Voltage for PSONE/Battery discharge

rawls · Post by **rawls** » Fri Jun 03, 2005 9:08 am

I have a couple of questions:

First, what is the LOWEST voltage a psone screen can be run off of. I know hit has some circuit stuff before its 7805s so what kind of voltage does this need?

Second, and this is somewhat related, what are the discharge characteristics of NiMh rechargable AAs. Specifically, when fully charged, they should be around 1.2 V, so 6 of them will be about 7.2 V. Now, as they discharge, their voltage will drop; does anybody know what the "bottom point" is? If it is 1V, then 6 AAs will end up at 6V, but if they drop to 0.8V, then 6 of them will be at 4.8V, which is lower than 5 and the 7805's won't work (and neither would the SNES that I am using with it).

G-force · Post by **G-force** » Fri Jun 03, 2005 9:22 am

The lowest voltage I have gotten the screen to run off was 7v.
Ben said there was something on the screen that needed 7v to run, but he couldn't remember what.

rawls · Post by **rawls** » Fri Jun 03, 2005 9:27 am

So if you run the PSONE screen of 6 NiMh cells, does it stop working before they are completely discharged?

Post by **gannon** » Fri Jun 03, 2005 9:29 am

I think they have a steady voltage in the range of 1.15V-1.3V between fully charged and discharged.

rawls · Post by **rawls** » Fri Jun 03, 2005 9:35 am

This still means that at full discharge, 6 NiMh AAs are (in series) at 6.9 V, which is less than 7.

Nonetheless, I think I'll just run the thing off of 7 cells, to be safe.

Turbo Tax 1.0 · Post by **Turbo Tax 1.0** » Fri Jun 03, 2005 12:46 pm

6 Ni-Mh is 7.2 not 6.9 i got my snes and screen to go off 6

nos_slived · Post by **nos_slived** » Fri Jun 03, 2005 5:36 pm

He ment when they hit 1.15V.

The lowest you can go while still using the 7805 is approx. 7V. 78XXs vary from unit to unit, but a general standard of 78XXs, is that they atleast require 2Vinput over their set output. This is usually closer to 2.2V, meaning a minimum of 7.2V input.

As for cut-off, that varies from manufacture to manufacture. I have seen a number of different datasheets, and they have all been different. They are usually pretty close though. Here is the datasheet for Energizer's Ni-MH.

Turbo Tax 1.0 · Post by **Turbo Tax 1.0** » Fri Jun 03, 2005 5:43 pm

sorry

yeah im running out my batteries now and the screen is getting slightly distorted but still playable, im thinkin about stickin another battery in there to keep the voltage up

chodges84 · Post by **chodges84** » Sat Jun 04, 2005 6:37 am

its ok to run it off of a 7808 though is it? won't be too many volts going through will it?

I'm sure I read some where it was OK to use one, but can't remember.

nos_slived · Post by **nos_slived** » Sat Jun 04, 2005 11:04 am

If you have a 12V battery source, you can use a 7808 to drop to 8V before going in to the screen. You end up wasting a lot of power though, because then you have a 7808 and two 7805s on your portable, and 78XXs use a lot of power to work.

rawls · Post by **rawls** » Mon Jun 06, 2005 3:22 pm

Well, if I use 7 NiMh AAs I should be fine, I think. I will already have a diode between the batteries and the systems so I'll lose anywhere between .25 and .6 volts, depending on which one I pick. If I pick a 0.6 one, then the voltage going into the screen will vary from 7.8 and 7.45 volts, approximately. I would rather have an extra battery taking up space than to have my system crap out before the batteries were fully drained.