This PIC software combines frequency counter and frequency lock functions. By adding couple of transistors and operation amplifier TL082, it is possible to lock the LC oscillator frequency. Frequency reference is formed from the measured frequency itself after the delay defined by parameter 0Dh, when the number of the consecutive samples (defined
Click here to download the full size of the above Circuit.
by 0Eh) of measured frequency are within the +/-20 Hz. Then the actual value is trigged as frequency reference until the SW detects that the lock conditions are not valid. Frequency is measured every 100 ms. Next the frequency actual is subtracted from the reference and the difference is compared to value zero to calculate the deviation. If the result is zero, it means that no deviation and also no need to fine-tune the oscillator frequency. If the result is negative it means that the frequency actual is higher than reference. This detects the direction of the needed frequency correction. Next the rough value of the difference is calculated. If within 20 Hz then only short 2. 4 ms pulse is controlled. If bigger then 100 ms pulse is controlled. By means of these few calculations we have information how to fine-tune the frequency of the oscillator to hold the frequency actual equal as frequency reference. Simple, is it These pulses are controlled to digital outputs RB0 or RB3 according to the sign of the frequency difference. The outputs are never simultaneously on because it means almost short circuit. The controller is made using TL082 operation amplifier. The first amplifier is an integrator by means of the capacitor C8 and R23. A time constant is R23 * C8 = 22 M Ohms * 2. 2 uF = 48 s. So the control is slow and it only fine tunes the oscillator frequency and this is of course the purpose of the controller. The VFO itself...
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: