Lithium-based (Li+) batteries are becoming common in portable equipment. They have desirable characteristics, but they are often in short supply. Lead times can be long unless you have a preferred-customer status with the battery manufacturer. A backup alternative to Li+ is therefore desirable, especially for smaller companies. This note describes
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a circuit that allows a nickel-metal hydride (NiMH) cell to be used in a circuit designed for a Li+ battery. It provides the same performance, size, and cost as a Li+ battery. A circuit that interfaces a NiMH battery with a lithium-optimized circuit should mimic the battery`s terminal voltage, which declines as the battery discharges. The nominal terminal voltage for Li+ batteries (3. 6V) is about three times that of NiMH batteries (1. 2V). As a simple approach, therefore, you can force the output of an efficent step-up converter to equal battery voltage times 3: 6V/1. 2V = 3. Allowing the circuit to run constantly during shutdown, however, consumes unnecessary power. The NiMH circuit`s equivalent leakage (its quiescent current) can be as a high as 200 µA during shutdown, which is unacceptable. In fact, only a power-control capability is needed during shutdown. Instead of maintaining 3x the NiMH voltage while in shutdown, you can run the proposed circuit in burst mode, which activates the step-up converter only when the circuit output drops below a defined threshold. When the output reaches the upper threshold, the step-up shuts down, allowing the output capacitor to discharge through the output load plus the NiMH circuit. Thus, the output voltage forms a sawtooth wave. If battery voltage falls below a lower limit, however, the circuit remains deactivated to protect the battery from depletion. The circuit of Figure 1...
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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