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> Altoids Power Pack - Is it feasible?, Portable power pack construction
zen_cabbie
post Nov 4 2004, 06:43 PM
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I think that this and this are great ideas for movie watching or wardriving. After finding a Penguin mints tin (only fitting) and following the basic concepts on the sites, I came up with a power pack that used 4 AA batteries, an LED and a switch (the latter two to add 1 volt of resistance). I can't really measure the amps, so I don't know if I'm close to meeting what the 5600 needs.

After getting a baseline test of Zaurus battery (Wi-Fi card on, brightness 100%), I charged it up and tried it again. with the battery pack in and on, the Zaurus had no more battery life than what it did before.

What did I do wrong, what am I missing? Has anyone gotten this to work, and if so, please help me figure this out.

Thanks in advance.

j
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V-Man
post Nov 5 2004, 07:54 PM
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The 7805 has three leads. One is to the input +, one to the input -, and one to the output +. I will dig up some schematics for the entire circuit this weekend if I can find them. If you are using it from a noisy supply, such as a vehicle's electrical system, you should use a couple of capacitors in the circuit. If you are using a regulated supply or a battery, you can forgoe the capacitors, but I still use them just to be safe. The regulator chip that is rated for 2A, has five leads. I will try to get the additional information you need.

Remember the safest way is using the regulator chips to eliminate the possibility of over-voltage damage, rather than using just a battery. A battery's output voltage will vary according to the charge. 4 AA NiMH batteries in parallel (what I use) will vary in voltage from 5.34V fully charged to 4.1V when depleted. Alkaline batteries have a higher initial voltage, I think that NiCd batteries have approximately the same voltages as NiMH batteries. I have never measured lead/acid batteries voltage drops in a 6V setup (all of my ham radio stuff uses 12V and my measurements were from a bank of 4 28AmpHour batteries). If I make enough money from off-duty jobs over the Christmas holidays, I will make a pack using the 5V regulators and either a 7.2V or 9V battery pack. I have not tested the results when the supply voltage drops to the point that the 7805 chip drops out of regulation. I will check that before using it on my beloved Z. I don't know if it just stops supplying power or if it passes whatever voltage it is receiving. If you intend to build anything to power expensive items (such as a Z), invest in an inexpensive multi-meter. It will be worth the money (probably less than $20).

V-Man
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