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  1. #1
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    3021 d e control question

    Hi,

    I am trying to do the following add a potentiometer to a 3021 de. I have a 5k pot and have looked at the pdf from leddynamics and I have the rotation right and the power source is above 5 volts, but the Leds don't dim. I need to know where do I hook the wires from the buckpuck into the Pot. The cntrl out goes to one of the outside tabs and the reference goes to the middle tab???. When I check the resistance on my multimeter this works, but when I put it in the circuit no go. Do I have it backwards, or do I have to gang the central out tab to one of the outside tabs. I usually just try until it works, but don't want to blow anything.

    Hope this makes sense. If not I will post pictures.


    THANKS
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  2. #2
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    Quote Originally Posted by zen bicycle
    Hi,

    I am trying to do the following add a potentiometer to a 3021 de. I have a 5k pot and have looked at the pdf from leddynamics and I have the rotation right and the power source is above 5 volts, but the Leds don't dim. I need to know where do I hook the wires from the buckpuck into the Pot. The cntrl out goes to one of the outside tabs and the reference goes to the middle tab???. When I check the resistance on my multimeter this works, but when I put it in the circuit no go. Do I have it backwards, or do I have to gang the central out tab to one of the outside tabs. I usually just try until it works, but don't want to blow anything.

    Hope this makes sense. If not I will post pictures.


    THANKS
    conectring the wiper to the unused outside one is best practice, but it should work without. the one supplied with mine doesn't wire the unused one to the wiper. as long as you use the wiper and one outside one it should work, the only thing that changes if you use te other out side one is the direction you have to turn the knob.

    if you short the control wires together (bypassing the pot) the LED should go out.

    if it doesn't check that you are getting volts out the ref pin relative to 0V.

    Stu
    What exactly is a rigid hard tail?

  3. #3
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    Quote Originally Posted by zen bicycle
    Hi,

    I am trying to do the following add a potentiometer to a 3021 de. I have a 5k pot and have looked at the pdf from leddynamics and I have the rotation right and the power source is above 5 volts, but the Leds don't dim. I need to know where do I hook the wires from the buckpuck into the Pot. The cntrl out goes to one of the outside tabs and the reference goes to the middle tab???. When I check the resistance on my multimeter this works, but when I put it in the circuit no go. Do I have it backwards, or do I have to gang the central out tab to one of the outside tabs. I usually just try until it works, but don't want to blow anything.

    Hope this makes sense. If not I will post pictures.


    THANKS
    any luck?
    What exactly is a rigid hard tail?

  4. #4
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    I didn't get a chance to work on it last night. I will post up hopefully tonight.

    Thanks again

  5. #5
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    It appears that I am getting a difference of 3.3mv across the reference pins, but nothing is translated to the lite. Do I have the wrong pot. I thought it was supposed to be a 5k pot? Can anyone else tell me what voltages differences they get across the pins of the pot. Does it matter which wire connects to what on the pot?

  6. #6
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    Quote Originally Posted by zen bicycle
    It appears that I am getting a difference of 3.3mv across the reference pins, but nothing is translated to the lite. Do I have the wrong pot. I thought it was supposed to be a 5k pot? Can anyone else tell me what voltages differences they get across the pins of the pot.
    if the pot is still connected the voltage will prbably depend on where the pot is set. the ref voltage is supposed to be 5V when measured between the battery 0 and ref. keep the black meter lead on 0v
    and measure the control, I think it should waggle between 0 and 5 when you move the pot.

    edit measure against the LED oV wire instead....thats what the data sheet indicates.

    I will try and connect my controller up tomorrow to check

    Dose it switch off if you short the control to ref?

    Stu
    What exactly is a rigid hard tail?

  7. #7
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    It doesn't switch off if I touch the cntrl to the ref pin. If measure between the led + and either the cntrl or reference wire I get roughly the input voltage

  8. #8
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    Quote Originally Posted by zen bicycle
    It doesn't switch off if I touch the cntrl to the ref pin. If measure between the led + and either the cntrl or reference wire I get roughly the input voltage
    do you mean led + or -. You should use LED - as your reference (black lead of meter)

    What voltage are you using to drive the controller? The data shet says it needs to be at least 5.25 if using the pot method.

    shorting the control and ref should switch it off, as stated on page 4 external on off control. Daft question maybe, but is it definitely a DE model?


    Stu
    What exactly is a rigid hard tail?

  9. #9
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    Definitley a DE model. I am getting correct readings I believe across the cntrl and reference pins. It just doesn't seem to make a difference with the pot. Voltage in is around 7.62 volts right now is it maybe running unregulated after the forward voltage and buckpuck??? VF should be at 6 + 1 volt for buckpuck, so it should still be regulated.

  10. #10
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    Zen, how many LEDs are you driving with the 3021 and 7.62 volts? Most power LEDs such as the Cree XR-E and the Seoul P4 require anywhere from 3.5 to 3.8v each, meaning that you would need at least 8v (probably more) for two LEDs or the Buckpuck will not be in regulation, thus the dimming won't work.

  11. #11
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    I thought the Seoul p4 stated anywhere from 3-3.2 for vf so I was calculating 6.2 plus another 1 for the buck puck for a total of 7.2. Which should put them in regulation. I will try a 10 volt battery to see if it makes a difference

    EDIT

    Nope no difference.
    Last edited by zen bicycle; 05-11-2007 at 05:58 PM.

  12. #12
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    Quote Originally Posted by zen bicycle
    I thought the Seoul p4 stated anywhere from 3-3.2 for vf so I was calculating 6.2 plus another 1 for the buck puck for a total of 7.2. Which should put them in regulation. I will try a 10 volt battery to see if it makes a difference

    EDIT

    Nope no difference.
    The volts increase with current, so if you have a 1000mA 3021 you're looking at about 3.8v per emitter.



    Maybe that 3021 is bad?

  13. #13
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    So how many Seouls are you trying to drive?
    Last edited by achesalot; 05-11-2007 at 08:46 PM.

  14. #14
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    2 seouls so it should work with 10 volts. I think the control is bad. I checked the pot I had on it and it was bad. I switched to a new pot and nothing happened. I guess whatever took care of the old pot took care of the control circuit too

    Thanks for all the help

  15. #15
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    Quote Originally Posted by zen bicycle
    2 seouls so it should work with 10 volts. I think the control is bad. I checked the pot I had on it and it was bad. I switched to a new pot and nothing happened. I guess whatever took care of the old pot took care of the control circuit too

    Thanks for all the help
    if ist doesn't switch off when you short the ref to ctrl its not the POT. That's why I asked you to do that test.

    Stu
    What exactly is a rigid hard tail?

  16. #16
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    I'm not sure if this is a post hijack or not but I'm having a small issue connecting a pot to my 3023 Buckpuck.

    The test pots I've been trying have a really small movement to change the light output. 95% of the pot movement is full power.

    I want a smooth linear shift from almost 0% light output to 100% with the pot.

    I can't find a 5k Pot small enough for my enclosure yet, so I've been fiddling with 100k pots I had laying around.

    Tony

  17. #17
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    Quote Originally Posted by Tony_J_Ross
    I'm not sure if this is a post hijack or not but I'm having a small issue connecting a pot to my 3023 Buckpuck.

    The test pots I've been trying have a really small movement to change the light output. 95% of the pot movement is full power.

    I want a smooth linear shift from almost 0% light output to 100% with the pot.

    I can't find a 5k Pot small enough for my enclosure yet, so I've been fiddling with 100k pots I had laying around.

    Tony
    I think its just that the pot is too big. the manual calls it a pot...but its being used as a variable resistor really. 5 percent of 100k is 5k ...so it fits with what you are saying. if you want it to dim to nothing try a resistor 5.2k or so (can't remembr if that's a prefered value) in parallel if you can't find a 5k pot. I think that should do it. I think these controllers shut off when 0ohms is between the control and ref pins. it won't be linear for pot position. it will happen quicker at the off end I think. but you should have full range of the pot position range
    if you don't want it to dim to nothing put a resistor in series to give the required brightness and subtract the difference from 5k to give the new parallel resistor value. for example a 2.6k and a 2.6k should provide half brightness at minimum. assuming the input is linear.

    for linear you will need a linear 5k pot
    not tried it...but it should work.

    Stu
    Last edited by Stuart B; 05-23-2007 at 09:15 AM.
    What exactly is a rigid hard tail?

  18. #18
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    I think, and I might be wrong here, but you should try a logarithmic taper or audio taper. The linear adjusts power in a linear fashion which doesn't look linear to our eyes. At least that is what I have read.

    If you find a source for small 5k pots let me know as I have had problems locating them also.

    Oh and the 3201 was bad. Got a new one and it dims like magik!

  19. #19
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    Quote Originally Posted by zen bicycle

    If you find a source for small 5k pots let me know as I have had problems locating them also.

    Oh and the 3201 was bad. Got a new one and it dims like magik!
    have you checked somewhere like RS (rswww.com no www. on the front)?

    good news too about the new one. did they swap it for free?

    Stu
    What exactly is a rigid hard tail?

  20. #20
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    I didn't ask them to replace it as I am pretty sure it was user error on my part with the battery pack. that fried the control circuit. Always double check your stuff!. I have a place locally like RS that I can get some stuff like that, but the problem with a lot of the online stores is that it is very hard to see what size they are. Measurements are helpfull, but you never know for sure until you get it in your hand. Also you pay X dollars shipping for a 60 cent part.

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    Thanks for the suggestions everyone !

    I need to get up to speed with basic electronics so this is a great exercise.

    I found this pot at a local Aussie store which is convenient since that's where I am.

    http://jaycar.com.au/productView.asp...Max=&SUBCATID=

    I'm getting one this morning and will try it out when I get home.

    Tony

  22. #22
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    Quote Originally Posted by Tony_J_Ross
    Thanks for the suggestions everyone !

    I need to get up to speed with basic electronics so this is a great exercise.

    I found this pot at a local Aussie store which is convenient since that's where I am.

    http://jaycar.com.au/productView.asp...Max=&SUBCATID=

    I'm getting one this morning and will try it out when I get home.

    Tony
    are you getting a 5k one? that says its 10k. you will have the same problem with the 10k....but it will be half way instead of 5%

    Stu
    What exactly is a rigid hard tail?

  23. #23
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    I was going to get a log version and then fiddle with resistors if they have a hobby pack of multiple values.

    It's the only pot close to a 5k in the size I need, I hope I'm getting closer to understanding resistance.

    Tony

  24. #24
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    Quote Originally Posted by Tony_J_Ross
    I was going to get a log version and then fiddle with resistors if they have a hobby pack of multiple values.

    It's the only pot close to a 5k in the size I need, I hope I'm getting closer to understanding resistance.

    Tony
    for a 10k try sticking a 10k res in parallel it should give a result like this (not including any log effects) left is Pot res in K, middle the resisor in k (always 10k) and on the right the resulting resistance in k of the 2 in parallel.

    10 10 5
    9 10 4.736842
    8 10 4.444444
    7 10 4.117647
    6 10 3.75
    5 10 3.333333
    4 10 2.857143
    3 10 2.307692
    2 10 1.666667
    1 10 0.909091

    note that when the pot is 5k the result isn't 2.5k...the resistance drops off quicker at the lower end.

    Stu
    What exactly is a rigid hard tail?

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