It's going to be the lamp (specifically, how much smoothing and regulation is performed after rectification) rather than the generator (they're all going to be outputting something more or less sinusoidal). Smoothing means storing energy in capacitors or batteries, which are bulky, relatively expensive and prone to failure, so it's a prime candidate for economising at the design stage.
Yes. I extracted the circuit from my old unused Basta Pilot Steady LED front:
Its just a rectifier (preceded by some backtoback (presumably highish voltage zeners to protect it) followed by 0.66Farad of standlicht caps (protected by a presumably 5.1V of paralleled zeners (with no dropper resistor: ie clamps overall dynamo voltage to 2Vrectifierdiode + 5.1 == 6.5V peak rather than the 8v5 peak corresponding to 6Vrms), with led driven via a 3.9R resistor (ie > 350mA). It flickers annoyingly. I suppose cheap super caps mightnt charge fast enough for smoothing, but my attempts to prevent warble in a reflectalite LED bulb powered by bottle generator thru just a bridge rectifier where made worse by large smoothing capacitor (10 or 20000uF).
Isn't the problem going to be that: load LED circuit sees smoothing cap charged to peak of dynamo voltage, draws current appropriate for that and empties cap before next half-cycle starts: ie at low speed led current needs to be kept lower so as LED is lit over whole half cycle?.
I found this
https://www.ebay.co.uk/itm/16V1F-2F-Farad-Capacitor-Module-2-7V-10F-Super-Capacitor-With-Protection-Board/232879025831?hash=item3638abeea7:g:m2YAAOSwTDNbar4f:rk:1:pf:0....I suppose you could do something neat with thyristors ... to keep the light off until the generator is up to speed...
I want some light at low speed too
, so...
.. Feeding dynamo lights DC from a battery isn't always a good idea.
Which is what I think Stzvo got wrong: LED dynamo lights are meant to be a drop in replacement for filament ones which work of DC quite happily, thus IMHO Stzvo should require that a dynamo hub front lamp must either work perfectly well from 6V AC or DC, or alternatively have a DC input (eg mini shimano style connector from which it (and any slaved rear lamp may be powered).
Honourable mention to the B&M 4DToplight Multi: Its 'standlight' is powered by a pair of AA....I can see an argument for a front light equivalent aimed at slow climbers, but I've never seen such a product.
I prefer no batteries INside dynamo lamps but as mentioned above a DC in connector (Shimano-Style spades) on the front lamp would seem OK. Also, rear lamps seem less annoying and I prefer line style lamps, but I was hoping given that hub rear lamps are usually slaved to the front, fixing the front flicker fixes the rear warble
... I can imagine half-wave rectification (either through failure or design) exacerbating the flicker, by effectively halving the frequency.
Arggh, surely not in high/medium end designs,
. Even the PIco 30 seems to have a bridge
https://forum.cyclinguk.org/viewtopic.php?t=120923&start=105#p1307428.
Also the dynamo-for-small-wheels-in-a-full-sized-wheel-to-save-weigh/drag tri will increase low-speed flicker (
Unfortunately it is a 26in wheel with matching generator
Some cheaper (ie low power) Axa front lamps are marked as 6V E bike compatible, similarly rear lamps: but not the higher power ones (which I want eg Axendo 60) it seems....