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I don't have a project yet -- but one I'm really interested in is having a Raspberry Pi run and store historical data from an air quality (particle) measurement

I don't have a project yet -- but one I'm really interested in is having a Raspberry Pi run and store historical data from an air quality (particle) measurement sensor. I'm hoping to measure how the air quality outside my home (near a freeway) changes during the day and night with traffic, and also how the indoor air quality is impacted. It outputs UART 9600 baud data (https://sensing.honeywell.com/honeywell-sensing-particulate-hpm-series-datasheet-32322550 https://sensing.honeywell.com/honeywell-sensing-particulate-...). Does anyone have a good link to some simple guides / advice on how to run such devices using a RPi? Thanks!

weaksauce 7y ago
Uart is just serial, you’d connect it to your serial pins on the pi and read serial from Linux like normal. Data is whatever the protocol Honeywell is using. Could be any range of things sent in a predictable pattern. Could be timestamp,temp,air quality,status, and then some kind of delimiter like newline or eor. Note the pi devices use 3.3 volts instead of 5 so you have to make sure Honeywell is not sending too much voltage as a logical high. There’s probably an easy way to convert it though using a voltage devider. How much do those sensors cost?
- klodolph 7y ago
  Minor clarification: UART is “just serial” but when people say “serial” they usually mean RS-232 or RS-422, and these don’t use 0V / 5V like you would for 5V logic. They use anywhere from 3-25V signals, with positive voltages for zeroes and negative voltages for ones. Your PC, if it has a serial port on it, probably sends around +/- 13V (this is typical, IIRC). So don’t hook up 5V logic parts to a serial interface. If you look at RS-232 interface chips they have integrated charge pumps and external capacitors to generate the Tx voltages from Vcc.
- weaksauce 7y ago
  actually I looked at it again and the honeywell uses 0-3.3vdc so you should be ok to use that directly. (obviously double check before wiring) you need to setup the device by sending a few packets to enable sensing/auto-sending of data that is a particular 32byte structure.
stroebjo 7y ago
Have a look it at https://luftdaten.info/en/home-en/ https://luftdaten.info/en/home-en/. Not exactly using an rPi, but the goal of the project seems to fit with your plan.
- TeMPOraL 7y ago
  I have a spare RPi2 sitting next to my router and running InfluxDB precisely for collecting Luftdaten readouts.

weaksauce 7y ago

Uart is just serial, you’d connect it to your serial pins on the pi and read serial from Linux like normal. Data is whatever the protocol Honeywell is using. Could be any range of things sent in a predictable pattern. Could be timestamp,temp,air quality,status, and then some kind of delimiter like newline or eor. Note the pi devices use 3.3 volts instead of 5 so you have to make sure Honeywell is not sending too much voltage as a logical high. There’s probably an easy way to convert it though using a voltage devider. How much do those sensors cost?

klodolph 7y ago
Minor clarification: UART is “just serial” but when people say “serial” they usually mean RS-232 or RS-422, and these don’t use 0V / 5V like you would for 5V logic. They use anywhere from 3-25V signals, with positive voltages for zeroes and negative voltages for ones. Your PC, if it has a serial port on it, probably sends around +/- 13V (this is typical, IIRC). So don’t hook up 5V logic parts to a serial interface. If you look at RS-232 interface chips they have integrated charge pumps and external capacitors to generate the Tx voltages from Vcc.
weaksauce 7y ago
actually I looked at it again and the honeywell uses 0-3.3vdc so you should be ok to use that directly. (obviously double check before wiring) you need to setup the device by sending a few packets to enable sensing/auto-sending of data that is a particular 32byte structure.

stroebjo 7y ago

Have a look it at https://luftdaten.info/en/home-en/ https://luftdaten.info/en/home-en/. Not exactly using an rPi, but the goal of the project seems to fit with your plan.

TeMPOraL 7y ago
I have a spare RPi2 sitting next to my router and running InfluxDB precisely for collecting Luftdaten readouts.