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).
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)
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:
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)
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.