Turn-key PCB assembly services in prototype quantities or low-volume to mid-volume production runs

Library for internal AVR temperature sensor

Modern AVR micros are equipped with internal temperature sensors that can be used to measure core temperature or simply be a source for fast learning ADC without external components. Its accuracy isn’t great for serious readings but enough for monitoring. Nerd Ralph decided to write small library allowing to read on-chip temperature. Every AVR have a slight different way of setting up ADC, so he managed library to take care of this process. Several #ifdef lines fixes things up when compiling code. Also he took care of calibartion routine which gave pretty decent readings. If you don’t need great accuracy, you can get away with this internal sensor, but for more serious applications, better use external calibrated sensor which isn’t affected bu chip core temperature and noise. Library can be found on Google repository. Continue reading

ATMEGA Core Temperature Sensor

It might come as a something new to you, that just like MSP430 some of the ATMEGA devices also has an inbuilt temperature sensor. This could be read by using an in build ADC with certain settings. Majority of the new chips have them including ATMEGA328P. The project is used to find the ambient temperature of the room by using a known temperature differential between the ambient air and core. The code is compatible with Arduino Leonardo and Arduino Pro Micro as they uses the same chip while for the others minor changes might be required. In order to use the temperature sensor correctly, he has set the ADC reference to the 2.56V internal reference, along with multiplexer being configured the temperature sensor. Initially, he has used a pack of ice cubes to calibrate the sensor as it gave a difference of 7 degrees. The next step he logged in the temperature values for  5 minutes and the result was ran through a 100 value running average filter, which helped him to find  out the idle temperature. Overall, a different… Continue reading

Proper composting with temperature logger

Big part of our waste is organic that can be composted. Simplest way is to put everything in to pile and wait. In urban area you can face a bad smell problem that would annoy neighbors. The only way to avoid bad smell is proper timing in aerobic and anaerobic decomposition stages. So this project was born to keep track of compost pile temperature and take actions if needed. Aerobic processes are much faster and generate lots of heat. Compost pile temperature monitor circuit consists of Atmega238 microcontroller which reads temperature values using metal can transistor. Voltage across transistor indicates temperature level. Reading occurs every 10 minutes as processes in compost are slow. By watching logs or simply following LED indicator it is possible to predict when aerobic processes are over and anaerobic take place what leads to bad smell. Simplest way to reset putrefaction in to aerobic again is to turn compost pile, so it could get oxygen. Continue reading

Temperature and humidity sensor with serial output

This is quite simple temperature and humidity measuring board based on Atmega8 microcontroller. It uses a standard LM335AZ temperature sensor attached to AVR ADC port and NONEYWELL HCH-1000-002 humidity sensor. Microcontroller simply sends data via RS232 interface – so it can be viewed and processed on PC. Original schematic uses MAX232 converter, but it can be easily replaced with TTL to USB converter like FT232RL. Continue reading

Dual digital thermometer with I2C interface

Stand alone digital thermometer is very easy to build – especially when microcontroller has an ADC interface built in. Tuxgraphics has posted a new cute thermometer project which uses two NTC temperature sensors. They are cheap and quite precise for most hobby projects. One problem that they are non linear. But this what microcontroller is for. Some basic semiconductor physics and math and characteristics is straighten. Device reads temperatures from two sensors – inside and outside. Both temperatures a displayed on standard HD44780 compatible display and additionally information is sent to PC via I2C interface. Why I2C and not UART? It helps to save the hardware like MAX232 and multiple capacitors. Having connectivity with PC is great – you can always call a small GUI to see current temperatures or by running cronjob you can collect a long term statistics or even publish on the web. Continue reading

Log up to 8 temperatures to a PC using RS232

If you want to have centralized up to 8 locations temperature readings – you should consider building this temperature logger. Design is really simple as it used up to 8 1-wire buss temperature sensors DS1820. Temperature sensor device is interfaced with LCD panel which is able to display up to 2 temperature values. It also has a separate DS1302 Real Time Clock (RTC) module with over 3 months backup. It also supports Wayne’s NTP format for updating the clock to a Time server. If you need to monitor more than two temperatures then you need to connect device to PC via Serial port. Any terminal software can be used for this. Full project files are available for download here. Continue reading