Bicycle enthusiasts love having few high tech gadgets installed on it. Usually there are speedometer, lights and other stuff that can be purchased around. In order to have full control and ability to add new features the only way is to start building your own bicycle computer. Great start can be so called ‘jazda’ bicycle computer. It is based on Atmega8 microcontroller with (seems) Nokia graphical LCD screen.

It is battery operated (3V) device with three buttons for selecting actions. It has plenty connectors for various sensors including mandatory wheel rotation sensor. With this sensor computer already is able to indicate speed and cadence (RPM). There are also a bunch of derivative parameters like distance max speed avg speed. Graphical LCD allows plotting some data like speed during time. Project seems to be in progress and more features are on the way.

When I was trying to search for cheap AVR programmers on eBay i came across a bunch of AVRASP programmers from China, they cost a lot cheaper compared to their premium counterparts, it was a surprise to know that when they arrived that these programmers (or hex loaders as I call them) are made using an ATmega8! I was astonished to learn that a microcontrollor is programming another microcotroller – something like recursive programming.

A cool dude that goes by the name of  jethomson had a brilliant idea of actually modifying the AVRASP programmer so that it would become an ATmega8 development board ready to take in code – he even made it compatible and programmable with the famous Arduino Environment. All that was needed to complete the transformation was a little soldering job, a push button, wires and an external programmer, that was for the hardware side for the software he played with the AVR fuses and added a few lines to the boards.txt file.

To demonstrate his work, he modified the USB Business Card to output  “All work and no play makes Jack a dull boy”.

Back in college we had this subject on Programmable Logic Controllers – which is used to control industrial motors, actuators and indicators while collecting input data from sensors? Why use a PLC? Well PLCs are compact, off the shelf, easy to program using Ladder Logic, its much lesser in cost and less power hungry compared to the other means of control while able to control high power instruments and machines.

Did I say much less in the previous paragraph? Well it cost less but not cheap – here is a home brew PLC. It doesn’t go in a black box [like the PLCs from Siemens] but it sure do high power control. The main controller of this PLC project is an ATMega8A-P which is rigged to an external EEPROM using I2C bus to be able to hold on more command sequences. The microcontroller is isolated from the high power devices. Inputs are made out of opto couplers – this would enable the microcontroller to sense from sensors that outputs voltages higher/lower than the limits of the AVR. For the output side, relays are used to switch on and off resources – the relays is driven through an isolating resistor that supplied the current that it needs to excite the coils which will in return activate the relay. Both output and input lines have their own LED indicators – for the user to see which relay is active and which input is at logic high – very useful when debugging your program. And more? The schematics is made in eagle thus you can edit and add stuff to it!

If you getting tired of using the ordinary touchable keyboard, which is require the users to enter the password one after one number, then it’s time for you to test out the AVR-Based Sensor Keyboard.

For your information, the AVR-Based Sensor Keyboard is definitely a wonderful device, as it’s built based on a modern microcontroller. Honestly, it has almost everything, which is needed to implement a touch sensor matrix.

The concept that being used for the AVR-Based Sensor Keyboard is based on the QMatrix Technology White Paper. The main goal is to transfer the charge through the sensor capacitance to a tank capacitor, until a charge sufficiently large to be measured builds up.

Then, a current will be applied to the tank capacitor. The time that it takes to reach zero crossing is measured as well. In this case, when sensor surface is being touched, the sensor is going to detect the user and verify the identity of the user instantly.

By the way, you might want to choose an ATMega8 as the test platform. Also, please pay attention on the builtin analog comparator, as it’s the most important components to detect the moment of zero crossing accurately!