The 555 frequency can be varied via adjusting the voltage at pin 5. However, the range and linearity of frequency adjustment is very limited. This is a way to greatly improve performance using the inverted 555 timer circuit that was previously posted. Q2 is connected in the common base configuration. In this mode of operation, the collector curren
Click here to download the full size of the above Circuit.
t is a function of emitter current regardless of the collector voltage. In this way, it can perform a linear charge function upon C1. The emitter must be driven from a negative supply voltage. Frequency is scaled to 10V = 10kHZ via R5. Frequency range in this set-up is 180 to 10kHZ. Q3 is wired as a self-biasing transistor by connecting the base to the collector and feeding it a bias current via R4. Voltage drop is 0. 6V. Originally, I had a 1N4148 diode and its voltage drop was 0. 45V that added too much offset to the emitter of Q1. Ideally, the voltage drop across Q3 should equal Vbe of Q2. This is a compromise because they are matched only under the condition of Ie = (9V 0. 6V) /R4 = 84uA. The emitter current varies from about 3 to 303uA. Lowest low end offset would occur with both transistors matched and R4 increased to 3M ”in that case, the hFE @ 3uA must >100 ”this looks practical, but would require a different transistor selection ”I did not experiment with this option. Q1 is a 2N4401. It varies from the 2N3904 in that its current gain (hFE) is optimized at a higher current. The reset current must be high due to its low duty cycle. Linearity is shown over two orders of magnitude. While not perfect, it shows how the circuit performs. The error on the low end is caused by input offset voltage that is not perfectly nulled via the voltage drop of Q3. On the high end, non-linearity is caused by the finite reset time of...
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: