Another Dynamo bike light (front + rear + standlight)

Hi everyone,

Not sure if it’s the right category…

Well, as said before, I build a dynamo bike light.
It is based on the circuit n°8 from pilom, whith additional standlight and rear light (that is still being built).

admire the paint skills (note that the switches on pic1 and pic2 are not the same. I did not draw everything).
The main supply wire passes through the front connector (the thin rectangle, before the front light) so that if the light disconnects, the electronics won’t have to suffer the open-circuit over-voltage of the dynamo (100+ V downlight, the legend says)

Resistor values may not be the real ones though.

I won’t explain the left part, pilom did it better than me.
The pilom electronic is in a 3D printed case, nothing special.

The frontlight and standlight capacitor are in a convoy s21 host.
The idea is to charge C4 through D10, with 2 leds voltage.
When the wheels stop, C4 discharge in 1 led through R4 (well, all the time actually, but it is negligible).

At the start, all the current passes through D7, and charges C4 through D10. When C4 voltage rises, it begins to illuminate gradually D9. When C4 is charged enough, D8 kicks in.
It takes less than 1 minute at driving speed.
When I stop, D9 stays lit. The fact that C4 (7.5F) is in the front light host allows me to unplug it from the bike and use to take something in my bag for instance, or to go piss or anything you want. The light stays for hours. I estimate it to be easy to find in a tent even after a whole night. The light can be used for lighting very close for several dozens of minutes. Far enough to be seen at a red light…

For the rear light, C5 is also charged while driving. The whole thing is an astable transistor oscillator, which goal is to blink alternatively 2 rear light that I can put near the wheel axle, and under the saddle for instance. Actually, the flashing pattern is weirder than that, but the idea is the same.

The leds are Nichia 219c 4000k 90+ CRI, that look quite nice, this is my first led light so I can’t really compare.
The optic is a carclo 10510 lens : triple elliptical. The beam is far from flat, almost round. I talk about it in another post.
If I had to do it again, I would use the last circuit of pilom’s page, which uses less parts for similar perf.
I would certainly use Cree XPL HI. They give a much flatter beam pattern, the 219c’s will be a pain in the ass to make road-friendly. Plus, I won’t really need high cri. This is a bike light, not a surgeon headlamp…

I anybody has questions, don’t hesitate. I will put real picture is the next days.

I was gonna do something like that. Still got an old-timey dynamo and antiquated front/rear hotwire fixtures that I wanted to bring into this century.

Just don’t forget- more Watts more harder pedaling.

Missing info ; that’s for my dynamo Hub…

Considering pedaling, I gladly share at most 10% of power, for some light on the road :slight_smile: This is mostly useful at night, where power is not the first concern

Im fine with 1 led and if riding countryside wearing headlamp.

Nice work! This reminds me of my dynamo light projects :beer:

What is the reason to use a flashlight as host, when one can cheaply get bike lights with more suitable beam patterns (e.g. sharp cut-off) second hand? Did you want something, that can utilize high CRI 3535 LEDs?

As an example here is a driver I made for the B&M Luxos: front (low & high beam) + rear + standlight (just a supercap)

Plastic host? And what about heat dissipation?

It is a “hybrid” host. The driver sits in the plastic bottom, while LEDs and MCPCB have direct contact to the aluminum lid.

Here you can see one of my first mods, with a circuit similar to the standard (same as pilom) one (no uC and no buck). I also used e17a at the beginning, because I liked high cri with lower color temp. However Osram Oslon might be better suited (smaller -> better projection / cutoff; higher current capability, easier to reflow). One needs LEDs which can be placed right next to each other with minimal free space inbetween phosphors. Thats why normal 3535 LEDs are hard to integrate into these lights, as one needs 6V - 9V setups.

In the most recent version of this mod there are two rows of 2 Osram Compact PLs each (high and low beam) which are controlled via mosfets. When in high beam mode, the uC measures cycling speed and dynamically adjusts high / low beam ratio (more high beam as cycling speed increases).

10$ Magicshine knockoff + 60x20lens + rectifier and cap.

A simple compromise for countryside :+1: … but I also want to cycle on the road and have all the dynamo lumens :smiling_imp:

Hi guys, sorry for the dead time, I had no notifications of your answers and summertime does not urges me to build the light.

Originally I choose the flashlight host because it is fairly easy to build, you can just put your stuff inside and go.

Considering the scavenged bikelight idea, my main concern is about the light output it can reach.
What led configuration are they made for ? I can’t see were you should put the mcpcb + led.
Plus how many leds can you put in the board without messing with the beam pattern (the reflector being made for only one source, I guess…)
I would very pleased to know how this could be built !

Just like you, I want to get the best lumen output, and a custom build looks like the best answer.
That is why I am leaning toward something like a triple XP-L HI with 10049 and 10048 carclo optics, in order to get a wide close field coupled with one or two narrow spots. But I can’t find literature about that, so I fear that I am missing something

The flashlight build might be a good starting point. Maybe u can try out one of these simple pilom circuits. Afterwards u can still opt for an even better solution using a scavenged proper bike light.

Regarding MCPCB + LED in scavenged bike light u can check this post out. There u can see the latest status of my build.

Literature barely exists… u gotta find out yourself :grin: .

Yup, the light is built and works, with Pilom 9. The problem is that a triple nichia 219c with carclo 10510 gives a very wide beam, that is not ok for road use.

Thank you, I would never had found that ! Glad Deepl is here ahah !

Finally, few pictures of the build.

The plastic case contains the main circuitry, based on Pilom 9. It has 2 switch : 1 general, and one to choose slow/fast mode (see pilom).

The light itself is made of a convoy s21a host. Inside, is a triple nichia 219c 4000K, with a carclo 10510 (20 mm triple elliptical)


1 Thank

Great setup, thanks for sharing!

Is it possible to implement automatic mode switching without a uC? Maybe with a frequency filter?

Thanks ! It’s a bit messy, but good enough for a V1 :slight_smile:

Sure you can, as pilom explains

He made a circuit for automatic switching for both methods : dynamo frequency based as well as led drive current comparison.