Excessive Heat with LM1084IT-5.0/NOPB and LED Strip

Other Hardware General Electronics
1

Hello all,

I am using the Makerduino UNO board to drive a 30 LED/m Neopixel Strip, which I have a 3m section of. All of this is being powered by a 12V 9Ah SLA Battery, which lead me to add a 5V 5A Voltage Regulator to get the required 5V for the LED strip. The strip is spec'd at 2A/m max current...

I'll include some images, and try to explain the many configurations I've tried: Main problem, everything works, but within 10 secs of powering on, the reg is hot enough to burn skin...after about 15 secs the lights start to act erratic and I disconnect power.

I have tested the regulator and it is putting out 5V

I have tested current flowing out of the 12V battery and saw about 1.5A while the strip was active
I have tested the current on the 5V output from reg and saw about 1.5A while strip was active...

in the current configuration the 12V Battery is supplying voltage to Vin for Arduino and also the Reg
I tried isolating the Arduino power by disconnecting Vin from the battery and running Arduino from USB power...and the Reg got just as hot.

Am I using the regulator incorrectly???

in the schematic view the LED strip is not included, just a 3 pin header, but the wiring there is correct, from Left to Right it is GND, Data, +5V...

Thanks in advance for your time :wink:

LED_Test_sch.jpg
LED_Test_sch.jpg1920×1035 271 KB

LED_Testb.jpg
LED_Testb.jpg1920×1164 679 KB

2

You are going to need a heatsink, and maybe a rather large heatsink.

The power dissipated in a linear voltage regulator is calculated as the voltage drop across the regulator (7V in your case) multiplied by the current. 7V x 1.5A = 10.5W. That's 10.5W worth of heat.

In order to get 5A out of that thing, you might need to lower the voltage drop and use a heatsink. I haven't studied the datasheet, but there may be a maximum power rating (usually specified with an "infinite heatsink" at room temperature) as well as voltage & current limits.

A switching regulator is more complicated (it requires an inductor) but switching regulators can be nearly 100% efficient. That means you can get more current out than you put in (with less voltage out, of course). In addition to reducing heat, your battery will last longer.

3

Thank YOU DVDdoug,

I guess the switching reg is really the best solution, I was just trying to avoid the hefty pricetag since I need 12 of these...ouch! But dissipating 10.5W through the other reg is not efficient at all...

4

If time is money, then I don't think $10 is much.

5V 3A buck converter.
6-32 V in.