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Thread: Standlight circuits (Will this circuit work?)

  1. #91

    Default Re: Standlight circuits (Will this circuit work?)

    Quote Originally Posted by Alex Wetmore View Post
    If you read the rest of the thread you'll see that Steve Kurt (and later me) are using the ZXSC310 as a LED driver for the standlight. This is similar to how you are using the bFlex.

    The bFlex seems like an odd choice since the minimum input voltage is 4 volts. The supercaps max out around 5.5 volts. So you aren't using much of the supercap's capacity. A driver that runs on lower voltage will give you a longer runtime or allow you to use a smaller (physically and capacity) supercap. The MaxFlex would give you about double the runtime just because it can run off of 2.5 volts. The ZXSC310 is great because it runs off of just .8 volts.

    alex
    Hey Alex,

    I am sorry I have not read the whole thread... & sorry that this post ended up off topic... sorry everyone

    In answer to your question, my capbattery pack on my dynobatt runs 3 LEDs, thus is a ~11v capbattery pack (using 2.5v /55F caps)... but when the caps drop below Vf for 3 LED's, I still have power left in my caps... I also wanted to run a flashing LED light when I stopped, had a spare bflex, so for this app it worked to drain most of the power left in the caps...

    the zetec is a great idea for this app... I will read the rest, so I can contribute better...


    Syc:

    I wanted to avoid a batt overcharge / undercharge circuit (not needed for the way caps work) & loved the fact that a cap has 1 mill cycles instead of a few hundred...

    K

  2. #92
    Flashaholic* Calina's Avatar
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    Default Re: Will this circuit work?

    [quote=syc;2715654]I see that this stuff is old hat for you guys :-)
    Looking back, bandgap also mentioned doing dynamo charged batteries for years in a thread that Martin started on Charging Li-Ion with ripple current.

    What I was wondering is, if we took advantage of the LM317L and protected li-ion batteries instead of supercaps, could we dispense with the zetex and use a circuit like this?



    quote]

    I can't see the picture on flickr.
    Is it just me?
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  3. #93

    Default Re: Will this circuit work?

    Quote Originally Posted by Calina View Post
    I can't see the picture on flickr.
    Is it just me?
    No it's not just you - I generally delete old circuits that are flawed and replace them with the corrected versions. But the links to flickr for the images don't track the replacement images. Bandgap requested that I post these schematics with big Surgeon General's Warnings on them, which is very reasonable considering that we're talking about Li Ion battery charging.

    I could go back and replace the link, but then the comments correcting the circuit would no longer apply. So I left it blank this time around.

  4. #94
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    Default Re: Standlight circuits (Will this circuit work?)

    I just remebered something Steve K pointed out to me a while ago.

    Li ion cells are a bit touchy (I don't know how touchy) about being charged at temperatures below 0C - which is one of the reasons he sticks to nickel cells as where he lives it gets a bit chilly in the winter.

    EDIT: I feel the need for another HEALTH WARNING

    "At cold temperatures the pores in the SEI are effectively closed. If charging a cell at severely low temperatures is attempted, lithium metal will plate on the surface of the SEI, resulting in two dangerous conditions, either of which can cause the battery to enter thermal runaway."
    From http://www.powermanagementdesignline...leArticle=true

    Steve
    Last edited by Bandgap; 12-03-2008 at 07:31 AM.

  5. #95
    Flashaholic* znomit's Avatar
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    Default Re: Will this circuit work?

    Quote Originally Posted by FrontRanger View Post
    To maximize the amount of charge stored on the cap, I scribbled out this little circuit:



    I don't have the parts laying around to try this myself. This won't be as good as the boost regulator, but will nearly triple the usable stored charge if it works as planned (3.5-2.5) becomes (5.4-2.5). Hope it helps.
    Tried this out today on an MC-E. Works very very well. Probably triple the usable runtime from the bare supercap. Definitely be in my next build.

  6. #96
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    Default Re: Will this circuit work?

    Quote Originally Posted by znomit View Post
    Tried this out today on an MC-E. Works very very well. Probably triple the usable runtime from the bare supercap. Definitely be in my next build.
    Right on. I always enjoy reading about your builds, so please do post it.

  7. #97

    Default Re: Will this circuit work?

    Quote Originally Posted by znomit View Post
    Tried this out today on an MC-E. Works very very well. Probably triple the usable runtime from the bare supercap. Definitely be in my next build.
    I've been quite happy with how it charges up the supercap, especially considering how simple it is.

    Here's the latest iteration of the LiIon trickle charger/standlight circuit. I think I've addressed the issues bandgap pointed out to me, but that doesn't mean I haven't screwed something else up


  8. #98
    Flashaholic* Calina's Avatar
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    Default Re: Will this circuit work?

    Quote Originally Posted by znomit View Post
    Tried this out today on an MC-E. Works very very well. Probably triple the usable runtime from the bare supercap. Definitely be in my next build.
    Did you build it? Any news on stand light circuits?

    Actually this post is just a bump: this thread is to good to let it go away in oblivion.
    Last edited by Calina; 02-03-2009 at 05:38 PM.
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  9. #99
    Flashaholic* znomit's Avatar
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    Default Re: Will this circuit work?

    Quote Originally Posted by Calina View Post
    Did you build it?
    Summer in NZ so light building not quite so urgent!
    Heres what I'm thinking.... an MC-E with the upper dice powered by a full wave rectifier and the lower on doubler. Both charge up a supercap and three 5mm leds (a much wider beam than the MC-E). Gives me a real dipped beam and a small light head.


  10. #100
    Flashaholic* Steve K's Avatar
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    Default Re: Will this circuit work?

    This is wandering off topic, but has anyone actually built up a MC-E and tried out the idea of a high and low/dipped beam? I love the concept, but wonder how well it actually works out. I'm behind on my standlight project, and I'm already contemplating building up a new light using the MC-E! I feel sorta guilty. :-)

    Steve K.

  11. #101

    Default Re: Will this circuit work?

    I have tried it with a MC-E in various reflectors, but not with TIR optics. To tell the truth the results were pretty disappointing. I tested using two independent power supplies to light the MC-E, each driving two adjacent dies, then switched one string off to see the effect. With only two dies illuminated the hot spot shifts, but not by much, and there is minimal change in the spill light. IMO not worth the hassle unless, like Ktronic has posted, you use a high powered string and a low powered string for high/low beam selection.

    I like the idea of 5mm LEDs for the standing light, a widely viewable light source is certainly better for visibility than a highly focused one.

  12. #102
    Flashaholic* Steve K's Avatar
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    Default Re: Will this circuit work?

    Quote Originally Posted by StevelKnievel View Post
    I like the idea of 5mm LEDs for the standing light, a widely viewable light source is certainly better for visibility than a highly focused one.
    thanks for sharing your experience with high/dipped beams & the MC-E. A shame it didn't work out, but certainly not that big of an issue.

    To date, my standlights have used four 5mm leds driven by the little Zetex boost converter. Not a bad arrangement, but I had wondered if they were as visible as a Cree XR-E or such. It seems like 5mm leds get rated differently.... I don't think I ever got figures for luminous efficiency for the amber 5mm leds that I'm using now.

    There's also the question of what color to use for the 5mm leds. I used amber on mine, mostly in the belief that they were more efficient than a similar white led. I'm not sure if it does any better at conveying the idea of "bicycle" when people see it than a white led would.

    Steve K.

  13. #103
    Flashaholic* znomit's Avatar
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    Default Re: Will this circuit work?

    Quote Originally Posted by Steve K View Post
    This is wandering off topic, but has anyone actually built up a MC-E and tried out the idea of a high and low/dipped beam?
    I've tried it in the lab using a boom SS reflector and just like StevelKnievel said its not fantastic, but I would like to see how well it does out on the road. My setup was one powersupply and a switch to select die pairs.

