1 year with batteries - temperature sensor project
Temperature sensor with alkaline batteries
Just a quick update on my XBee/ LCD/ temperature sensor project which I originally started in 2011 (last blog entry: XBee temperature sensor project ). I had to replace the already used battery cells which I put into the sensor about one year ago (August 31 2012) because I got some timeouts on my receiver. The
voltage came down to 3.34 volts and this is a point where the low dropout regulator (MCP1700) keeps quit working sometimes even when the load is only about 25 mA every four minutes when the XBee (end device, sleeping) sends the temperature data to the coordinator.
Voltage development temperature sensor
The three battery cells had a voltage of around 4.1 volts when I started using them for the sensor, so they were already down from their original voltage/ capacity which is around 1.5 volts per cell for unused batteries.
Why did I use used battery cells and not new ones? Because they were lying around and I was wondering how long some spare, already used cells would last during time and different weather conditions. And they lasted almost one year!
The temperature sensor is located outside and we had temperatures of around -15 to +30°C during the year. The chart you see is far from scientificly accurate but gives you a raw picture of the voltage curve for those cells (GP super alkaline).
Next I will replace the batteries with some rechargeable batteries. There are some nice energy harvester ICs on the market - maybe this will be the next power supply for my sensors. Stay tuned.
Spot weld now very strong with tungsten electrodes
2.4mm tungsten electrodes
I replaced the steel electrodes from my home built spot welder with 2.4 mm tungsten electrodes which I took from my AC/ DC TIG welder. The welding joints are now very strong. It is almost impossible to separate the two metal reeds without damaging it.
What's up next? I still manually trigger the weld and the next tests will be with a time controlled weld with the help of an Arduino. I also have to built a better post to hold the electrodes and some sort of mechanism to adjust the distance of the two electrodes to be able to weld different sizes of rechargeable batteries with variable widths of welding points.
Motor control and telemetry data added to RC Surfer
I just added some controls to my RC Surfer project. I can now control the power of the dc motor by a slider on my Android phone for the full scale (that's analogWrite() 0 to 255 on my Arduino). This is done by the "ENA"-Pin (enable bridge A on the L298 motor driver IC) and using PWM on the Arduino.
Remote control app with data transmitting and receiving
I also have a "Start" and "Stop" button for any "emergency" case. Later I will add the functionality to stop the engine if the bluetooth connection will be interrupted.
I also added some telemetry data coming from the RC model. For now it's the voltage of the rechargeable battery pack and the temperature of the motor driver IC.
I did some first tests outdoors and had a range of a about 40 meters (~130 foot) with my bluetooth connection. Curently I'm using the Itead Bluetooth Shield V2.2 from IteadStudio. The range might be more than enough for later tests. There is still the option to exchange the HC-05 module with a XBee but I would then loose the option to control everything with my Android smartphone. For the moment the connection is sufficently reliable.
Of course the speed and direction will later be controlled by sensors of the smartphone.The slider is just for early tests.
I'm currently doing at least two projects at a time (and more in the queue) which I will elaborate later on in this blog.
Spot Welder
Spot welder test
The first project is a homemade spot welder which I'm building together with Knudt and Sebastian for the Hamburg Makerspace Attraktor. The device will be used for connecting rechargeable battery cells or join together thin sheets of metal. The whole thing consists of a 1 Farad/ 16V Capacitor (originally used for car hifi), a 13.8V/ 2A power supply, some Mosfets and an Arduino with a graphical display (at the moment it's a Nokia 5110 LCD display). The Arduino will do the controls, while the Mosfets will handle the power dissipation to the electrodes.
On the right there is a picture of an early test. You can see the capacitor in the background, on the breadboard there is an Arduno Nano and the Nokia LCD display. We are using scrap steel "electrodes" at the moment but will possibly change this with real tungsten welding electrodes.Oooh, and obviously no XBees involved this time.
RC Surfer
Years ago I bought a so called "RC Surfer" for cheap (you have to google this because mine is disassembled and I can provide no photo in action).
Cheap were also the contents of this RC controlled surfer. There was a motor driver with a relay, a 27 MHz radio control and a servo controlling the rudder. The power control was only "on" and "off" and the servo reaction to the input on the remote control was at least working.
There was no feedback of voltage or temperatures and no extra features like light etc.
At the moment I'm working on the new motor controls. I have a prototype L298 motor driver board which supplies at least 2A to the original dc brushless motor I'm still using. It consumes about 1A so I'm happy with the L298 for now. You can control the motor speed by using the PWM on the Arduino and connect it to the enable pin on the L298. You can also power the motor forward and backward what was not possible with the original motor driver.
The first test run worked quite well and the next addition will be the rudder control with a new servo. At the moment I'm using a joystick out of a scrap PS2 control - later I will command the RC Surfer with my android phone and a bluetooth connection. If that doesn't work, I will use a XBee/ RC combination with a traditional remote control.
Possible features might be telemetry which sends data like current used, voltage, temperatures, cam etc. Or what about a water canon?
On June 3rd I had a short presentation on Arduino basics, part 2 in the Hamburg (Germany) Makerspace Attraktor .
The participants learned about the serial communication (USART) and the ADC both with the Arduino IDE, how to program in C/ C++ and how to manipulate the registers directly.
The paper (pdf) is downloadable here (sorry folks, it's only available in german).
ThermalCam with MLX90614, Arduino UNO, XBee Series 2 and prototyping shield
A project I'm working on for some weeks now is a cheap ThermalCam based on the Melexis MLX90614 IR sensitive thermopile detector chip (more on the chip from Melexis: MLX90614 )
There are lots of people out there, who already built a working version with this $35 device, but most of them use a wired connection and a Java graphical user interface (GUI).
I wanted to get the thing wireless and also to build my own GUI where I may customize some things that I miss with the Java-version. I chose a XBee Series 2 configured as a Router AT with 57600 baud and Processing for the GUI. I'm already done with the data transmission part. I can control the ThermalCam with some buttons in the Processing sketch and get the data out of the chip but it still lacks a nice GUI and a webcam overlay.
This awesome project was first developed by two german pupils Markus Kohl/ Max Ritter for "Jugend forscht 2010" (german science competition for pupils). Well done!
I already made some thermal images with the Java program and here are some examples.
Sitting at the desk, waving my hand. Background dark blue: windows, right orange square: tft screen
Raspberry Pi with voltage regulator (left bottom), main chip (middle) and ethernet chip (right)
Laptop laying flat on the ground, upper half display, lower half keyboard/ mainboard
4/02/2013
Arduino UNO Rev. 2
Arduino basics presentation
On April 1 I had a short presentation on Arduino basics in the Hamburg (Germany) Makerspace attraktor .
The participants learned about the Arduino environment, the IDE and how to program a sketch so that it blinks an led.
The paper (pdf) is downloadable here (sorry folks, it's only available in german - again).
