One PIC to act as a keypad driver though plus some primitive stuff to tie them together (when the time runs out disable the keypad and beep, when the correct button is pressed increment the score counter and regenerate). The random number generator is really bad. It relies on the inaccuracy of RC timing circuits! You have two 555 chips, one is set as a very fast astable (oscillator), the other as a much
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slower monostable (switches "on" for a while when the input is pulsed before switching itself off again). The output of both is ANDed and sent to the clock of a counter chip, so when the monostable`s input is triggered the counter counts up very quickly for a short space of time before the monostable switches off again and there`s your "random" number. The `8` and `2` outputs of the counter are ANDed together and connected to the reset pin, so when the counter reaches 10 (8+2) it automatically resets to 0. Click for a circuit diagram. In the photo, the two small 8-pin chips are evidently the 555s, and I guess that the chip on the right is the 7-segment display decoder, the one to the left of that is the counter and the second left chip is a series of AND gates. The logic is this; it sets the rows of the keypad high, then checks the columns until it finds one that`s connected, at which point it outputs the result. If no key is detected it outputs %1111. It also checks if the "random" pin is high (this signifies a new random number is being generated) and if so it outputs %1111 anyway. In the bottom-left of the photo is the logic to detect when to increment the score (it checks if the current value isn`t %1111 - that is, it only accepts a "correct button" result if the button isn`t %1111, which indicates no button pressed). If all is hunky-dory it triggers a monostable to fire once (the 555 next to it) which increments 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.....
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