  14. #104

    Default Re: Will this circuit work?

    Quote Originally Posted by StevelKnievel View Post
    I have tried it with a MC-E in various reflectors, but not with TIR optics. To tell the truth the results were pretty disappointing. I tested using two independent power supplies to light the MC-E, each driving two adjacent dies, then switched one string off to see the effect. With only two dies illuminated the hot spot shifts, but not by much, and there is minimal change in the spill light. IMO not worth the hassle unless, like Ktronic has posted, you use a high powered string and a low powered string for high/low beam selection.
    Thanks for the report. It sounds like the only really effective way to get a gradient in the light pattern is to either use some curved reflector or mount LEDs on the heatsink at 2 different angles.
    The curved reflector on those German lights looks far too difficult to easily reproduce using surplus parts.

    Incidentially, bandgap got back to me and said the last circuit for LiIon battery should be good once you add one more resistor in series between the diode and the transistor. Here's the current diagram - not sure if I'll ever build this, but putting it here in case someone wants to pick it up and try it.
    Last edited by syc; 03-01-2009 at 07:22 PM. Reason: Added circuit diagram.

  15. #105
    Flashaholic* znomit's Avatar
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    Default Re: Will this circuit work?

    Quote Originally Posted by Steve K View Post
    To date, my standlights have used four 5mm leds driven by the little Zetex boost converter. Not a bad arrangement, but I had wondered if they were as visible as a Cree XR-E or such. It seems like 5mm leds get rated differently.... I don't think I ever got figures for luminous efficiency for the amber 5mm leds that I'm using now.
    I tried an amber led today.
    Side by side test with an XR-E(Q2 or 5) using the tight cree optic. Both driven off 5.5V supercaps thru resistors, I set the amber at 100mA and tried different resistors on the XR-E until I got similar looking brightness. I think around 50mA and still brighter than the amber.
    Quite disappointing, the amber faded much faster. Looks like I'll stick with power leds.

  16. #106

    Default Re: Will this circuit work?

    Quote Originally Posted by syc View Post
    I updated the original diagram with the LM317L circuit on flickr and replaced with a diagram with a warning about tolerances and the worse case possibility. I've updated the link in my original message here, but other messages (such as Alex's) will have broken images.

    I also built up the circuit variation that frontranger suggested to improve the charge voltage of the supercap. After building it and taking some measurements, I was only seeing a little over 6v across both of the Cree R2's, and the diode clamp was dropping the charge voltage at the supercap to just over 4v.

    It turned out that a single diode provided enough of a drop so that the supercap got just over 5v, and this is what I ended up with:



    The standlight seemed decent for a "be seen" light and it lingered around for quite some time. But I think I'm going to pick up a 50 and 100 ohm resistors and see it looks with those - the second supercap may come in handy with the lower resistance.

    I'm really glad that there was so much feedback on these circuits as well as getting a chance to prototype it - this current circuit seems much better than the original one that I wired up last night.
    Is that single diode clamp a Schottky or silicon diode?

    -Jim G

  17. #107
    Flashaholic* Steve K's Avatar
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    Default Re: Will this circuit work?

    Quote Originally Posted by sfCyclotourist View Post
    Is that single diode clamp a Schottky or silicon diode?

    -Jim G
    Seems like a silicon diode might be best in terms of not exceeding the super-cap's voltage rating. If the LEDs have a forward voltage of 3.5v, then there will be 7v across the two of them. The forward voltage of 1.4v for the silicon diode will put 5.6v across the super-cap, which should be okay.

    regards,

    Steve K.

  18. #108

    Default Re: Standlight circuits (Will this circuit work?)

    When I measured the voltage across the 2 LED's, it turned out to be closer to 6v than 7v, so I was able to get away with only a single diode to get the current into the 5-5.5v range for the supercap. The variation in Vf for the LED's means there's room for tweaking if you measure the actual values.

