My friends who live in California, USA, said that he likes to party with friends. With alcoholic beverages. And the need to drive a car. He does not want illegal traffic and to ensure the safety of everyone, so thought to buy this alcohol tester to the car. I agree. But he wondered how, Can we build it? I highly recommend this circuit. Advantage of it is easy to use, show the alcohol level with the 10 LED. Use the parts less. So is not difficult to build and cheaper. The working principle of the circuit. The heart of the circuit in Figure 1 is an alcohol sensor(sensor1), which features sensitive to the substances of alcohol. When we apply the power supply of 12 volts into point J1 then turn ON switch S1 to provided the voltage supply to this circuit. The voltage is maintained level of voltage constant of [...]

This is a circuit sound alarm when an engine start spreading the heat. Although every car will have a temperature gauge. But in some cars. May be no warning if the engine is overloaded with heat. Or the driver may not have noticed the temperature gauge can cause problems. The circuit in figure 1 When the temperature of the engine increases. The resistance of the thermistor decreases. Thermistor is connected to R1 for divide the voltage of the power supply to pin 2 of an op-amp IC1-LM741. This voltage will decrease as the temperature rises, by at VR1-100K is used to adjust a reference voltage at pin 3 of IC1. When a voltage at pin 2 lower than pin 3, IC1 will be switch close makes has voltage at output pin 6 to send to IC2. The IC2 is connected as an astable multivibrator to the sound signal generator circuit [...]

A Salt intake in large quantities is not good for the body and also causes of diseases such as kidney disease, high blood pressure, heart disease and paralysis. We should not eat too much. But the recognition of salinity, but may differ. Therefore should be a good barometer. I highly recommend The food salt & salinity tester meter circuit, because it is simple circuit and cheap too. The circuit ideals. We use the comparator circuit by an op-amp IC. Which is the difference between the volume resistance or conductivity of the solution foods has salt is constituent. In with sensing probe immersed or dunk in the water or food. Then Showing amount of salt much, Appropriate salinity, and a little salinity with 3 different LED colors. How the circuit works. The circuit ready running When dipping or dip the probe into the solution or food. Then press switch-S1, by has [...]

I like planting trees, because trees are more useful to us. However, I always have problems with moisture content of soil,Each plant needs water is not as same. Watering or soil moisture is not good. May cause damage to our trees. With these problems, I think the electronic system to solve this problem. For example, to check moisture level of the soil. We see from the outside, may not be good enough. Sometimes we see that the soil is dry.But it may be appropriate to plant moisture that, when we add water. It may be possible to root rot. To determine these characteristics. It saves water, too. I collected several circuits below. 1. Automatic watering a tree A trees should be taken care of as well. This circuit allows for watering trees, can be done automatically.When soil moisture levels decrease, to values that are defined.(Which can be determined by the [...]

In electronic instrumentation is needed.One friend of mine, once said that a good tool. Not need to be expensive. It is important to use enough. Today I will try to collect circuits Simple Voltage Indicator. by LED and Zener diode You look into the concept. Although is small circuits. But it might make circuits great work was complete. 1.Visual zero beat indicator This circuit is suitable for an indicator to audio signal lower than 3Vp-p. In the circuit, we use a very small parts with only two of the LED display and built-up resistor for current depression. Light-emitting diodes(LED) connected with reverse polarity provide a visual indication of zero-beat frequency. Each Led is on for only half a cycle of the input. When the input frequency is more than 1 kilohertz away from the zero-beat frequency, both LEDs appear to be on all the time. As the input frequency comes [...]