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12v step down question

Discussion in 'General Electronics Discussion' started by evader, Sep 11, 2012.

  1. evader

    evader

    6
    0
    Sep 11, 2012
    hello - I am working on a camera project and need help with the electric part of it.

    I have an outdoor camera that is powered by a
    UB1280 12v battery
    The flash on my cameras are weak
    So i purchased several slave flashes (neewer slave flash)
    this is an example of the flash
    http://www.ebay.com/itm/NEEWER-AUTO...era_Flashes&hash=item4abba4657f#ht_3200wt_932
    (edit: i should mention the goal is to not have to use the 2 double AA batteries, i'm looking to power the slave flash off the UB1280 12 battery)
    They take 2 AA batteries. which is around 3 volts together.
    so i purchased a LM2596s "step down" circuit
    (not from this buyer, but it looks just like this one)
    http://www.ebay.com/itm/LM2596S-DC-...ultDomain_0&hash=item337bde5cbb#ht_2418wt_970

    when hook all this up and adjust the voltage down to 3 volts.
    i press the test button on my slave flash, and sure enough it does flash.
    so it's working
    my problem is its the step down module is getting very hot, so hot it's melting the hot glue on the back of it.

    this set up is meant to be left outside unattended. and i can't have a fire.

    So my questions are, am i doing this right?
    is there a better way?
    can i do anything about the heat problem?

    Thanks!
     
    Last edited: Sep 11, 2012
  2. CocaCola

    CocaCola

    3,635
    4
    Apr 7, 2012
  3. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,191
    2,692
    Jan 21, 2010
    Is it hot all the time, or just when the flash has been used?

    Are the slave flashed triggered wirelessly (or optically) or via a sync cord?

    Have you measured either the input of the output current to/from these modules?

    edit: CocaCola, it is a switchmode regulator.
     
  4. CocaCola

    CocaCola

    3,635
    4
    Apr 7, 2012
    Oops, glazed right over that part :p Something is likely wrong it it's getting that hot...
     
  5. evader

    evader

    6
    0
    Sep 11, 2012
    optically - when the slave flash see's the camera flash, it fires.
    this set up is sufficient for what i'm doing.
    but they are unattended long term, so using 2 double AA's isn't ideal.

    I measured ~11.xx volts from the 12v battery (it hasn't been charged in a little while)
    and i step that down to 3v
    I measure the ~3v on the output of the LM2596 module. so it is stepping down.

    as for your fist question, I don't know.. i was afraid to leave it hooked up, as soon as i noticed the glue on the back melting, I unhooked it.
    but i do admit i was pressing the test button many times.
    however, this flash does need to be able to take multiple flashes in a row.

    I will check tomorrow without pressing the flash button and see if the LM2596 gets hot on it's own.
     
  6. evader

    evader

    6
    0
    Sep 11, 2012

    I was afraid of that.. any idea why?
    I suppose a heat sink would be mandatory then? or do you just feel something is wrong all together?
     
  7. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,191
    2,692
    Jan 21, 2010
    Yeah, that would explain it.

    The flash will draw a huge current from the batteries (if it can) and they too will get hot if you do this. However the batteries can't supply the current that the regulator can.

    I bet you noticed that the flash was ready to fire really quickly :)

    Just fire it less often.

    There is a small risk that the high current available could damage either the regulator or the flash, but it's only a small risk.

    There are current limited versions of these power supplies and you might consider one of them (and limit the current to (say) 2A).
     
  8. evader

    evader

    6
    0
    Sep 11, 2012
    if that turns out to be the case, then i'll be ok, it's programmed to take 2 or 3 pictures in a row every 1 minute.
    so flash twice and then rest 1 minute. that should be okay. but i'll test more tomorrow.
    thanks for the ideas and feedback!
     
  9. evader

    evader

    6
    0
    Sep 11, 2012
    and my project has come to an end.. I thought i would post and give you all a good laugh since you were kind enough to help me out.

    Tonight i was testing the "pressing test flash" many times is what heated up the step down module.. this turned out to be a correct assessment of my situation.
    Using a laser thermometer, i was measuring the chips and circuit board to monitor the temps.

    when i only pressed it 2-3 times per minute, the board never heated up. so this was good news..

    I happen to measure the temps on the 330v 140uf capacitor in the flash and it was reading around 112 degrees. i used my multimeter to measure the voltage and placed the probes on the side of the flash case.. i decided to touch the capacitor and feel how hot it was, the reason i did this is because the step down board was measuring 80-90 degrees, but yet wasn't hot to the touch..

    well you can probably guess what happened. the capacitor shocked the **** out of me and
    as my hand and arm was flung back, one of the probes fell into the flash case and crossed or grounded the cap, and a huge loud pop and flash was heard.

    so as the numbness in my arm lingers i decided to just deal with the weak flashes this year and buy new cameras next year.. i'm sure my wife and kids will thank me for not being stupid and staying alive..
     
    Last edited: Sep 12, 2012
  10. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,191
    2,692
    Jan 21, 2010
    Hahaha. Yeah. Glad you're laughing because the charge stored on some capacitors in flash units can kill you.

    But you've learned something about capacitors -- they bite. And I'll bet you won't be getting your fingers near them again.

    The bang associated with the rapid discharge can be pretty impressive too. Check your probe, you might find that it's vaporised part of it :eek:

    I honestly didn't realise you had the high voltage parts exposed or I would have warned you.

    Is the flash still working? (Or are you still a bit too much in shock to approach it?)
     
  11. evader

    evader

    6
    0
    Sep 11, 2012
    when i was a kid, i stuck my hand inside a tv (tube) set and got the shock of my life.. so I've experienced a jolt before, i just didn't expect touching the side/insulated/covered part would shock me. i was touching to feel for temp, since it was reading 112 on my laser thermometer. and as i said the step down was reading 90-ish and didn't feel warm at all..

    this was meant to be unattended and left back in the woods. a fire would be really really bad as you can imagine. so i was going to put a fuse in line and use silicone caulk to seal all the cracks/joints. but if the insides were going to overhead/melt, that wouldn't do obviously either, so temps were important to check. i just could have done without the jolt :) perhaps this was not the best idea, to much risk for too little reward.
    i'll just cough up the dough next year for new cams and save my self the headache and risk of using something that wasn't intended to be used outdoors or with a 12v power source :)

    I did hook the flash back up and it does indeed work lol
     
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