Plasma disc PSU overheating

Thread Starter

roblloydwales

Joined Aug 20, 2009
9
Hi all, Please be patient as I am a novice, I recently bought a plasma disc which is designed to operate on 2 x AA batteries, I really would like to run it from a plug in power supply, so I attached it to a PSU with 5V, 500mA USB output, it runs great for a few minutes, but then starts to fade and the PSU overheats. The plasma disc runs for hours on a 5V battery pack and is drawing around 250mA.
Any ideas as too what is happening and how to solve the problem would be greatly appreciated.

Here's a link to the plasma disc if it's any help, perhaps someone has done this in the past.
http://www.ebay.co.uk/itm/New-Fancy-Mini-Pocket-Plasma-Disk-Sensor-Lighting-Plate-Home-Disco-Party-Decor-/230860613677
 

sailorjoe

Joined Jun 4, 2013
361
Two AA batteries would only generate at most 3 Volts for power. But depending on how it's wired, it could be only 1.5 Volts. If you have to pursue this, try a 3.3 volt wall wort. If that still causes problems, build a 1.5 volt power supply that runs off your 5 or 3.3 volt wall worts.
 

Thread Starter

roblloydwales

Joined Aug 20, 2009
9
Thanks for the replies, but your missing the point guys, the disc runs perfectly for hours powered by a 5V (or more precisely a 4.5V) rechargeable battery that is designed for running USB powered devices.
There's not much drain on the battery and doesn't get warm.

The AA batteries are in series, so definitely 3 Volts.

Built a 3V 1.5A regulator (LM317) circuit yesterday, it overheats in minutes, replaced LM317 with LM350 and still overheating, but like I said, the current draw is only around 250mA so cant see that being an issue.
 

#12

Joined Nov 30, 2010
18,186
Your problem is with the regulator circuit. Post your schematic for the regulator. Be sure to include the voltage you are feeding it.
 

#12

Joined Nov 30, 2010
18,186
You are missing the capacitors which stop the regulator from oscillating. Look at the datasheet for the proper construction.
 

#12

Joined Nov 30, 2010
18,186
Now that I'm not in a hurry to get to the bank before it closes, 12 volts reducing to 3 volts at 1/4 amp creates 2.25 watts of heat in the regulator. A TO-220 package will be at 112.5C above ambient temperature, very, "burn your fingers" hot with no heat sink. You need to glue a coin to the chip or give it a "real" heat sink so it has more radiating surface.
 

Attachments

Last edited:
Top