The current sourcing/sinking capability of the I/O pins on Raspberry Pi is quite limited. According to the Wiki page, the current limit for each I/O block (e. g. GPIO0 through GPIO27 combined) comes at only 26 mA maximum, which is only capable of driving a couple of LEDs at a time. Also the I/O pins are 3. 3V only, and going beyond the current or v
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oltage limit could result in permanently damages to the chip. If we only need to boost the output current, we could use a simple transistor or MOSFET to overcome the current limit. Alternatively, we could use a Darlington array chip such as ULN2003 for the task. ULN2003 ²s on-state input voltage is well below 3. 3V and can be driven directly from Raspberry Pi`s I/O pins conveniently. Keep in mind though, due to the limited current capability of Raspberry Pi the maximum speed at which ULN2003 can be driven is limited due to its relatively large input capacitance and input current requirement. So while ULN2003 can deliver a rather high load current, it is only suitable for interfacing with slower peripherals that operate at a speed no higher than a couple hundred KHz. What if we need to interface both the input and output with 5V logic In this case, a bidirectional level-shifter is needed. When speed is not an issue and the load current is low, a simple resistor divider may be used. For high speed applications however, we would need a dedicated level-shifter. Analog Devices` ADG3300 is designed for this very situation. One of the key benefits of using ADG3300 is that this chip has an internal one-shot generator that ensures fast rising and falling edge of the signal transients and thus can be driven at a speed well into the MHz range. Another benefit of AD3300 is that no directional control pin is needed, the level-shifting...
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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