Quote:
Originally Posted by deadmike
Hello i live in japan and am trying to find an ac adapter to use with my e-reader. Does it have to be 5.2V or will voltage under that be ok. I can't seem to find 5.2 here.
thanks
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I think you can build yourself a filter that gives you exactly 5.2 volts.
You only two parts
1. an integrated circuit 7805
2. a 32Ohm resistor
and of course a soldering iron, Reader compatible jack, some wires and perhaps a cooling fin (a piece of aluminium, or a cooling fin from an old processor would do)
see
http://peterflemming.ca/flemmweb_cur...inear/7805.pdf
for basic use of 780x IC.
You solder resistor to the "ground" pin, to adjust output voltage.
Let us compute what resistor you need:
Id current (from the "ground" pin) is, according to the datasheet, 6mA that is 0.006A.
You need to "burn" 0.2V in the resistor, so the regulator will give you 5.2 volts.
R=U/I so in our case R=0.2V/0.006A
http://www.google.com/search?q=0.2V%...=Google+Search
so you solder 32Ohm resistor to the "ground" pin and get exact 5.2Volts.
Please check your circuit under load with a voltmeter before connecting it to the Reader.
If you want to get really fancy, (and use circuit according to the manufacturer specification ;-) ) download
http://www.st.com/stonline/products/...re/ds/2143.pdf
and have a look at the Figure 19. - Circuit for increasing output voltage.
You compute R1 and R2 resistors to get exactly 5.2 volts.
you will need:
1. 7805
2. two resistors
3. two capacitors
If you show the picture in any shop that sells parts to hobby electronic builders (IF there are soch shops in your country) the staff should be able to help you to select parts. In my (relatively small) town there are several shops where you can buy such parts and get a good advice from the staff.
Finally you connect any DC power source that gives more than 7V and you are done.