Car Speed Alarm Schematic

When we are driving sometimes we do not know the speed of our car, especially when we are in the course of the highway so nice and straight, if the car's speed is too fast or faster than anyone could lead to accidents that do not want to happen. The circuit then requires the Car Speed ​​Alarm is to alert the driver who did not notice the speed because the roads are nice and straight. Even this series can be set speed, for example, we set when exceeded 100km/h the alarm should sound.

The workings of the circuit:A piezo buzzer will sound. Speed ​​pulse is inserted into the base of Q1 and the resulting waveform at the collector is fed through a RC network to the input of an LM2917 frequency to voltage converter, IC1. The resulting voltage is fed to three comparators (IC2d-IC2b) which has a reference voltage at the inverting input they are set by the 10-turn trimpots VR1, VR2 and VR3. The output of each comparator is applied through another RC network to the gate of an SCR. Anode of the three SCRs are commoned comparator inverting input connected to the left, IC2a.Non-inverting input is set to 2.3 V with a trimpot VR4. In use, once you exceed the speed setting for the comparator in particular, relating SCR to briefly pull the pin 2 of IC2a ​​low and short beep is emitted by a piezo buzzer. Then, if you exceed the speed setting that followed, another beep will be heard. The idea is to make each setting speed of several km / h higher than it actually is, so if you are driving at the correct speed in a particular zone, the buzzer will not sound. But as you increase speed, the buzzer will beep once because you exceed the speed settings for each zone. In this way, there is no need to constantly switch setting the pace as you pass through different zones and you can choose to ignore the beep is not "illegal".

Digital Anemometer Schematic

The series is a series of electronic digital anemometer to measure wind speed that is widely used in the field of Meteorology and Geophysics Agency or weather station. The name of this tool comes from the Greek word Anemos, which means wind. The first designers of this tool is Leon Battista Alberti in 1450. In addition to measuring wind speed, the tool also can measure the magnitude of the wind pressure.

As we know, wind is air that moves from one place to another. The wind blows because some parts of the world gets more sun than anywhere else. Land surface air temperature in the heat makes it rise. As a result, the air expands and becomes lighter. Because it is lighter than the surrounding air, the air will rise. Once the heat was rising, its place was soon replaced by the surrounding air, especially from the air above the cooler and heavier. This process occurs continuously, as a result we can feel the movement of air or what we call wind.

Anemometer is designed to measure and record wind speed distribution of 0-17 meters per second +. It was designed for high reliability, ease of construction, and for a wide range of environments. Data logged for 30.46 days (1/12 of one year), and then stored for 11 months. Data can be retrieved with a laptop computer at any time within 12 months of logging. Windmeter is self powered by a solar panel and battery.

Digital Stopwatch With 7-segment Schematic

You may have heard or seen such an object called Stopwatch hour. Stopwatch function to find out how long it takes in an activity. Usually the stopwatch is used in a variety of races: race, swimming, or even racing.

Stop watch is made ​​with a digital timer IC LM555 and IC MM74C926 4 digit counter with multiplexed 7-segment LED. MM74C926 consists of 4 digit counter, an internal output latch, NPN output for controlling the source of common cathode, 7-segment display and an internal multiplexing circuitry with four multiplexing outputs. Counter the negative edge clock face. Clock continually be produced by the timer IC LM555. The circuit works with a 5V power supply. It can be easily assembled on the PCB. Enter the circuit in a metal box with provisions for the 7-segment display, turn the switch S1, start / stop switch and reset switch S2 S3.

Digital Stopwatch reset the circuit by pressing S3 so now the display shows '0000 '. Open switch S2 to stop watch to start counting time. If you want to stop the clock, close S2. Rotary switch S1 is used to select different time periods on the output of the astable multivibrator (IC1).

Knight Rider Running Light Schematic

4017 Knight Rider circuit, the 555 is wired as an oscillator. It can be adjusted to give the desired speed for the display. The output of the 555 is directly connected to the input of a CD 4017.

Part List :

R1 22kΩ

R2 220Ω

VR1 50kΩ Preset

C1 1µF 16V

C2 0.01µF (103)

C3 10µF 16V

D1 – D10 1N4148

D11 – D16 LED

IC1 NE 555

IC2 CD 4017

The input of the counter is called the CLOCK line (555). The 10 outputs become active, one at a time, on the rising edge of the waveform from the 555. Each output can deliver about 20mA but a LED should not be connected to the output without a current-limiting resistor (220Ω in the circuit above).

The first 6 outputs of the chip are connected directly to the 6 LEDs and these “move” across the display. The next 4 outputs move the effect in the opposite direction and the cycle repeats. The animation above shows how the effect appears on the display. Using 6 LEDs, the display can be placed in the front of a model car to give a very realistic effect. 

VU LED Indicator Schematic

VU LED indicator is simpler and smaller than their analog, and very common in audio equipment. This version is based on National Semiconductor IC, and using the logarithmic version. Each LED operates with a 3dB difference from before, and the jumper is provided to allow dot or bar mode.

The circuit is completely conventional, and is based on application notes from National Semiconductor. The circuit is shown in the picture below and you can view it with a single IC and some discrete components. DC to the LED is almost filtered - C1 are included to ensure that the IC does not oscillate, and is not a filter cap.

This allows a higher LED current with lower dissipation than is the case if the DC is fully refined, and full smoothing would also require much larger capacitors. This will increase the size and cost of the project - especially important if you want to use in larger quantities that may occur with a mixer or analyzer.It could not be simpler. At the maximum level that you want to operate the equipment (as shown on the audio millivoltmeter or an oscilloscope with a signal applied), adjust VR1 so that the signal light to all the green LED (L1 is the most sensitive, and L10 showed the maximum level, so L1 to L8 should be lit ). If the input directly from the speaker output, an additional series resistor should be used in terminal "Aud" input to reduce the level. This can be determined by calculation (I leave it to you) or by experiment. As a guide, for 50W amplifier, an external resistance should be about 47k ohms.If you calibrate the meter for the power amplifier, set the output to a level below clipping. Adjust the level control until the LED turns on. In this way, if (L10) LED bulbs last when you're listening to music, you'll know that you are very close to clipping, and volume should be reduced.