B&M Dlumotec Oval Plus first impressions

[the_riviera_kid]

I had my first night ride with my new dyno light yesterday. Mixed lighting conditions from extremely well lit (no headlight needed to see clearly) to quite dark (although never zero ambient lighting

Comments

[wintal]

Hmm, I have the Lumotec IQ Cyo Plus - compared to my 1W dinotte, I would say the dinotte has a brighter peak brightness, but is _much_ more focussed. I find the Cyo will happily illuminate cars parked in driveways as I ride past them, for example.

I'm pretty sure I get flickering well above 10km/hr... I have wondered if it's to do with having a rear supercap backed light connected as well... will have to cut it out of the circuit sometime and check. I think it's more normal to just have one supercap in the loop, and have the rear light connected to the front light to get battery-backedness. I ended up getting a slightly wrong model of light - there's _way_ too many options and they didn't have the right one in stock. Mine has no on/off switch, so I ride around with the light on all the time ;)

My light mount is also a bit shitty - I currently have it mounted to a hole I drilled in the mudguard, but it's moving around too much for my liking. I used to have it connected via a bolt going through the fork's brake hole (the one for road style brakes), but that was getting in the way of the cantilever brake cable. I need to find another option (or stiff the mudguard a lot :P).

[the_riviera_kid]

My current mount gives me about 2mm clearance from the brakes in two different places (the horizontal brake cable between the arms, the edge of the travel agent when the brakes are applied). The original suggestion by the LBS gave me more clearance for the brakes, but unfortunately it hits the headset.

I was thinking of the IQ Cyo R Plus as a likely upgrade path, but I haven't looked into any alternatives yet. Flickering above 10km/hr definitely sounds like something isn't right. Has it always flickered, or is it a sign of something wrong with the supercap?

[wintal]

I'm not sure what to do about the mount. The cantilever brakes I have need a cable that goes straight up to the stem pretty much, so the light gets in the way if it's there. I think placing a piece of steel bracket to strengthen the mudguard up to where I mount the light is probably the go. I do actually like having the light a bit further forward, as less of the light ends up splashing onto the guard/wheel.

I'm not convinced of the need for the 'R' model - the close range light (4 metres and closer) sounds pretty useless to me at normal speeds - that's ~1 second at 20km/hr, not really time to do much ;) You might want to get the 'N' bit though - as you expressed a dislike of the flickering light when wheeling it around you'll probably want it to be turned off. These lights seem to switch to a 'low power' brightness when the wheel goes below a certain speed, and then flickers as it's being wheeled around.

It has always flickered. I think I'm probably supposed to not care, or maybe I'm supposed to always go faster. I will disconnect the rear light at some point and see if that makes a difference, as it's drawing power from the hub too.

[the_riviera_kid]

The internet suggests a (surprisingly, as per my comments below) large number of people mount their lights on the mid-fork braise (the one usually used for a front rack). I would think this would put the light too close to the ground (limiting the forward throw and making it less visible to other road users), plus I'd think spoke-shadows would drive me a little batty, but I concede I've never tried it myself.

You're quite right about the N, I had intended that (there are just too many suffixes to keep track of). The R was partly for the near field (although your point on 1 second is well made), but also for the integrated reflector (as you've noted before, I already have a large number of things mounted on the front, so I'm trying to rationalise and perhaps eventually remove my accessory bar).

I find it hard to believe that a flicker at 10km/hr is by design - indeed, I vaguely recall that the German legal requirement for brightness is measured at not much faster than that. I'll be interested to hear the results of your back light-less testing (that certainly sounds like a plausible cause).

[wintal]

Hmm, maybe I should try the mid-fork mount. I admit my thinking is much like yours, seems a bit low etc, but it is conveniently out of the way of everything else.

Not sure on the flicker thing, I seem to recall (though I don't remember where from, so i'm likely wrong) that the particular light I have doesn't conform to the german laws - it's export only. Probably doesn't matter anyway - even when flickering it's flickering between 'low brightness' and 'full brightness' and the low brightness would still pass german requirements easily.

This light is supposed to be brighter than the R, but I'm not sure if the power draw is higher or if it's just to do with the field of view. I disabled the rear light yesterday to try and compare, but haven't done any proper testing yet. My ride into the parking lot this morning looked like it was flicker, despite having just come off a 40km/hr downhill section and doing about 15km/hr. Maybe I should pull out a multimeter and do some testing - was always wanting to do that - test current draw etc to see what was going on.

My initial plan was to do my own rectification and battery/supercap backing, but I gave up on that due to the difficulty of getting a decent reflector for a homebrew solution (and the fact that a proper light was only $70). I'm tempted to return to it as a potentially better solution than the light I have.

[the_riviera_kid]

The reading I've done suggests that both R and non R use the same emitter at the same voltage, the only difference is in field of view (the R spreads the same power over a larger area).

Finding a proper cycling-specific lens/reflector is definitely the biggest issue in a homebrew light. I need to point mine so far down to avoid dazzling traffic (even at low beam) that I'm really not getting the best light out of it. As you say, if you can get a real light for $70 it doesn't seem worth the effort (indeed, if there were more mid-range battery powered lights with decent reflectors at the time, I might not have bothered with the homebrew. The main thing making it worthwhile was that it was still significantly cheaper than a dyno wheel).

I've seen plenty of people online happy with rectification/filtering/standby lighting via a few diodes and a bank of AA rechargeables. I'm not sure I'd try charging expensive devices via this route (although many people do), but burning out a $10 LED seems an acceptable risk. (Alas, my homebrew has about 8.5V minimum power input, so it's not a suitable solution for me.)

[wintal]

Hmm, rectification is easy enough via 4 diodes (I was a bit worried about the power loss due to the 0.7v(? it's been a while) drop. You should be able to get whatever output voltage you need with a buck-boost converter. There's single chip solutions for that nowadays (even if there wasn't the circuits fairly simple). Maybe there's a problem with this I don't see - I bailed out of electronic eng into IT ;)

[the_riviera_kid]

In my case the light controller (I bought a complete controller board rather than going DIY) incorporates a buck converter. I picked that over boost because buck is usually slightly more power efficient, and it's easier to get more total power capacity by adding extra batteries in series, rather than having to worry about putting cells in parallel.

Throwing a bank of batteries into the mix just gives you some power smoothing and standby light for free.

I'm not aware of any problems you haven't seen. Heat dissipation shouldn't be an issue (if it is the efficiency is probably too low to be useful anyway). I must concede my recollection of this sort of thing from studies is quite vague.