Simplest Attiny85 based watch

We are used to see different kinds of DIY watches. Some of them try to stuff lots of functionality, other make fancy time telling format or simply mimic smart watches. But why not build a watch that only tells time in a simple manner. This Attiny85 watch is what it does. Schematic is very simple and straight forward – Attiny85 microcontroller, 12 LEDs, push button, three resistors and coin cell battery. Such simplicity allows building small watch shaped PCB where all components are fit to look nice and light. Since microcontroller comes with only 5 I/O pins (excluding reset), LEDs are connected using smart Charlieplexing method that allows saving pins for simple I/O tasks. The only shortcoming of this watch that time is counted using microcontrollers internal clock which may … Continue reading

Playing with bit-bang Ethernet on Attiny85

When going down into Ethernet or any other signal, you find that there is nothing more than ones and zeros. So practically any programmable device theoretically can send any information in any format. The only limit is RAM space, speed and signal conditioning. Cnlohr was able to squeeze Ethernet functionality in to small Attiny85 microcontroller. He was able to do so without external circuits – twisted pair was directly attached to microcontroller pins. This is really dangerous way to do, because Ethernet signal this way is forced to be tied to mcu ground. Ifthere is a DC offset in the line, it can cause damage. Normally there is a magnetics involved in signal line. Anyway this is great hack showing that anything is possible with minimal component count and small … Continue reading

Posture sensor helps you sit straight

If you spend lots of time by computer, you notice how hard is to sit straight. Over time you lean down, slide under the table or find other position that seems to be comfortable. Well there are two theories of this thing – first of all naturally your body tries to find best position to prevent you from pains and fatigue. Anyway prolonged leaning may result in back or neck pain. So siting straight may prevent from those problems. Bu how to control yourself when you are focused in to your task. You can always feel how you are sitting. Coretech Robotics suggest simple project that may help to sit upright by reminding you all the time. Device consists of ultarsonic sensor HC-SR04 which measures distance from your head. It … Continue reading

Reducing interfacing pin count for nrf24l01

Sometimes we get caught in situations when we need direct solutions without figuring things out in more efficient manner. For instance microcontrollers and pin count. When we need more pins, we start looking for bigger MCU even if processing power is enough even if one additional pin would change the situation. So sometimes this is not effective to waste money and even design to get one or two additional I/Os. Some people may use I/O port expanders or shift registers to get more pins. But as Ralph shows we don’t always need head for obvious. There are tons of discrete electronics components around that may save the day. This time he suggests interfacing well known nrf24l01 RF module to small MCU like Attiny85 by using 3 pins instead of 5. … Continue reading

LED Based Fireflies

This project is about a LED based asynchronous fireflies which were used as a Christmas project. The aim of the project was to make a low-power, low parts count module that can sense when it’s dark and then mimic the blinking patterns accordingly. For the project he’s using an Atiny85 along with an external clock which was programmed by setting external fuse-bits which is a conventional way to set clock source or frequency in almost all type of AVR’s A good things about the project is, it’s completely hand-made and that include the making PCB’s at home. To etch the PCB cupric chloride was used which is one of the quickest process to etch PCB but the time might depends upon the temperature. Also, to transfer the PCB design, from … Continue reading