7.2volts? i thought you needed 12v ?

peacefrog226 · Post by **peacefrog226** » Tue Jun 21, 2005 1:32 pm

hi, im new to the forums, and im almost done my own n64p.

just for thesting, i have had it riunning off of 8 alkaline AA's.

this provides me ith the 12V to power the screen and board, and with the sony car charger thing, gives me 3 volts to power the rtest of the board.

now im in the market for rechargeable batteries.

while searching around the formuns (which arw fantastic by the way), i have neen a lot of people using 7.2 volt rechargeable batteries. how does this work?
i would love to use those if possible, but could someone explain how they would power my unit?

thanks!!!!
eric

warbaby · Post by **warbaby** » Tue Jun 21, 2005 1:44 pm

i havent tried powering it off 7.2 volts, but im pretty shure theres a 7805 in there. so it is possible, but DC-DC adapters run off of 12 volts... now yu wouldnt be able to power the 3.3V circuit. you would need to create a seperate circuit (2 C's er sumthin), or scrap the DC-DC converter and use sum kinda linear converter...

peacefrog226 · Post by **peacefrog226** » Tue Jun 21, 2005 1:47 pm

thanks for replying!

so i einatly need a 12 volt source

ok thats what i thought!

thanks!

nos_slived · Post by **nos_slived** » Tue Jun 21, 2005 2:14 pm

Actually, you can use 1 or 2 extra 7805s with resistors to drop it to 3.3V, but if you already have a 3V convertor, you can just use 12V batteries.

daguuy · Post by **daguuy** » Tue Jun 21, 2005 3:49 pm

do the car adapters only work with 12v? would it work if i gave it 8.4v?

nos_slived · Post by **nos_slived** » Tue Jun 21, 2005 3:53 pm

Some can go lower, but most can't drop below 10.2V or something.

monkeymagic · Post by **monkeymagic** » Tue Jun 21, 2005 7:02 pm

awww crapppp

i just ordered some small lithium packs they are at 7.2v they cost a bloody lot aswell.

i was planning to just feed the n64 with 7.2v on the 12v line as i thought the n64 only needs 5v after it comes out from the 7805 and feed the 3.3v by connecting a in car charger which happens to output 3.3v.

i was sooo naive about how complex this project will be

cant i replace the components on the n64 to make them more effiecient, surely they are better components available today arent they or is too much work?

nos_slived · Post by **nos_slived** » Tue Jun 21, 2005 7:06 pm

You are fine using 7.2V, you just can't use that 3.3V adaptor, unless it will work on 7.2V. If it won't work that low, just use some 7805s with a resistor to make 3.3V.

Post by **Triton** » Tue Jun 21, 2005 9:09 pm

both the car adapters i took apart had 7806s in them but they were 12-6v converters so i dunno

daguuy · Post by **daguuy** » Tue Jun 21, 2005 9:21 pm

do 7803s exist?

nos_slived · Post by **nos_slived** » Tue Jun 21, 2005 9:34 pm

I have searched google and never found any evidence of 7803s existing.

Post by **Triton** » Tue Jun 21, 2005 9:38 pm

i have no idea

nos_slived · Post by **nos_slived** » Tue Jun 21, 2005 9:55 pm

The best option would be an LM117 or LM317.

chodges84 · Post by **chodges84** » Wed Jun 22, 2005 11:47 am

I've also looked for 7803's but never found them. As nos_slived points out a LM117 would be a good bet, but I'm sure that when I looked at using one it wasn't quite as simple to use as a 78xx reg would be. On some that I've seen there are only 3 pins, and I don't know howyou change the output voltage. I think I'll buy some and have a bit of a play with them with my multi meter

daguuy · Post by **daguuy** » Wed Jun 22, 2005 1:13 pm

i read the manual thing for LM117 but i don't understand it. could someone explain how to get 3.3v with it?