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operations:temphumidmonitor_hardware [2019/03/25 21:18] Jim Lovell created |
operations:temphumidmonitor_hardware [2019/04/03 23:22] (current) Jim Lovell [Connections for the DHT22 sensors to the RJ45 bus] |
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===== Hobart and Yarragadee ===== | ===== Hobart and Yarragadee ===== | ||
+ | These sites have a Raspberry Pi located in the antenna with DHT22 temperature and humidity sensors attached. They are also equipped with a 4-channel 12-bit analog to digital (ADC) board so that up to 4 analog signals could be monitored if needed. The DHT22 sensors are connected together on a bus that uses RJ45 connectors and CAT5 cables to daisy-chain up to 6 sensors from a single RJ45 connection. | ||
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+ | The Raspberry Pis have an Adafruit Perma-Proto HAT to manage the wiring and to mount the ADC. Here's what it looks like (no RJ45 connector attached):{{ :hardware:img_1404.jpg?direct&200 |}} | ||
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+ | * {{:hardware:thschematic.pdf|Schematic of the connections (PDF)}}. Links to details on the hardware: | ||
+ | * [[https://www.adafruit.com/product/2314|Adafruit Perma-Proto HAT]] | ||
+ | * [[https://core-electronics.com.au/attachments/DHT22.pdf|DHT22 temp/humid sensor datasheet]] | ||
+ | * [[https://www.adafruit.com/product/1083|ADS1015 12-Bit ADC - 4 Channel with Programmable Gain Amplifier]] | ||
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+ | ==== Connections for the DHT22 sensors to the RJ45 bus ==== | ||
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+ | The DHT22 has 4 pins but pin 3 is not used. | ||
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+ | {{ :hardware:dht22-pinout.png?direct%300 |DHT22 pinout}} | ||
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+ | Each one requires a connection to power and ground plus a unique GPIO port on the Raspberry Pi for data. The RJ45/CAT5 has 8 wires. Two are reserved for power and earth so that leaves 6 for sensors. The RJ45 terminal blocks have a different wire colouring to the CAT5 cable. Here's how they are allocated: | ||
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+ | ^ RJ45 Pin number ^ CAT5 wire colour ^ RJ45 terminal block wire colour ^ GPIO# or power assignment ^ ID on unit ^ | ||
+ | | 1 | orange/white | grey | 4 | TH1 | | ||
+ | | 2 | orange | orange | 17 | TH2 | | ||
+ | | 3 | green/white | black | 18 | TH3 | | ||
+ | | 4 | blue | red | +3.3V | | ||
+ | | 5 | blue/white | green | GND | | ||
+ | | 6 | green | yellow | 27 | TH4 | | ||
+ | | 7 | brown/white | blue | 22 | TH5 | | ||
+ | | 8 | brown | brown | 23 | TH6 | |