Need constant on, momentary, AND OFF!

Discussion in 'The Projects Forum' started by Avalanche Breakdown, Apr 29, 2007.

  1. Avalanche Breakdown

    Thread Starter Member

    Mar 22, 2007
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    Looking for some help in determining the best, and cleanest way to achieve three different modes of operation for my red laser build.

    It's a red, 16X DVD diode, running 3.2V (two E2 lith. primaries), with a 2.7 Ohm resistor in series with the pos. diode leg, and a 100uF cap in parallel across the pos. and neg. legs. I stuck a DPDT alongside a momentary button for multiple switching options. In the first iteration, shown below, I really screwed the pooch, and blew my first diode with a dead short to the batteries.

    Got another diode, fixed the switching to allow constant on with the toggle thrown forward, and the momentary button can be used with the toggle in the opposite direction. Problem is, the button also works when the DPDT is in the middle position. Of course, I meant for the middle position to be complete off... ah, a day in the life of an EE noob.

    The picture you're about to see, will make even the most basic EE 101 student cringe. Ignore the dead short from batteries to laser diode... as mentioned, that's been fixed, but leads to where I'm at now. This is just to show the DPDT, and the button. The bottom two wires come from the batts, and the top two go to the laser.

    [​IMG]

    Unfortunately, I have no good pics of the present wiring... but hopefully it won't be neccessary to sort this out.

    What would be the proper way to hook all this up to allow for all three modes?
     
  2. Avalanche Breakdown

    Thread Starter Member

    Mar 22, 2007
    20
    0
    Additional pics.

    The beforementioned cap and resistor.

    [​IMG]

    Switch and button... topside view.

    [​IMG]

    Just for entertainment... the laser casing, and the channeled, little heatsink it's AS epoxied to.

    [​IMG]
     
  3. mozikluv

    AAC Fanatic!

    Jan 22, 2004
    1,437
    1
    here's a crude stab of what you want to happen based on what you have describe

    moz
     
  4. Avalanche Breakdown

    Thread Starter Member

    Mar 22, 2007
    20
    0
    Thanks for the schematic, mozikluv. :) I may not be understanding it fully, but as far as I can tell, it might not be the right solution for this project.

    Fortunately though, I think I've figured out the answer. Should be able to get around to it soon, and see if I don't blow it up again. Still can't believe the pure genius wiring in the first pic. What the heck was I thinking?!
     
  5. mrmeval

    Distinguished Member

    Jun 30, 2006
    833
    2
    Is there a current limit circuit in that device?
     
  6. wireaddict

    Senior Member

    Nov 1, 2006
    133
    0
    Try connecting the + battery lead to the toggle switch common terminal as Mozikluv suggested, connect a terminal on one side of this switch to your laser circuit & the terminal on the other side of the switch to one terminal of your N/O pushbutton switch. Now connect the other PB switch terminal to the laser circuit [& also the opposite toggle switch terminal]. This will give you constant operation, momentary operation & off, depending on toggle switch position. Also note that you only need one half of a DPDT toggle switch or, in other words, a SPDT switch or else you can always parallel the contacts.
     
  7. Avalanche Breakdown

    Thread Starter Member

    Mar 22, 2007
    20
    0
    mrmeval - The only current limiting is the resistor and cap. The resistor provides a safe range of operation from 3.2V by slightly underdriving the diode, while the cap serves to soak up any transients from on/of switching. However, the next laser build will be using a constant current driver, and hopefully run from a single Li-ion... depends on what driver I wind up with.

    wireaddict - Upon actually using my brain, that's exactly what came to me yesterday! It's so simple! We need one of those forehead smacking smilies here. And you're right about only needing a SPDT. I bought the DPDT before knowing anything, figuring it would give me the most wiring 'options' in case it was needed.

    Should be able to fix it by tonight.
     
  8. Avalanche Breakdown

    Thread Starter Member

    Mar 22, 2007
    20
    0
    Done!... as of a couple nights ago. Not only are all three modes now present, but it operates noticeably brighter! My soldering technique is much better than when I started three months ago, so all switch connections are highly improved.

    Pics coming soon. Thanks again, guys!
     
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