  19. #109
    Flashaholic* Steve K's Avatar
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    Default Re: Standlight circuits (Will this circuit work?)

    Quote Originally Posted by syc View Post
    When I measured the voltage across the 2 LED's, it turned out to be closer to 6v than 7v, so I was able to get away with only a single diode to get the current into the 5-5.5v range for the supercap. The variation in Vf for the LED's means there's room for tweaking if you measure the actual values.
    was the voltage measured when the dynamo was driving the LEDs, or was that with a DC power supply? If you were measuring the voltage while using the dynamo, you are probably reading some sort of averaged DC voltage instead of reading the peak voltages.
    (this would be the point where you mention that you used a 'scope to measure the voltage and let me know that you know what you are doing....)

    Personally, unless I did use a scope to be sure that the peak voltages weren't going to overstress the super-cap, I'd go with the silicon diode. There's also the issue of reliability too. Caps tend to last longer when they aren't used all the way up to their voltage rating. In some caps, the capacitance actually decreases when you try to use them anywhere near their rated voltage. Weird, but true. I'm thinking primarily of some ceramic caps that have very large values for the package size. Haven't checked any datasheets of supercaps to see how they behave.

    Anyway.. there's very little risk to personal safety to use either diode. The worst that might happen is you kill the supercap, which might short out, and shunt all current away from the LEDs.
    hmm...
    I take it back. There is some risk. Make sure your trial runs are during the day, and abuse it as much as you can (i.e. ride fast down steep hills, make sure it's a hot day, stop and start a lot). Bring a spare light. Better to kill the supercap during the day than when you actually need it.

    have fun, but be careful

    Steve K.

  20. #110

    Default Re: Standlight circuits (Will this circuit work?)

    Quote Originally Posted by Steve K View Post
    was the voltage measured when the dynamo was driving the LEDs, or was that with a DC power supply? If you were measuring the voltage while using the dynamo, you are probably reading some sort of averaged DC voltage instead of reading the peak voltages.
    (this would be the point where you mention that you used a 'scope to measure the voltage and let me know that you know what you are doing....)
    Well, this may not assure you that I know what I'm doing, but here's what I did anyway

    I used 6 freshly charged NIMH AA batteries in series. I was a little worried that it would be too much current, since I had read estimates of around .8a to 1a current direct drive from NIMH AA. But after trying the LED's and not frying them, I used that as the reference - assuming that the stack of batteries was a loose upper bound on what the dynamo would produce (some sites show bottle dynamos producing as much as .75a)

    I don't have a scope, or even a nicer grade of dmm - a friend keeps offering to let me use his bench with all his nice gear, except that I usually do this stuff random evenings when I'm feeling like doing some electronics dorking, so it won't do to show up on his doorstep suddenly at 10pm...

    I used this on a commuter - I'm assuming JimG is going to be using these on his rando events, in which case he should probably measure this stuff more carefully than I did. I'd hate to be stuck in rural Marin county on some rainy night without lights.

  21. #111
    Flashaholic* Steve K's Avatar
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    Default Re: Standlight circuits (Will this circuit work?)

    Quote Originally Posted by syc View Post
    I don't have a scope, or even a nicer grade of dmm - a friend keeps offering to let me use his bench with all his nice gear, except that I usually do this stuff random evenings when I'm feeling like doing some electronics dorking, so it won't do to show up on his doorstep suddenly at 10pm...
    It may be worth buying a cheap DMM for tasks like this. I think I bought one for $20 or so, and it does a tolerable job of measuring the basic stuff. Certainly handy when I need a couple of meters and my Fluke is handling the jobs that require some accuracy.

    AA cells can put out quite a few amps when shorted. I don't know that I'd just wire a couple across a valuable LED. It might be worth picking up a few low resistance power resistors. Maybe 10 ohms, rated at 1 watt? Wire them in parallel for lower resistance, and in series for higher resistance. Personally, I built up a simple power supply with a transformer, bridge rectifier, LM317 adjustable regulator, potentiometer, a few small resistors and caps, etc. Then I can slowly increase the voltage while monitoring the current through the LED. Once you've got a power supply, there are a lot of odd jobs that you'll find for it. :-)

    Steve K.

