This project allows you to log temperature under 2 operating modes: Standalone, the system works standalone and can record a max of 2 temperatures or connected to a PC’s RS232 port thus having the ability to record up to 8 temperatures. The circuit is also interfaced with an LCD that can show 2 temperatures at the same time. It also has a separate DS1302 Real Time Clock (RTC) module with over 3 months backup and supports Wayne’s NTP format for updating the clock from an NTP server. The circuit is controlled by a Atmel AT90S2313, source code and schematics are provided.
LCD Temperature Monitor: [Link]
Jesper writes: This is another project which fullfills a need. I once built a frequency counter using plain TTL chips. That was long before the CMOS HC versions, even before LS was available. It could measure up to 50 MHz and worked quite okay, but the TTL chips was extremely power hungry. I think there was about 20-25 TTL chips on that monster. Well, but the old counter is now somewhere in the shed, and as I now again needed a counter, I did a bit more modern design.
It uses only 4 chips - 3 HC TTL’s and an Atmel At90S2313 microcontroller. It has a 5 digit LED display plus one used as a band indicator. Even with the LED display, the current consumption is less than 50 mA. It counts up to at least 52 MHz. I couldn’t find any signal source in the lab that could supply more than 52 MHz, so it may go a bit higher, but the fClock(typ) for the HC590 is about 35-40 MHz, so you shouldn’t really count (no pun intended) on more.
AT90S2313 Based Frequency Counter: [Link]
This is a simple circuit which can detect when you touch a sensor connected to one of the sensor inputs. It can be used to add a touch switch to your computer for example. It uses an AVR micro controller, the AT90S2313. Anyway, the basic idea is really simple. Make one pin output and another input. Connect a resistor between these pins. The resistor together with the human capacitance (about 100 pF) forms an RC network. The AVR set the output to low and then make a transition from 0V to +5V. 5 µs after this switch, the logic level at the input pin is sampled. If someone is touching the probe connected to the input pin, the capacitor (=human) will not be fully charged, and the input will be a digital 0 and vice versa.
DIY Touch Sensor: [Link]
Electronic combination lock always fascinated me since i was a kid, playing with blinking LED circuits. At that time i was always thinking on some sort of electronic combination lock that i could add to my bedroom door, but unfortunately i wasn’t working with micro-controllers at that time so it was very difficult to put together something like this. But these days you can easily build a project like this, the parts are available everywhere.
Electronic combination lock with AT90S2313 or ATtiny2313: [Via] - [Link]
