Light / Dark Relay Switch
A simple light / dark activated relay switch circuit, suitable for many applications like the automatic switching of the lights in a shop window or a room according to the ambient light level. The circuit uses a light dependent resistor (LDR). A light/dark option has been incorporated. The term 'light/dark' is used because the circuit has a PCB-mounted switch on board. In one switch position a light-to-dark transition will activate the relay. In the other position a dark-to-light transition is required. So you can use the falling light on the detector to switch on a normally off circuit or switch off a normally on circuit. The relay is on when LDR uncovered and relay off when LDR covered. Adjust VR1 for light sensitivity. LED will turn on at the same time with relay.
This DIY lightning detector circuit is a very sensitive static electricity detector that can provide an early warning of approaching storms from inter-cloud discharge well before an earth-to-sky return strike takes place. An aerial (antenna) formed of a short length of wire detects storms within a two mile radius.
The circuit emits an audible warning tone from a piezo buzzer, or flashes an LED for each discharge detected, giving you advance warning of impendig storms so that precautions may be observed.
LM386 Audio Probe Amplifier
LM386 audio probe amplifier is an essential tool for troubleshooting audio stages in audio related circuits such as amplifiers, oscillators, function generators, phone circuits, radios and lots of our other projects. It is a very handy piece of test equipment that can be built on pre-drilled board and will make a perfect addition to your electronic collection. There are lots of things that can go wrong with an audio stage. It can produce distortion or a “hollow” sound, go weak or simply fail altogether.
Likewise tone circuits can present a number of faults and it is very handy to be able to “hear” what is going wrong.
It is not sufficient to measure the DC voltages on these stages. This only gives a partial picture of the conditions and does not tell you the quality of the audio being processed. To determine this you need a piece of test equipment that will let you see or hear what is being processed. Some of the projects you can test with the Mini Bench Amplifier are tone circuits while others are audio circuits. Tone circuits and audio stages are surprisingly difficult to test unless you have an audio probe or a oscilloscope. Oscilloscope is an ideal piece of equipment but if your budget does not extend this far, the next best thing is an audio probe.
Microphone Amplifier with TDA7050 IC
Here's a simple microphone amplifier based around TDA7050 IC. There are many schematics, the choice fell on the amplifier chip TDA7050, the only downside was it that it was not appointed to the microphone. By adding a resistor R1 in the scheme by 4,7 kOhm - amplifier can no longer work with conventional condenser microphones.
If you remove the resistor R3 - the alarm will be put on a small speaker with an impedance of winding 32 Om'a.
Voltage amplifier is powered by 3 - 5 volts, but as the amplifier must be nourished from 12 in the scheme of linear stabilizer was added at 5 V.
This scheme was checked with headphones (current consumption was 50 mA) and connect to the line input of your TV.
Linear scale - Small size
40 to 208 beats per minute
Motion Activated Camera
I made a relatively simple attachment to my Canon SLR to create a motion activated camera using Arduino. A lot of this was based on and inspired by the intervalometer project at The Honey Jar. I made some changes to his circuit to use a 4N35 optocoupler instead of reed relays.
One Button Digital On-Off Switch
The load is driven by the MOSFET IRFZ44 and 4093 AND gates are used in the circuit. The output of the 4093 IC drives the MOSFET. Only one button allows you to change the on-off state of the electronic circuits in which you use this switch. The circuit schematics is above. Click image to see the larger schematics diagram.
Oscilloscope Probe Schematic & Anatomy
Passive Probe are the most general used scope probe. As the name "passive" suggest, it is made from passive components resistor, capacitor & wires. The leading scope probe maker are LeCroy, Tektronix & Agilent.
Passive probe usually comes with attenuation factor of 1:1, 10:1 and 100:1. Attenuation factor of 1:1 means whatever signal being probe at the probe tip will be shown exactly as it is at the oscilloscope input. So a signal of 1V at the probe tip will be detected as 1V at the scope input.
Attenuation factor of 10:1 means that a signal of 1V at probe tip will be detected as 0.1V at the scope input.
PAL/NTSC Video Text Generator
Perfect low cost solution for:
* New video security installations
* SSTV transmitters
* Amateur video
* Existing installed security installations
* Scientific experimentation monitoring
* and any other application that needs the time and date recorded on an image!
Park Assist Circuit
Park Assist circuit was designed as an aid in parking the car near the garage wall when backing up. LED D7 illuminates when bumper-wall distance is about 20 cm., D7+D6 illuminate at about 10 cm. and D7+D6+D5 at about 6 cm. In this manner you are alerted when approaching too close to the wall. All distances mentioned before can vary, depending on infra-red transmitting and receiving LEDs used and are mostly affected by the color of the reflecting surface. Black surfaces lower greatly the device sensitivity. Obviously, you can use this circuit in other applications like liquids level detection, proximity devices etc.