I'll be teaching a class on how to setup a Pirate Box at the Generator on March 22nd. Check out more info and sign up here.
Want to carry around a world of important data, like Wikipedia, and health guides?
Need a way to share a bunch of files with some folks?
Come learn how to make a PirateBox a tool for sharing information in a secure offline manner!
With some inspiration from the potential snow storm last week, I endeavored to test my emergency preparedness for heating my apartment when the power is out. I never did lose power, but the test was successful and I am happy to know that if I did lose power in the winter, I can keep warm at home.
I attached an inverter to a marine battery, then plugged in my Rinnai heater and it ran just fine. The Rinnai does buzz a bit loudly, but that's because the inverter does not produce a "true-sine-wave" signal. I tested the setup with a box-fan attached to the inverter as well and it worked fine.
With the fan and the heater both running on LOW the draw was 115W. Some quick and super dirty math approximations tell me that the battery (if fully charged) will run this about 11 hours. This would be longer if the box-fan isn’t running (less power would be used).
105 Amp hours (sticker value, full charge)
105 Amp hours x 12v = 1260 watt hours (approximate average voltage)
1260 watt hours / 115 watts = ~11 hours
Of course, the inverter can be run from any 12V source. My Honda Civic has an alternator with a faceplate rating of 70Amps. Some quick math tells me how much power this can potentially provide.
70 Amps x 12 Vdc = 840 Wattsdc
I believe the inverter is well within the ability for the alternator to run. So the car could potentially run the inverter as a generator as long as there is gasoline in the tank.
Check out the rest of the info and pictures at my blog.
Since my previous post I have added a couple additional temperature sensors to my piHouse project. One is an outdoor temperature sensor that I previously programmed but never installed outside, and the other is a new sensor in my bedroom. This involved some hardware planning and effort installing because I had to run a cable through the house and outside, but once I tested the new cable run, it was relatively simple to duplicate the software for the sensors I already had.
The part of this that took the most time was pulling the cable and then soldering the connections. The biggest problem I have is placement of the outdoor sensor. I am having issues with direct Sunlight.
Here are some highlights, you can find the whole story here. This time I also include some examples of the commands I use on the raspberry pi to obtain the data.
When testing my hardware connections, I use this command to ask the pi to take a reading and then display the result to the command line:
[email protected] ~ $ cat /sys/bus/w1/devices/28-00000512f401/w1_slave 2>&1
Laboratory B is all set up and ready to see you at Champlain Mini Maker Faire this weekend! The event is on Sat. October 4th 10am - 5pm, and Sun. October 5th 11am-4pm at Shelburne Farms in Shelburne Vermont.
Lab B has been at the Maker Faire since it started 3 years ago, and like last year and the year before, we'll be teaching kids & adults how to solder! FairPoint Communications made a donation to help provide kits, and we have four kits from SparkFun in the mix this year; Weevil Eye, Big Time Watch, Simon Says & Mr. Roboto.
From our excerpt in the schedule:
"Join the folks at Laboratory B for a self-paced soldering workshop. We bring the soldering irons and the kits, you bring the desire to learn. We will have kits from SparkFun and all the required supplies and safety gear for you to sit down and learn how to solder, and when you finish you take the kit home! Have you soldered in the past but are not familiar with some of the newer techniques such as surface-mount soldering? No problem! There will be beginner kits, intermediate kits, and advanced level kits to fit all skill levels."
In March I posted about using my Raspberry Pi to monitor my furnace and the temperature of my apartment. I moved over the summer and the new apartment does not have the same type of heating that the last apartment did. So I had to make some changes.
The Pi now interfaces with a Rinnai heater, which was slightly more complicated than the furnace thermostat.
Here are some highlights, you can find the whole story here.
I've been working on a Raspberry Pi project and got it running this weekend. This post is about the hardware and the installation. I will post later about how the code works.
I have been using microcontrollers for a long time now. I started in college as part of the program and have never stopped. Professionally, educationally, hobby, I've done projects of all types.
Recently I decided to try something with a Raspberry Pi. It is the next step up, basically being a little computer. This was so I could play with Linux again (it's been years) and do something with a web browser. These are things I don't have experience with and have been interested in learning for some time.
