I got one of those RGB LED matrix things for my birthday and wasn’t sure what to do with it. Then I found this awesome library which has Python bindings and can control it nicely even from a Raspberry Pi. Conveniently I had a spare Raspberry Pi 1 B+ sitting around so I hooked it up. After playing around for a while, I got the demos working.
Get data directly from a MQTT broker for getting live data (e.g. travel times in traffic, weather conditions) and for command and control. This allows me to connect the screen to my home-assistant home automation system.
Assemble various built-in elements like giraffes, animated text, rainbow text, pictures, animated gifs into various scenes that rotate through on the screen to display the information in various fun and/or useful ways.
There are Temperature and Duration sprites that you can define high and low values of so they’re red when they’re bad and green when they’re good, and anywhere in between.
You can set the scenes to be just random or you can control them through MQTT.
It’s intended to be very configurable but since it’s brand new some extra development is needed to make everything perfect. Send in your ideas and requests and code changes!
A relatively complete example configuration file is in the repo. That demonstrates using MQTT, connecting MQTT topics to various sprites, building your own frames of animation by hand, and adding in gifs and images from file paths. Note that you have to set an environmental variable or two to get the fonts right and whatnot.
I have a website or two and sometime wish I could get notifications whenever someone visited them, just for fun. Well I did it, and now I can get beeps in my home whenever anyone visits. It’s kind of cool to hear it go off, though normally it will be annoying, so we need a switch for it.
My mom has one of those on/off furnaces (EDIT: actually it’s a boiler) that heats up water and circulates it through pipes around the house that have little radiator fins. She wants it to turn on before she wakes up so it’s not so cold in the morning. In this post, I explain how to turn a normal furnace into a smart furnace for only a few bucks.
Oh this is exciting! I’ve been trying to figure out how to get motion events from my IP camera into my home-assistant instance running on my Raspberry Pi, and I just did a successful test! It works! Hooray. Briefly, I set up an email server on the Pi, have the camera email the Pi, have the email server trigger a script which parses the email for key words and sends MQTT signals as appropriate, at which point the home-assistant MQTT client sees them and triggers automations (like blinking a light to scare people off). Here’s how I did it.
As documented earlier, I made one of those CRT-in-a-winebottle things. I used a cheap 2-stage mechanical vacuum pump for it. Well, it was so good that my boss wanted to use it as a science demo at some dinners he gives, so it’s been permanently transferred to work. So I need a new pump, and a new chamber!
I just configured a pretty slick burglar alarm with the open-source Home-Assistant platform running on my Raspberry Pi. It can be armed to trigger when a door is opened and/or when a motion sensor goes off.
Then, a sequence of events happens:
An IR LED turns on my stereo
A sound file I cobbled together starts playing. It starts with a computerized voice saying that yourentry been detected and recorded, then it beeps for a while (giving you time to disarm), and then it goes into a blaring siren noise. Quite the escalation!
A light blinks on and off a few times
A camera takes a series of snapshots of the area
An email is sent to my phone with the snapshots, showing me what’s going on
You may have seen my earlier post about my new home automation setup. Well I just upgraded it! I just finished testing out a new infrared remote control send and receive capability and it is pure awesome. Here’s what I can do now from within home-assistant:
Turn on and off my new DeLonghi portable air conditioner from Costco, and set the temperature to whatever
Turn on and off the TV and press any buttons from its remote control
Turn on and off the stereo and virtually press any buttons from its remote control (which I never even had!)
Use an old random blueray remote control to set scenes, turn lights on and off, etc. (basically do anything under home-assistant’s control)
This post is about how I did it on my Raspberry Pi.
I went over to my friend’s house last night to help get home-assistant on a Raspberry Pi working for his z-wave door sensors and siren. The Ecotech sensor showed up fine but the Aeotech recessed one (Recessed Door Sensor Gen5 , ZW089-A) did not show up by default. After poking around in the logs for a while, we realized that it was sending BASIC_SET command classes instead of BinarySensor commands. Apparently (I thought I had fixed this already), home-assistant doesn’t recognize the BASIC_SET commands just yet. But looking at the config file for this device, we discovered that config item 121 changes which kind of report this sensor sends: Continue reading Using an Aeotech recessed door sensor in home-assistant
In this post, we’ll take a brief measurement of regular old FM radio stations and try to determine where we are. It’s like a GPS but with local FM transmitters instead of satellites. I did this just for fun. I wonder if it could be used for indoor location and stuff? It is nowhere near as accurate as GPS. But whatever.
