Hi all, Tomorrow I'm working on a power supply to replace a 9v battery. All I have is a *5 volt regulator. I think can use a voltage divider on the output, then tie the normally grounded leg to the center of my divider to bring it up to 4 volts. So I have 4 + 5 = 9 volts. If I used 5.1K and 4.3k in series to ground. that would give me 9.1 volts. However there is some current from the reference pin. So, I don't know how to calculate the proper ratio and how much current do I need to flow through my divider. Should I put a capacitor across the lower leg of my divider? How big? Thanks, Mikek *My local Radio Shack only carries 5V and 12 V. PS. In case this isn't feasible, Here's the scene, I have three devices, an infrared transmitter (9v) an infrared receiver (4.5v) and a walkie talkie (4.5v). I have tested both of the 4.5v units on 5 volts and I'm comfortable they will be OK. I'll be running this all from a 9v wall wart, we'll say it puts out 14v at no load. The big load is the walkie talkie during transmit ~350ma. At idle it is less then 10 ma for all devices combined.

You can stack regulators: hang the ref pin of one 5V reg on the output of another. See U9:U10 here: Dang, I could have done that with U11 and U12, too. -- John Larkin Highland Technology Inc jlarkin at highlandtechnology dot com Precision electronic instrumentation Picosecond-resolution Digital Delay and Pulse generators Custom timing and laser controllers Photonics and fiberoptic TTL data links VME analog, thermocouple, LVDT, synchro, tachometer Multichannel arbitrary waveform generators

"amdx" ** Your stupid problem - fuckhead.

Have 5v regulator need 9 volts

Jan 24, 2013 29 Replies

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amdx 13 years ago

Hmm... I guess you just get hum if the troughs go below 10.7v. :-) Mikek

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John Fields 13 years ago

Yes, precisely. The regulator input needs to be at least 1.7V higher than the output, at all times, for its own internal circuitry to work properly.

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Michael A. Terrell 13 years ago

I have all those on my hard drive(s), and can print them out if needed. Some data sheets that were made from catalog pages, where the OEM never prnted a real datasheet. :)

As long as they aren't trying to design electonics with crayon & newsprint. ;-)

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Phil Allison 13 years ago

"amdx"

** Your stupid problem - f*****ad.

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amdx 13 years ago

Is that you Phil? It's seems a little weak. Imposter!

Mikek

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krw 13 years ago

No, Phyllis is normally weak. ...or were you commenting on the "little"?

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amdx 13 years ago

When testing, my line voltage was 123.3vac. When I got to my boat and checked the line voltage it was 112.9vac with my heater running. I decided to use a 12v wallwart instead of the 9v. The 9v Wallwart only had ~ 0.4 of headroom at full load.

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kaweeziur 13 years ago

What's a walkie talkie? That sounds like some sort of gay sex device!

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amdx 13 years ago

Your persuasion has jumped to a conclusion.

In case you're really confounded, here's a link.

formatting link

Mikek

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Michael A. Terrell 13 years ago

Don't feed trolls.

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