Two cheap CMOS ICs and a few transistors was all that was required to rebuild my elderly TTL automatic morse keyer into a low current lightweight battery powered iambic morse keyer. Sometime over the past year or two, my elderly Accu-Keyer gave up the ghost and died. I built it more than 30 years ago (!) from the original TTL IC-based design
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published in the ARRL Handbook. It was an accurate copy of the original, right down to the printed circuit board which I made using nail polish as resist and ferric chloride etchant. As I was tearing the old keyer apart, I instantly recognised the PCB production method I`d used by the quality of the resulting PCB. It was not very pretty, and I certainly could not reuse the PCB simply by replacing the dead ICs with new CMOS devices. In those days, the Accu-Keyer was the most popular design. Most of those keyers used TTL chips, and the current drain worked out to be a few hundred milliamps. Running it off batteries was hardly practical, and I never tried. But there were times when it would have been useful. In fact, I was never very happy with the keyer. The power supply was my biggest gripe, and my own fault. I made it using a rewound transformer. I was a poor high school student in those days, without much money to spend on the hobby. To get the right voltage for the power supply - I needed 5VDC - I found a transformer somewhere, pulled it apart, and rewound the secondary by hand. The problem was that the darned transformer used to hum like crazy because I was unable to clamp up the laminations adequately. I guess I could have dipped it in varnish or something, but I never got around to it. The hum wasn`t too bad when it was all enclosed inside the little box. Even so, every time I turned it on, I would hear that hum, and...
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....
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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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