Simple Electronic Multimeter High cost deters many hobbyists from buying a conventional multimeter. Since it is difficult to obtain cheap 50 uAor 100uA meters which are essential for a highly sensitive multimeter, an electronic alternative device is suggested to serve the purpose. The circuit shown here gives economic and safe ranges covered to th
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ree values : (i) 0-15V, (ii) 0- l5mA, and (iii) 0-150mA. The ranges can be extended with suitable modifications. The 741 operational amplifier acts as a null detector. its output is equal to the voltage at point A minus the voltage at, point B, multiplied by the device`s very high voltage gain. lf VA is slightly greater than VB, the output is limited by the supply voltage to about 7 volts. lf VA is slightly less than VB, the output is about 2 volts. At the point at which the output changes from low to high or vice-versa, VA is equal to VB to within a very small margin of error. With the switch set to the position shown in circuit diagram (15V range) the potential difference between points A and C is The forward voltage drop of the diode D3 is about 0. 6V and largely independent of battery condition. About 0. 5V appears across the variable resistance VRl and a known fraction of this indicated by a scale on the potentiometer appears between points A and C, i. e. it compares the known reference voltage with a known fraction of the input voltage. On the two current ranges, the reference potential difference is compared with the voltages developed across R4 plus R5 on the l5mA range and R5 only in 150mA range. T `D2, a light emitting diode, with its current limiting series resistor R9 indicates whether the output of the operational amplifier is high or low. The diode D1 and the condenser Cl provide the facility of measuring...
This project fits more for custom made battery casing that can have more space to hide things inside. This switch with few alterations can be used for any other project as well but is designed based on e-bike needs! This project use a clever functionality of....
The circuit described here uses ultrasonic oscillations and operates based on the propagation velocity of these oscillations in the air. Thus, we can easily determine the distance of two points if the time within which the wave travels this distance is....
Sometimes the precious metals are hidden too deep and are not detected except with complicated devices. In many cases, however, small pieces of precious metal buried near the surface can be detected by relatively simple means. Everyone is very attractive to....
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The principle behind a metal detector is really very simple. Proof of this is the circuit that follows, in which it proves that the construction of a metal detector can be done in the minute, with few components that we find very easily everywhere. With the....
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In the past the sounding (sea bottom measurement) was done with the "bullet", that is, with a heavy lead object that the seamen plucked into the sea hung from a calibrated rope. As soon as the "bullet" reached the bottom, the depth appeared directly from the....
This Amplifier was designed to have the following specifications: Distortion less than 0.1% at full power of 100W even at 20KHz. Power has to be attributed to an extended bandwidth. The output transistors must be protected against short circuits. The power....
A series of LEDs serve to alert the gardener when plants need water. Using two conventional digital integrated LEDs and a series of LEDs, we make a very useful device for gardening. The device detects the amount of water in the pot and alerts the grower.....
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