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LimaBiker posted:Smell? Quite hard. Seconding infrared. You might want to point it at the back of the cars to pick up the tailpipes.
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# ? Mar 24, 2024 21:30 |
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# ? Mar 28, 2024 12:38 |
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So it's not even a running engine, just the smell of hot metal and grease and such? Detecting that by smell is a science project that is much more involved than running a wire, imo.
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# ? Mar 24, 2024 21:33 |
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Shame Boy posted:You'd need to know what kind of vapors that smell is made of first, but there's plenty of sensors that can detect basic molecules like CO concentration or volatile organic compounds or something like that that might work Yeah I already tried with an SGP-41, it was a complete failure Also, is there an underlying reason that the narrow FoV IR thermometers are so loving expensive? Even one dimensional ones are $40
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# ? Mar 24, 2024 21:45 |
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Shame Boy posted:You'd need to know what kind of vapors that smell is made of first, but there's plenty of sensors that can detect basic molecules like CO concentration or volatile organic compounds or something like that that might work Yeah surely the easiest way is to just detect the car itself. When the car arrives, start a timer and turn it off after that. To detect a car you could use a distance sensor of any kind (IR reflective, IR beam break, ultrasonic, you name it), or something in the car (eg some kind of transponder, or an RFID tag - you can get systems that operate at a reasonable distance). You could also detect the state of the garage door using a similarly wide number of options. You could even detect yourself! Something like when your mobile joins the wifi, kick on the purifier for X time. This only works if you're only leaving via the car and only people who's phones you can ID are using the garage. All of those are going to be way cheaper, more reliable, and ultimately simpler than trying to detect exhaust gasses. However, gas detection is dope so if you want to do it that way because it's cool then more power to you, and please continue posting about the project as it's a fun one!
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# ? Mar 24, 2024 22:27 |
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Skinnymansbeerbelly posted:Yeah I already tried with an SGP-41, it was a complete failure The IR gun thermometers on amazon have gotten pretty cheap, one there is as low as 9 bucks. You might be able to break one of those open and hijack what it is doing.
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# ? Mar 25, 2024 00:20 |
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Poop Alarm is starting to take form. I'm going with a PLC-like design, because I've always wanted to build an electrical control panel with DIN rail and terminal blocks and relays. Raspberry Pi Zero 2 W to run the show. 12V 3A step-down for beepers and misc HMI devices. 5V 5A step-down for the Pi Zero a power-hungry USB peripheral. 4x PLC-style digital inputs. 7x low-side outputs, 500 mA/ch. Good for driving relay coils. 4-channel leak sensor (simplified design from previous post). RF module, receiver for keyfob remote. There's a lot more I/O than I need. But I figure once I have a controller in the garage, I'll find other things for it to do. Control engineers: Do PLCs count their inputs and outputs starting from 0 or 1? I feel like I've seen both, and I'm wondering if one convention is dominant, or if it's just random based on manufacturer and history.
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# ? Mar 26, 2024 02:13 |
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Poop Alarm? Sewer Sentry? Brown Alert?
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# ? Mar 26, 2024 02:14 |
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ryanrs posted:Poop Alarm? Number 2.0
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# ? Mar 26, 2024 02:58 |
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Stool Tool
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# ? Mar 26, 2024 03:16 |
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Potty Spotter
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# ? Mar 26, 2024 03:51 |
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Brown-out Detector
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# ? Mar 26, 2024 20:19 |
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Might work better with an arduduino
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# ? Mar 27, 2024 14:08 |
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espp32
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# ? Mar 27, 2024 20:44 |
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# ? Mar 28, 2024 12:38 |
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Changes: I put the Raspberry Pi Zero on the wrong side of the board. It needs to be aligned with the right edge so that the microSD slot is accessible on the left side. This board will be mounted on a DIN rail, so there will likely be tall modules on both sides blocking access. Only the top and bottom edges are open. The Pi Zero will be plugged in face-down, because that's how the standard GPIO header is placed. Pi HATs are supposed to be small and mounted on top of the Pi. But upside-down mounting should be fine. The USB and HDMI ports will still be visible, because they stick out a little beyond the edge of the Pi. But the microSD slot will be completely hidden, and it'll probably be annoying trying to insert the card. So I drew a little picture to help you find the slot. Moving the Pi to the right side evicted the RF module. I'll hand-solder it to the back of the pcb, which is probably a quieter location for it anyway. Renumbered the I/O starting from zero. It really does seem to vary by PLC brand. Replaced the 500 mA darlington low-side driver with discrete SOT-23 MOSFETs. Turns out that chip's 500 mA rating was largely aspirational. It could probably drive my seven 24V industrial relays just fine, esp at room temperature. But if you tried to drive several 12V automotive relays, it could overheat. I felt it was under-powered for what should be a bank of general-purpose outputs. I replaced it with a 74HCT244 to boost my 3.3V logic to 5V gate drive for a bunch of 0.12 ohm MOSFETs. Low Rdson means you never have to give a poo poo about coil current or duty cycle. e: Am I supposed to fuse these outputs? I don't think a polyswitch is fast enough to save a SOT-23. I see electricians talking about fusing PLC outputs, implying that the PLCs don't have internal protection, maybe. OTOH, with 7 outputs, I can tolerate some attrition. Ablative circuit protection lmao. e2: I think a 1.25 A polyswitch should melt before this 0.036 ohm MOSFET. I think that combo should be able to short out a big 24V supply and live to switch again (maybe). Probably worth the extra $3 for reliability in the face of wiring mistakes. ryanrs fucked around with this message at 06:01 on Mar 28, 2024 |
# ? Mar 27, 2024 22:47 |