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A scope probe is built to minimize ringing by adding resistance. A X1 is better than a piece of co-ax, but a X10 probe is more effective than a X1. A X10 probe has the effect of reducing capacitance by a factor of ten. The trade-off is that is also attenuates the signal by a factor of ten. That is, 1/10 the signal applied to the tip of the probe actually reaches the input of the oscilloscope.

LCD display consists of an array of tiny segments known as pixels that can be manipulated to present information. As a result of this technology, many types of this displays are used in applications like calculator, watch, messaging boards, clock, equipments, machines and a host of other devices that one can think of. Most of the Display types are reflective, meaning that they use only ambient light to illuminate the display. Even displays that do require an external light source consume much less power than CRT devices.

Smoke detectors are generally used in advanced alarm systems. Most of this professional devices use gas-detectors, ionization rooms or radioactive elements as sensors. In this circuit we are not using any of this complicated components. Instead of these, we are using two LDRs and one LED. LM1801 special-purpose IC ,which is designed especially for smoke detectors, provides us building this circuit by using the minimum number of components. It includes one internal zener supply, two reference voltage outputs, one voltage comperator, fixing diodes and one 500mA output transistor.

For the electric R/C enthusiast, a tachometer can be a very useful piece of equipment. When I first built this tach back in 1995, it was essential, as there were very few off-the-shelf electric R/C power systems that just worked. At that time, you had to experiment with batteries, speed controls or switches, connectors, and wiring, and a tachometer was a tool to help you measure the results.

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 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.

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

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.