How to test MC-E?- Mtbr.com
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  1. #1
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    How to test MC-E?

    I'd be very grateful for some advice on how to troubleshoot my Dinotte-style light. In particular, how do I test an MC-E to check if it's cooked or OK?

    Here's some background; Basically my dinotte-style light was working nicely, until few couple of weeks back when I upgraded the (gutless) NiMH battery-pack in favour of a shiny new 11.1V LiPoly pack. As hoped, battery-life improved dramatically improved with the LiPo setup, however after the first recharge cycle I suspect perhaps I may have inadvertently over-charged the pack somewhat? From memory, the voltage was around 12.3V fresh off the charger. Then for whatever reason, I noticed the the light was running hotter than usual, and before I knew what happened Sput! and the light was dead.

    So after feeling grumpy & disappointed all week, I disassembled the light and checked everything the connections with a multimeter. No obvious shorts or broken connections, but just a bit of a 'dark-brown' smell (from the wiring that is, not me). My multimeter has an inbuilt diode-tester, and using this I've verified that each of the MC-E's 4 dies light-up OK (ie. individually, one at a time). But the MCPCB is the 4-S series-type, so my diode-tester doesn't make enough Vf to test all 4 dies in series. So my question is; can anyone suggest a simple test-circuit that'll light up a 4S MC-E without risk of cooking it?

    And assuming the MC-E has survived OK, then any tips on troubleshooting a MaxFlex2 driver?

    Thanks in advance
    Andrew
    Brisbane, AU

  2. #2
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    Simple constant current driver: lm317
    http://users.telenet.be/davshomepage/current-source.htm
    You need a wall wart/battery that outputs a few volts above the led Vf.

    Alternatively use a resistor off the battery/wall wart.

    But if you've checked each die and they're ok, just check the continuity between dies and from the first and last die to the +/- terminals.

  3. #3
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    Thanks for the info Znomit
    Brisbane, AU

  4. #4
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    I guess the maxflex has gone to direct drive, because the battery voltage was higher then the forward voltage of the led. At that moment something would have probably melted. The combination of driver/led/battery isn't the best there is. With 7.2V li-ion battery you would have been better off.

    Since all the dyes led up with the diode tester the MCE is still fine. I can't imagine the pcb from the MCE is broken by a bit too much current. The maxflex would break a lot earlier.

  5. #5
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    Yes, you say you "inadvertantly overcharged the battery?" But a fully charged 11.1V (3 cell) lipo should be 12.3 to 12.6V so you didn't overcharge it.

    As superfast has already said you really need a 2 cell (7.2V nominal, 8.4V max) pack for a boost driver and 4S LEDs.

    Toby

  6. #6
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    Thanks guys, you've confirmed what I suspected already; I let my driver go into direct-drive, and getting cooked. Ah well, I''ve learned my lesson, so now I'm cogitating on plan B. Possibly something a little different, but re-using those 2x 11.1V LiPo battery packs.
    Brisbane, AU

  7. #7
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    Not too many options I am afraid. Replace the battery pack or replace the driver and the leds. With a 2s-2p led pcb you could use 1 (or 2 cheap ones) buck drivers. Or maybe you can trade you battery packs with someone else.

  8. #8
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    well, I use a 11.1V LiPo with a 2s2p MCE and a buckpuck and it does very nicely

  9. #9
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    Quote Originally Posted by tobymack
    well, I use a 11.1V LiPo with a 2s2p MCE and a buckpuck and it does very nicely
    Ah, that's a good suggestion, thanks! Out of curiousity, what's protecting the LiPo against over-discharge with this setup?

    Based on my reading, LiPos don't like getting discharged below ~2.7V per cell (ie. 8.1V in my 3S configuration). So I guess you need to watch the light's brightness, and disconnect the battery just before it dies?
    Brisbane, AU

  10. #10
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    Your batteries aren't protected against over discharging?

  11. #11
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    no, no protection against over discharge. And you can't tell that battery is getting low by the light brightness as the buckpuck keeps regulating well below 2.7V per cell. 2s2p gives me around 6.3V Vf so the buckpuck is ok down to around 7V with no noticeable dimming.

    At the moment I just have a battery level meter which tells me if the battery is getting lower. My mark 2 version has low voltage cutoff, it has been designed and tested but not made/fitted yet as other things have distracted me......

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