Dyno powered triple cutter R2

unterhausen

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What did you use to make the hole -- a holesaw?

Thx,
-Jim G
A holesaw will certainly work for that. I use holesaws for things like this all the time. The only consideration is that I figure a stock holesaw cuts about 1/8" larger than its nominal size. Depends on how well things are tightened down and the shape of the teeth. Some people grind down the teeth to get closer to nominal.
 

znomit

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Been a while between builds but heres my latest.
Smaller, easier, brighter, smarterer.

Theres been a few ideas from here and over on MTBR that I wanted to try out, and I wanted to try a reflector setup.

Heres what I came up with

  • Brightness adjusts smoothly as speed increases
  • Bright standlight with reasonable runtime.
  • Single mode, no high low.
  • Small all in one design.

Firstly, I've been chasing lumens for a few years now, going from 2 to 3 to 4 to five and then back to three LEDs. Last year while in between builds I resorted to using an old dual cree p3 build, using those nice tight cree optics. Had a good ride with it. Occurred to me two LEDs with the right optics should be enough.
Settled on XP-E R2s in Khatod KCLP20 optics. On smooth, one stippled. Around 6 and 11 deg FWHM.

I've been a fan of Martins circuit 10 for a while as it gives good low speed and high speed performance. But you need to flick a switch (yes, flicking a switch is actually quite a chore after 10hrs on the bike), and you only get 500mA.
With only two LEDs the low mode shouldn't be needed as you get light down to around 7kph in high mode. So 2 LEDs and a single mode circuit.
Ktronik showed that you can tune the circuit to give boost at certain speeds. A little investigation showed I could design in whatever peak I wanted. 40kph seemed like a good speed as there aren't many places where I spend a long length of time going faster than that. Yes, Im overdriving the XPs a wee bit.

Heres the curve for a dual led tuned for 40kph. Nice.
mAlm.jpg


My previous standlight was a simple supercap across one LED, very simple, worked ok, but Frontranger in this thread shows a simple way to power the standlight for longer, and brighter. The cap charges off both LEDs with the voltage limited by a string of diodes, and powers one LED through a resistor. This means more power for longer.

Heres the complete circuit.
I used 4 caps on the input instead of two as I found they got quite warm.
dyno1.jpg


Heres the bits, theres a few diodes and resistors hiding between the caps on the right.
parts.jpg


All together. 8cm long.
After squeezing everything in I used carbon fiber to seal the ends as the plastic end caps from my previous build use up too much space.
Mylar seals the front holes.
build.jpg


Very efficient use of space in there. Bit annoyed the super cap isn't straight. :shakehead
xray.jpg


On the bike
bike.jpg


Only had one city ride(damn this cold) in the bright moonlight but it seems to work well. Nice spot and a good spill.
The standlight is very bright, rivals my cateye, and lasts for a useful amount of time.

Righto, that should do it until the XP-Gs arrive. :D
 

znomit

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Ride report Updated, now with more lumens and less flicker...

Out for a gentle spin in the hills tonight. Nice and dark before moonrise, clear skies.

In general it works very well. The smooth increase in lumens gives a good amount of light at all speeds. Around 50m visibility at max speed.

The beam pattern is very good, but I really don't like the sharp cutoff from reflectors.

The standlight works really well. Seems to be constant brightness for around 2 minutes, as my eyes get dark adapted. Drops off slowly from there.


Update on the complaints below. One of the carbon end caps was shorting out a diode. :ohgeez:
Fixed this and now the light is twice as bright and no flicker at all. Really really good beam up to 25 kph and kinda nuts after that. :twothumbs


One problem was the strobing of the LEDs below 12kph. This was quite significant around about 9kph. However the standlight and my blinky make enough light to ride by at those speeds so I can switch it off if needed. Or pedal harder maybe :D
This hasn't been a problem for and other light I've made, but I usually use a 4700uF cap.
 
