An alternating display for my version 1 nixie clock led me to think of new logic designs for switching signals to the display. I took the design of my version 1 nixie clock, tossed out the 4013 flip flop and two 4017 counters, and redesigned the hours section and the reset circuits. A 4081 (quad 2-input AND gate) was used instead; a single gate serves as a Set/Reset
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bistable, another gate basically takes in the signal when the hours reach 13 and goes HIGH to reset the hours, and the last two gates serve as buffers (one for the 60Hz line). There were several modifications mainly to drive a single meter (the meter used is a Heathkit "Antenna Impediance Meter" or a 0-100uA meter). The outputs of the 4017s were converted to analog signals using a homebrew DAC with a chain of transitors and resistors. First, a 500K pot was used and wired with one transistor in series. Tune the pot to one digit on the meter, record the resistance of the pot, retune the pot to the next digit, record the resistance, and so on. A resistor ladder was created from the recorded resistances to convert the digital signals to analog signals. For the meter to display 0, the resistance is open and the meter outputs nothing. For the meter to display 1, the signal has to go through the entire resistor ladder (total of about 520K), for 2, it goes through less resistance, and so on until the least resistance causes the meter to display 9 (maximum). The clock circuits are always on so there are always four analog signals being produced. A 74HC4851, a cool 8-channel analog switch mainly for audio, is used to switch one of the four analog signals to the meter. A separate 4017 and a free running 555 oscillator set to be variable from around 1/4Hz to 1Hz is used to switch the channel inputs on the 74HC4851 to allow the display...
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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