hurt anything, except for your legs and cardiovascular system.

The standlight works better than I expected, the LED stays lit for a good 3-4 minutes, although after a minute or two is very dim. I've seen the standlight on the Edelux in action, and it is much better overall -- brighter and longer-lasting. The Cyo is similar in comparison.

My goal with this light was to have multiple LEDs for good brightness at speed, but then to be also able to switch back to a single LED for slow-speed climbing or off-road riding. Since there's no smoothing cap, I get some flicker at very low walking speeds, but that mostly goes away at 4-5 mph. At those very low speeds, the SON28 hub doesn't produce enough voltage to pump current through all 3 LEDs, but it lights up a single LED well enough.

Curiously, spinning the front wheel by hand, it seems that there's more resistance/drag when the light is running in 1x mode than in 3x mode -- the wheel doesn't spin as freely when powering 1 LED vs. 3. Although things seem to work fine, I'm worried that I might have a partial short somewhere. Any other ideas?

The drag that you feel when spinning the wheel is a result of current flowing through the dynamo. You can prove this by disconnecting one of the wires at the dynamo and spinning the wheel. See how long it spins? Now disconnect both wires, and short out the terminals with a paperclip or other conductor. Spin the wheel again... notice how much faster it stops!

Hook up the wires to the dynamo, turn on all 3 leds, and watch the leds when you spin the wheel. Since it takes a fair bit of speed to generate enough voltage to forward bias the three leds, they may not be lit up during your spin test. If they aren't lit up, they aren't conducting current. If they aren't conducting current, then they won't produce drag at the dynamo. So... at relatively low speeds, I'd say that the behavior that you've observed makes sense. I don't think there's anything to worry about.

Steve K.

 

[sfCyclotourist]

When I went back and looked at the comments on the photos, I saw the reference to my iBob e-mail. Boy, I was surprised that the tinypic URLs still work!
The use of a manual switch for the hi/lo beams is pretty basic, but certainly suitable to those who aren't used to building up circuit, and the reliability is very good. Plus, you've maintained the option of converting to a 4 led arrangement, in case you feel the need for a little more light. It's good to have some flexibility.

Right. Plus, after using this light on an all-night ride this weekend, having the ability to manually switch between modes is a useful thing -- riding behind another cyclist clad in reflective gear, much of your headlight beam is bounced back towards you, which can be a bit blinding -- having the ability to dim your light a bit is helpful! Plus, with 6-10 other bikes with head lights around, you just don't need a super-bright light.

Can you explain what you mean by "switch the current from the hub"? If you are wiring the switch in series with the dynamo and bridge rectifier, such that current is interrupted, and no current flows, then that's a good thing. It does require that the switch be rated for 100 volts, though.

Right. What I meant is that one set of poles on the switch interrupts the current from the hub BEFORE it reaches the rectifier. And good point about the switch -- fortunately the one I'm using is rated 3A @120VAC.


Thanks!

-Jim G

 

[sfCyclotourist]

UPDATE: OK, I spent this past Saturday night pedaling my bike behind this head light. I can now report that I'm VERY pleased with the function of this light! I was riding in groups of 3-10 riders, and found it helpful to keep my light switched to the "low beam" single-LED mode when riding behind others, otherwise much of my headlight's beam got bounced back towards my eyes (off of their reflective gear), blinding me a bit. When riding fast down a hill, I'd switch to the full 3-LED mode for extra brightness. There is no real discernible difference in drag between 1x and 3x modes either, which I was surprised by. I rode with several folks who had Edelux lights, plus one guy who had a Cyo, and my light on 1x beam is less bright than those lights, while on 3x beam it's slightly brighter. The width of my beam was slightly wider than those from the other lights, too.

Things I need to tweak include aiming the beam upwards a bit more for increased throw, and tracking down a minor loose connection (which fortunately wasn't a major headache during the ride!). Also, I found that the mini toggle switch I used is a little too easy to bump -- I inadvertently switched the light off a few times while reaching down near the switch. I'd use a multi-mode pushbutton switch if I had it to do again.

Overall, though: SUCCESS!:thumbsup:

 

[sfCyclotourist]

I should also give props to Znomit's Triple XP-E Side Shooter, which was a major source of inspiration for my housing design. Thanks man! :bow:

 

[Calina]

Are you running the LEDs at 500 mA or did you put a capacitor to increase the current?

