I love the smell of hazelnut coffee in the morning.
I'm starting a project that involves repurposing my mom's dumb coffee machine so that, upon demand, it'll brew coffee. The coffee machine itself is a drip-coffee machine that boils water in a reservoir and drips it through a coffee paper filter containing the coffee grounds.
This thing is as easy as a hack can get.
A basic on-off switch starts the water-boiling/dripping process. Basically, I'll use a uC and some code to determine how/when/from where this switch is turned on and off.
I plan on building a new enclosure for this thing later on and would like to know the components a little bit more thoroughly. Looking at the interior (where the nodes are color coded - verified with a continuity test), I'd like to know what the white cylindrical device is (to which the orange and dark green nodes are connected).
Note: I just checked and the orange and dark green nodes are actually the same node.
Note: I just checked again and it's a little bit more complicated than a simple switch.
/dev is right, it's just a thermostat that turns power off when the plate is hot enough ( AKA thermoswitch )
That explains why when I plugged the machine in and turned it on, it was sometimes not conductive across the thermostat's terminals.
I'm now trying to determine the function of the switch:
I measured the AC voltage across various nodes and learned that there was an AC 124V difference between the light green and orange (and light green and dark green) nodes when the switch was toggled on.
(1) The switch is not conductive across Light Green/Dark green nodes when the center connection is removed
(2) The orange node and dark green nodes are sometimes connected (knowing that the device is a thermo-switch, it'd make sense that it's probably conductive only when the plate isn't dangerously hot).
(3) I haven't tested the voltage difference across the dark green and light green terminals with the center connection removed and the machine turned on.
I think by measuring the current passing through the orange node, I can use a relay to control when AC current is allowed to flow. Would this be a good approach? More generally, how do people safely control 120V line with a uC?
It looks to me like it's wired up with the heating element in series with both the thermostat and the switch.
If both switches are on, the heater runs, otherwise it does not. This would be consistent with it's role as a coffee pot.
If the power switch is off, power is not applied to the heating element.
If the power switch is on, and the thermostat is on, power is applied to the heating element.
If the power switch is on and the thermostat is off, power is not applied to the heating element.
Since the power switch breaks the connection above a certain temperature, that provides temperature control.
The second wire going from the AC cord to the power switch probably drives an indicator light (often a little neon bulb)
