Posted on Thursday, April 28, 2011 • Category: Sensors
This circuit uses a Dallas DS1621 temperature sensor which indicates the temperature of the device. The temperature sensor has an thermal alarm output, which becomes high when the temperature of the device exceeds a user defined value. When the temperature drops below a user defined value, the alarm output becomes low. In this way any amount of hysteresis can be programmed. The values are stored in a special register of the device that is nonvolatile. The signal of the alarm output is amplified by a BC557 PNP transistor, that drives a relay that can switch a heater element or a blower on or off. The temperature settings and readings are communicated to/from the device over a simple 2-wire serial interface. An ATMEL 90S2313 microcontroller controls the serial communication to/from the DS1621.The microcontroller also controls three LED, only one of the LED's is on when the temperature is within a certain range. The range of the temperature in which the LED's are on can be set by the user in the program code. The circuit needs to be powered by a 5V power supply, which can be obtained from a wall-wart.
Build Accurate LC Meter and start making your own coils and inductors. This LC Meter allows to measure incredibly small inductances making it perfect tool for making all types of RF coils. LC Meter can measure inductances starting from 10nH - 1000nH, 1uH - 1000uH, 1mH - 100mH and capacitances from 0.1pF up to 900nF. The circuit includes an auto ranging and reset function to make sure the readings are as accurate as possible ... [more]