This is a very simple circuit where the PIC and an internal 1kHz sinewave table do all the hard work of making an accurate sinewave. Then it needs only a few external parts for filtering. The sinewave has a very high frequency accuracy as it is generated from a xtal. And with appropriate filter parts the sinewave is quite low in distortion. This m
Click here to download the full size of the above Circuit.
akes the device useful for calibration testing and any use where you need a mathematically correct sinewave of a very precise fixed 1kHz frequency. The sine table was created in Excel spreadsheet and makes a sine ranging from PWM 14 to PWM 86, a total PWM amplitude of 73% which is accurately distributed around the mid voltage point of 50% PWM. The sinewave was deliberately made at this amplitude to get the best performance out of the PWM system. The sinewave has some tiny error in each sample, but every sample has been rounded up or down to the closest PWM value to a perfect sine. The max error for any sample is less than 0. 68% of the sine amplitude. Hopefully this will not matter in the final operation as the important thing is the overall shape of the sinewave, because all the tiny PWM errors will be easily integrated out by the hardware filter. A PIC 16F628 was set up with nothing more than a 5v regulator and 20MHz xtal (and a few PSU caps etc). A trimmer cap was used to trim the 20MHz xtal to better than 1 PPM against my GPS tuned frequency meter. This means the 1kHz output will be 1000. 000Hz (+/-0. 001Hz). The PWM output from PIC pin RB3 was filtered through a 1k trimpot and 0. 22uF cap. The trimpot was adjusted to about 800 ohms, and the output of the filter is shown below on the scope; The sine wave is about 3v amplitude peak to peak. You can see the 50kHz PWM frequency as the fine sawtooth "hash". But importantly,...
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: