Power Supply – Part 1

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Hey folks, how are you?

So, some time ago in one of my classes we soldered a small variable power supply, I has in the need of one anyway, but unfortunately the supply had a lot of noise, I tried to use the ADC of an atmega8 and a LM35 to check the temperature of my room and the temp has varying considerable more then when the power was coming from my usb port.

And it was a pain to have to adjust the power to 5V everytime, burned a chip because I forgot to do that…

So that is why I decided to use the transformer from the old board and make a new board with a regulated 5V output and a variable output also. And since I was gonna do that, might as well do a decent enclosure.
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Serial

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First the important things.

HAPPY NEW YEAR!

That Raijuu.net may do better in this new year to come.

Now the rest.

I’m finally on vacation, which should give me more time to improve the site, but unfortunately, the more time you have, the less you do.

And since i’m on the beach right know (I’m on the south hemisphere, meaning right know it is summer! Suck that north hemisphere!!!) without my faithful workbench, no projects for a while.

Anyway, to at least put something on the site, im uploading a old project of mine that probably most of you will not find useful.

Its a simple RS-232 to TTL converter.
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γcard

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I’m currently doing a project for one of my classes, and since I’m in charge of anything involved in electronics for the whole project, I decided to make a board that would allow me to use an ATmega8 or Atmega168 (since there is a possibility that the Atmega8 memory will prove insufficient) in a protoboard.

The concept is old, and there is a bunch of others great solutions out there, like the Boarduino, RBBB, Alex from Tinkerlog has even made one in a prototype board. All this examples work great and would solve the problem for me right way.

But, you know, I never did like to do any-thing simple when I could do it ass-backwards. (A virtual coke to anyone who gets this quote)
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Paper Silk Screen

No project this month since I’m to busy working, really, I can’t stand to look at another PCB, I made like 20, 25 boards in one month, my hands smells like ferric chloride.
That and I can’t find a MAX3232 in dip package around here, gona have to order one on-line and that takes time…

Anyway, I needed to make a prototype for a friend, and since I was not the one to use it and didn’t want to make a sketch with the positioning of the buttons and LEDs I decided to try something I have seen in some blogs for some time.

And as you can deduce from the title of the post and the big photo over there, I printed a silkscreen for board on paper and before soldering everything put the paper between the board and the components.

Surprisingly, it turned out great, I don’t know why, but I thought that the heat was definitely going to stain the paper.

But I still have a doubt, I used masking tape to hold everything down, but there got to be a better way.

Anybody who has used this method before knows a better way to glue the paper on the board?
Glue? Hot Glue? Glue Stick?

USBJoy

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This is a board for the USBJoy project made by Sergey Ryumik for the Russian magazine “RADIO” (2007,number 1, page 28-31), which was made using the firmware from ObDev that implements USB protocol on the AVR chips.

Basically, it is a PlayStation controller to USB adaptor. (Yes, I play to much videogame and I know it).
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More videogames…

Last week my good friend Gabriel invited me to a game party to test his new TV, which has a VGA input that allowed us to display his note screen on the TV. I was working on 3 different projects at the time without a focus on one, but since one of the projects was a board for the USBJoy project that I found on the ObDev site, I rushed to make a prototype of the board to test it and have fun at the same time.

The prototype worked well under Windows XP and Linux, should work on Mac to, since it is a HID (human interface device).

The USBJoy connects Dendy (Russian NES), SEGA Mega Driver II and PlayStation I and II to the computer trough a USB port, but the board that i’m making only works with PlayStation I and II.

Anyway, the layout of the board is ready, I just need to make one board and test it before putting on the site.

So probably this week or the next the project should be up.

MJoy

Not a real project this time, most likely an implementation of another person project.

If you like to play videogames in your computer as much as I do, you probably already heard about the MJoy, which is an USB joystick made by Mindaugas that uses an ATmega8 and have 24 buttons, one hatswitch (or POV or D-Pad depending on the game) and 6 analog axes.

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It’s oriented to flight simulators games, but can be used for any game, it’s should work wonderfully if you are trying to build a MAME cabinet (Uh, I might try that later).
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This is BETA!

All right, first post that has anything to do with the real theme of the site, which is electronics by the way. (As you can see, I do know how to write in English)!!!

Ok, enough small talk, let’s start…

If you ever used an uC you already know that it is a pain to make for the 42º time the things they always need, like, power supply, crystals, programmers headers, MAX232 circuits, etc…

So its common ground to build little dev boards for the uC that you always use. In my case it is the fantastic ATMega8 or theATMega168, and of course the others pin compatibles uC of the family, like the 48 and 88.

Because of that I made this little board that for now doesn’t have a name (I’m thinking something like “βCard” or something like that, if you have suggestions leave a comment).

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So let’s introduce you to what this board has in the guts:

  • Petite size, only (78,74 x 54,61 mm)(3,10 x 2,15inch)
  • All pins are brought out and have three connectors each
  • 1 “Power good” LED, I like to use red but be my guest and put green or blue if you like it (but for blue you probably will need to change the resistor)
  • Standard Reset button
  • 6-pin standard ICSP header
  • Standard 2.1mm DC jack (actually, I think I use 2.5mm, but that just seen to be standard where in brazil) with 5V (I love the 7805, don’t you love him to?) regulator to run on 7V-15V power (DC)
  • External power entry, selectable with a jumper
  • 1N4001 diode protects against using incorrect wall adapter
  • All through-hole parts so it is easy to solder
  • A 4 pin connector for general purpose (so you can connect a external rs-232/TTL converter or a USB connector or implement I2C bus, or anything that uses just 4 pins or less)
  • A connector for a crystal with its two ceramic capacitors, or a 3-pin ceramic resonator.
  • There are no connections between the power and ground sections and the analog power section (Agnd, Vref, AVcc), which will make your life easier if you ever want to use a different reference for the analog section. And if you are happy with the standard, there is a power supply connector located nearby. (It’s recommended to jumper the pin Agnd to ground and Vref and AVcc to the positive power supply if you don’t want to use a different reference)

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(Top View)

The whole thing is very simple, the only part that has some electronics is the power supply, which is so simple that probably any person who knows a bit about electronics must have made something very similar at least once.

As you can see in the schematics, it is a simple 7805 power supply, the power goes in, then there are some capacitors to filtrate the power from spikes, then the 7805 regulate the 7-15V to 5V and then there are more capacitors just to make sure.

There is also a pull-up resistor connected to the reset pin, to make sure that the pin is going to stay at 1 unless the button is pressed or the programmer connects the pin to 0.

Aside from that, it’s basically just a mater of connections, like the ICSP connector.

Just so you know, the holes in the board are bigger than they have to be. That is to make easier for you to make it at home, I have difficulties in finding drill bits smaller then 1mm (0.039inch), so I made all the holes 1.1mm (0.043inch), this shouldn’t be a problem for you if you decide to send your board to be made by some company, you will still be able to solder all the components.

The vias are all 0.016inch, so you wont find any troubles with that to.

So here are the files for making the board:
(Ps: The schematics and the board were made in eagle 5.0, so I’m not sure if it works in eagle 4.16. If you are having any problems and you’re using 4.16 try to download the new version from the CadSoft site.)

The schematics and the board file in eagle format.
The schematics in PNG.

These are released as-is under
Creative Commons 3.0 – Attribution – Share Alike

Yes, I know what you are thinking, why haven’t anyone made something like this before?
Simple! They have! But I wanted my board to have some details that their boards didn’t had, like a small purpose connector, one sided copper layer with large holes so that any beginner could make one at home, etc…

But that doesn’t mean that I’m not grateful to then, their board and schematics helped me as I hope mine will help you, even if just give you an new idea for your project I will be happy. And since I’m talking about then:

http://www.evilmadscientist.com/article.php/card
Which is probably the project that gave me the most ideas (as you can see, my board is practically a revision of their boards, I admit that they gave me the idea, I’m just tuning it a little)

http://www.ladyada.net/make/boarduino/
And of course, ladyada, which is the person who gave me the idea of having a site. Thank you!
Oh, and the power supply design it’s from her.