Battery life?

[jeonlab]

Unfortunately, no one seems to have an answer for my previous post on the 16MHz resonator. So anyway, I set the fuse bit for internal oscillator at 8MHz and assembled on a tiny breadboard with only one IR LED (940nm, 20degree beam, 100mA) AND two supercaps (10F, 2.7V) which is charged by USB as shown below.



It works quite well. I tried at home on Sony, Sharp, LG TVs without any problem. I use it not only turning OFF the TVs but also turning ON the TVs.

However, the problem is the power source. Even though I added a 50ohm resistor to the IR LED, with the supercaps (of course it has much little juice than real batteries), I could use it only a dozen times. There are also other things that limits its lifetime such as using internal resonator (varies upon temperature and power voltages) and I used ATtiny85, not 85V, but it must be mostly because of small capacity of the supercaps (although it is 'super' ).

So, my question is, how long can you continuously use the Adafruit's 4 LED TV-B-Gone with AA alkaline batteries or NiCd, NiMH?

Thanks.

Jinseok

[CharString]

Cool, I'm looking for information on powering the TV-B-Gone with capacitors.

Most threads in the forum are about concealing it and longer battery life.
I'm looking for just the opposite: I have a broken Supersoaker gun and wonder if I could turn in this into a bad ass, in your face, pump action, TV-B-Gone.

I only have this rough idea:
- use magnets and a coil to turn the pump into a "pump action dynamo"
- convert the AC, that you create by moving the magnets through/passed the coil, into DC with some diodes
- use that DC to charge some capacitor
- power the TV-B-Gone circuit with that and connect the trigger to the switch

I'll be looking into the Mosquino Power Board designs for more information on how to handle power.
How do you make sure you don't overcharge your caps? Did you just calculate the time from the voltage and current of USB and the capacitance of your caps, or do you use some protection circuit?

[john444]

Hi Jinseok,

how long can you continuously use the Adafruit's 4 LED TV-B-Gone with AA alkaline batteries or NiCd, NiMH?

At about 100-mA each the IR-LEDs pull quite a bit of power from AA cells.
According to Wikipedia: (This table should provide a rough difference between cell types)
Carbon/Zinc - 0.4 to 1.7-Ahr
Alkaline - 1.8 to 2.6-Ahr
Li/FeS2 - 2.7 to 3.4-Ahr
NiCd - 0.6 to 1.0-Ahr
NiMH - 0.8 to 2.7-Ahr
NiZn - 1.5 to 1.8-Ahr

Operating time is difficult to predict.
It depends on the cell voltage at which the IR-LEDs no longer emit enough IR to operate TVs.
Also, NiMH start out at a lower voltage, the LEDs will not emit IR as bright as when using Alkalines.
It makes it hard to say how long batteries will last.

Try a couple of different cell types and let everyone know your results.
John

[john444]

Hi CharString,

This is almost a new thread.

Sounds like a fun project. I can envision going into some public place and ‘shooting’ the TV.

How do you make sure you don't overcharge your caps?

Charging a capacitor is not the same as charging a cell or battery.
Jinseok cannot ‘over charge’ a 5.4-V cap from a 5.0-V source (like USB).

Although, it could be possible to exceed 5-V into capacitors from a “pump-action dynamo”,
I would quickly get tired of trying to charge a 5-F cap this way.
Each pump generates only a tiny amount of electrical energy. It will take a long time to charge up 5-F.
It may not even be possible to charge the 5-F cap to 5-V due to leakage current within the cap.
If you have some dynamo type device that could over-charge the cap then,
a red + blue LED across the cap would begin conducting at about 5-V, preventing 'over-charging'.

Most of the energy needed to make the TV-B-G work is used by the IR LEDs.
That is why people are looking at rechargeables and high capacity AAs.
If you may have the space in the super-soaker, consider installing three ‘D’ cells instead of AAs.
If you use C or D cells, you will also need to add a series resistor to the IR-LEDs.

Sounds like fun though, John