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mvolke1:
Hey All,

I had this 12 volt adapter kicking around so I tried powering a couple LED buttons with it. The test worked well, but I was wondering if anyone could tell me if this is safe and how many LED buttons I could power with it. Thanks for any help!

PL1:

--- Quote from: mvolke1 on October 18, 2014, 07:46:48 pm ---I had this 12 volt adapter kicking around so I tried powering a couple LED buttons with it. The test worked well, but I was wondering if anyone could tell me if this is safe and how many LED buttons I could power with it. Thanks for any help!

--- End quote ---
Depends on the exact LEDs you are planning on using, but the pictured 9v, 450mA adapter should have no problem powering at least 22 average LEDs rated for 12v.

20mA per LED * 22 LEDs = 440mA

If needed, you can probably add a few more LEDs since you're running 12v LEDs on 9v which means the current limiting resistor is a higher value than needed = less current draw.

Before adding more than 22 LEDs be sure to use your multimeter to measure the average current draw of the LEDs.

Each LED added in parallel with the others will draw the same current.

If 20 LEDs draw 360mA (18 mA each), 24 LEDs will draw 432mA. (18 mA each)


Scott

mvolke1:

--- Quote from: PL1 on October 18, 2014, 08:31:18 pm ---
--- Quote from: mvolke1 on October 18, 2014, 07:46:48 pm ---I had this 12 volt adapter kicking around so I tried powering a couple LED buttons with it. The test worked well, but I was wondering if anyone could tell me if this is safe and how many LED buttons I could power with it. Thanks for any help!

--- End quote ---
Depends on the exact LEDs you are planning on using, but the pictured 9v, 450mA adapter should have no problem powering at least 22 average LEDs rated for 12v.

20mA per LED * 22 LEDs = 440mA

If needed, you can probably add a few more LEDs since you're running 12v LEDs on 9v which means the current limiting resistor is a higher value than needed = less current draw.

Before adding more than 22 LEDs be sure to use your multimeter to measure the average current draw of the LEDs.

Each LED added in parallel with the others will draw the same current.

If 20 LEDs draw 360mA (18 mA each), 24 LEDs will draw 432mA. (18 mA each)


Scott

--- End quote ---

Thanks so much for the reply!

So I should be good with running 14 buttons in total then?

12 would be these: http://www.ebay.com/itm/281100072416?_trksid=p2060778.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT

2 would be these 100ma @ 5v DC Per button: http://groovygamegear.com/webstore/index.php?main_page=product_info&cPath=73&products_id=295

PL1:

--- Quote from: mvolke1 on October 18, 2014, 08:35:29 pm ---12 would be these: http://www.ebay.com/itm/281100072416?_trksid=p2060778.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT

--- End quote ---
No problems with these.

They have the current limiting resistor inside the LED holder and will light with any voltage from 5v - 12v.




--- Quote from: mvolke1 on October 18, 2014, 08:35:29 pm ---2 would be these 100ma @ 5v DC Per button: http://groovygamegear.com/webstore/index.php?main_page=product_info&cPath=73&products_id=295

--- End quote ---
Trying to run these on 9v will let the "magic smoke" out of them UNLESS you change the resistor or add another current limiting resistor in series.

You should ask RandyT if he can do one of two things for you:

    1. Swap the built-in resistor for one that will work with 9v.

    2. Tell you the correct resistor (Ohms and Watts) to add in series for it to work with 9v.
        (Ask what resistor to use for 12v while you're at it, since that is a more common LED voltage.  ;D)


Scott

mvolke1:
Thanks again Scott! What's the magic smoke? Will it burn it out?

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