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Showing posts from 2015

Installing a 3 phase energy meter in your home

About 2 years ago, I decided that it would be a good idea to log how much electricity I was using. If the endeavor resulted into an internet connected device, that would be even better. So I set out looking for an energy meter. I was looking for one which had an interface which would all me to connect it to the computer (or Raspberry Pi or an OpenWrt device). Since I have 3 phase supply coming into my house. There are 5 wires coming into my main electrical distribution panel: Red, Yellow, Blue, Neutral and Earth. The RMS voltage between any one of the 3 live wires and neutral is 230 volts. I selected the Selec MFM383C which is a 3 phase meter with Modbus interface. I also used 3 nos. current transformers : Selec SPCT-62/40-100/5-1.5(1T)-0.5 one each for each phase line (Red, Yellow and Blue). These transformers are of the ratio 100:5. The connection scheme is as shown below. One has to take care to make sure the direction of wire passing through the current transformer and the

OpenWrt 15.05 Chaos Calmer on TL MR3020 with rootfs on external usb drive

The latest version of OpenWrt is quite bulky. Although it feats neatly within TL-MR3020's 4MB flash, doesn't leave enough space to install the modules required to shift the root file system to an external drive. My TL-MR3020 with FT232RL board to access its serial console and a USB hub with a flash drive in one of its slots. In previous versions of OpenWRT, you had 840KB of space left on internal 4MB flash to install the essential kernel modules for usb, usb mass storage and ext4 which are all essential for mounting USB flash drive. My Weather Station used TL-MR3020 flashed with OpenWrt 12.09 and used this methods. In the latest version just about a few hundred kilobytes are left after flashing the image which aren't enough to install the modules required for mounting USB flash drives. So we have to resort to the following steps: Open up your TL-MR3020 and solder in a USB-UART (FT232RL) board to gain access to its serial port. Install the toolchain for compi

Hacking a Logitech MK220 wireless keyboard and mouse combo for a community computer

Recently during my stint as a Teach For India Fellow, I have been building Community Computers for use at my school. These involve creating an easy to carry box with projector, computer, speakers and wirless keyboard/mouse all stuffed in. After building one based around Intel NUC PC  I decided to think of ways of decreasing cost of the Community Computers and make it more user friendly for our not so tech savvy teachers. Towards that, I thought of using an old non-HDMI VGA projector paired with a Single Board Computer APC 8750 which runs Android OS and has a VGA video output which makes pairing with an old projector possible.. If you think about it, a computer that runs Android would be more successful with teachers as compared to a Windows based PC. Teachers now days have access to smart phone so that are already comfortable with using Android. If you install appropriate apps on an Android based community computer, they can play all kind of content - videos, photos, PDFs etc. Also

Community Computer using Intel NUC PC

NOTE: Here is  the list  of various other Community Computers that I built using various other projectors and single board computers over the few months of my fellowship. As I began my Teach For India fellowship, I got inspired by the K-Yan and decided to build my own community computer for my own class of 48 7th graders. I tried building one using a Raspberry Pi , but the results left much to be desired (Couldn't install Prezi, wasn't powerful enough, video player required commands to operate, no internal storage etc). That's when I came across Intel's Next Unit of Computing (NUC) PCs. These are small form factor PCs built for portable applications like interactive kiosks etc. Since these PCs only have and HDMI output, I would need an HDMI capable projector. So I asked my friends for donations and went shopping and bought these: BenQ MS521p  [Cheapest HDMI Projector] INR 30,000 Intel DN2820FYKH  [NUC PC] INR 9,340 8GB Low Voltage 1.35V SODIMM DDR3 RAM Kingst

A Security Cam that pushes video clips to your phone: Motion Pie + PushBullet

What? Raspberry Pi running Motion Pie. USB Webcam is connected to it. A bash script pushes small snippets of videos (shot when motion is detected() to your phone. How? Signup for PushBullet  and install the android app on your phone (and chrome extension on your browser) Take a Raspberry Pi and connect a Raspberry Pi Camera or USB Webcam to it. I used a UVC USB Webcam. Format a SD Card on your computer and write the Motion Pie image to it. Here is how  to do it. Connect your Raspberry Pi to your home WiFi router using Ethernet cable. My house has CAT5 wire running through pipes concealed in the walls. Perform basic configuration on the Raspberry Pi using its web interface.  Administrator password. (Otherwise you wont be able to connect to it using SSH/PuTTY) Setting the timezone. Network setting - I used static IP address. Enable FTP write support. Video Device - Camera name or rotation etc. File storage: I used "network share" option to point back to the