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Thread: potentiometers?

  1. #1
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    potentiometers?

    Hello guys,

    I am making two more LED light setups. Both are going to be 6 SSC P4 LED's. One is going to be using dual 3021-D-N-1000 buck pucks. And the other is going to be using dual Bflex's. My last one I used dual 3023-D-N-1000 buck pucks but didn't have the ability to dim the lights. So these 2 new ones I should be able to dim them.

    Now on to the questions. For the dual 3021-D-N-1000 buck pucks I want to use a potentiometer to dim them but don't know which one to use. I started looking around and there are alot of different kinds. Also I want to use a single one to dim both buckpucks at the same time. Is this going to be a problem? Also want to use a 3 way toggle switch to turn the lights on. So one switch will be off, high, low (what ever the pot is set at). I am waiting on some parts so I can't test for myself. I am guessing that if I have the CTRL lines connected it will be max and if I seperate them it will be off (or vice versa). So for high I just make them connect, and for low it wires them to the pot.

    Please let me know if I am wrong or this can't be done. I want to get the POT soon so when all the parts come in I can start playing with it

    Thanks in advance as you guys are always helpful.

  2. #2
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    i would use a single pot that has an on/off switch attached.....much cleaner than a bunch of switches. wiring a pot is easy stuff.

    that said, i tried 3 different pot switches and the 1A current was too much for them, they burnt after about 2 minutes. to go up in current rating means a much much bigger switch, at least the ones that i found. if you find a high current pot with a small profile, post a link...
    what would rainbow unicorn do?

  3. #3
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    *******YOU SHOULD HAVE A 3021 DE 1000 **** The DN is not dimmable and will not have the cntrl and ref pin

    on the 3021 DE you can use a 5kohm audio taper pot. You can wire it to both pucks without worry. On the 3021 when you short or connect the cntrl pins the light turns off. It doesn't put almost any current so any pot should be fine, and it has the added effect of completely turning your lights off. So you really don't need swithces, but you can add one it you want simple on off.

    Sorry I can't help with the taskled. only a fatman driver, but I think they both use a
    50kohm pot, but it does not turn them all the way off so a switch would be necessary.
    HTH

  4. #4
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    thanks Zen. I figured out that the 3021 DN was not dimmable once it arrived. The website doesn't have pics or descrption so I didn't know. I am going to have to reorder the right pucks now. But my led's are coming by sea turtle from deal extreme so they will probalby still come around the same time.

  5. #5
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    Sorry to hear that I was hoping to catch you before you ordered. If you have to reorder I would highly suggest the 3023 DE if you can find them. The wired leads make it a lot easier to work with.

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    Yeah, sometimes I wonder if I don't make things clear enough on my bikelight website, but then there's this big photo on the electronics page:



    Really, I know it can be confusing, and some people don't care about dimming... just wanting on/off. I've grown to prefer the dim-able 3021-D-E-1000 over the bFlex/nFlex and all it's click modes, and it's a good bit cheaper. I just wish it was as thin as the bFlex. The podded unit is nearly indestructible, but it's a tight fit into the lights I build.

    I'm with Zen, if you can find a 3023-D-E-1000 wired, it's easier to work with than soldering to the pins. Also, a wired connector is available that slides onto the pins of the 3021, but that makes it even more bulky... yet I still managed to fit it all in a small dual Lux V light... so it's doable.

    Oh and for the pot, a 5k audio taper is a little smoother on the low end than a linear, but either will work.I don't know about driving two BPs from one pot... it might cause some issues, but I'm guessing you would just feed the 5v REF from one BP to one end of the pot and then back to the CTL pin of both BPs from the center pin (wiper) of the pot. - I guess if you could find a dual 5k pot (for stereo audio applications) that would be ideal if it would fit inside your housing.

    The more I think about it, using one pot between two BPs should work fine. The REF pin is just a 5v reference voltage that could be shared as I described above. The CTL pin just looks for 0 - 5v as a control voltage to vary the brightness. I don't believe there is any feedback between REF and CTL. (But I've never tried this, so don't blame me if they explode!) Hey, that's what playing with electronics is all about anyway... I've fried more than a few expensive components experimenting, but I gained a valuable education!
    Last edited by achesalot; 08-13-2007 at 11:51 PM.

  7. #7
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    Quote Originally Posted by ferday
    that said, i tried 3 different pot switches and the 1A current was too much for them, they burnt after about 2 minutes. to go up in current rating means a much much bigger switch, at least the ones that i found. if you find a high current pot with a small profile, post a link...
    See http://www.jameco.com/webapp/wcs/sto...oductId=286767.

    It's a 5K linear taper pot with a switch rated 250VAC @ 10A.

  8. #8
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    The 3021/3023's datasheet indicates that a 5Kohm, linear taper potentiometer should be used.

    As for switches, I think you could rig up something suitable with a DPDT on-off-on switch. E.g. see http://www.jameco.com/webapp/wcs/sto...oductId=138907. The middle position would be off. Flipping the switch to one of the "on" positions would turn on your high beam. Flipping the switch to the other "on" position would enable the low beam. One of the poles (of the DPDT switch) would be used to switch power to the 3021/3023. (Part of) the other pole would be used to connect the potentiometer to the CTRL pin. My reading of the datasheet shows that the device is at full power when the CTRL and REF pins are disconnected (or at a high resistance). That means that you'd have your high beam when the Pot is disconnected and your low beam when it's connected.

    If you're willing to turn the LEDs off by connecting the CTRL and REF pins together, you can get by with a SPDT on-off-on switch. (E.g. http://www.jameco.com/webapp/wcs/sto...roductId=72557.) In this setup, the switch's common terminal would be connected to the CTRL pin, one of the non-common switch terminals would be connected to the REF pin and the other non-common switch terminal would be connected to the Pot. So, one of the "on" positions would actually turn the LEDs off, the middle ("off") position would be the high beam and the other "on" position would be the low beam. A (seeming) disadvantage to this approach is that the battery is always connected to the 3021/3023. However, this is not as bad as it sounds since the datasheet indicates that the device draws less then 500uA when the CTRL pin is high (i.e. connected to REF).

    If one or both of these doesn't make any sense, I can try to post a schematic.
    Last edited by KevinB; 08-14-2007 at 05:29 PM.

  9. #9
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    IMHO, if you're going to use a dimmable 3021 there is no point in having both a pot and a switch. It's just a quick spin of the pot and the light is off... why clutter up your light interface with both a pot and a switch. Also, a very light duty pot will suffice. There is only 5v and very little current going through the pot if using the REF + CTL pins for dimming... not the full one amp of current. If you are putting a pot in line between the ouput of the Buckpuck and LEDs that is just plain wrong and will damage the driver. WHile you are not using your light, unplug it from the battery. And trust me, the audio taper works better than the linear taper... not a big difference, but it's a little less touchy on the low end... thus giving a little better transition from off to dim.

    Dimming the light is important for a few reasons. One, it helps keep the light from overheating while stopped, two, it is more polite to keep from blinding your fellow riders while stopped at a trailhead chatting, three, it will improve your battery life when full output is not needed, and four, and this is a big one....it makes HID owners very envious

  10. #10
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    In my latest project I'm using a DPDT 3 position switch like Kevin talks about, but wiring each 'on' position to a trim pot on the control pin. Each will have its own setting, one will give me a low beam of roughly 350ma, the other a high beam of 700ma, and the switch is in the off position, the 3021 puts out the full 1000ma for a "turbo" setting for extra light in the tricky bits. I guess I'd rather have preset levels so I can simply flip a switch for low, medium or high beam rather than trying to dial it in just before that tricky bit of trail. The trim pots also allow me to dial my brightness in after a ride if I feel the lowbeam is too low or the mid beam needs a little more or less light for normal riding.


    Trim pot

    I've gotten it to work on a breadboard, but still finishing the housing (similar to Achesalot's design with some ideas from scar's design, too). I'll post the project upon completion.

