Reflow hotplates are a wonderful tool for PCB assembly if you can keep your designs single-sided. The 946C hotplate in particular has been on hackers’ radar for a while – a 200x200mm working surface hotplate available for under $100 is a decent investment. As with other reflow tools, it was a matter of time until someone made a replacement controller for it. This one, you’ll want to keep in mind – it’s a replacement controller project by [Arnaud Durand] and [Elias Rodriguez Martin], called Reflow946.
Keeping to best practices, the board is a drop-in replacement for the stock controller – swap cables over and go. The host processor is an ESP32, and it lets you can program reflow profiles in using BLE, with a Python application to help. The whole design is open-source and on GitHub, of course – keeping with best 3D printing traditions, you can already order the parts and PCBs, and then assemble them using the hotplate you’re about to upgrade. As far as aftermarket controllers go, here’s no doubt this board gives you way more control in reflow and lets you compensate for any possible subpar calibration while at it.
Since the casing of the hotplate is metal, [Arnaud] recommends an ESP32 module which has an external antenna connector. You also need to watch out for compatibility – turns out, only some hotplates sold as 946C will fit this board, so talk to your seller if you’re about to buy a hotplate capable of this upgrade. Almost makes us wish that these ovens had revision numbers, maybe a letter at the end of the model number or something!
Hotplate reflow has been one of our favourite PCB assembly methods for a while, and hacker ingenuity has given us different ways to do it – frying pans full of sand, PTC heaters with flat surfaces, and even PCBs designed to reflow PCBs. Not yet familiar with what reflow means? Let’s get you up to speed!
We thank [Abe Connelly] for sharing this with us!
Open-source #Bluetooth reflow controller for the 946C hot plate using #ESP32. This controller replaces the original board. https://t.co/zbGDrLhWYW pic.twitter.com/iHjVU38IiW
— Arnaud Durand (@DurandA23) September 20, 2022
200x200cm would be one large bed :)
teehee oh indeed! thank you, fixed!
Right?!
This uses Python on an ESP32-WROOM-32U (MicroPython or CircuitPython?) The Python example uses Bleak (Bluetooth Low Energy platform Agnostic Klient) [1] to let the ESP32 act as a BLE GATT client to receive what I assume is the reflow profile from some sort of GATT server, a PC or phone maybe. I took a quick look at the software example [2], it looks woefully incomplete, no PID control loop, no display driver, no button scan, etc. So I suggest you download the full Git Master instead. A schematic in .pdf is available [3] in addition to the KiCAD files. So is a complete BOM.[4]
It is a nice design, but I would have taken a different approach. C/C++ instead of Python, WiFi instead of BLE, and the reflow profile loaded as a CSV file on a SD card or entered via a web interface. The profile can be plotted on a web page served by the ESP32 in near real-time.
* References:
1. Bleak
2. Software Example
3. Schematic
4. BOM
I’m under the impression that all the software functions you mention as missing are part of the firmware, not the Python software. The Python software just sends the profile to the firmware, which executes it. Though I also think that the software might be a work-in-progress.
Heating fr4 pcbs underneath until the top side solder paste melts, is a bad idea. Use hot air gun from top side to control the melting point. Hot plates are safe only on aluminium pcbs.
could you tell us more about why it’s a bad idea?