Yet Another Cycling Forum
General Category => The Knowledge => Topic started by: EdinburghFixed on 08 February, 2011, 07:50:29 pm
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I mentioned on the audax board that I was getting an IQ Cyo to play with, given that two lights are needed on PBP and my old Ay-Ups are getting shonky. Thought it would be worth documenting here since there's a wider audience.
On the understanding that you can run them DC from a standard battery, I soldered the dynamo tabs to a stock DC plug and in around 5 minutes time had the Cyo (plus wired tail-light) running happily from my Ay-Up battery.
However, when I actually had call to use them in anger (on Sunday's Nippy Sweetie), I was disappointed to find that the Cyo really doesn't put out very much light at all, even in the bright central "shaped" section of the beam. It was fine for pootling but I felt uncomfortable going fast, to the point where I just drafted someone with a brighter light when we got up towards 30mph.
By comparison, my 3 year old Ay-Ups are good for 40mph descents, as I've demonstrated to myself on several brevets as well as an unlit commute with many downhill sections.
Of course, the question is low consumption or inefficiency? In other words, does running the IQ Cyo on DC power simply draw a fraction of the current or is the DC to DC (!?) conversion burning ampage for nothing?
Tonight I broke out the multimeter to find:
Ay-Ups full beam - 290mA
IQ Cyo - 190mA
B&M Toplight Line Plus - 20mA
This is something of a relief - it means the Cyo is dim because it draws little current, which is not the worst thing in the world. Rigging up my remaining Ay-Up as a high-beam for descents would give me much prolonged battery life (50% more).
However, I'm curious as to why the Cyo draws so little current. I understand that it will accept 500mA from a dynamo hub - it would be nice to wire the one light with a high/low mode if possible.
Does anyone have any comment on the internal wiring of the Cyo that might shed some light on this? Should I dismantle it and wire the DC input directly (bypassing whatever the rectifying system might be)?
My electrician-foo is weak. I know only what I learned in standard grade physics.
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What voltage are you putting across the Cyo?
I've just taken a multimeter to mine, which is fed off 5.9V DC thanks to a nifty little DC-to-DC converter.
My Cyo has the standlichghththtght function, so ignoring the spike in current when it first gets turned on (charging the capacitor), it settles down to about 130mA, and it's adequately bright. (Especially as the brakes are siezed on, so the bike won't actually be going anywhere.) :facepalm:
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What volt.... ^ what he said.
I believe the Cyo runs optimally from 7.2V DC (or at least that's what the manual says). The manual also says something about getting the polarity right, though I'm not sure what happens if you don't.
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My manual says 7.5V max and it's running from 7.4V (measured) at a current draw of 190mA. So 1.4W - half what it should take from an AC source.
I've tried powering it through the taillight connectors as apparently this circumvents some losses (in the sensor, rectifier, etc) but it doesn't seem noticeably brighter and still draws... 190mA.
It's very strange. I wouldn't say I'm unhappy because having a light that runs forever is also worthwhile, but it's vexing to not understand why. As I said, I'd be quite happy to ride with it at normal speeds (especially on dry roads) but I found myself dragging the brakes descending a straight hill which I basically knew was debris free - not ideal.
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I'm not sure how far it answers your question, but I found the discussion on bikecurrent (http://lists.topica.com/lists/bikecurrent/read) interesting - the thread that matters is titled 'B&M IQ CYO Internals'.
I don't pretend to understand all the discussion - I am not an electrical engineer, whereas these guys are practitioners with enquiring minds.
Still, I get the feeling that Pawel Danielewicz has been running a CYO on more than 8.5v DC, driven from the connectors that bypass the polarity-dependent circuitry that works with the usual dynamo input wiring.
You might want to think about posting your question on the bikecurrent list. I don't think there's an explicit answer there already.
HTH.
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If the light is doing peak rectification onto an internal capacitor (most likely), then at 7.5V RMS AC, the internal DC voltage will be 10.6V (less the rectifier drops)
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Thanks for the link - that's quite a good discussion (although you're right, it doesn't really help me! Maybe it's implicit to all of them...)
At the end of the day I could dismantle the light and simply replace the internals with a voltage regulator (so it works just like my Ay-Ups only with a good quality reflector). But, part of the attraction of getting a dynamo light to run DC was that ultimately, I'd quite like a dynamo.
The new Philips LED light runs from batteries, of course, but it is almost 3x the price I paid for the Cyo, so not as attractive for experimentation - especially as I understand it has some sort of complicated button operation. On my recumbent, lights are down by my feet and anything which requires me to dismount to flick on "high beam" is a nonstarter.
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I think you'd be pretty safe going up to 10V DC. But then it's not my light.
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Maybe they're being cautious about a recommended dc power because of cooling issues?
i.e. if it were running with a dynamo then you could expect plenty of airflow when there is higher power available. But a battery can (and will) keep applying full power when stationary, leading to higher internal temperature and reduced lifetime.
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It's either that or they're assuming a current-limited source. The thermal issue does seem a bit more likely, given that it seems that the Cyo isn't close to the dynamo's current limit in normal operation. It's a bit expensive to do the experimentation to find out, though.
I'm not familiar with Ay-Ups, but could the Cyo be operating normally, and just outclassed by FRIKKIN' LASERS? I certainly prefer a bit more light than just a Cyo if I'm doing 30mph or more, especially if it's on a bike that's unforgiving of dodgy surface features.
You describe the Ay-Ups as good for 40mph descents. I've done a couple of 40mph descents with the combination of a Cyo, Ixon IQ on full whack and a head torch, which I'd describe as barely adequate. And that's on the Streetmachine, which is about as immune to unexpected surface hazards as bikes get.
The Cyo's a great light, but any dynamo light's going to be easily outclassed by something designed to get only a few hours run time for a reasonably sized battery pack...
I'll also add that rower40's Cyo appears to be about as bright as either of mine running from dynamo power at a normal riding pace.
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I don't know the Cyo directly but I assume it uses the latest Cree XPG R5 emitter at about 3W. Whether your battery can give it 3W at the voltage it needs (about 3.5 - 4V as I understand the datasheet) depends on the battery and the voltage regulation. Since the Cyo is designed to run from a dynamo, I would not like to speculate what its electronics ends up doing with a DC source of about 7V. If it can make sense of the 7V DC it still has to be able to get the right current from the battery. 190mA is no where near enough by the sound of it; if it used the battery voltage without any losses (not likely but I don't know what the actual losses might be) you would need about 500mA from the battery to get anything like the full power from the light. Silly question, but I suppose the beam was in its 'high' mode.
EDIT: it can't be the battery's fault, of course, since it powers your au-ups which will be less efficient (light output per Watt) than the Cyo.
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Chasing the links above, you would ideally want a current limited source. The IV curve is basically a rectified diode, and the voltage/current when connected with a dynamo thus behaves as you'd expect from that. See the message below
Topica Email List Directory (http://lists.topica.com/lists/bikecurrent/read/message.html?mid=813775202&sort=d&start=13195)
I-V Curve: (x-axis is voltage, y-axis is current [actually voltage over 1ohm resistor])(http://www.nscl.msu.edu/~daniel/IV.png)
So they might just be suggesting a 7.5V limit to stop somebody from connecting a bench power supply at 9V without checking the current limit first...
If the light is doing peak rectification onto an internal capacitor (most likely), then at 7.5V RMS AC, the internal DC voltage will be 10.6V (less the rectifier drops)
No, that would only apply if both voltage and current were nice clean sinusoids. Not the case by a long way, judging from the information from the post linked.
None of which helps EdinburghFixed get more light, unfortunately.
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To be slightly more helpful, Pawel's graphs show a peak current of ~600mA on the dynamo, averaging more like 350mA. He doesn't specify speed for the test, but he's going past dynamo poles at about 160Hz if anybody familiar with typical dynamos would care to convert that.
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If the light is doing peak rectification onto an internal capacitor (most likely), then at 7.5V RMS AC, the internal DC voltage will be 10.6V (less the rectifier drops)
No, that would only apply if both voltage and current were nice clean sinusoids. Not the case by a long way, judging from the information from the post linked.
None of which helps EdinburghFixed get more light, unfortunately.
Plus I'm talking complete guff anyway - because the 7.5 volt rating isn't an AC from dynamo - it is a maximum allowed DC voltage.
So ignore me - and don't exceed 7.5V
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Looking at the waveforms, I am certain that the output from the dynamo is being rectified onto a capacitor in the lamp. This explains why there is no current flow below about 4V (No current will flow until the dynamo voltage is higher than the voltage on the capacitor.
If you invert each half voltage cycle, then what you get is aprox the voltage waveform on the capacitor - which peaks at about 7V with about 1V ripple. (Disallowing for any diode drops - I assume they are using shottkey diodes or similar to minimise losses)
So if you are really putting in 7.4V, then you should be seeing full brightness. However, what is not explained is why you are only measuring 190mA (1.4W). What are you measuring the current with?
You don't need a current limited source - there must be internal current regulation in the light, or the LED would only last milliseconds.
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Well, I'm using a basic multimeter, in series to read the current.
It reads about 190mA, and when I plug in the wired tail lamp, it rises to 210mA (separately I have measured the taillight at 20mA so this all tallies).
rower40 reports that at 5.9V DC his Cyo draws 130mA, so 7.5V / 190mA is not incompatible with that.
It's a lipo battery with some circuitry, but clearly it's not current limited as it will happily supply two pairs of Ay-Ups at almost 300mA each = four times the current drawn by the Cyo.
I just find it a bit hard to visualise. If I cut the wires and touched them alternately very very fast (creating a crude AC source, like a dynamo) the light would suddenly draw over 500mA? ???
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That all seems to make sense.
I just find it a bit hard to visualise. If I cut the wires and touched them alternately very very fast (creating a crude AC source, like a dynamo) the light would suddenly draw over 500mA? ???
Instantaneously, immediately after you make the connection, as the current rushes in to top-up the internal capacitor. The current averaged over the whole cycle will be lower. If you took zero time to change polarity (ie. feeding it a true square wave), I wouldn't expect the capacitor to have time to discharge, so the current ought to be more or less the same as with DC.
It does seem increasingly likely that they're being conservative about the DC rating for thermal reasons (possibly in the rectifier? DC would mean that all the heat's being produced in two diodes rather than four...).
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I don't think so. If you look at the waveforms linked to by Tom, the voltage waveform from the dynamo is close to an AC square wave (round topped) with a peak voltage of 7V. When this is rectified, it'll be pretty damn close to 7V DC - but in that instance is running at about 2.1W.
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*peers*
Hmm, good point well made.
There's something interesting going on...
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Ok, I was conflating two issues and being sloppy with my words earlier. Let me try again...
Looking at the waveforms, I am certain that the output from the dynamo is being rectified onto a capacitor in the lamp. This explains why there is no current flow below about 4V (No current will flow until the dynamo voltage is higher than the voltage on the capacitor.
Yes, definitely a rectifier in there, and a capacitor on the other side of it. The bigger question is what does the load beyond those look like?
And I'm suggesting that the answer is a diode, in terms of its current-voltage response. This basically means that it consumes very little current until you approach a threshold voltage, then quickly consumes a lot as you try to rise beyond that. Partly because that's what you'd expect from an LED and partly because it would explain the currents seen.
So if you are really putting in 7.4V, then you should be seeing full brightness. However, what is not explained is why you are only measuring 190mA (1.4W). What are you measuring the current with?
Well, if my hypothesis is correct then the current consumption is highly sensitive to voltage in this region. So if you were to apply 7.5 or 7.6V then the current would be significantly higher than 190mA.
You don't need a current limited source - there must be internal current regulation in the light, or the LED would only last milliseconds.
What I meant was a source which was actively controlled to limit current, not apply a fixed voltage. i.e what I should have called a current source (http://en.wikipedia.org/wiki/Current_source). The point here is that because the load is very sensitive to voltage, if you were to try and apply any given voltage source (http://en.wikipedia.org/wiki/Voltage_source) then you may end up with significantly different currents. The variation largely is due to manufacturing tolerances, and temperature change. So you ideally want a circuit that varies the applied voltage in order to achieve a given current supply accurately.
They are suggesting a conservative voltage limit because they're afraid someone might not understand the above, and want to keep them on the safe side of the actual limit. What isn't clear is what the real current/power limit is. My guess is it's thermal, and they don't want to say what because it depends on airflow and they want to clearly make sure they've recommended something is safe when homebrew nutters come back and blame them after they fry their LEDs.
There is a bit more information about the upper limit protection, and about applying dc, if you read down the quoted messages in the post I linked before.
It's a lipo battery with some circuitry, but clearly it's not current limited as it will happily supply two pairs of Ay-Ups at almost 300mA each = four times the current drawn by the Cyo.
It's not a case of a magic current limit for the battery - the battery has an effective internal impedance and voltage and this in combination with the load determines current. The highest current it can supply is when it's shorted and is only outputting at 0V. At open circuit with no current it will give largest voltage. As soon as you draw some current it goes down, but the result is highly dependent on the load I-V curve.
Assuming you don't have a bench power supply to check dc current against voltage, can you redo your test with a fully charged and a very low battery? And at the risk of being insulting, can I check you're measuring the battery voltage when loaded in both cases, not open circuit? :P Similarly for your 7.4V answer - was that open circuit or at 190mA?
I just find it a bit hard to visualise. If I cut the wires and touched them alternately very very fast (creating a crude AC source, like a dynamo) the light would suddenly draw over 500mA? ???
No. Well, except in the instantaneous sense Kim said.
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I don't think you are right there Tom. The load beyond the capacitor will be a current regulator followed by the diode.
Power leds (certainly the one in the CYO) have a typical forward voltage of about 3 to 4V. If you apply 7V from the capacitor (which has been charged by the rectified AC waveform) then the led will pop very very quickly.
Therefore there must be a current regulator between the capacitor and the diode. Now it would seem that this regulator is pretty far from a perfect current source - since the input current increases with increasing voltage. It could be as crude as a resistor - although this would be very wasteful of power, so I don't think that will be the case.
EDITED TO ADD
This is probably going far further than the OP is interested in - but we are in luck. Someone has dissasembled the fly (predecessor to the CYO)
Schmivits for your amusement: B&M IQ Fly Senso Plus dissection (http://schmivits.blogspot.com/2008/10/b-iq-fly-senso-plus-dissection.html)
You can see the PCB in the 5th photo - click it for full size.
There is an inductor on there - that means it is a switched mode current regulator - should be absolutely bob on, so the behaviour of EF's light on DC is a little odd.
In summary - dynamo voltage is rectified onto the capacitor. That'll be the black one. The blue one is a super cap (1F, 5V) which is used for the stand light function.
The roughly 6-7 volts will be stepped down by the switching current regulator to drive the required current into the LED.
One thing I've noticed on the CYO is that it switches to a low power mode very shortly after the wheel stops turning. This is a definite mode change, not a result of the power disappearing.
I'm wondering if the CYO powered from DC is not recognising a high enough voltage, and is staying in the low power mode?
EF - how confident are you regarding your voltage measurement?
EDITED SOME MORE
Pictures of the CYO's guts.
BUMM Cyo open (Album) - Fotoalbum auf MTB-News.de (http://fotos.mtb-news.de/s/12234)
More info here
http://www.weli.org/themen/technik/Licht/iq-fly.html
The volt/current chart on that page suggests that they have not implemented a proper current control (although it must be providing some current limit function). If they were, I would expect the current to go up with volts until the regulator were able to deliver the controlled current - then I would expect the input current to drop as the voltage increased further (constant power into the led). From the graph at this link, it appears not to be the case.
Tom may be right that the way to get full power out of the light with an external battery is to provide an external current source, rather than voltage source.
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One thing I've noticed on the CYO is that it switches to a low power mode very shortly after the wheel stops turning. This is a definite mode change, not a result of the power disappearing.
I'm wondering if the CYO powered from DC is not recognising a high enough voltage, and is staying in the low power mode?
Ah, of course! That would make a lot of sense...
Hmm, maybe the mode change is sensitive to frequency rather than voltage? Not as stupid as it might sound, as it would avoid oscillations around the switchover point...
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I don't think you are right there Tom. The load beyond the capacitor will be a current regulator followed by the diode.
Yes, I was talking more of its behaviour than what was actually there. Certainly I was expecting some kind of switched mode to change the voltage, but that doesn't rule out the diode load characteristic.
That curve you found for the Fly is very revealing. The difference to the 'warm' curve doesn't bode well for a simple battery supply, alas..
It could be as crude as a resistor - although this would be very wasteful of power, so I don't think that will be the case.
I was giving them the benefit of the doubt on that one. ;D
EF - how confident are you regarding your voltage measurement?
+1
More info here
http://www.weli.org/themen/technik/Licht/iq-fly.html
The volt/current chart on that page suggests that they have not implemented a proper current control (although it must be providing some current limit function). If they were, I would expect the current to go up with volts until the regulator were able to deliver the controlled current - then I would expect the input current to drop as the voltage increased further (constant power into the led). From the graph at this link, it appears not to be the case.
Actually makes a little sense for a dynamo driven light, if you're expecting the limit to be thermal...
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Just to confirm - I measured the voltage under load. That is, I ran the Ay-Ups (measured the current at 290mA) and then measured the voltage across the rejoined wires with the light still on, which was 7.49V.
It's interesting that there is no thermal grease between the diode and the heatsink in the dismantled Fly - it would seem to me that this is pretty fundamental.
It sounds increasingly like if you want more light from the Cyo, it's a straight swap on the existing circuitry with some kind of dimmable driver. As it is, I'm going to take it out on another wet night somewhere and make a call on whether I'm happy with it driven at 190mA (which would be nice, no dismantling needed).
For descents, I can just switch in the Ay-Up (and in any case, I need two lights on the bike for PBP).
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Fair enough. I'd still check the current with a fully charged and nearly flat battery.
If you're going to open it up and start substituting the circuitry anyway, it might be worth exploring exactly what the circuit is first to see if you could achieve what you want more easily with a couple of component changes?
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Do we take it that you've checked it with the battery connected on both polarities?
IIRC the B+M instructions said that there was a specific way to connect, even though it normally takes AC
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I am surprised you need a brighter light than a Cyo - is there a lot of street lighting? Don't get me wrong, it's never a bad thing, but I found that the even 2x Ixons on top of a Cyo wasn't a huge improvement in brightness - it was spreading what light there was around that made it helpful. Indeed, I've found on unlit lanes, just 2x Ixons on the 10lux setting is plenty on known roads, even descending at 60kph. FWIW, mine are mounted down on the low rider mounts, so they are set quite horizontal, so pick our road imperfections at quite a distance. At 2xIxons on the 40lux, I am told I look like a motorbike.
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I think it's putting out a fraction of the light it should - my understanding is that the draw on a dynamo hub is ~500mA, but I'm only seeing 190mA. Also, it's visibly less bright than a three year old entry-level asymetric beam headlight, which shouldn't be right :facepalm:
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Just an update - last night I did a big loop to extend my commute home on a fancy. As a result I had the chance to give the Cyo a more demanding test riding along the unsealed surface of the Union Canal in inky darkness. Without the slightest hint of street lights or other riders, this was my first chance to be brutally honest about the Cyo's capabilities at 190mA.
Actually, I was pleasantly surprised. There is plenty of light to ride at 15mph and I was still fairly happy at 20mph. I think if I'd had my old light for comparison I might have preferred it, but it was certainly bearable.
I'm not sure I'd recommend this option unless you explicitly want a long-runtime not-so-bright light (but then it did cost £35). If it could be switched to draw an amp like MTB lights but with the same reflector, it would be an all-out win.
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Further follow up:
Not so good.
I rode with the Cyo on a couple of 200's and on many commutes, and was rather satisfied. Last couple of days I've had trouble with it refusing to light up properly (comes on super dim, like a cheap LED blinkie).
I thought perhaps my old Ay-Up lipol battery might simply be dying, so last night I tried swapping it with another, but no better.
Fair enough, I thought - I can try this with a 6 cell NiMH (7.2v) RC battery. Again, no dice, so it looks like something in the light has broken.
However, I was able to get it to light up easily at full brightness through the tail light connectors. Gambling that the tail light could handle it, I wired both lights in parallel (by poking the battery wires into the tail light connectors along with the headlamp wires!) and WIN. Back in business.
However this morning by the time I got to work, the Cyo was not lighting up at all, although the taillight was chugging away quite happily. So either the Cyo is fully broken now, or the voltage of the battery has fallen below some kind of threshold required to get any light at all (which sounds plausible to my non-electrical brain...)
Either way, looks like I might need to take it apart and wire up the LED directly.
Does anyone know what the design voltage of dynamo taillights are, please? My google-fu is weak (or I'm not hitting the right sites) and I like the toplight line plus enough to want to preserve it...
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Incandescent dynamo taillights are 0.6 watts, used with 2.4 watt headlights, all nominally 6 volts of course.
There are some LED headlights that are happy being driven on DC, Inoled for one. IanH sells them.
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Yes - B&M document the use of DC power in the manual of the IQ Cyo, which is what gave me the idea to buy one (since I don't own a dynamo).
So the tail-light is expecting 6V, I guess it will be tasting as much as 7.5v - wonder if it will nuke. It certainly hasn't been a problem for an hour this morning, so perhaps it's just a case of LED life in the millions of hours, rather than billions. :)
The next question is - should I try to run the Cyo LED at a full 1000mA, or hold back with a 700mA driver? I guess the question is how good is the heatsinking...
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I'll keep updating since somebody other than myself may well want to run a dynamo rig from DC:
After a forum appeal, I met up with another Edinburgh rider who has a dynohub, to poke my Cyo wires onto his prongy bits. To my surprise, although dead to the world of DC, the light behaved impeccably with AC. I have no idea how it can have half-broken.
My trouble with powering via the taillight leads, however, was simply battle damage between the tail light and the lamp :facepalm:
Aaaanyway.....
At 8.2V from the fully-charged NiMH pack, the tail light still draws just 40mA - the same as at the nominal voltage. This encourages me that it will not be adversely affected, since to my layman's eye, if there's no more current, there oughtn't to be any more heat.
Second, at 8.2V the Cyo itself now draws ~290mA - well up on the ~190mA it drew at 7.4V (I recall this was predicted by someone up thread). :thumbsup:
The NiMH is looking like a bit of a win. For about £7 a pop you can pick up a new RC 6 cell which will drive the combined lighting system for a healthy 12 hours.
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I wouldn't worry too much (within reason) about what voltage you apply to (LED) tail lights. They're going to be designed to cope with the scarily high (several tens of volts) voltages you can get from a lightly loaded dynamo, so are likely to be doing something with zeners and resistors to keep the magic smoke where it belongs. The likely failure mode is overheating the zener clamp (assuming a very simple linear design), and it's going to take a lot more than 125% of the rated voltage to do that.
I agree that if it's drawing the same current, it's going to be okay.
Interesting, though not entirely surprising, that the Cyo worked fine with AC...
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Because the eve of PBP is a great time to put your lighting system in jeopardy, I experimented with the voltage tolerance of the Cyo. I'm using an AA battery holder for the event since it's easy to buy AA's and harder to recharge stuff, and I tried 6x Lithium AAs.
I measured a voltage of 9.8V being drawn at which point the Cyo was burning through 500mA.
It didn't seem to get hot or complain in any way, but for the sake of prudence on the eve of a 1200k, I shorted one of the holder positions with a wire to give a five cell battery at 8.2V.
Just another data point for general bemusement.
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In case it's of any help to anyone. As my SON is KO for the moment, for my ride down to meet up with the family after work on Friday night , I used 5 Evolta hybrid AAs in series on my Cyo N Plus (60 Lux version). I used my little Cateye backup lights for going through London, so I didn't light up properly until about 10 pm.
I was expecting about 3 hours, but in fact they were still giving me good light at 3 am when I arrived (It took me a good two hours longer than I hoped). The light is not quite as bright as when running the dynamo, but easily enough for riding.
The cells started out at about 1.45 V with the pack giving about 6.8 V (where does the rest go?) with the light off, and about 6.6 with it on. I forgot to check them before I put them on to recharge last night.
They were housed in a Maplins 8-gang battery box with 3 slots shorted out, and +ve wired to the earth (white stripe) wire on the Cyo.
One last thing. The rear B&M 4D Light only lights up 2 of its 4 LEDs. I am waiting to see whether I have damaged it, or whether it is something to do with AC vs DC.
On the whole it seems like a workable backup solution although I would rather run with the SON and not have to think about it. No doubt you could run 6 or more cells for a brighter light, but I'd just as soon stay on the safe-but-adequate side.
Hope this helps someone.
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One last thing. The rear B&M 4D Light only lights up 2 of its 4 LEDs. I am waiting to see whether I have damaged it, or whether it is something to do with AC vs DC.
Mebbe not much help wrt a dynamo - but my 4D senso-multi-whatever (used battery-only) lights all 4 with fresh batteries, but only 2 when they're getting low.
