Non-contact AC detection

Alex from insideGadgets had an interesting project last year on non-contact AC detection and I wanted to try it out and learn how it works. He hooked one leg of a 1M ohm resistor to GND and a wire to the other that goes to an Analog input. The wire acts as an antenna and…

DHT22 accuracy test part 2/2

I have measured the relative humidity as per my set up, and got steady readouts exactly in the 75% area as expected: DHT22 Library Demo Requesting data…Got Data 25.50C 75.20% Integer-only reading: Temperature 25.5 C, Humidity 75.2 % RH Requesting data…Got Data 25.50C 75.20% Integer-only reading: Temperature 25.5 C, Humidity 75.2 % RH Requesting data…Got…

DHT22 accuracy test part 1

I have been boggled for a while about the Relative Humidity data that I gather, I get some higher than expected reading. I blogged about this in this post and @Dimitrios suggested in the comments that my box my be causing the issues. He sent me a 3D printed Stevenson screen to try, but I…

Cheap DIY power monitor

My father asked me to create a standalone power monitor for him, he’d like attach it to some appliance and see its momentary and accumulated over time power consumption. Using OpenEnergyMonitor’s resources that was an easy task to do. I used a SCT-013-000 current transformer to sense the current and a 9V transformer to sense…

Scope screenshots

One of the cool things about having a digital scope is that you can take screenshots and post them in blogs :). I wanted to check how a Funky v2 was behaving, so hooked one to measure its current consumption using the voltage drop over a resistor (supposedly 10 ohm, but my multimer measures it as…

Oscilloscope

I have finally decided to get myself an oscilloscope, my choice ended up to be a Rigol DS1052E. The model seems to be pretty popular, and for a price tag of 309 EUR with delivery, I could no longer resist. So I got it yesterday evening and had to explore it. I have never before…

Soil moisture sensing revisited

I have previously created a DIY soil moisture sensor, but wiring it required couple resistors. I was recently reading a post by JCW on using a light sensor and figured I could simplify my setup using the same basic idea – using an Analog input with the internal pull-up enabled:   That pretty much simplifies…

RFM12B End of Life

EDIT March 2015: [It has been two years since this post, and the RFM12B is still widely available. I guess the rumors at that time were exaggerated widely.] There has been bad news for the RFM12B ecosystem last week, namely the news that the RFM12B module has been declared in its End of Life. There has been…

Wallpaper prank

I wish I did this for April 1st, but here is it anyway 🙂 I wanted to test out the HID keyboard features of the Arduino Leonardo compatible Funky v2, so during my research on the subject  I accidentally stumbled upon a project called “USB Ducky“; One of the example uses was to use the…

Toying with a 1.8″ TFT LCD display

I got myself a 1.8″ TFT LCD display from ebay, attracted by the low price. The display also has a SD card slot. It comes without any documentation and you are presented the joys of figuring out how to drive it yourself. Googling further, I found out that this is a ST7735R (datasheet) module, luckily quite similar to…

Raspberry Pi as IP webcam

I noticed this Instructable the other day and had to try it since I had an old USB web cam laying around. I found that the instructions contained some inaccuracies, here are my steps: sudo apt-get install motion sudo nano /etc/motion/motion.conf Locate and change: Daemon = OFF to ON webcam_localhost = ON to OFF webcam_port = desired…

pChart-ing emoncms data

pChart is a neat PHP charting tool, I have been using prior to switching to emoncms. Emoncms has multigraphs available, that are much more interactive, but they are slow too. I also have had some issues with certain feeds that just won’t visualize and never got to the bottom of the problem. I missed my…

New laptop

I got myself Santa brought me a new laptop couple days ago, an Asus K56CM. I am no brand slave, I just pick one that fits the budget I set aside and what covers my basic requirements. I prefer not to spend days reading reviews, but rather go to a computer store and visually and physically like…