The analog interface is a very simple analog to digital converter which accepts the analog video output of the RF/IF board and puts it into a form that can be read by a PC Games port. The joystick input of the games port essentially converts a resistance in the range 0 to 100k ohms into a binary number from 0 to 255. The interface transistor looks
Click here to download the full size of the above Circuit.
to the PC as such a variable resistance, whose value is roughly proportional to the input voltage. The proportionality is not linear, but then neither is the receiver output. It can be used as a relative value, or it can be calibrated if a good quality signal generator is available. However, this is not necessary. It is necessary however, to set up the interface in accordance with the output values that it will receive from the RF board. This process is described later. The eight data outputs of register one are used to tune the radiospectrograph across the frequency band. These are fed to the digital to analog converter interface as previously described to produce a voltage that varies from 2 to 28 volts. This is applied to the tuning pin of the RF tuner. The two least significant bits of register 3 are used to select either low band (VHF-Lo) or the high band (VHF-Hi) of the RF tuner. Asserting bit 0 selects VHF-Lo, while asserting bit 1 selects VHF-Hi. Note that both bits 0 and 1 must not be asserted together. Also realise that the hardware does an inversion of the values presented by the software to these two register bits. A small QBASIC program that cycles the parallel port data byte from 0 to 255 can be used to set the max and min voltages output by the digital to analog converter (sweep generator). The code is listed below. `File name DACTEST. BAS `DAC test `produces a sawtooth ramp dly = 0 `increase to increase...
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: