One way to measure the distance is to use ultrasonic transducer which is cheap and robust. Paoson Woodwork constantly needs to measure distances inside room while installing furniture or doing repair work. So he came up with idea of building an universal distance meter which would measure distances in all four directions at once.
He put electronics in to his custom made plywood enclosure where he made openings for sr04 ultrasonic transducers. He put an LCD in front, along with two buttons for unit selection and function. Additionally there is a bubble level tube included to keep things straight when hanging on the wall. All you have to do is to hang the meter on the wall and it displays the distance on LCD for in all four directions. It can display the area of wall with a single button press. There are other programs available along with area and distance. These are Rel – to measure relative distance, Total – to measure total distance between two opposing surfaces.
If you are working on capacitance sensitive projects, it is recommended to check capacitor value before use. Practically any multimeter already have capacitance measure mode. If you are not satisfied with its range or want to have dedicated device, consider of building one. Braulio777 have written pretty illustrative instructable where he shares all building steps on how he built cap meter. It is capable of measuring capacitance from 0.000pF 0.001pF to 1000uF.
The meter is built around Arduino where external components are assembled on separate Arduino proto shield with 16×2 LCD on top. He run several tests that prove that meter works within specs. With enclosure and battery it becomes decent portable meter.
Frequency is very important parameter of any signal. No matter if you are generating or synthesizing signals, you most likely need to measure its frequency. When signal frequency is bellow 40kHz and amplitude is near 5V then you can build frequency counter on Arduino with standard LCD screen. If measure signal is 5V (or 3.3V) level then you can feed it directly in to Arduino input. In other cases you need to use limiting circuit like amplifier or voltage divider. But this small project assumes that voltage is fed directly to microcontroller input.
In this example signal comes to digital pin 12 where function pulseIn() counts number of pulses during specified time. Program itself is only few lines of code, and hardware is straight forward so putting it to work condition is only a matter of minutes.
Cats are sneaky pets that don’t like to obey the rules. If you are nearby, then you can keep an eye and chase away. Normally your voice does the trick. But when you are not at home, cats can do what ever they want. Lucky resistor decided to put end to cats domination at home and started a new project called “Cat Protector”. It’s a device which once placed on some area, prevents it from cats visit. Device simply detects cat movement and then speaks recorded phrases with owners voice.
Before building a final product, he first of all made a prototype, to see if this is efficient way to control the cat. After confirming, this works 100%, he finished it with portable enclosure and other elements. “Cat Protector” is based on Arduino Uno. Cat motion is sensed with Panasonic motion sensor AMN32111 which connects to Arduino with three pins. Masters audio is recorded in to SD card which is accessed with Data-Logging shield. Audio is played back through Microchip MCP4821 DAC interfaced to Arduino via SPI. Audio the is amplified on low power amplifier and then played with small 0.2W speaker. There is also a dual color LED used to indicate operation of device. Once built, it can be placed on any surface and hope that cat obeys voice disapproval commands all the time.