The project I settled on was a monitor for the furnace in my apartment. This monitor will measure temperature(s) and sense if the furnace is running, then log this data. There will be a web interface that will draw graphs of the data on a daily basis. There will also be an LCD screen on the pi so that I can see the current data without needing a web browser.
Part 1: Hardware
The first step was to make sure I could sense whether the furnace was running. My furnace is controlled by a thermostat. A thermostat is a temperature controlled mechanical switch. Mine looks like this (The wire hanging down was added later):
I needed to open this up to see how it worked. So, I pulled off the ring on the front and exposed 3 screws holding it to the wall. I took out the screws and pulled the switch off the wall. I was left with a mounting plate that included a set of screw terminals with a 2 conductor wire attached. This is the wire running to the furnace in the basement that controls the furnace.
The screw terminals were labeled as RH and W. I took out my mult-meter and started doing some measuring.
Open (Furnace off): RH -> W, 25.8 VAC
Closed (Furnace on): RH -> W, 0 VAC @ 95mA
This means that I need to monitor the voltage across terminals RH and W. If voltage is present, the furnace should be off. The 95mA is mostly unimportant because the thermostat is going to stay in place. I just need to make sure the pi doesn’t draw so much current that it turns on the furnace on it’s own. I drew up the below circuit to accomplish this using a rectifier circuit and an opto-isolator fed into GPIO24.
In this circuit, when the thermostat is open, the 10K resistor attached to the terminals limits the current feeding the 4 diodes, which function as a bridge-rectifier. This rectified AC then drives the LED of the opto-isolator. When the LED is lit, is turns on the transistor, shorting GPIO24 to GND with a 1uF cap for smoothing because its an AC signal. When the thermostat is closed, there is no current driving the opto-isolator and GPIO24 is pulled up to to 3.3V by a 100K resistor.
With the furnace monitoring designed, I had to decide on a temperature sensor. Unfortunately, the raspberry pi doesn’t have any built-in analog inputs. This was a little disappointing because it’s a standard feature on most microcontrollers I have used, however this is a computer. After a little research, I settled on a sensor that uses the Dallas 1-wire protocol. This is a serial bus that is similar to I2C. I liked it becuase there is pi support and since it is a bus, it is expandable (multiple sensors) without using more inputs. I found some DS18B20 1-wire Temperature Sensor ICs in a probe package with wire attached on Amazon, a bought a few.
Following the datasheet recommendations, I wired up the temp sensor like this:
The last piece for this was an LCD screen. I did some research and picked a product from Adafruit that has a 16X2 RGB LCD Screen and 5 buttons on a “shield” style board that plugs into the GPIO header on the pi. I ordered one and when it came in, I soldered it together.
After much programming (That will be a future post), I had all the parts working. So it was time to put the unit together. I plugged the LCD screen into the pi, then soldered some wires to the backside of the header-pins on the LCD shield. The other ends of the wires go to some proto-board where I built the schematics pictured above. I then added a 2-conductor wire in parallel to the thermostat and connected the other end to the pi’s “furnace” input. I wired up the Temperature sensor. I mounted it all to a bookshelf and fired it up.
Potential new member Charles stopped by the Laboratory to use the soldering station. Seems he tried an external antenna on his Samsung phone and the connector broke on him. This external antenna connector bypasses the internal antenna, so when it broke the phone could no longer use the 4G LTE antenna! Thus Charles was stuck with only 1x service (teh suck!). Charles used the Labs microelectronics station to desolder the broken connector. He then bridged the circuit with a bit of wire. Service went from 1x to 4G with 3 bars with this simple fix.
Lab B President Sam and VP Justin appear on Cooperative Vermont to discuss the Lab and the history of hackerspaces. Interview starts around 7:40...
Join with new and experienced Ruby programmers in working through Ruby the Hard Way! This free to low cost way to learn about one of the most exciting dynamic, reflective, general-purpose object-oriented programming language out there! These session will be scheduled regularly soon, but for tonight the jam starts at 6 PM at Laboratory B.