  11. #11
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    Nice website - I've been looking for a driver I could control with a external 0-10Vdc signal. 0-5 will do though. Thanks Achesalot.
    my 2 cents on dimming . After using a taskled for about 2 weeks now I have found 2 light levels - low & high is all I need. If I come up on opposing traffic a click gets my light out of there eyes. another click and high beam is on. Hold the button and the light turns off. Very simple and easy. I tried the multi mode that has 4 light levels and found it unnecessary. Also multi light levels with a single pushbutton means you have to toggle through levels to get to the level you want. I like my setup cause the button is next to my shifter. If on a downhill or tec trail the thought of taking my hand of the grip to dial a pot.... But as stated there are good reasons to have multi level control. I would look into something like a 1P5T rotary switch. Each position would have a different resistor value. The rotary switch will have a nice solid tactical feel and would be less likely to get damaged from water. - IMHO

  12. #12
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    As follow up, here's a few pics of what I'm talking about breadboarded. While I'm intruiged by the high tech B-flex, it's $44 plus shipping from Australia now that Cutter is the exclusive distributer. Compared to $13.99 for a dimmable buckpuck and less than $10 in parts from Radio Shack.

    Since I needed to disassemble one of my old homebrews to start machining the housing for my new lights (needed to know the thickness of the lenses), I used the lights to experiment with switchable dimming and shorting out LEDs at the flick of a switch. Like my two pound aluminum heatsink?


    High beam-Left switch in the off position causes zero voltage to reach the control pin, so you get full brightness. The right switch is also off, so none of the LEDs are turned off. What is hidden is the other lead coming off the left switch going to the other pot.


    Low beam-Left switch uses one of the two pots to allow some voltage to reach the control pin, so you get minimal brightness. The right switch is turned off, so all LEDs are on.

    The mid-beam isn't shown because the only difference is that the other pot is engaged, but from the photo, the 700ma beam and 1000ma beams look exactly the same from this angle (but make a fair bit of difference in how it lights up the room).


    Super-low beam/walking beam-Left switch in the same position as the photo above, but the right switch is turned on, shorting out the right and left LEDs independently (two pole switch). This is the ultimate in energy conservation, consuming perhaps 1 watt, while providing enough light to see your computer and friend's faces without blinding them (a pet peeve I developed after all my friends got HIDs). I guess you could call it a courtesy lamp.

  13. #13
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    ahh haven't seen thier thread in a while. Just to give you guys an update.

    got the 3021 DN exhanged with the one with the ctrl pin.

    Wired up a small pot that controled both 3021's at the same time. Just sodered the ctrl wires of each 3021 into one when it when into the pot.

    Used a mini pot like the one rockymtnway is displaying.

    My goal was to put it on a 3 way switch. So while you are riding you don't have to try and fiddle around with the pot to turn it so a mini 3 way switch was mounted on the bars right next to the shifter so you could go from high (1000ma) and low (what ever the pot is set at) and off. To do this I had to run a three way switch (on-on-on). If I used a tradional 3 way switch it would look like this (on-off-on) but when you go off with the ctrl wires it would be at full (1000ma). So it took me a good while staring at the on-on-on switch to wire it as (off-on-on) off would be high, middle would short out the ctrl wires, and the last on wouuld be running to the pot. But everything works great now.

    Don't ask to put up a wire diagram of the switch, it had 6 post on the back and my notes are on a napkin somewhere that i drew while eating dinner at a resturant till i finally figured it out. The switch didn't come with any instructions so alot of testing was done to each pole till i figured out what each one did, hehe. If I had to wire another one it would probalby take me another hour, hehe.

  14. #14
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    Where did you find an on-on-on? All I can find is the on-off-on configuration in small switches.
    Train 'til you puke. Cheat to win. Party like a rockstar. We miss you, Jan!

  15. #15
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    i got it at my local electronics store. Torrance electronics to be exact but i don't think they ship, its a small store but have alot of cool stuff.

  16. #16
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    Quote Originally Posted by rockymtnway
    Where did you find an on-on-on? All I can find is the on-off-on configuration in small switches.
    Jameco has several 3 position rotary switches. One example is http://www.jameco.com/webapp/wcs/sto...oductId=101558.

    I have no doubt that Mouser, Digi-Key, and Newark have similar products.

  17. #17
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    Quote Originally Posted by rockymtnway
    Where did you find an on-on-on? All I can find is the on-off-on configuration in small switches.
    Here's a link to Newark Electronics with 16 possibilities. This is where I bought mine. They ship very quickly!
    http://tinyurl.com/2ccmx9

    Or go to www.newark.com and search for "dpdt on on on"

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