Reading FM radio signal power
The first step is to get a reading of all the nearby radio stations. I used gnuradio and a HackRF One software defined radio. A simple flow-chart that takes the FFT and dumps it to a file is all I needed. I had to throttle the I/O or else my computer would freeze. I used 16M sample rate to have as wide a bandwidth as possible.
The file sink saves the FFT results in 4-byte integers and just has one 1024-length vector after the other. In a few seconds, I had a 50 MB of data. I did all the post-processing in an external Python script.
I’ve always dreamed of having a “smart-home.” There’s just something cool about being able to flip switches and read sensors and have a program turn a light on when you open the door, but only if it’s dark. This post is about home automation.
My wife got me an early birthday present: Philips HUE Color-Changing LED lights! They’re incredible. Look:
Right now I’m controlling them with my tablet, which is fine for changing colors and setting light alarms. I can even control them from afar thanks to my VPN. I will soon hook them up to my nascent Raspberry Pi powered home automation system (using the open-source Home Assistant program) that will allow me to trigger them based on various events like motion, doors opening, weather changing, or whatever. The future is here!
Each bulb uses 9 Watts but makes the same amount of light as a 60W conventional bulb, so they’re very eco-friendly. Furthermore, since they’re LEDs, they should last for 15 years of normal use! They communicate with a little hub that uses the ZigBee protocol (like Bluetooth but lower power and lower speed, good for home automation stuff).
Downside: They’re pretty pricey. I expect their coolness to drive demand enough to bring supply up. Expect these bulbs for $10 in the next few years.
Sending and receiving text with Morse code light pulses across the room (or to your neighbor) is a fun and cheap project you can do on a Raspberry Pi or Arduino or any other microcontroller. This post explains how I did it, and how you can do it too.
The hardware is simple and cheap. Here’s my parts list:
Raspberry Pi B+ as the controller. This does the sending, receiving, and signal processing.
Photoresistor – Just a little guy that has variable resistance based on how much light is hitting it
A 220 Ohm resistor – to make a voltage divider with the photoresistor for reading the input signal
MCP3008 10-bit Analog-to-Digital Converter (ADC) – Since the RPi doesn’t come with an ADC, this is required for converting analog voltage from the photoresistor into a signal I can process on the RPi.
Laser module – to transmit with laser light. I got one from sunfounder.com for like 3 bucks.
You can learn how to use the ADC at this Adafruit tutorial. I decided to talk to the ADC with the RPi’s hardware SPI interface, which I had already enabled. I wanted to be able to go very fast. (You can alternatively do SPI off of GPIO ports with software, if you prefer.) The laser just hooks directly between a GPIO and +5V. Here’s the layout:
Sensors are fun!I wanted to keep an eye on the temperature of one of my home physics projects and realized I needed a thermocouple and a convenient way to read it. This post is about how I got one and wrote a Python program to send the data from a Raspberry PI over the network to my laptop, which plots the results in real time.
I bought a K-type thermocouple for several dollars that ranges from -100°C to 500°C. The Seebeck effect that makes it work only gives microvolts per degree so I needed a good amplifier for it. And since I wanted to read it on a Raspberry PI (which only has digital inputs), I’d need an analog-to-digital converter (ADC). Conveniently, the MAX31855 does amplification and ADC and is like $15, so I got one. Sweet. There’s even a Python library for it that makes it easy to access. Double-sweet.
Alright, this is an oldie, but ah… well… it’s and oldie where I come from. In 2005, I had some healthy spare time and decided to build a flux capacitor. I posted the details on my old webpage. I just rewired a battery pack on it and it’s working fine so I figured it was time to get it back online again. So, here it is. How to build a LED flux capacitor.
In the movie Back to the Future, Dr. “Doc” Emmett Brown completed his life goal of making the flux capacitor a reality. Here’s the story:
“I was standing on the edge of the toilet hanging a clock, the porcelain was wet, I slipped, hit my head on the edge of the sink — and when I came to I had a revelation! A vision! A picture in my head! A picture of this! This is what makes time travel possible! The Flux Capacitor.”
-Doc, Back to the Future
Unfortunately, I didn’t have room for the time circuits or nuclear reactor to generate the 1.21 jigawatts that the flux capacitor needs to travel in time so we’re going to have to go with the next best thing: A 30 LED sequencer!
Since I’m on a late 1800s physics kick, I’ve been staring at my Crookes radiometer a lot.
You might remember these from the hands-on museum. Today, these are just novelty items, but back in the 1800’s, there were actually scientific instruments that could quantitatively read out the amount of incoming radiation (like visible or infrared light). They were generally read out using a calibrated spinning disk with slots in it. It’s like when you have a fan spinning in a dark room, and you adjust a strobe light until it looks like the fan isn’t spinning. Then, if you know how fast the strobe is blinking, you know how fast the object is spinning. This is called a stroboscope.
Well, I don’t have a stroboscope. But I do have a digital camera and a computer. As it turns out, I can read the Crookes radiometer using that!
Or, why I built a cathode ray tube in a wine bottle.
I was leisurely reading Linus Pauling’s textbook, General Chemistry, the other day, and I found the history he threw in there with the science to be thrilling. For instance, I learned quickly that the Greek word for amber, elekton, forms the base of our word electricity, so named by William Gilbert in the late 1500s because the ancient Greeks knew that rubbing amber with wool would attract feathers and stuff. As a nuclear engineer whose job it is to make electricity, this was a fun revelation. Pauling continues to mix physical realities with the experiments used to prove them, and doing so, he quickly arrives at the cathode ray tube. After reading and thinking about it, I had another revelation. It turns out, I realized, that some large fraction of modernity, from the world order to modern health, the environment, politics, and the media passed through a cathode ray tube. Here’s how.
So, I have to tell you about the hot tub project. It’s been going on for a few weeks now and we just basically finished it. I (with some help from Jesse) have set up a microcontroller to control and monitor the hot tub. We have a temperature sensor mounted on the heating element tube and we wired in a relay to control when the heater turn on. Then we wrote code to allow it to interface with email, the internet, and even text messages! For real. Look:
Haha! Here are some more gems:
and you can control it with this form:
Or you can just control it from the command line:
So here’s what’s going on. Firstly, there’s an arduino connected to a USB port of the computer in the basement. Here’s a pic:
One of the digital pins on the Arduino is connected to a OneWire bus with three temperature sensors hooked up to it with a pull-down resistor connecting the bus to the 5V line. That’s the green wire. The ground is white ground. The three sensors are hooked up (in parasite power mode) to 30 feet of indoor/outdoor CAT-5 wire from Home Depot. I surrounded each temperature sensor with a piece of 3/8″ O.D. copper tubing (which is miraculously already corroding) and pinched them down and sealed them up with Silicone. Here’s a pic of the outdoor sensor.
Anyway, yeah. The last sensor, the one on the tub, is wrapped in lots of insulation from the hardware store to try to keep the outdoor temperature from affecting the hot tub readings.
On another digital pin (the orange wire), we have a relay circuit that we can turn on and off easily. In the hot tub, it connects the wire that connects the coil of the main heater relay. So it’s a relay for a relay, effectively. We just set the temperature dial very high and use the Arduino to cut it off when we want. We got the circuit from here. Here’s a copy of that:
Nice. I used a relay that can handle up to 30A, 240V, with a 12V coil. I got the 12V by splicing off of the hard drive power cable inside the computer (blue wire, with white blue as ground. That’s the same ground, but we didn’t want to tap into the fragile cat5 wire again). That’s unfortunate because it requires the computer be on to have the heater on. A better design would not rely on the computer to maintain control of the hot tub.
The rest of it is just software. I’m using the pySerial module to read and write to the USB tty device in 32-bit Ubuntu 8.10 Linux. The code that I compiled on the Arduino chip simply accepts simple characters through the serial port and does as asked. It knows how to turn heater on, off, read temperatures, and tell whether or not the heater is on. I’ll build some safety logic in soon. Right now, all the control logic and communication is done in Python on the computer. I have an Arduino class that abstracts the commands the Arduino knows. Then there’s the hottubController class that checks the sensors and turns the heat on and off accordingly. It calls the communication class, that checks for commands in an IMAP email account, submits temperature information to a MySQL database on my server, and sends command responses via SMTP. The text messaging functionality works simply because you can easily use the text-to-email gateways used by many major phone companies. The MySQL stuff is done with the MySQLdb python module, which is fairly simple.
Still to come: predictive hot tub times. Since the heating is very linear, it’s possible to extrapolate the time at which the tub will reach a given temperature. You’ll get a text that says: “the hot tub will be ready at 10:37PM” How cool will that be at the bar?
With all the copper, casings, arduino, sensors, relays, silicone, insulation, and various other tools I bought during this, it’s up to about $100, not including the computer. Not bad!
In case you’re wondering or debugging the hot tub controller, here are some more details.
Out at the hot tub, you’ll see a silver toggle switch. Under normal operation, this should be in the center position. To shut down special features and go back to plain-old hot tub, put the switch in the up position. This gives control of the hot tub back to its internal thermostat. It also disables the 10 second heater delay relay.