My final project, cycling rollers, requires a method of sensing the rotational speed of one of the rollers. Typically speed sensors on cycles work by detecting the passing of a magnet attached to a spoke on one of the wheels using a Hall Effect sensor or a reed switch. I intend to use a similar principle to determine the road speed of the rolle
Click here to download the full size of the above Circuit.
rs by placing a magnet on one of the rollers and counting the number of rotations in a known time. As an initial step towards this, I want to establish that I can use a Hall sensor in this way by having it illuminate an LED as it passes. This feature will be incorporated in the final design to allow a user to determine the speed sensing is operational and will allow me to start developing with the Attiny44. The first step in the design was to select the current limiting resistor for the LED. Once I understood that the maximum allowable current was 40mA and that a voltage drop of 1. 8V was needed across the LED a minimum 80R resistor was needed. I mistakenly believed that a 10K resistor could be used as I did not initially understand that a current of order of 10mA is needed for the LED to illuminate. Ohms law indicates a resistor around 320R, hence the selection of 500R. I reviewed the data sheet for the Allegro A130x series of Hall sensors in the FabLab inventory and determined they were suitable for my need. One feature of their operation was the output signal was centred on Vcc/2 swinging up to Vcc and down to Gnd depending on the polarity of the magnet passing the sensor. This meant that I needed to use an Analogue to Digital Convertor on the Attiny44 to read the input signal which in turn determined that a bit on Port A would be required for the input signal. I reviewed the data sheets for the Hall sensor and 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.....
characters left: