Earlier I presented a project on how to measure temperature with a LM35 and an Atmega8 microcontroller and display it on LCD. In the current project an Arduino board is used and the temperature reading is sent to a PC. A software is written for PC to display the data received on USB from the Arduino. It shows temperature value both in Celsius and Fahrenheit, numerical and as a bar-graph and a histogram with 100 data points.
The sensor is connected to one of the analog inputs of the Arduino. The code for microcontroller is very simple since all it does is convert the analog output of the sensor to digital and send it to PC and it does that every second.
The PC software is written in Processing, all code is available in the link.
Arduino Thermometer: [Link]
Keyless entry has been used for quite some time in automotive industry by most car manufacturers even though such a system may not be in their standard package. The owner receives a card or a small device, much like a remote control, and just by approaching the car, no buttons pushed, the car senses the master and opens its doors.
In this project is presented a method to build your own keyless entry system. Your RFID will be a Nike footpod which will send the secret code to its iPod receiver. This receiver communicates with an Arduino Pro Mini through an iPod Serial Board. The Arduino listens for the right code from the RFID and gives lock/unlock commands.
You can give these commands to your car’s fob or adapt it to the internal wiring of the door’s lock/unlock mechanism. This can be pretty tricky for there are several systems used for door locking. In some European cars like Volkswagen, Seat, Skoda the command for lock/unlock is given on a single wire. For example if on this wire the computer sees a firm ground then it will unlock if it sees a resistance to ground then it will lock or the other way around. In these case you will need to use diodes or relays.
Asian cars usually have two wires, one for lock one for unlock. You will need negative or ground to control these wires. Things complicate however with the more expensive cars as they use vacuum systems or sophisticated computers inside the door. Usually these cars when equipped with a factory keyless entry system have a sensor behind the door handle that must be triggered in order for the doors to unlock, even if the car senses its owner nearby.
Powering our keyless system requires that you find a permanent 12V supply in your car. Look at fuse box, under the driver’s kick panel behind the steering wheel for thick wires and use a multimeter to measure the voltage. Do not trust thin wires as their 12V can disappear after car’s computer falls asleep. Usually that happens between 15 to 30 minutes after locking the car. Be careful with this because serious damage can be caused.
Other difficulty you can experience, as the project’s author did, is the car’s door locking settings. If you unlock the door but do not open it the car might lock it again after a short period of time. You can change these settings from the car’s computer with a diagnosis tool.
RFID Keyless Entry: [Link]
When i first saw this project i thought this could be turned into one of those dance steps learning game. The device consists of a 3×3 matrix of buttons. The system memorates the sequence in which you press the buttons and then plays it for you by lighting a LED under those buttons. You can also program multiple sequences. If you don’t press any button for a longer period of time, 4 seconds i believe, the device goes from recording to playback.
It is quite an interesting memory game, and can be transformed into a larger project. Like in one of those smart houses… in case you get lost this device will show you what path you took. On the other hand the algorithm behind this project can be used in beat generators, sequencers, power distribution sequencers and many others.
The Nove Bit as it was called is using Arduino and a TLC 5940 microcontroller. Source code is available for download as well as some instructions on how to build it.
9 Bits Visual Memory: [Link]
Here is a good project for those who want to start with robotics. Fairly simple and if you are using a breadboard there is no soldering involved. It is a vehicle that follows a light source using two LDRs, two servo motors, two wheels and an Arduino as its brain. The two LDRs are placed one on the left and one on the right side of the vehicle and each one controls the motor from the opposite side.
Although this project can be done using discrete components alone, using an Arduino allows you to further develop the project. Light is detected by the two LDRs. Each LDR is connected in series with a resistor between Vcc and ground forming a voltage divider. The joint point between the LDR and the resistor is connected to one of the Arduino’s analog inputs.
You will need to play a little bit with the values of the resistor so that you get the right sensitivity for light detection. A variable resistor could be very handy. The motors who spin the wheels are two hacked servo motors. Since servo motors don’t spin 360 degrees there is a way explained in the project to transform them into gear motors.
Servo motors are however pretty easy to control with the microcontroller. You have a center value which will make the motor stand still and if you add or subtract from that value it will make it go forward or reverse. You will need to run a few tests to determine these values and to adjust the light sensors.
Braitenberg robot with Arduino: [Link]
Arduino based projects are very popular, because of its versatility, ease of operation and pretty large amount of projects available to be put into practice. This being said it’s not unexpected to see clones being made like the Coreduino.
Named like this because it uses the core of the Arduino board, the ATmega168 microcontroller and its oscillator components 16Mhz Xtal and the two 15pF capacitors. Coreduino’s PCB is smaller and can be easily connected to a breadboard. There are soldering bridges that let you power the board from ISP or USB. The programmers were built on separate PCBs and this way you can use the same programmer for many Coreduino boards. USB and Serial programmers are presented.
The USB programmer uses a FT232RL chip to convert data from USB to serial and send it to the ATmega. It can also power your Coreduino board and you can select the logic level to either 3.3V or 5V. The serial programmer has two level shifters made with discrete components and you can have RTS or DTR line to reset the Coreduino but you can not power the board with it.
In the project you will find all schematics and PCB layouts, everything you need to get it done.
Arduino Board Clone: [Link]
