how to make a negative voltage?

[bacteria]

Anyone got an easy to follow diagram of how to make -5v out of +7.4v (or a bit more)? I need about 200mA on -5v (negative 5v).

[gtmtnbiker]

Anyone got an easy to follow diagram of how to make -5v out of +7.4v (or a bit more)? I need about 200mA on -5v (negative 5v).

I haven't done electronics in years but you just need to find some sort of voltage regular circuit to give you 5v. For negative, it's just a matter of reversing polarity (e.g, positive input attached to ground, negative input attached to 5v).

[CRTGAMER]

Anyone got an easy to follow diagram of how to make -5v out of +7.4v (or a bit more)? I need about 200mA on -5v (negative 5v).

I know when you are involved, an intense, cool portable mod happens. I'm guessing you are trying to pull from a chargeable battery; maybe a 7.2?

Maybe a DC to DC converter might work?
https://www1.elfa.se/data1/wwwroot/webr ... 959803.pdf

[bacteria]

Not sure if the item you referred to is ok or not CRTGAMER.

I found this item on ebay but "a bit expensive": http://cgi.ebay.co.uk/Negatron-dc-to-dc ... 563b3ea0c3

gtmtnbiker - easy to downsize the current to 5v with a 7805 or simlar, however making a negative voltage is not so easy. I hear that if you just reverse polarity by + to - and - to + you end up destroying your electronics/short it. May be ok off a separate supply, I don't know, however idea is to run various voltages off one supply.

The 7.4v supply is going to provide 7.4v, 5v and 3.3v; however also needs to provide -5v (that is the issue one). May need to provide 12v too, that is fine.

As you ask CRTGAMER, I have managed to buy a French ColecoVision console, which has SCART; ie RGB as native. Bloody ColecoVision consoles however need 12v (will probably run run off 7.4v), 5v and -5v. Will test when I get it.

Looking for an alternative to the ebay item mentioned above - ideas?

[CRTGAMER]

Looking for an alternative to the ebay item mentioned above - ideas?

Slick acquiring a SCART Coleco, didn't kow they existed. Is SCART common option on Euro Retro consoles?

If not a portable and that -5V is an isolated circuit, maybe its own dedicated power source? Transformer power "Bricks" are pretty cheap.

[gtmtnbiker]

gtmtnbiker - easy to downsize the current to 5v with a 7805 or simlar, however making a negative voltage is not so easy. I hear that if you just reverse polarity by + to - and - to + you end up destroying your electronics/short it. May be ok off a separate supply, I don't know, however idea is to run various voltages off one supply.

I don't see how it would destroy it but then again, I'm not an expert in this area. I would suggest posting your question on an electronics forum such as this one:
http://www.electro-tech-online.com/

http://www.google.com/search?hl=en&q=+site:electro-tech-online.com+how+to+get+negative+5v&ei=3EvLS6OILJGHsAb-tsSeAw&sa=X&oi=forum_cluster&resnum=1&ct=more-results&ved=0CAwQrQIwAA

[bacteria]

Thanks for the advice, i'll ask them.

CRTGAMER - yes, it's interesting - in the UK the ColecoVision and Intellivision were RF only, yet the French versions of these had a SCART version; the SCART of course has native RGB, composite and I think S-video too. This means better video qualtity and no need to mess about with composite line amplification, etc.

Found this out on research.

Here is a link on the Coleco SCART: http://www.nightfallcrew.com/?p=1660

The audio of course can be taken from the audio chip better.

Posted question on that forum: http://www.electro-tech-online.com/gene ... post869362