Using three pins to drive three LEDs and read three buttons

Sometimes in more complex projects it is a waste to dedicate a line for every LED or button. If you thinking of selecting bigger microcontroller because you need additional pin to drive LED, think of smart way out. Francois AUGER & Philippe Fretaud have shared their technique of interfacing three LEDs and three buttons with three I/O pins.


They used special Charlieplexing method of connecting all together and then wrote code piece to drive LEDs and read buttons. Three additional diodes allow reading buttons without affecting other components. Using three additional diodes is way more efficient than expanding number of pins. See video bellow of live action. Continue reading

Arduino controlled toiled saves gallons of water per day

Lots of water is wasted in toilets around the world. Standard toilets flush about 6500ml of water mo matter if you are doing light or serious business. Some toilet flushers have dual button where one allows partial flushing, but it is not used in most cases -especially by kids. So TV Miller decided to automate water saving process here. He adopted Arduino system which fills only half of tank with water. This is more than enough to flush human urine. This is most often used option. If someone wants to do serious business, there is a button that once pressed fills tank full while you’re here.

Toilet has several improvements including electronic flush release mechanism based on servo. If this is not enough there is a bluetooth channel which allows flushing toilet with your smart phone. But probably most welcome feature of it is that it helps saving water – about 2 gallons per day. What if 1825 people would install this setup – they would save 1000000 gallons per year.

Ambitious project of measuring most of physiological signals

Human body emits many signals that can be captured for diagnostics. Probably most heard of them is ECG (Electrocardiogrphy). But there are many more bio-signals that can tel much about our health status. These are EEG (Electroencephalography) – brain activity, EMG (Electromyography) – muscle activity, ENG (Electronystamography) and EOG (Electrooculography) – eye movement. Each of these signals are very weak and irresistible to noise. To there is a special care taken of analog part of circuit.


Analog part is driven by ADS1299 – 8-channel 24 bit ADC which takes care of reading ECG signals. Digital part is based on ATSAM3X microcontroller which is Arduino compatible. Currently project is at ECG measuring position. But since it’s been released as open source project, it will grow up to include the rest measuring options. To track its current stage and add your thoughts you can at github.

Monitoring beehive with Arduino

Bees are best and probably only source of honey. If you have beehive at home, you know that it need taking care and monitoring of conditions. If you miss something your bees may swarm and migrate. So it is important to keep an eye on hive temperature and humidity. Marc has been working on beehive monitoring system that allows reading its temperature and humidity. He’s chosen DHT22 temperature and humidity sensor which is easy to interface to Arduino.


His intent is to expand project to do more than monitoring temperature. He wanted it to send SMS when hive parameters goes beyond threshold. Other planed features include measuring the weight of hive to determine the amount of honey; additionally there shall be entrance activity and buzz monitoring. Also movement detection near hive to prevent vandalism. But since summer is almost over, most of plans are left for winter to accomplish. To see whats already done you can head to github resources.