  22. #112

    Default Re: Standlight circuits (Will this circuit work?)

    Quote Originally Posted by Steve K View Post
    It may be worth buying a cheap DMM for tasks like this. I think I bought one for $20 or so, and it does a tolerable job of measuring the basic stuff. Certainly handy when I need a couple of meters and my Fluke is handling the jobs that require some accuracy.
    Actually, I do have a _cheap_ DMM, but I discovered it was so cheap, the current measurement only goes to something like 250ma. I should see what DX has that is less junky.

    Personally, I built up a simple power supply with a transformer, bridge rectifier, LM317 adjustable regulator, potentiometer, a few small resistors and caps, etc. Then I can slowly increase the voltage while monitoring the current through the LED. Once you've got a power supply, there are a lot of odd jobs that you'll find for it. :-)
    I went to a local "recycled goods" place and picked up a wall wart that outputs 3.6v 300ma to use for single LEDs. These old wall warts cost less than a can of soda. I would be a good idea to pick up one with more output and then do the LM317 thing like you suggest.

    But first, I think I'll dig out that breadboard and finish that dynamo light I started wiring up...

  23. #113

    Wink2 Re: Standlight circuits (Will this circuit work?)

    HI and welcome back to the standlights thread! Maybe I'll be the first back on... I had submitted a couple of posts a few weeks ago but it looks like they went west with all the other post-November messages.

    So I recall that we were discussing my intention to add a third LED to Frontranger's suggested circuit and my query as to where exactly the 'feed' for the supercap should best leave the +ve rail - before all the leds or between led 1 and led 2? I was still experimenting with varying results. Well in the interests of simplicity I've gone back to the 2-led circuit and built it up inside a small Hammond 1455 series box. It turned out to be a very complicated way of doing things but I've just finished it and it works fine. Steve Kurt has previously asked how long the standlight stays on for? All I can say is that it's daytime 'bright' for 5 mins and still has a reasonable glow (enough to read something close up) after 15. I'll post a photo when I am able to.

    Next light is going to be built on a bit of open 40mm alloy channel with no enclosure and any electronic bits inside an old piece of celluloid chip tube. I've had enough of 'engineering'!

    Regards to all,

    Savvas,
    Adelaide.

  24. #114

    Default Re: Standlight circuits (Will this circuit work?)

    Latest light - works a treat!

    Savvas.

    Last edited by Savvas; 03-12-2011 at 11:51 PM. Reason: picture not showing...

  25. #115

    Default Re: Standlight circuits (Will this circuit work?)

    Where can I find Zetex ZXSC310 or any equivalent driver (international delivery for France).

    Thanks

  26. #116
    Flashaholic* Steve K's Avatar
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    Default Re: Standlight circuits (Will this circuit work?)

    how about Farnell?

    it looks like they sell the ZXSC310.

    regards,
    Steve K.

  27. #117

    Default Re: Will this circuit work?

    Did anyone, Steve? Alex? get a standlight circuit built using a ZXSC310? I'd be very interested to hear how it worked. I have no experience with surface mount components so might struggle to emulate it but I'm willing to give it a go if it's worth it.

  28. #118
    Flashaholic* Steve K's Avatar
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    Default Re: Will this circuit work?

    I've used the ZXSC310 in three standlight circuits currently on my bikes. They are powered from a single AA nicad cell, and drive four 5mm amber or red leds. It works quite nicely. This is the latest; a taillight and standlight for my commuter 'bent. There are a few pics and schematic in that set.