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FrontRanger

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Another nice build, znomit. :thumbsup:

...
I wanted to try a reflector setup.
...
Settled on XP-E R2s in Khatod KCLP20 optics. On smooth, one stippled. Around 6 and 11 deg FWHM.

From that X-ray picture it looks like the two optics are aimed identically. Or do you have some means of adjusting them? Thanks.
 

znomit

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From that X-ray picture it looks like the two optics are aimed identically. Or do you have some means of adjusting them? Thanks.

Yes the beams are parallel.
I spent a lot of time thinking about optimal angles between the beams, and got nowhere. I know that in town my triple points down a little to give me a brighter spot and on country roads it actually points up, this gives a smooth beam and the lack of near hotspot means I can see further, even though over half of the lumens are going into the sky. I did some excel sheets that calculate beam distribution on the road based on gaussian optic outputs, after a lot of work concluded that parallel was probably ok. Its hard to tell without detailed intensity plots. The Khatod ones kinda suck as they go from 0 to 10 to 40 to 60 degrees. I sent them a nice email asking for more data points but nothing came back. Plus who knows how well the XP-Es will fit that data. :confused:

Road testing the optics individually they aren't the best but combined they blend very well together. Its a nice smooth transition from the nearby spill out to the tight spot. I'm well happy. Doing it again I'd probably go for the KCLP17CR in place of the 20ST, but I'd likely miss the wider spill in the corners.
 

syc

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Jun 10, 2008
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This is a really smart and elegant light - going to have to go back to the breadboard and re-arrange stuff now!!!

Thanks for all your work documenting the design and performance!
 

znomit

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Bit of an update.
A few rides told me the light was more than bright enough, and I wasn't getting a lot of love from oncoming cars. :rolleyes:

I added a high/low mode by putting a switch on one of the capacitor pairs.
Was a little tricky as the are epoxied in pretty well. I made a small perspex endcap that houses the switch, perfectly positioned near my finger. Is very very nice to use.
On high mode during descents I just need to slow down to 40 in the corners and I'm getting maximum power, nice boost in brightness. I haven't found the peak on the low mode yet, must be over 60.

Heres the bulb lumen chart
dualduallm.jpg


Build and circuit
dualdual2.jpg


On the bike.
dualdual1.jpg
 

Martin

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..I added a high/low mode by putting a switch on one of the capacitor pairs..
Ouch znomit ! This suggestion really makes me nervous so I have to say something.
By disconnecting one of the cap pairs, you are un-tuning the circuit an the remaining two caps get hit by rather high AC voltages across them. And they are just two, not 4 that can spread the heat. And you have epoxied them so if they decided to vent, they couldn't.
I recommend you don't disconnect one of the pairs but you bypass all 4 caps: Go back to the original 4-cap arrangement and add your switch b/w the dynamo and the point where the diodes connect the two capacitors. When the switch is closed, you will not have a power peak anywhere and the caps are not at risk. Your legs will also put less power into the dynamo.

Now I doubt that reducing the LED power will be a big relieve on your oncoming traffic. You could try to obtain proper optics for road use (sharp cutoff above a certain vertical angle), flip a diffusor over the light - or you could just point the light downwards in traffic.

On the matter of oncoming traffic in ones beam:
Strangely, in my area, this is much less of an issue than it was some years ago when cars would horn and cyclists would spit or shout. What happened is that meanwhile, more and more cyclists switched to the StVZO-approved Busch & Mueller dynamo LED lights but instead of pointing them down on the road, they point the hotspot right up into other people's eyes. That hotspot is hotter than with an off-road beam. Riders did this with halogen for better visibility, now they do it with LED. Motorists and cyclists seem to put up with it, police can't really fine a cyclist when his StVZO-approved headlamp is slightly unadjusted - the problem is corrected in a second. Bottom line, people got accustomed to being annoyed by bright bike headlights and it seems to be mostly tolerated.
 

znomit

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Ouch znomit !

