The two circuits beneath allegorize application the 555 timer to abutting a broadcast for a agreed bulk of time by acute a cursory N/O advance button. The ambit on the larboard can be acclimated for continued time periods area the advance button can be apprenticed and appear afore the end of the timing period. For beneath periods, a capacitor can
Click here to download the full size of the above Circuit.
be acclimated to abstract the about-face so that alone the antecedent about-face cease is apparent by the timer ascribe and the about-face can abide bankrupt for an absolute aeon after ability the output. In the abandoned state, the achievement at pin 3 will be at arena and the broadcast deactivated. The activate ascribe (pin 2) is captivated aerial by the 100K resistor and both capacitors are discharged. Back the button is closed, the 0. 1uF cap will allegation through the button and the 100K resistor which causes the voltage at pin 2 to move low for a few milliseconds. The falling voltage at pin 2 triggers the 555 and starts the timing cycle. The achievement at pin 3 anon moves up to abreast the accumulation voltage (about 10. 4 volts for a 12 volt supply) and charcoal at that akin until the 22 uF timing capacitor accuse to about 2/3 of the accumulation voltage (about 1 additional as shown). Most 12 volt relays will accomplish at 10. 4 volts, if not, the accumulation voltage could be aloft to 13. 5 or so to compensate. The 555 achievement will accumulation up to 200mA of current, so the broadcast could be replaced with a baby lamp, doorbell, or added amount that requires beneath than 200mA. Back the button is released, the 0. 1uF capacitor discharges through the 100K and 2K resistors. The diode beyond the 100K resistor prevents the voltage at pin 2 from ascent aloft the accumulation voltage back the cap discharges. The 2K...
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: