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dankamongmen / dankdryer

firmware for the world's best filament dryer
Apache License 2.0
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need temp sensor in hotbox capable of high temperatures #22

Closed dankamongmen closed 2 weeks ago

dankamongmen commented 1 month ago

we already have a temp sensor for the MCU built into the ESP32-S3, but we also want to measure the hotbox temperature. a DH18B20 is probably not suitable, as it's only rated up to 125C, and only retains full accuracy through 85C. i've got some LM35DZs which ought work, though they want 4--30V and are analog. either way, get a thermistor up there, hook it up to the ESP32-S3, and measure the hotbox temperature.

dankamongmen commented 2 weeks ago

We now (as of 0e1c962c) have three holes in the hotbox suitable for the LM35's leads.

We're already doing an ADC read every cycle, so I think we just need hook things up and verify it.

dankamongmen commented 2 weeks ago

The LM35 is operating in a nasty thermal environment, and on about ten centimeters of poorly-shielded AWG22. Let's give it some bigger boxing gloves. Put a 0.1µF bypass capacitor across its power and ground leads. Put a 75Ω resistor and a 0.22µF capacitor in series between the signal and the wire. These recommendations come directly from the datasheet.

dankamongmen commented 2 weeks ago

as of 7e28b07a we're getting plausible values from the LM35 in STP tests.