Say hello to my tiny friend!... Or an update on the ATtiny 45/85 development board.

I've been working on an ATtiny 45/85 dev board for a while now. It went from it's infancy of no external power input to being a toddler and using an FTDI cable to supply the 5v needed. Now it's a teenager and has on-board power with 5v regulation:

It's the third revision of the board I've done, and it's also the largest of them. Still, it's not too expensive from OSH Park or BatchPCB. It now has a power jack and 5v power regulation (should be able to plug that Arduino power adaptor in and get her to fly) circuitry, ISP header, reset switch and two sets of broken out headers. The two sets of headers do serve a purpose. The first and inner set are for 'shields', while the second, outer, set is for both breadboard use and to give access to any unused pins that a 'shield' may not be using. It doesn't have an external crystal etc... as it shouldn't need one (as far as I understand), but the next revision will likely include a ceramic resonator, or at least be able to plug one in if wanted.

The board came from the want and need for an easy to use board for the ATtiny 45 and 85 (mainly the 85) that included all I would need to use it to make a Toaster Reflow Oven, but also be viable for use with other projects.

To further this idea of ease of use I designed an AD595 K-type thermocouple amplifier 'shield' for the dev board:

This is the second revision of the breakout board. It started life as something very basic, with the bare minimum for what I needed... I also cocked up my first prototypes. The thermocouple solder pads (which aid in getting better readings) were not accessible to solder to. So in this version I rectified this, in a very ugly way. But it works.

This revision also has an alarm LED, which will alert you if a thermocouple isn't connected or if the chip is damaged in some way. I also now use a 3-pin screw terminal to connect to the relay board I will be using (http://www.sparkfun.com/wish_lists/36307).

The AD595 is rather useful as you only need one pin on the microcontroller side of things and it's dead easy to work out the temperature:

Signal Values

The nice thing about the AD595 is that the signal it generates is linear with temperature. This means that it is really easy to convert from an analog reading to a real temperature. Secondly, the AD595 outputs 10mV/C which is simple to work with. at 1V, the temperature is 100C, at 2V, the temperature is 200C, etc. With a reference voltage of 5V, the sensor can make readings up to 500C.

The way to read the temperature is easy. First you convert an analog reading to voltage, then you multiply by 100 to get the temperature in celsius:

Voltage = analogRead(X) * 5.0 / 1024.0; //Note that 5.0 is the A/D reference voltage. Celsius = Voltage * 100;

Or, to simplify:

Celsius = ( 5.0 * analogRead(X) * 100.0) / 1024.0;

-- Taken from http://reprap.org/wiki/Thermocouple_Sensor_1.0#Signal_Values

It does mean that the breakout board can only output up to 500°C since it only has 5v to work with, but we don't need to go higher than that for a reflow oven (I imagine it wouldn't be hard to bring the 9v from the power adaptor up to the AD595 to give it a 900°C working range). I'm going to be using the firmware from the Pleasant Hardware reflow controller (http://pleasantsoftware.com/developer/3d/reflow/) as the basis for my code. He managed to get full PID controlled temperature management, 3 'programs' and a minimalistic UI into the limited memory of the ATtiny 45!


Anyway, this is just an update of what's been happening with the dev board. More to come about the reflow oven!

Prototype boards have arrived.

My prototype boards have finally arrived from BatchPCB (they got here a week or so ago) and DorkbotPDX (a couple days) and I'm rather chuffed with them! I'm having to order parts in as my local electronics store would have to order them anyway and I prefer Little Bird Electronics =)

They're bad photos I know, but my camera is out of action at the moment so I used my phone. A DSLR it ain't, but it gets the job done. I messed up on the AD595 breakout board as the thermocouple solder pads are now covered in solder mask. My bad. I'm altering the design to fix that.

When I have the three boards up and running I'll do a post for each of them, hopefully working flawlessly...

What I've been up to.

It's a simple question with a rather simple and probably boring answer...

If you look at the top of this blog you'll see a list of three pages. The first is for my CNC mill and corresponding controller, the ArduFrauenfelderCNC, which I have been refining in both the controller and the physical mill (which I'm design in SketchUp in 3D), the next is an Arduino shield for programming the ATtiny 45 and 85 microcontrollers (they're somewhat compatible with the Arduino IDE meaning they're pretty darn easy to code) and the third is for an ATtiny 45/85 development board and it's accompanying breakout boards.

They're all ATtiny related, except for the CNC controller, because ever since reading High-Low Tech's articles on programming these little chips using the Arduino platform (http://hlt.media.mit.edu/?p=1229 http://hlt.media.mit.edu/?p=1695) and seeing Pleasant Hardware's Toaster Over reflow controller (http://pleasantsoftware.com/developer/3d/reflow), which uses an ATtiny as the brains, I've been infatuated with the tiny things.

The reason for this outburst of stuff? I'm currently studying Library Sciences through TAFE as an external student and they close between the end of October and only reopen in February the next year meaning I have a fair amount of time on my hands, which I've been putting into designing things I've been putting off. I'm currently in the process of refining all the boards I've published on my GitHub account.

In fact I'm having the programmer shield made by BatchPCB and am hopefully getting the development board and thermocouple breakout board made through the DorkbotPDX PCB service (NOTE: I've now paid for the two boards to be made by the DorkbotPDX service and am on the December 5th run! Can't wait to get my hands on those little purple prototypes XD). Once I get my prototype boards from BatchPCB and DorkbotPDX I'll construct them and publish it here (and hopefully finally use my four year old instructables account) with construction steps and videos of the board and what they can do, hopefully - fingers crossed.

I've also designed a development board for the ATtiny 44/84 as it has a few extra pins, just incase the 45/85's 8-pins aren't enough. I really only needed to swap out the ATtiny45/85 for its larger brother. There's also an Arduino-based ATtiny44/84 and 45/85 programmer in the works, where the ATMega328 is running the ArduinoISP sketch and is solely used to program the ATtiny chips, meaning you have to use an ISP header and programmer if you want to program it outside of the Arduino IDE (it's probably not that useful, but I have time on my hands I'm not using doing anything else so what the hell!).

I'm also currently trying to put together a RFID location aware and talking/singing teddy bear for my lovely niece. It's taken directly from the pages of the latest Make Magazine (Volume 28) which is about toys!

And I'm finally contemplating entering my CNC mill in the intsrucables ShopBot competition, though I don't know I'll get it all finished by the cut off period (I thought a DIY CNC mill in a competition to win a professional CNC would be ironically funny xD). 

Anyway, that's what I've been up to, and will be up to, in the near future.