Tuesday, 6 December 2011

Dynamo A Go-Go

Once an engineer, always an engineer. Not long after I decided to start pushing my self to ride longer, I hit upon the problem of lights & winter. Specifically losing track of battery charge through daily usage as well as getting bored of constantly charging batteries and having stuff charging up on every available surface. Fast forward a couple of years, lots of research (aka reading internet forums), desparately recollecting the electronics of my engineering degree, the purchase of a couple of text books and several prototypes later and I have spent the last 18months riding, off the race course, illuminated by a hub dynamo powered light: the deanamo.

I made my first light over two years ago and was pretty convinced enough light could be had to make this viable off road and in technical trails, but there were several problems:
  • The light turned off when I stopped
  • The light didn't even come on until I was moving at a half decent speed
  • The speed needed to get a decent amount of light was actually pretty fast
  • When the light finally came on, with my crude smoothing, it was so flickery, it made your eyes hurt
  • Did I mention it turned of when you stopped?
  • Oh, and I knew little about how to overcome these problems
Two years of prototypes later and I think I've overcome all of this. My little winter project, that has actually taken hundreds of hours, has finally reached the final throws of development (although I must confess I have a few new thoughts I want to try out, once an engineer, etc!). 
Head unit is super compact on the bars & no battery weight swinging around on the stem or top tube
Compact <100g circuit tucked at the bottom of the right hand fork leg, sealed in a  bit of innertube
The deanamo definitely stays on and gives out plenty of light when the bike is stationary!
The K-Lite head unit up close
Through all this I have been aware that Kerry Staite of K-Lite in Australia had also made, and been tinkering with, a dynamo light. He makes a lovely little battery light too, it is this that the dynamo is based around. He was kind enough to let me get my hands on one of his head units with his current dynamo circuit and after a bit of discussion with him, a tweak by him to his circuit to my suggestion as a result of my homework and experiments and a the exchange of a few ideas between us, have helped us both move forwards. I have made some further "tweaks" to the circuit to give it my full deanamo functionality to my own preference (I know Kerry is tweaking his to his own liking as I type too). Thanks Kerry. Here it is, and very happy I am with it too. 
Another standlight picture, just because I'm so happy with the end result!
I'm not to blame for the name, someone else christened it for me, and it stuck
I have also had the great pleasure of getting my hands on a disc dynamo hub from SP Dynamo, their tiny, disc compatible, super light (410g) PD-8 model to which I have paired the light. This has been rolling around on mid week thrashes and my daily commute to work for just over a month now, or for about 1000miles, and so far it's been nothing but reliable and worry free.
The SP Dynamo PD-8 hub dynamo, 410g and plenty of power
I can't wait for the SP dynamos to be more widely available, and they come in lots of pretty colours too. I need one of the <400g SV-8 hubs on my road bike too now.
Ooh, shiney! (I therefore need and want these!)
So, there you go, a dedicated off-road dynamo: the deanamo

My little project is nearing completion, at least for now. Final tinkerings are taking shape and new ideas sre being put on hold for now, so.......  watch this space! :-)


  1. Hi Rob,

    I enjoy reading your blog. I am especially impressed by the Deanamo. Are planning to work with Kerry (kLite) to put it on the market?

    My GF and I are heading off on yearlong(ish) tour of C & S America in February. I am in the process of building up a hardtail 29er with the SP PD-8 dynamo.

    I suppose my requirements are a bit different to yours because I probably won't be doing much of my trail riding at night (though I have enjoyed night riding the past with Cree battery lights). I am more interested in a good charging solution for Garmin and iPhone. I have some basic electronics background, but given the timescale, I probably don't have time to build, test and refine my own circuits. Would you recommend the relatively expensive "Plug II+" over something like the Softhema or Kemo circuits?

    Nice work!

    All the best,

    1. Hi Lars,

      Thanks for your kind words :-) I know Kerry, but he doesn't need my help developing his lights. We keep in touch with thoughts about dynamo lights as we both set our standards very high and are always looking for ways to develop a better light, and he makes some great products with his dynamo lights.

      If you're after a light and a charging solution, and you want a really good light too, you have two options:

      1) Buy a light and a separate charger of your choice then twiddle a few wires to rig them up with a switch to select between light or charger. This really leaves you with the k-lite or Exposure Revo to choose from if you want a bright light and good standlight ;-)

      2) Buy the k-lite light, external battery and charger kit that's all designed to work together. This might be the best option, as well as the best value, for your needs. K-Lite will be able to answer on Garmin & iPhone charging

      I have found several Garmins of mine and my friends not fussy on charging, but at least one of their models can be fussy with stop/start operation from a dynamo, for this an intermediate external battery is my recommendation, I think one of the K-Lite options includes this function. If you're using a Garmin 800, I have found this isn't necessary, but you do get a "external power lost" temporary message (which I can live with).

      I've no experience of the "Plug" charger, but my Softhema has been a case of one working flawlessly and the second never working and no response from Softhema (despite me sending it back) so the jury's out on that one! The Kemo product looks ugly but works very well, and is much, much cheaper than the Plug too. Again, if it's just charging you're after, I'd go to K-lite as today they're the only people offering this with the possibility to integrate it into you're light at a later date.

      I'd recommend coupling whatever you choose with the SP PD-8 dynamo hub as it's the most efficient and lightest out there. Looks like you've gone that way already though, luckily for you. Only the SON is comparable but this costs over twice as much!

      Enjoy your trip, sounds like you and your GF are setting yourselves up for a truly grand endeavor


  2. Rob,

    Is the Revo Exposure essentially based upon the same circuit that you are using or have you made additional tweaks.

    To be honest it looks as if both the K-lite and Revo offer just about everything you would want in a light, I'm just wondering if there is more?


    1. Hi Paul,

      I'm note sure I understand your question of whether there is "more". However, I do agree, full heartedly, wit your conclusion that these lights offer everything you could want with a light; bright, lightweight, immune to cold weather battery issues and always there & available.

      I've made a few different versions of my own light, but a DIY dynamo light doesn't get near to the compact package and robustness of a well made bought solution, to be honest! It's not like battery lights where you can buy a complete, well made, circuit off the shelf, you need to be assembling your own discrete components.

      All of the lights out there are a little different, the specs, package and accessories differ between these lights so I'd get the one of the two you've identified above that closest suits your needs, you won't be disappointed.