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Anyone used one of the new Luxos B lights with a battery pack like this? I'm too cheap for a dynamo and I really like my dura ace hubbed front wheel, but want a good light. I'm happy to wire it up myself with a 6xAA battery pack.
Would the voltage vs mah usage be similar to the Cyo, given they are both designed to run off the same dynamos? That's probably a stupid assumption given the LEDs will be new and no doubt the circuitry :-\
I've ordered a cheap multimeter off ebay so I can check voltages in places, and I guess I can check the current draw when it is hooked up a running?
Oh yeah, should I start a new thread for this?
Cheers,
Adam
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Looking at the manual (http://www.bumm.de/fileadmin/user_upload/179/179_LUXOS_B_U_Anleitung.pdf):
Please note: The headlight can only be powered by a dynamo (AC).
Connection to a DC power source (battery) is not possible.
Only special e-bike versions of the LUXOS E can accept DC power from 15
to 75 V. Please ask your specialised retailer.
Given that the Cyo manual explicitly specifies voltage and polarity for DC operation, I'm not optimistic.
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RTFM Adam.
Thanks for that! That would have been embaressing if I bought that, fiddled with it, and it didn't work, or worse I busted its electronics.
Oh well, I'll go the cheaper Cyo route instead aka this thread :-)
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Looking at the manual (http://www.bumm.de/fileadmin/user_upload/179/179_LUXOS_B_U_Anleitung.pdf):
Please note: The headlight can only be powered by a dynamo (AC).
Connection to a DC power source (battery) is not possible.
Only special e-bike versions of the LUXOS E can accept DC power from 15
to 75 V. Please ask your specialised retailer.
Given that the Cyo manual explicitly specifies voltage and polarity for DC operation, I'm not optimistic.
Possibly something to do with the circuitry that reads the frequency of pulses from the dynamo, then changes the beam pattern depending on your speed? Question is, does this get fried or merely confused by a DC supply?
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Possibly something to do with the circuitry that reads the frequency of pulses from the dynamo, then changes the beam pattern depending on your speed? Question is, does this get fried or merely confused by a DC supply?
Ah yes, that would make sense. Being stuck in nearfield mode seems likely, at the very least.
Cobbling together a low-loss H-bridge and oscillator (if that would even work) is well into the territory of more effort than fitting a dynamo. Especially given the price of bottle dynamos.
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To add a datapoint:
I'm in the process of adding electric assist to barakta's trike. With a large battery and regenerative hub motor, this will make the existing bottle dynamo redundant. My plan is to use a high-efficiency switching regulator to step down the buss voltage to something appropriate for the existing dynamo lighting (a 60lux Cyo N Senso Plus and a pair of Spanninga Pixeos).
To that end, I disconnected the dynamo and hooked up a bench power supply to confirm it should work. Taking care to observe the correct polarity (DC positive to the earth - black wire with the white stripe - on the Cyo), I fed it the recommended 7.2V, and observed that all lights illuminated and the sensor and respective stand-light functions worked as normal. Slowly tweaking the voltage up to the 7.5V recommended maximum, I observed a *dramatic* increase in light output. I briefly went to 7.7V, but didn't see much of a change in brightness. Removing the power source would cause the Cyo to dim to standlight brightness within a second or so. Steady-state current at 7.5V was of the order of 300mA for all three lights, and output was comparable to that when driven by the dynamo at 12mph+ (I didn't go as far as deploying the turbo trainer and wiring for A/B testing). The Cyo didn't appear to be getting particularly warm.
I conclude that the Cyo is *very* fussy about voltage when fed by a DC voltage source, and wouldn't be surprised if component tolerances play a part. If I were building a battery pack for one, I'd want to use a regulator.
My plan is to use a AG8105 (http://www.semiconductorstore.com/pdf/newsite/silvertelecom/Ag8100.pdf) PoE regulator module to drop the nominal 48V (actual 52V+) battery voltage to 7.5V for the lights. Measured efficiency is about 88% at these loads. The 20Ah battery should be able to run the lights continuously for about 2 weeks if you don't ride anywhere :)
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Thanks Kim. Funnily enough, your name was mentioned to me by a friend as we were discussing my wobbly dynohub and the possibility of running my Cyo from batteries. Having read your posts I'm not going to try that route. And TBH given the distance I've had from the Shimano dynamo, replacing like-with-like is a reasonable option.