Many blind and deaf-blind persons use portable electronic devices to assist their everyday lives but it is difficult for them to test the batteries used in this equipment. Talking voltmeters are available but there is no equivalent usable by deaf-blind persons. This battery tester uses vibration and a user-settable control to enable blind and deaf
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-blind persons to test both ordinary and rechargeable AAA, AA, C, and D cells and 9V batteries. For ease of use and maintenance the device is powered by the battery under test. The design is dominated by the fact that the pager motor will operate down to only 0. 7V. With a 0. 3V drop from the switching transistor, a weak cell, at 1. 0V, will only just operate the motor. This means that the 1. 5V cell sensing circuitry cannot be isolated from the 9V test terminals using steering diodes - they would introduce too great a voltage drop. The solution was to duplicate the level sensing circuitry for each set of test terminals. On the 1. 5V side of the circuit, a resistance network consisting of two 10kO multi-turn trimpots (VR2 & VR3) and user control VR1a produces an adjustable proportion of the voltage of the cell under test. VR1a selects a division ratio between the low and high limits set by the trimpots. The resistance of VR1a is 10 times larger than the resistance of these trimpots to minimise the interaction between their settings. The voltage from the resistance network is applied to a combined threshold detector and current amplifier formed by Q1 to Q4 and associated components. When the threshold (about 0. 6V) is exceeded the pager motor is energised, causing the battery tester to vibrate. In use, VR1 is first set to its fully counter-clockwise position, then a cell is connected. If the cell`s voltage exceeds the 1V low...
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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