The battery tester uses four transistors and two LEDs to indicate the condition of any battery you want to test. Q3 and Q4 are connected in a Darlington configuration that has extremely high gain. LED L2 lights when a small positive potential appears on the base of Q3. Transistors Ql and Q2 form a direct-coupled dc-amplifier circuit. The output of this stage drives the red LED LI. Rotary switch SI is used to select different ranges (which have been previously set by adjusting trimmer resistors PI through P5).The positive (+) lead goes through the selected contacts of SI to the biasing resistors R3, R4, and R5. The negative (-) lead of the battery under test goes to the ground or common lead of the circuit and the (+) side to one side of PI through P5.
Click here to download the full size of the above Circuit.
LI Red LED,L2 Green LED,PI through P5 5-kohm trimmer resistor,Rl 100 kohm,R2, R3 33 kohm,R4, R5 470ohm,R6 12 1 W,S1 2 P6 position NS rotary switch,S2 NO pushbutton switchDepending on the position of SI, a particular trimmer resistor (wiper lead) is selected. That lead goes through the contact on SI to resistor Rl and into the base of npn transistor Ql. If the battery is good enough, (+) voltage goes to the base of Ql, turning it on. This turns Q2 off, which then allows Q3 to turn on. That causes Q4 to turn on and light green LED L2.If the battery is weak, Ql will not turn on, which will cause Q2 to be biased on by R3, which in turn lights red LED LI. When Ql is on, it biases the base of Q3 negative, and causes Q3 to be turned off. That prevents L2 from turning on.The circuit operates in the same manner for all ranges except the first two, where a 9-V battery has been added by SI to be in series with the input voltage to allow for testing of very low voltage batteries. That is because at voltages below 2 Vdc, LEDs will not light and the circuit would be unable to set a low-voltage (2-V) battery without the additional internal-battery voltage. A load resistor has also been included; it allows the battery under test to be connected to a load to give a better indication of its condition. That load resistor is connected across the battery when normally open (NO) switch S2 is depressed.
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.....
characters left: