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by simonmsh
Thu Jan 02, 2020 12:50 pm
Forum: Automation, sensing and robotics
Topic: HC-SR04 ultrasonic distance module won't read any further than 100cm
Replies: 8
Views: 536

Re: HC-SR04 ultrasonic distance module won't read any further than 100cm

There's a GPIOZERO setting called max_distance that defaults to 1 metre. I set it to 4 metres for my application. My application was detecting not dogs but burglars. I'm not sure the sensor is well suited to reliably detecting one-off events like this, the false-positive rate is too high. It works b...
by simonmsh
Fri Nov 29, 2019 3:46 am
Forum: General discussion
Topic: Raspberry pi ecological footprint
Replies: 60
Views: 2390

Re: Raspberry pi ecological footprint

The Pi is very good for what it is. My concern is when people buy them to turn them into clocks and similar devices, using exponentially more energy and resources than what an actual clock does... I think this is worth noting. I currently have 4 Pis in my house doing various housekeeping/monitoring...
by simonmsh
Thu Nov 21, 2019 7:01 pm
Forum: Automation, sensing and robotics
Topic: SR04 ultrasonic sensor wrong at regular times
Replies: 2
Views: 211

Re: SR04 ultrasonic sensor wrong at regular times

Thanks for the reply. I hadn't heard of gpiozero, but I've just tried it and the results are much smoother. I'm still seeing the occasional rogue reading at 27 or 47 seconds past the minute, but gpiozero seems to reduce or eliminate them most of the time. I will have to investigate further.
by simonmsh
Thu Nov 21, 2019 6:10 pm
Forum: Automation, sensing and robotics
Topic: SR04 ultrasonic sensor wrong at regular times
Replies: 2
Views: 211

SR04 ultrasonic sensor wrong at regular times

I'm trying to create an intruder detector for my house using a Pi 3B+, an SR04 ultrasonic sensor and Python. Most of the time it correctly detects a wall about 3m away (about 20ms roundtrip) but at regular intervals, it returns much shorter distances. It happens about twice per minute, at about the ...
by simonmsh
Wed Nov 20, 2019 6:21 pm
Forum: General discussion
Topic: magnetometer for detecting objects
Replies: 4
Views: 358

Re: magnetometer for detecting objects

I tried to do a bit of car-detection with the magnetometer on a Sense Hat. It seemed to be able to detect a stationary car (1 tonne, mostly steel) at 3 metres, but not moving cars at 8 metres. It also has a fairly sensitive accelerometer, but I wasn't able to detect the ground vibrations of passing ...
by simonmsh
Tue Jul 09, 2019 6:51 pm
Forum: Automation, sensing and robotics
Topic: Monitoring gas/water/electricity
Replies: 10
Views: 5996

Re: Monitoring gas/water/electricity

That's an odd method, i never heard of that. how accurate is it ? You can't get any pulse from your meter ? I haven't done a rigourous analysis of accuracy, but my feeling is that the error is less than 20% and probably less than 10%. It helps that my boiler is an older non-modulating model where t...
by simonmsh
Tue Jul 09, 2019 12:09 pm
Forum: Automation, sensing and robotics
Topic: Monitoring gas/water/electricity
Replies: 10
Views: 5996

Re: Monitoring gas/water/electricity

I don't have a smart gas meter either, so I attached some DS18B20 temperature sensors to the water pipes going into and out of my gas boiler, and use a Pi to estimate the amount of gas used. After a bit of calibration, that gives me reasonable estimates of my gas consumption. I've also discovered so...
by simonmsh
Wed Jun 05, 2019 4:56 am
Forum: Automation, sensing and robotics
Topic: Using RPi to power off/on PVRs
Replies: 11
Views: 1108

Re: Using RPi to power off/on PVRs

@ Simonmsh: The TV Hat certainly looks interesting. What EPG and interface software do you use? I just use TVHeadEnd running on Raspian, which I think is the most common configuration. By default TVHeadEnd uses the standard EPG transmitted with Digital Terrestrial TV, although it can be configured ...
by simonmsh
Tue Jun 04, 2019 5:37 pm
Forum: Automation, sensing and robotics
Topic: Using RPi to power off/on PVRs
Replies: 11
Views: 1108

Re: Using RPi to power off/on PVRs

Apologies for not answering the question, but have you considered fitting a TV Hat to your Pi and running TVHeadEnd? I have, and it's the most reliable and feature-rich PVR I've ever used.
by simonmsh
Sat Jun 01, 2019 6:22 pm
Forum: Automation, sensing and robotics
Topic: Sense hat magnetometer data
Replies: 6
Views: 4031

Re: Sense hat magnetometer data

Apologies for resurrecting an old thread, but I'm also seeing temperature dependence of the magnitude of the B field returned by my Sense Hat. In my case the relationship is negative with a gradient of about -1 micro Tesla per degree Celcius, so I might be missing something. I'm reading from the RTI...

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