Power!!!!!

ransoman · Post by **ransoman** » Thu Apr 06, 2006 6:38 am

I don't know if this is the right place to post this question but here goes.

I have a basic breif in my head of how my mega drive/genesis portable will turn out, the only issue is power. I want to use the sony ps1 screen because i don't want sonic to blur.

The GOAC i will use is the radica and it runs off 4 X AA batteries (6v)
The screen needs 7.5 volt (i believe, can you confirm)

My possibilities are either, run the GOAC via 4xAA and the screen off a 9v battery, This has been discussed in another topic but no-one seems to have come to a definite conclusion.

Or, running the whole thing off 5 AA's, Would the GOAC handle the extra 1.5v though or will it fry? And will the screen run well on that number of batteries (on my first topic i was reccomended using 6 AA but i want to keep the battery count as low as possible).

would either of these work? what would the battery life be like?

I am a total Noob when it comes to battery power so any help you can give would be greatly appreciated.

scherzo · Post by **scherzo** » Thu Apr 06, 2006 7:07 am

It's best to run both off of 5 AAs. See, no matter what, the GOAC need a regulated 5v current, which you obtain by running anything from 7v to 20v through a 7805. I can't remember if the GOAC from a Radica has a 7805 on its main board. I think it does.

What screen are you using? A PSOne screen? If so, that also has its own 7805. You only need one for your whole setup. So my advice would be to run the 7.2v from the batteries into the screen, which is 6 rechargable AAs.

SIDE NOTE: If you're going to use alkaline batteries only, you can get away with 5 AAs (7.5v), but then you're stuck to buying batteries forever. 5 rechargables works if you're using an LDO instead of a 7805.

BACK ON TRACK: Then take the regulated 5v from the screen and supply it to the GOAC, bypassing the GOAC's 7805, which should be removed.

As for 9v batteries, yes, they provide 9v of current but they die fast.

ransoman · Post by **ransoman** » Thu Apr 06, 2006 8:21 am

Thanks for that, Is a 7805 a voltage regulator then? What does it look like?

Sorry about the noobish questions. Power is not my strong point.

ransoman · Post by **ransoman** » Thu Apr 06, 2006 8:44 am

scherzo wrote: SIDE NOTE: If you're going to use alkaline batteries only, you can get away with 5 AAs (7.5v), but then you're stuck to buying batteries forever. 5 rechargables works if you're using an LDO instead of a 7805.

double post, sorry. How long would the batteries last like this? (5AA's)? as long as it is longer than the Nomad then that's cool.

timmeh87 · Post by **timmeh87** » Thu Apr 06, 2006 10:36 am

http://benwiki.gptheatre.co.uk/index.ph ... Regulators

alkaline batteres may start out at 1.5v fully charged, but their voltage drops pretty linearly as you discharge them. by the time they are "dead" they are at like 1.1v. so keep that in mind. 5 alkaline matteries will START out at 7.5v, but by the time they are half-dead, they might only be 6.5 or 6.

scherzo · Post by **scherzo** » Thu Apr 06, 2006 10:47 am

timmeh87 wrote:http://benwiki.gptheatre.co.uk/index.ph ... Regulators

alkaline batteres may start out at 1.5v fully charged, but their voltage drops pretty linearly as you discharge them. by the time they are "dead" they are at like 1.1v. so keep that in mind. 5 alkaline matteries will START out at 7.5v, but by the time they are half-dead, they might only be 6.5 or 6.

Oh, I didn't know that. How does the voltage drop for most rechargables? Do they stay just about 1.2v until they're drained?

timmeh87 · Post by **timmeh87** » Thu Apr 06, 2006 11:30 am

yeah, nimh batteries stay almost constant at 1.25v. they actually start out around 1.35 or so, briefly. if they are fully charged.

lithium batteries start at 4.2 but quickly drop to about 3.8. they spend most of their life between 3.8 and 3.4ish. dead at 3.

the voltage on rechrageble battery packs is the average voltage.

here, i found pictures.

alkaline:
http://lib.store.yahoo.net/lib/zbattery ... -curve.gif

nimh:
http://lib.store.yahoo.net/lib/zbattery/nimh-curve.gif

pretty dramatic difference.

scherzo · Post by **scherzo** » Thu Apr 06, 2006 1:38 pm

Nice charts. I'll never consider designing something for alkalines only again.

geekbait111 · Post by **geekbait111** » Thu Apr 06, 2006 5:02 pm

oh yeah and if you want it to have more life than the nomad, do the LED mod to the PSone screen. Go to http://www.extremetech.com/article2/0,1 ... 354,00.asp for the LED mod and how to open the case of PSone screen.
It'll reduce the battery consumption from 1 amp to .5 amp for the screen

. And around .3 or .2 amps for the radica.
-I have one question, is the radica able to play all the games genesis can? Or only several?

ransoman · Post by **ransoman** » Fri Apr 07, 2006 2:11 am

Got the book now so i have learned a lot more about the power and White LED modding the screen.

To answer that question, the radica has 6 games built into a rom chip, It is possible to replace that chip with a cartridge slot but i am not sure on compatibility. when i have built mine i will make a compatibility list.

geekbait111 · Post by **geekbait111** » Fri Apr 07, 2006 3:51 pm

yah... I knew it could be replaced, I was wondering more like why a radica can't support as many games... that's the only thing keeping me away from a radica portable instead a real genesis portable... so I'm doing gen v3.
Oh well... but meow!