Placing watch on the ring

Building a wrist watch is quite a challenge, but when we want to squeeze electronics in to ring then real fun begins. It becomes even harder when using building blocks that are meant for prototyping. Anyway take a look at following instructable, where 陳亮 have put decent looking ring watch. He had to squeeze Attiny85 microcontroller which comes in SOIC package. It’s been soldered on small prototyping PCB. Another large part of it is display. It’s 64×32 OLED display module with SSD1306 controller on board. Display is a biggest part of all and determines the ring width. Ring watch also carries s CR1220 battery with expectancy to last at least for half an year. Three push buttons gives ability to change settings. Time is counted internally and here helps Paul Stoffregen time function arduino library. Continue reading

Attiny85 driven music card player

Music cards are not something new. But those that you normally get play annoying tunes that are low quality. Dmitry thought that he can do better. So he started building his own version of music card. His goals were to have full fidelity playback, random songs each time and be small enough to mimic gift card. To accomplish this he had to solve several problems like playing quality sound with Attiny85 microcontroller. It seems that he’s done this pretty well by generating 64MHz on one timer with PLL which his used to generate PWM based analog output. Another 32KHz timer generated actual music sampling. Music has to be stored in SD card in WAV format. Then they are picked by using uFAT library. Another issue were music volume. Since Attiny85 could source up to 20mA with 3.0V battery is could provide about 60mW power which is really low. One option could be adding power amplifier, but since signal is digital, he ended up with using full bridge driver out of four MOSFETs. This way he was able to reach 5.8W… Continue reading

Transferring data to AVR over audio line at 12kbps

When you need to transfer or stream data from one device to another there is always some dilemma what technology to choose. You can pick many ways of doing so. For instance these can be USB, USART, IRDA, RF, WiFi, Bluetooth, SPI, I2C, etc. but when you are using small micros like Attiny85, you start thinking about code size and simplicity. Another thing is availability. If you need to send data from computer or portable device, options become even more limited. WiFi or Bluetooth is too expensive comparing to overall project cost, USART is thing of past unless you use adapter. Jari even tried optical screen flickering method, which appeared to bee to slow and not reliable. So he thought what interface is always there and doesn’t require many pins. So he remembered modem idea. Audio line is almost on every consumer devices including PC, smart phones. It can also be easily implemented on any microcontroller. So he started playing with data transfer overs audio line. To send data you need only one wire (and pin). Sending data with sync… Continue reading

Attiny85 based dual lead acid battery charger

Superbender has a constant problem with his camper bus batteries. Normally camper is left over the winter and so batteries dies without proper care. In camper there are two batteries – main starting and auxiliary. So he decided to build a dual battery charger to keep them alive over the winter season. He already had a 15V 5A power supply which seemed to be just right. Since batteries will be connected to charger over all winter time, charging current doesn’t play a significant role. Charging circuit is pretty simple. Control is based on Attiny85 microcontroller which controls both charging channels. Two ADC channels are used to read voltages of both batteries Resistor dividers scale voltage down to microcontroller level. Charging circuit is controlled by transistors that are optoisolated from microcontroller. Battery charger works in charging and monitoring mode. It compares voltages of both batteries to upper 14V and lover 12V thresholds. When lower limit is reached – charging of this battery begins, when it’s been charged to 14V, then charging is stopped. During long time, normally there will be one… Continue reading

Small controller that logs data and controls things

Sometimes you might need simple device that would log couple analog or digital channels. We all know that Arduino can do all of this and even more. But in order to save time something out of box would be better. Iviny though of this and build compact data acquisition device which is capable of logging or driving 2 digital and 2 analog channels. This is Attiny85 based small Arduino DAQ with V-USB based communication. It simply logs data to computer or drives pins. Project comes with python script which allows plotting data and controlling pins with few mouse clicks. Currently logging speed is up to 150samples per second, but it seems that future firmware versions should increase this limit. Original design comes in custom 3D printed case and looks really attractive. Continue reading

Protect Your SD-Card for real

You always wanted to save your SD-Card from viruses, malware and Trojans. The solution to these is to make them write protected. As of now USB-device exist which can be made write-protected but are very rare to find and are expensive.  For SD-cards they do have a write-protected switch but you can easily bypass it using OS tweaks. The sdlocker developed allows to truly write-protect any SD card by toggling the TMP_WRITE_PROTECT bit on the flash memory controller of the card itself. Together with a USB card reader, this write-protected card can then be used as a read-only USB drive. The sdlocker is built around an Attiny 85 controller. The schematic is also been included along with the code on the website. The code is fully compatiable with avr gcc for those on linux system or you can even use avr dude which is a very famous programmer for the AVR series of controller. The good thing is that you ca edit the code based on your requirement and the level of security you require to protect from malwares. Continue reading