- Mon Jan 08, 2018 4:49 pm
btidey wrote:First thing to bear in mind is that the Breville schematic shows a live chassis (no isolation transformer) so anything attached will also be live. That makes working on it a significant safety risk and should only be attempted if you really know what you are doing. One can lower the risk by running the machine through an AC isolation transformer and preferably an RCD trip device. Any deployment must also ensure that no external connection can be made to the ESP8266 whilst machine is powered.
The Sunbeam schematic doesn't show powering arrangements. So you would need to dig into that further.
Having said that monitoring inputs are relatively easy and one could just use resistor dividers to lower any 5V logic down to 3.3V
Outputs are more tricky as you have to deal with conflict between the internal drivers and your logic. You can insert a relay or SSR in the main power path.
The Breville seems to have controls for power, hot water, steam and flow. The last three seem to be pulled up to +5V through 10k resistors. So one can drive these via open collector bjt or preferably n channel mosfets. The power seems to connect +5V direct to P65 so probably is better handled by a mosfet switch or relay in parallel with those contacts.
The Sunbeam looks easier as all the controls are grounded switches going via pull ups into the control logic. I would just put open collector bjts or mosfets in parallel with those so one could just simulate pressing the switches.
Wow, that's an incredible help thanks! The Sunbeam is the better machine, and so that's the one I intend to hold on to and which modifying would be of most value.
I've not worked a whole lot with AC power. I'm a Mechanical & Mechatronics Engineer, but most of my electrical work has just been out of personal interest at home, so I'm not real clued in on AC power circuits and isolation. I assumed that I could piggy-back the factory IC, connecting to the 5V+ & GND for power, and it'd be all good, but maybe not, it sounds!
At the moment I might not need to drive any Outputs, I'll likely just use the ESP8266 to emulate the Power and Manual buttons, then read the Flow Meter signal to measure extraction time. Can I not drive the outputs directly, without MOSFETS, because by the time a 3.3v High runs through a 5v logic level shifter, it'll likely lack the required current?
I was wondering whether voltage dividers would sap current and interfere with the standard wiring, is there any difference in that regard, between voltage dividers and logic level shifters?
I've updated the schematic a little to suit the sunbeam and include the logic level shifter (it's still rough). Greatly appreciate the help!
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