It is very easy to use and consumes so little current that it will work for the battery`s shelf life. The circuit uses a standard LM35DZ sensor (IC3) whose analogue output voltage is buffered by an LM358 (IC2A). The voltage is read by the microcontroller and converted into a BCD value so it can appear on the multiplexed 7-segment displays. The display will switch off after approximately 30 s unless button S1
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is pressed. In this way battery power is conserved. Pressing the button again will show the temperature. In the prototype two 0. 56 (14. 2 mm) common cathode (CC) green displays were used to show the current value of the temperature. The meter can show temperatures between 0 and 100 C. The first time it is used the meter has to be calibrated against a known reading. Preset P1 can be varied to change the value of the temperature by about 4 C. Press the but-ton and then turn the preset until the correct value of the temperature is shown. The microcontroller used is a PIC16F684. This has been chosen because it has a number of inbuilt functions and most importantly an internal oscillator which obviates the need for an external crystal, freeing up pins for I/O activities. Two 7-segment displays are connected in a multiplexed fashion. The displays are alternately switched on and off by the BC547 transistors. Each display is blanked before displaying the value to prevent ghosting. A temperature sample is read every 30 s to prevent the value displayed from changing due to fluctuations in the temperature. An LP2950 is used to regulate the supply volt-age to 5 V. This is a low dropout regulator which can work down to 6 V hence juicing the battery for the last drop of energy. The thermometer may also be run from three AA dry batteries in series with no series regulator. The PIC software can be downloaded free of charge from the...
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....
Many times for various reasons we forget or can not water the plants that we have in our homes. And many humidity sensors units just notify us with a beeping sound or with a flashing light, that the pot needs watering. But what if we are away from home? This....
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....
The sub-harmonic bass generator is a sound producing unit for guitars. The sound it produces looks very much like that of the bass guitar. The octave generator is sometimes quite unusual since it does not produce any of the usual ways of coloring the sound,....
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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