Electronics-Lab.com Blog

This small thermometer board uses the Microchip TCN75 device. It is a cheaper clone of the LM75, it costs about 2,50 Euro. The TCN75 comes in a SO8 packaging. The TCN75 is a serially programmable temperature sensor. It has an output that is programmable as either a simple comparator for thermostat operation or as a temperature event interrupt. Hysteresis is also programmable.

TCN75 Thermometer - [Link]

The TC77 is a serially accessible digital temperature sensor. Temperature data is converted from the internal thermal sensing element and made available at anytime as a 13-bit two’s compliment digital word. Communication with the TC77 is accomplished via a SPI and MICROWIRE compatible interface.

TCN77 Thermometer – [Link]

This circuit uses a Dallas DS1621 temperature sensor which indicates the temparature of the device. The temperature sensor has an termal 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 amonut of hysteresis can be programmed.

Temperature Indicator - [Link]

Alberto writes:

The Witness Camera is an automated, self-recording surveillance camera, that uses a gigabyte-class flash card as recording media. I designed the Witnesscam because available surveillance solutions were too expensive or impractical for home use. I built the system from a VGA CMOS colour camera, a passive-infrared (PIR) movement sensor, an ATmega32 processor, and a 1GB SD-card. The prototype looks like an ordinary alarm detector. But when it detects people moving around, it silently starts recording.

Make a “Witness camera” - [Link]

Water Level Buzzer is a simple kit which will buzz when water reaches the sensor level.

• Input – 9 VDC @ 40 mA
• Output ??? Buzzer
• Terminal pins for supply voltage
• Power-On LED indicator
• Four mounting holes of 3.2 mm each
• PCB dimensions 32 mm x 35 mm

Water level buzzer - [Link]

Climate controller reads temperature and humidity values from SHT11 where are temperature and humidity sensors combined. Temperatures scale reaches from -40 to 123ºC or (-40 to 254ºF) while humidity readings can vary from 0 to 100%.

Controller board can control three distinct CD outputs with 10A load or 2 DC outputs and one AC up to 4A. This project can be ideal for greenhouse control, small room climate control or in other areas where temperature and humidity has to be sustained. Complete project files including C source, hex file, schematic and PCB can be downloaded here.

PIC based climate controller - [Link]

David writes -

One of the first lessons that an electronics student learns is that an LED provides light from current flow. But, did you know that an LED put in backwards provides current flow from light? Yes! It’s true. [via]

Make a color sensor from a reversed LED and Op amp - [Link]

How Motion Sensors Work

The heart of common motion detectors is a pyroelectric sensor, which is essentially a FET with a window in the case opening onto an infrared-sensitive gate. Changes in the level of IR light with a wavelength corresponding to body heat cause changes in the drain-source resistance, which the circuit monitors.

The real trick is that the sensor is then placed behind a multifaceted lens that (loosely speaking) “chops up” the view of the world into smaller cones of heightened visibility and intervening areas of lessened visibility. Think of a stage polka-dotted with multiple spotlights, only actually seeing that way rather than merely illuminating that way.

Parallax Motion PIR Sensor – [Link]

Led Puck is a board that consists of a few leds, an accelerometer a controller and a mcu. The accelerometer senses the titl of the board and lights up the approprite led lights, telling you the direction that the board is titled. Follow the link to see a video of the device in action. Cool!

LED Puck: Tilt sensing led board - [Link]

lond writes:

This accelerometer logger is a logger unit for measure forces on a roller coaster and save them to a SD-card. This is the fifth version of this unit. It’s also possible to modify the software in the unit so it can measure other things if it can be connected to a i2c-bus. I use a LIS3LV02DQ from ST-Microelectronics to measure the forces, a uALFAT from ghielectronics.com to manage the SD-card, a HCMS2915 display and a PIC16F876 to control every thing. I also use a Canon NB-4L battery (the same model i have in one of my cameras) to power the unit.

Accelerometer-logger with SD-card memory - [Link]