Now that I’ve got the MCE Remote all built and in service (works quite nicely!), I need a new project. I’m interested in getting involved in surface mount devices. The reason for this is threefold - there are certain devices that aren’t available in through-hole packages, when using SMT you can typically make a board a lot smaller, and lastly individual SMT components not on breakout boards are typically a LOT cheaper than the already-soldered part.
There’s a few ways to handle surface mount. You can use a normal soldering iron, really steady hands, and a lot of patience. You can use a hot air gun (I’m probably going to get a rework station for this). Or you can use a reflow oven. The reflow oven “cooks” the components onto the board, and if handled properly is the best and easiest way to solder a whole bunch of components onto a board.
A professional reflow oven costs a large amount of money, but it’s possible to press-gang a normal toaster oven into the task by modifying it so that it can be temperature controlled and given a normal reflow temperature profile. There are kits available to do this, like this. However, in the spirit of adventure (and not wanting to mess with a PIC when Arduino is familiar), I decided to roll my own…
Behold! The first schematic of the Arduinoven;
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| The Arduinoven v1.0 |
This schematic is entirely theoretical at the moment (I haven’t breadboarded any of it), however much of the design was lifted from the Arduino Severino board, which has many of the features I wanted. I simply extended it a lot to add all the extra functionality. The design has been assembled so that each section can be tested largely independently to simplify breadboarding when I come to that stage. With the design, there were a few key features I wanted to adhere to;
- Must be suitable for production by somewhere like BatchPCB (and can therefore be two layer).
- Must have entirely through-hole components.
- Must use an ATmega328p and be programmable through the Arduino IDE
- Be able to store a significant amount of temperature data (that’s what the i2c EEPROM is for)
- Use an LCD and press buttons for an interface (uses an i2c LCD module)
- Relay and thermocouple connections need to be on the actual oven itself, but the Arduinoven will be a removable device (hence the DIN-5 connector)
- Be expandable in case additional hardware is desired (hence all the pin headers)
- Use RS232 for serial communications to a PC
- Fit onto a Eurocard-sized format PCB (100x80mm)
All in all, I’m pretty happy with how the design’s looking. More information once I receive my shipment of parts and I can start with the prototyping. Once I’m happy with the prototyping, I’m intending to get the board manufactured by BatchPCB so I can get something professional looking.
Note: Call me suspicious, but I think that the Severino’s schematic is in error and C8 (C5 on mine) is around the wrong way. I’ll look into it more before I actually breadboard anything.