To know whether it is freezingyou only need tomeasure the temperature. This has to be done accurately, of course, and therefore we need to choose atemperature sensorthat we have some confidence in. The choice has again been made for a type that we have already used in many previous Elektor circuits, theLM35CZ(-40 to 110 °C). Thissensor is not exp
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ensiveand generates an output voltage that is proportional to thetemperature in degrees Celsius(10 mV/ °C). AnLM35is normally powered from a single-ended power supply and 0 °C corresponds to an output voltage of 0 V. It is therefore not possible to measurenegative temperatureswith an LM35 in the standard application circuit. It is however possible to measure negative temperatures if its output is connected to a negative supply voltage via a resistor. There needs to be a current of 50 A through this resistor (R2 in the schematic). We only need todetect the freezing pointwith this circuit. That is why there is acomparatorafter thetemperature sensor, which turns an LED on if the temperature has dropped below 0 °C during the course of the night. To ensure that the comparator operates properly it is necessary that the measurement value can become slightly more negative with respect to the input. To solve this problem, a diode (D1) has been connected in series with the ground connection of the LM35. The voltage drop across D1 (because of the small current through the LM35 this is only 0. 47 V) acts as `negative` power supply. Since the non-inverting input of comparatorIC2 is connected via R3 to the anode of D1 it functions as the 0 °C-reference level for the comparator. connecting the bias-select input (pin 8) to the power supply voltage. There is no need for the detector to be fast and it will therefore work well with the opamp...
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....
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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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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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