1/27/2024 0 Comments Prototype reflow ovenI have not yet sent the boards off to manufacture as I like to leave it a week or two before doing so, as it allows me to review the design with a clear head and pick up any obvious errors in the design. The OpenReflow software I am currently writing will be closed-source, but a fork of the ReflowDuino will be available on my Github which will fully support this unit, with the exception of the Learn function and some extra functionality available using the inbuilt menus. The ATMega32U4 is fully compatible with the Arduino ecosystem, so it makes it ideal for an open source project, as it's easily mod-able, and the programming header is included in the board design. Unfortunately there wasn't enough IO for all of the LEDs and the display together so I've elected to add a single IO expander to drive the output LEDs. I chose the Atmel ATMega32U4 micro-controller to manage this project, as it has enough IO pins to do all of the critical services, as well as native USB support, so no tertiary USB driver circuitry is required. From this header almost any device imaginable could be easily integrated into the unit. For extra extensibility there is also a GPIO header with 1 analog IO, 2 digital IO, 3v3 and 5v outputs as well as ground. I also wanted the native capability of the unit to be able to handle services such as automatically opening the door for cooling, running a circulation fan (for ovens that support it or I'm able to find a way to build it) and generic outputs for other switchable devices. There is ample board space for an additional module however. While the current design does not support WiFi, Rev 2 of this project would include support for a Wemos D1 mini module to allow for WiFi control, howevert this wasn't included in Rev 1 for now, to keep it simple. The best part of the design is it now has the capability for not just relying on arbitrary tweaking of timings for building the best reflow profile for each oven, it instead has a 'Learning' option, which allows the OpenReflow software to profile the oven and automatically adjust the profile timings for Preheat, Soak, Reflow, and Cooling to ensure temperature ramps are smooth, and we minimise overshoot. One of my favourite additions to this project is the use of a soft-power button to remove the need for a power switch, and allow for the micro-controller to automatically power down the unit in the event of an error or just as a power-saving measure.Īlthough the unit can be controlled from a PC or a phone/tablet, I wanted the OpenReflow to be able to be completely controlled independently of other hardware, so the on screen menus, buttons and rotary encoder mean that the entire unit can be fully configured and controlled without the Bluetooth module. What I have introduced to the design which are novel are the standardised indicator LEDs for the reflow oven status and progress, power indications, a rotary encoder for navigation and control, independent button controls and lastly a Nokia 5110 display for showing temperature and graphing the profile. The project box is plastic so is safe for the board to be mounted in directly, and it is designed with screw terminals on the PCB to allow for a side-mounted Mains inlet and outlet plug to ensure we don't have to worry about cutting and splicing too many mains cables for the oven.Īs for control, I hesitated on removing the Bluetooth BLE controller for the PCB, however as this was going to be an open source project, I opted to make the Bluetooth controller optional in the design. Considering we're playing with MAINS VOLTAGES here, I considered it prudent to go for a very safe option. The SSR is by far the most expensive component, however it is fully optically isolated and is very simple to drive and control. The design is intended to fit inside a standard project box and doesn't require any heat-sinking aside from the sink that comes built into the SSR (solid-state relay) chosen for the design. To date, I have completed the Schematic diagrams and the PCB layouts. Many polished solutions for this exist on the market, however they were well outside my price range, and never wanting to miss an opportunity to build something, I put myself to work designing a new alternative. Other projects existed, or I could have bodged one up using some relays or SSRs and an Arduino, however I wanted a complete and polished solution. The design is inspired by the 'Reflowduino' project as when it came time for me to build my own Reflow Oven, the only suitable project was the Reflowduino, and I couldn't buy them any more, as they had been discontinued. The OpenReflow project is an Open Source Hardware Reflow Oven Controller module that is designed to work with most 120v and 240v toaster ovens, to provide a consistent, reliable and flexible reflowing control.
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