FREE DC-DC CONVERTERS!!!

timmeh87 · Post by **timmeh87** » Sat Nov 19, 2005 12:32 am

they emailed me.... maybe you never actaully hit the "ok" button or something. log in and see if theres still samples in your shopping cart.

G-force · Post by **G-force** » Sat Nov 19, 2005 4:59 am

In the words of Peter Griffin - "Frickin shweet!". You rock man, thanks for showing us how to do this.
What I really hope is that even though it says it requires 9V input, I can use 7.2V (since I already built a 6AA holder onto my case). Fingers crossed.

x24 · Post by **x24** » Sat Nov 19, 2005 6:52 am

i sent the order away the last time i sent a msg here and mine just arrived at the door..

S q u e e ! · Post by **S q u e e !** » Sat Nov 19, 2005 7:26 am

@G-Force: Minimum input voltage is 9v, sorry.

@Everyone: Do I have to put caps on the lines, because the data sheet says it's optional.

**EDIT**

Better question, what does it do? Does it really make a difference if I have caps on the lines? And what voltage rating of a cap should I get, the voltage I'm inputting?

timmeh87 · Post by **timmeh87** » Sat Nov 19, 2005 7:47 am

the output cap isnt optional i dont think. or at least it isnt for the 1A version. i never actaully looked at the datasheet for the 2A one, i assumed it was the same. anyhow, its good practise to put caps on your input lines. (and the output line of the dc-dc is the input line of the '64) unless youre too cheap to shell out 50 cents for one (or too lazy to hack one off an old board), you should just put the caps on.

------------------------

in related news, i might change my setup a bit. after talking to the same 4th year electrical dude, im definitely going to the one-battery setup. he ordered me what is called a "buck-boost" converter SPECIFICALLY to convert a single li-ion to 3.3v. what it is is basically two dc-dc's side by side that can convert voltage up, OR down, depending on what the battery gives out (li-ions range from 3 to 4 volts depending on discharge).

also, i ordered a protection IC from maxim (same deal as ti... free), so my batteries wont explode. they should be here in about two weeks. so. i guess ill have time for studying. lol.

and the total cost of my psone screen is 45 canadian, including shipping!

i plan to completely document my work, complete with more pictures and diagrams and such. i also might use some microconrtolers for something, just because i can (www.microchip.com - free microcontrollers). i think the protection chip i ordered can interface with i2c, which microchips PIC's can also do. so im thinking of using that to make a battery meter out of a row of couloured led's. that would be cool.

[edit @ squee]
capacitors are basically "current resivoirs" they save up electrons, so when something needs a lot of electrons for a short amount of time, it will empty out the capacitor, - instead of drawing a lot of current though a sensitive circuit (or not drawing it at all, because the circuit just cant handle that much current).

they also have a voltage-moderating effect, so that slight "blips" on the input voltage will be "smoothed out". they are absolutely nessecary on noisy lines like the ones coming out of an ac-dc converter, but batteries give out very clean voltage, for the most part. but they are a good idea anyways.

the voltage rating is the max voltage the cap is rated for before it breaks. it is completely independant of the farad (unit of capacitance) rating, so that a 100 microfarad capacitor rated at 1v will do the exact same thing as one rated at 1000V, except the 1v one will break at more than 1v, and the 1000v one will be bigger and more expensive.

in general, it is usually fairly smart to use a value at least twice as the max voltage you expect to pass though it. the one i used was 26 volts.

Post by **marshallh** » Sat Nov 19, 2005 9:43 am

@tim Thanks for the great explanation, couldn't have said it better myself

@G-force You've got to run your N64 off of at least 8 cells to get 9v min. input. You should make a vacuum-formed case for that

timmeh87 · Post by **timmeh87** » Sat Nov 19, 2005 10:10 am

instead of 8 nimh cells, you could just use 3 li-ions. if you can afford it, and know how to properly protect them (and once i finish the documentation of mine, you will), then there is no reason not to. they are way better.

also, if you are curious, you can learn more about electronic components here:

resistors:
http://en.wikipedia.org/wiki/Electrical_resistance
http://en.wikipedia.org/wiki/Resistor

capacitors:
http://en.wikipedia.org/wiki/Capacitance
http://en.wikipedia.org/wiki/Capacitor

inductors: (the are sort of the "compliment" to a capacitor)
http://en.wikipedia.org/wiki/Inductance
http://en.wikipedia.org/wiki/Inductor

its a lot fo reasing, but if you dont understand any of it, you really shouldnt be trying to make electric circuits. (but you also dont have to understand ALL of it. some of that crap is way beyond even me

)

madc0w · Post by **madc0w** » Sat Nov 19, 2005 10:18 am

he knows all of that, he is a mod, isnt he?

also, i think he just wants to use what he already has.

timmeh87 · Post by **timmeh87** » Sat Nov 19, 2005 11:02 am

that was just a general message to anyone who was reading the post. like you.

nos_slived · Post by **nos_slived** » Sat Nov 19, 2005 11:54 am

timmeh87 wrote:they emailed me.... maybe you never actaully hit the "ok" button or something. log in and see if theres still samples in your shopping cart.

I had definitely hit okay, but I forgot that I had changed the recipient name when I confirmed the details, but never changed the name in the account profile. I just did it, and I got my notification email.

G-force · Post by **G-force** » Sat Nov 19, 2005 11:57 am

I know I'm supposed to use 9V-15V according to the datasheet. I was just hoping that it might work anyways (with less efficiency or something). I already glued the 6AA holder onto the case, so I wouldn't be able to change it without trashing the case. *sigh*

madc0w · Post by **madc0w** » Sat Nov 19, 2005 12:31 pm

timmeh87 wrote:that was just a general message to anyone who was reading the post. like you.

thanks for clarifying, even though i already know that stuff.

nos_slived · Post by **nos_slived** » Sat Nov 19, 2005 12:54 pm

A bit of information for people using a PSone screen with their portable. You probably know that you can't run the PSone screen on anything over(or around) 9V, which means you need to bring down the voltage a bit before going in to your screen. I was checking out TI's site again, and I noticed that they also have both 5V and 8V models, and both have free sample offers. This means that you can use the 8V model for your screen's input, and replace all the 7808s with the 5V model(I can't remember the efficiency for most 7805s, but I'm sure it's lower). Keep in mind that the PT5101 outputs 5V up to 1A with 90% efficiency, while the PT78HT205(5V up to 2A) is 85% efficient, so low draw circuits can use the more efficient model.

timmeh87 · Post by **timmeh87** » Sat Nov 19, 2005 2:51 pm

G-force wrote:I know I'm supposed to use 9V-15V according to the datasheet. I was just hoping that it might work anyways (with less efficiency or something). I already glued the 6AA holder onto the case, so I wouldn't be able to change it without trashing the case. *sigh*

i looked around the site for you, there dosent seem to be anything that outputs 3.3v with anythign less than 9 on the input side.

however, maxim offers a wide range of chips with your specifications. i believe since it is just a chip that it requires external components and a circuit board. but. it is an option. this one looked the simplest

http://www.maxim-ic.com/quick_view2.cfm/qv_pk/1139/ln/

be careful what you order, if you do. some of these chips are about the size of a pea and nearly impossible to solder to.

the link i gave you is 4 - 16.5 volts input. read the datasheet before you decide to order. i didnt. i have no idea how complicated this thing is (but it only has 8 pins... some of them have 20 or more)

or you could just accept inefficiency and stick with a reg. dc-dc's arent for everyone.

Post by **marshallh** » Sun Nov 20, 2005 12:06 am

Or you could use an LM2670-3.3 by National.