TV-B-Gone battery droop
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- rubidium
- Posts: 43
- Joined: Sun Nov 18, 2012 10:36 am
TV-B-Gone battery droop
I did a little test the other day and took a standard Adafruit TV-B-Gone with 2x AA batteries and put a scope across the battery pack output terminals. As the code executes, the waveform that I observe indicates that the voltage supplied by the battery pack droops by about 1 volt during the duration of each firing of the LEDs. I read somewhere that Duracell alkaline AA's have an ESR of about 0.12 ohm, so that 2 in series would give an effective ESR for the pack of about 0.24 ohm. That leads me to believe that each of the 4 LEDs is drawing a peak current of about 1 amp. Considering the "absolute maximum rating" of 600mA for PN2222 collector current, I would have thought these transistors in saturation would prevent anything as high as 1A from ever flowing. Or am I interpreting my measurement incorrectly?
- adafruit_support_bill
- Posts: 88093
- Joined: Sat Feb 07, 2009 10:11 am
Re: TV-B-Gone battery droop
Actual ESR changes with temperature and discharge. You will probably get more reliable numbers measuring current directly.
Please be positive and constructive with your questions and comments.