    I also used a slightly different design in my latest headlight. I drew up the schematic a couple of years ago, but just got around to building and debugging the circuit this winter. The standlight drives one of the 3 watt Crees that are part of headlight, and uses a small regulator to charge the nicad. The design also adjusts the # of LEDs that are powered as a function of the dynamo speed. At low speeds, only two LEDs are powered At higher speeds, 4 LEDs are powered. This gives good light at both high and very low speeds (3.5mph). In addition, it gives me a way to "dim" the lights when meeting another bike or ped on the multi-use path. The board is built, so now I need an opportunity to pull the light off the bike for a couple of weeks and get the board installed in the light.

    The ZXSC310 is a handy little part. It'll provide a brighter standlight than any of the commercial stuff I've seen.

    regards,

    Steve K.

  29. #119

    Default Re: Will this circuit work?

    Very impressive. That looks like an ideal circuit. I hope you don't mind, but it raises lots of questions for me:

    Did you use the diode or Mosfet rectifier?
    Which is more efficient?
    Is the battery still a single AA or are there two in this case?
    Is the switch to isolate the battery when parked?
    Should the inductor be connected to v_drive as opposed to D5?
    Can you give me a quick outline of how the speed sensor circuit works?

    Sorry for so many questions
    Nick

  30. #120
    Flashaholic* Steve K's Avatar
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    Default Re: Will this circuit work?

    Quote Originally Posted by nicknoxx View Post
    Very impressive. That looks like an ideal circuit. I hope you don't mind, but it raises lots of questions for me:

    Did you use the diode or Mosfet rectifier?
    Which is more efficient?
    Is the battery still a single AA or are there two in this case?
    Is the switch to isolate the battery when parked?
    Should the inductor be connected to v_drive as opposed to D5?
    Can you give me a quick outline of how the speed sensor circuit works?

    Sorry for so many questions
    Nick
    Q1: Did you use the diode or Mosfet rectifier?
    A1: mosfet rectifier. With the modern mosfets with very low resistance, the power dissipation is very small, which means that the mosfet can be very small. I think these mosfets are basically SOT size packages. The lower voltage drop really only matters if you have to produce light at low speeds. Part of my commute takes place on a 14% hill where my speed drops to 3.5mph, so this is important for me.

    Q2: Which is more efficient?
    A2: the mosfets are clearly more efficient. Whether or not it matters is a separate question.

    Q3: Is the battery still a single AA or are there two in this case?
    A3: it's still a single AA. The Zetex boost regulator doesn't produce a lot of output power, so a 600mA-hr nicad is enough to run the standlight for a half hour or so.

    Q4: Is the switch to isolate the battery when parked?
    A4: yes. It might be nice to have a circuit that shut off the standlight after 10 minutes or so, but long duration timers like that tend to be complicated. There are some new timer circuits that excel at long durations... don't recall the part numbers, though.

    Q5: Should the inductor be connected to v_drive as opposed to D5?
    A5: No. This is a boost regulator. The transistor Q10 pulls the inductor low in order to get some current flowing in the inductor. After the current has reached the desired level and sufficient energy is stored in the inductor's magnetic field, the transistor turns off, and the magnetic field energy causes current to continue to flow through D5, thereby powering the LED. I am wondering if Q8's collector should be connected to D8's anode instead of D8's cathode. My circuit works, but I might have modified it without remembering to update the schematic. Otherwise, the circuit is trying to charge the battery at the same time that it is discharging it.

    Q6: Can you give me a quick outline of how the speed sensor circuit works?
    A6: Google "missing pulse detector" for an idea. Basically, the dynamo waveform triggers the first one-shot. It generates a pulse which triggers the second one-shot. The second one-shot has a fairly long pulse, so if it is regularly triggered, the output is steady. If the dynamo goes fast enough, the first one-shot is triggered so often that it never times out, so it's output is a steady DC voltage, and the second one-shot changes to the other output voltage. It makes more sense when I draw out the pulse waveforms, but it can work. BTW, I should mention that I borrowed this idea from Mr. Bandgap.

    regards,

    Steve K.

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