Which optics did you use?

 

[znomit]

Cheers sf.

Thats a nice mounting spot.

Im thinking of doing something similar with an MCE. One die on all the time (daytime running light and low speed/bunch light) and three switchable. No boost just a smoothing cap on the three and a supercap on the single.

Does the single led light up immediately when you start off or does it take a short time to charge the supercap? I found the triple in doubler mode gives enough light after the first pedal stroke(while I'm clipping in) but my 5 led was a little lacking.

 

[syc]

I rode with several folks who had Edelux lights, plus one guy who had a Cyo, and my light on 1x beam is less bright than those lights, while on 3x beam it's slightly brighter. The width of my beam was slightly wider than those from the other lights, too.

[snip]
Overall, though: SUCCESS!:thumbsup:

Excellent!!!

 

[sfCyclotourist]

Are you running the LEDs at 500 mA or did you put a capacitor to increase the current?

Which optics did you use?

The LEDs are running at the hub's output current, which is 500-600mA.

Adding a capacitor won't increase the current -- not sure what you're getting at there?

See http://pilom.com/BicycleElectronics/DynamoCircuits.htm#Basics

A capacitor can be added in parallel with the set of series-wired LEDs to smooth the DC current output from the rectifier. I didn't use one of these -- previously I'd built a single-LED dyno-powered light using a smoothing cap, and it still flickers in spite of that -- so I left it off here.

I did add a supercap parallel to one of the LEDs to provide some stand-light functionality -- this works OK, but not as good as commercial lights.

 

[sfCyclotourist]

Cheers sf.

Thats a nice mounting spot.

Thanks, it was inspired by a friend's bike/light...

I'd been planning to build a 50mm cylindrical housing using a 3x or 4x round optic, and mounting the resulting light under one side of my front rack. The problem with this is you often get a shadow cast by the front wheel. Then, when I saw your side-shooter, I realized I could build a "light bar" that'd sit right at the front edge of my rack under my front bag, it all just clicked!

Im thinking of doing something similar with an MCE. One die on all the time (daytime running light and low speed/bunch light) and three switchable. No boost just a smoothing cap on the three and a supercap on the single.

I would LOVE to build a different version of this light using an MCE with individually-switched nodes. However, it doesn't seem like good optics are easily available yet (meaning: not at DX, where I've bought most of my recent parts). Plus, I already had the LEDs and optics that I used on hand.

I'd also like to build an even smaller version using the new tiny XPE LEDs!

Does the single led light up immediately when you start off or does it take a short time to charge the supercap? I found the triple in doubler mode gives enough light after the first pedal stroke(while I'm clipping in) but my 5 led was a little lacking.

The single LED does seems to light up quickly -- it takes a (very) short bit for the super cap to charge up to work well as a stand light.

 

[sfCyclotourist]

Which optics did you use?

I used the cheap-but-excellent Cree optics at Dealextreme.

I had to file the sides of the white plastic optic holders a bit to get them to fit inside the 1-inch square Al tubing.

 

[Calina]

The LEDs are running at the hub's output current, which is 500-600mA.

Adding a capacitor won't increase the current -- not sure what you're getting at there?

See http://pilom.com/BicycleElectronics/DynamoCircuits.htm#Basics

A capacitor can be added in parallel with the set of series-wired LEDs to smooth the DC current output from the rectifier. I didn't use one of these -- previously I'd built a single-LED dyno-powered light using a smoothing cap, and it still flickers in spite of that -- so I left it off here.

I did add a supercap parallel to one of the LEDs to provide some stand-light functionality -- this works OK, but not as good as commercial lights.

Read about this here: http://forums.mtbr.com/showthread.php?t=452480 . Posts 14 to 19
And there. Martin's site: http://www.pilom.com/BicycleElectronics/DynamoCircuits.htm circuits 5 to 7.

I used the cheap-but-excellent Cree optics at Dealextreme.

I had to file the sides of the white plastic optic holders a bit to get them to fit inside the 1-inch square Al tubing.

Thank you. DX is down at the moment but I'll check on it later.

At what mA rate do you discharge the supercap?

