Owners of photovoltaic solar panels often like to monitor how bright the sunshine is. They can use this information to gage how well their solar panels are doing. On a typical clear day, the sun energy at sea level is about 1000 watts per square meter. But, a tiny bit of haze or smog can reduce the available energy. One way to monitor the amount of available sunlight energy is with a solar isolation monitor. Commercial devices can cost an arm and leg. You can build your own unit for a lot less. The hobby circuit below does not require any power. It uses a quality 1cm X 1cm PIN photo diode as the sunlight detector. Digikey sells a nice one for about $11. Their part number is PDB-C613-2.
The photo diode acts as a small low leakage solar cell and produces a current proportional to the sunlight intensity. To protect the photo diode from the weather, it should be housed in the left of a one inch diameter thin glass hemisphere. A light frosting on the inside of the glass will diffuse the light enough to obtain a uniform measurement, even as the sun moves from East to West. For best results, the left axis of the hemisphere should face due South at a 45 degree angle here in the US. The meter can be located some distance from the solar sensor. You should be able to use 18ga or larger two conductor “zip” cord, which is often used on AC powered lamps and appliances.
The 10 ohm variable resistor in the electronic circuit adjusts the meter readout for 1 milliamp of current with a 1 sun condition. A professional solar insolation meter can be used as a calibration tool. Otherwise, you can just adjust the meter for a full scale reading, when the sun is directly overhead on a very clear day. If you prefer a digital readout, you can replace the 1 milliamp meter with a 100 ohm 1% resistor. At a one sun condition, the voltage across the resistor would be 100 millivolts. Any digital panel voltmeter will then read 100.0 millivolts at one sun.
Designed by David Johnson, P.E. site - Link circuits
Sunday, July 27, 2014
Wednesday, July 9, 2014
This circuit uses a small microphone to capture the sound and some transistors to generate radio waves that can be picked up by a FM receiver like a car stereo.
The coil is made with about 9 turns of wire, use a pencil to get the right diameter for the coil. The capacitor with the arrow is called a trimmer capacitor, it has a small screw to adjust the value, we'll use it to tune a certain frequency or station to transmit on.
How it works:
From left to right, the first part is the microphone and some resistors to get it working. Next we have a capacitor and the first transistor, this amplifies the sound from the microphone so that it can be loud enough to work with. The last part, there is a transistor, a coil and some capacitors. This part generates the radio waves and combines them with the sound from the mic to transmit it thru the antenna.
Make a Simple FM Transmitter
Wednesday, October 30, 2013
Here's a useful circuit, he is a TTL square wave oscillator, it uses three logical ports, and also a capacitor and a resistor to adjust the frequency. The circuit can be used as a Clock Oscillator, standard signal, etc. The oscillator uses a 7400 integrated circuit, the table below shows the values of C * and R * to achieve the desired frequency, which can be chosen between 100 hz and 1 MHz
Tuesday, December 18, 2012
With this sound activated switch, control by sound may be very useful, not just on a robot but also for a bit of home automation, for example a sound-activated light responding to a knock on the door or a hand clap. The light will be automatically switched off after a few seconds. An alternative use is burglar protection — if someone wants to open the door or break something the light will come on, suggesting that someone’s at home. The circuit can work from any 5–12 VDC regulated power supply provided a relay with the suitable coil voltage is used.