SparkFun Forums

[Grimm Spector]

Anyone know the proper way to hook up one of these to get a 3.3v output? I'm worried about frying the chip if I mess it up, so I'd rather not try it on my own the first time. Thanks.

[brennen]

Check the datasheet. Starting on page 9, there's a really extensive application note that should tell you all you need to know.

[geekything]

Grimm,

R1 should be 220ohm, R2 360ohm for exactly 3.3vdc. The Sparkfun breadboard kit uses 240 and 390 which gets you close enough at 3.28vdc.

The 1117 is exactly the same as a 317 regulator which might help you find schematics.

There's a 317 calculator at:

http://www.electronics-lab.com/articles/LM317

Depending on your application, you may require good decoupling caps.

-marc

[geekything]

P.S: I like to use 1/4Watt resistors -- but you might get away with 1/6 or 1/8Watt resistors depending on your app.

-marc

[brennen]

Looks like I missed the fact that there are variable ones too.

[Grimm Spector]

oh sweet, thanks guys, that helps I didn't have time to read the entire spec sheet either, guess I should've looked further, but input is always good just in case

[Philba]

You really need to completely read though a datasheet. there is no substitute for that. you don't have to read and understand everything but at least look all the way to the end. you will notice little things like schematic diagrams and so on. while the aren't always complete, there is almost always enough information there to get you started.

[Grimm Spector]

You really need to completely read though a datasheet. there is no substitute for that. you don't have to read and understand everything but at least look all the way to the end. you will notice little things like schematic diagrams and so on. while the aren't always complete, there is almost always enough information there to get you started.

Normally I would but it only showed as having two pages on my system, I should probably update my adobe.

[bertrik]

Is this for some kind of project of yours?
Please let us know about it.

[Grimm Spector]

well looking at some various projects currently for this particular item but my main one is going to be a portable power type thing and I need to take some chained items coming out to around 12 volts and use an alternator to make it into 120 V AC power at 60 Hz of course, I was wondering if anyone has suggestions on this, would it be possible to use a PIC or ARM or something and PWM output? Or is there a better way? I've never had to use an alternator before, so I wouldn't know where to begin building one, maybe some high rated capacitors and a transistor setup would do me for the alternation if I measure it just right, trying to of course get as close to a pure Sine as possible.

[silic0re]

Are you looking at building something that will take in 12v DC and convert it to 120v AC so that you can power those devices that use 120v AC? If so I think you mean an "Inverter". There is a wealth of information on these devices and you can find a lot of schematics (and other information) with a google search:

http://www.google.ca/search?hl=en&q=inv ... 120V&meta=

I don't know a great deal about inverters, but I think the most common design you will find today is essentially an oscillating circuit running off the 12v DC that generates a sine wave, then feeds this wave into a transformer to step up the voltage to 120V. You mentioned using an alternator, but as far as I know those are little DC motors (generators) that use the torque/angular momentum generated from a gas engine to turn a DC motor and generate some juice. I remember hearing about some old DC -> AC converters that used motors. I think they used a DC motor with the shaft connected to a 3-phase AC motor (or something) and just tapped one of the phases of the 3-phase to get 120V AC. I could be completely wrong on that last one, though!!

hope that helps in some way

[Grimm Spector]

Are you looking at building something that will take in 12v DC and convert it to 120v AC so that you can power those devices that use 120v AC? If so I think you mean an "Inverter". There is a wealth of information on these devices and you can find a lot of schematics (and other information) with a google search:

http://www.google.ca/search?hl=en&q=inv ... 120V&meta=

I don't know a great deal about inverters, but I think the most common design you will find today is essentially an oscillating circuit running off the 12v DC that generates a sine wave, then feeds this wave into a transformer to step up the voltage to 120V. You mentioned using an alternator, but as far as I know those are little DC motors (generators) that use the torque/angular momentum generated from a gas engine to turn a DC motor and generate some juice. I remember hearing about some old DC -> AC converters that used motors. I think they used a DC motor with the shaft connected to a 3-phase AC motor (or something) and just tapped one of the phases of the 3-phase to get 120V AC. I could be completely wrong on that last one, though!!

hope that helps in some way

yup, I got it backwards, my bad, hehe thanks I'll have to review inverter information, it sounds a LOT easier than building an alternator :-\

next step, figure out how to solder SMD...anyone have bright ideas?

[brennen]

I'm pretty sure there's a big SMD soldering tutorial on SparkFun's main page under the tutorials link.

[Grimm Spector]

I'm pretty sure there's a big SMD soldering tutorial on SparkFun's main page under the tutorials link.

well it's fairly straight forward but I have issue with small objects sometimes, some days my hands shake bad due to an adrenalin imbalance. paste, parts, hot air...