 

[sfCyclotourist]

Read about this here: http://forums.mtbr.com/showthread.php?t=452480 . Posts 14 to 19
And there. Martin's site: http://www.pilom.com/BicycleElectronics/DynamoCircuits.htm circuits 5 to 7.

Ah! Apologies, my bad! I'd forgotten about adding tuning capacitors -- never paid too close attention to that, honestly. I've not progressed much past Martin's #2 circuit. That simple design seems to work great as is, and the extra capacitors will just require additional room inside a housing or external box. As I previously mentioned, I did away with capacitors entirely with this light, save for the one that powers the stand light.

At what mA rate do you discharge the supercap?

No idea. It's literally just wired in parallel to that one LED. It's a memory-backup 5.5V 1F super cap, so it's "slow burn" and I suspect only outputs a trickle of current.

http://www.allelectronics.com/make-a-store/item/CBC-17/1-FARAD-5.5-VOLT-SUPER-CAP-/-/1.html

 

[znomit]

I dunno about the necessity of tuning caps.
I build lights so I have enough to ride comfortably at 40+ kph although generally Im doing 25-30, I can do with less light at the lower speeds, and the curves converge at higher speeds. Its actually better to have a curve that ramps up slowly. A detuned system would work better... 10lm per kph would be good.

 

[Steve K]

I dunno about the necessity of tuning caps.
I build lights so I have enough to ride comfortably at 40+ kph although generally Im doing 25-30, I can do with less light at the lower speeds, and the curves converge at higher speeds. Its actually better to have a curve that ramps up slowly. A detuned system would work better... 10lm per kph would be good.

That's my thought too. I like the general principle of matching the load to the source, thereby getting the max power out, but it gets tricky with adding caps in series. The cap value is only useful over a modest part of the speed range, plus there are issues with the types of caps available. Aluminum electrolytic caps have a fairly large change in value over the temperature range that I ride (0F to 95F), and their failure rate is rather high compared to other parts used in the bike light (assuming proper derating for all of the parts).

And then there's the issue of capacitor size. The darned things are bulky and need to be protected from the environment. Shoving them up the steering tube doesn't meet my standards for packaging.

My preference is for adding leds in series as the dynamo speed increases. This has its own set of issues, so I won't try to tell you that it's the perfect solution. I think it has better reliability than the series capacitors, and reliability is my top priority (well, second to actually producing usable light). Adding a manual switch as in Jim's design has a slight impact on reliability. My plan is to build a circuit that switches in a second set of leds at certain speed, which is more convenient. Properly built, it shouldn't impact reliability, but I'm not sure that the average person would have the skills and knowledge to do a proper build.

Honestly, I think that leds have improved enough that two Cree's in series is good enough for 95% of my riding. Add a standlight, and you're pretty much done. ... Except that I have this urge to build it from a MC-E ....
Just waiting for some suitable optics to become available!

Steve K.

 

[Calina]

That's my thought too. I like the general principle of matching the load to the source, thereby getting the max power out, but it gets tricky with adding caps in series. The cap value is only useful over a modest part of the speed range, plus there are issues with the types of caps available. Aluminum electrolytic caps have a fairly large change in value over the temperature range that I ride (0F to 95F), and their failure rate is rather high compared to other parts used in the bike light (assuming proper derating for all of the parts).

And then there's the issue of capacitor size. The darned things are bulky and need to be protected from the environment. Shoving them up the steering tube doesn't meet my standards for packaging.

My preference is for adding leds in series as the dynamo speed increases. This has its own set of issues, so I won't try to tell you that it's the perfect solution. I think it has better reliability than the series capacitors, and reliability is my top priority (well, second to actually producing usable light). Adding a manual switch as in Jim's design has a slight impact on reliability. My plan is to build a circuit that switches in a second set of leds at certain speed, which is more convenient. Properly built, it shouldn't impact reliability, but I'm not sure that the average person would have the skills and knowledge to do a proper build.

Honestly, I think that leds have improved enough that two Cree's in series is good enough for 95% of my riding. Add a standlight, and you're pretty much done. ... Except that I have this urge to build it from a MC-E ....
Just waiting for some suitable optics to become available!

Steve K.

If you keep waiting just a little more you will be able to build it with upcoming Cree XP-G ;-).