Sander Hoksbergen
Still Fresh
- Joined
- Jan 22, 2009
- Messages
- 59
christo930 said:Can a 9v alkaline battery provide much of a charge? Most 9v batteries only have a few watt hours in them. Can it provide the current? Maybe a rechargeable 9v battery would be better (since a rechargeable provide more current). If anything, I think it would better to make it use AA or possibly AAA batteries.GizmoTheGreen said:What you need:
Hot-glue gun
Soldering iron
Solder
Soldering grease
A few cables
1x LM7805 or similar
1x Heatsink of some kind
1x 100µf 10v+ capacitor
1x 10µf 10v+ capacitor
1x 104 ceramic capacitor
1x USB Female
1x 9v battery connector
1x non-momentary power switch
Optionally 1x led and matching resistor
Now connect it together!
schematic in a bit...
Result:
5v USB charger, charge anything that can charge via usb, on the go!
Chris
The amount of Ah is the same as a regular AAA battery except at 9V (Does not last long). Gizmo then proceeds to dump 4V over a linear regulator. So what exactly is the power equivalent? A bit more than 3 AAA batteries connected in series. How long will this last you ask? 15-20 minutes MAX.
A better idea would be to use a switching regulator. This requires switching logic (plenty of analog chips available), a coil with the correct inductance range and a capacitor to reduce output ripple. If you do the math and find some nice components you could make a specifically adjusted regulator with ~95% efficiency. Actually, I once made a DC-DC converter from 12V(Car battery) input to 16V(Laptop) output in a university project, capable of sourcing 4A and still 93% efficient.
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