Martin thanks for the comments, they don't get switched very often and are positioned in each corner of the housing with some epoxy so they should transfer the heat out. Is there a voltage spike when switching? They are 63V caps and aren't fully encapsulated in epoxy.
The idea is its mainly a wet/dry mode. The lumen curve really suits my riding.
They have about 200km on them so far. I always ride with a low powered backup light on too so I'm not likely to ride off a cliff. If they do pop I have a good reason to upgrade to XP-G :D

For oncoming cars just being able to dim or flash high lets them know they need to dim for you. It works on 9/10 drivers. I find once they get close picking up my water bottle like I'm going to toss it through the windscreen works well too. :twothumbs
 

Martin

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If there's a voltage spike or not that depends on the speed and then at the exact time when the switching occurs. I can imagine that the switch would slowly suffer from arcing, but wouldn't bother unless the first one fails (which will probably never happen).

For the sake of the capacitors (and everyone else who may copy that circuit), I would still feel more comfortable with the switch bypassing all four caps. The resulting power curve is similar except you get some more light at very low speed.

You found a great way to get rid of old lead-acid water bottle batteries ! :devil:
 

ktronik

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Ouch znomit ! This suggestion really makes me nervous so I have to say something.
By disconnecting one of the cap pairs, you are un-tuning the circuit an the remaining two caps get hit by rather high AC voltages across them. And they are just two, not 4 that can spread the heat. And you have epoxied them so if they decided to vent, they couldn't.
I recommend you don't disconnect one of the pairs but you bypass all 4 caps: Go back to the original 4-cap arrangement and add your switch b/w the dynamo and the point where the diodes connect the two capacitors. When the switch is closed, you will not have a power peak anywhere and the caps are not at risk. Your legs will also put less power into the dynamo.

Now I doubt that reducing the LED power will be a big relieve on your oncoming traffic. You could try to obtain proper optics for road use (sharp cutoff above a certain vertical angle), flip a diffusor over the light - or you could just point the light downwards in traffic.

On the matter of oncoming traffic in ones beam:
Strangely, in my area, this is much less of an issue than it was some years ago when cars would horn and cyclists would spit or shout. What happened is that meanwhile, more and more cyclists switched to the StVZO-approved Busch & Mueller dynamo LED lights but instead of pointing them down on the road, they point the hotspot right up into other people's eyes. That hotspot is hotter than with an off-road beam. Riders did this with halogen for better visibility, now they do it with LED. Motorists and cyclists seem to put up with it, police can't really fine a cyclist when his StVZO-approved headlamp is slightly unadjusted - the problem is corrected in a second. Bottom line, people got accustomed to being annoyed by bright bike headlights and it seems to be mostly tolerated.

this is maybe my fault, :eek:

I might have suggested it in a post...I saw what looked like a one sided tunned circuit in circuit 7 on your info page...

dynamo6sbp.gif


I though that if that worked by itself, why can't I switch in / out, a extra parallel string, like we did in the early days...disregard SW1, look @ SW2

DoublerSymetricalMinimized2.JPG



I guess I missed something!?!?!


I was hoping some way that I could use the 2 power curves represented by the 100 & 200uf peaks...

powercurvema.gif



K
 

Martin

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Hi Kerry, long time no see (my fault)

Well, when I went from the 2 caps to the 4 caps, I reduced their capacity, thereby making them smaller. I think we wanted more smaller caps rather than fewer large caps, to help the mechanical arrangement.

The 4 caps are also mandatory when using semiconductor switches with a hub dynamo. So the pencil drawing is an intermediate step towards the auto-switching circuit with MOSFET transistors. Nothing you should actually build, after we found nicer, simpler circuits.

Now if you don't want the boost of the capacitors, it's safer to bypass them all instead of moving the resonance upwards in hope that it is never reached. You never know what happens when it IS reached.

Alternatively, when you use a voltage doubler, LED current is cut in half. My circuit no.10
 
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Martin

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Aehm - Kerry, if your intention is to switch power curves and not to dim the light as Tim is trying to do, it is of course valid to switch this string in/out. And you are free to add as many more strings as you like...
 
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