Simple, highly sensitive capacitive ON/OFF switch pads change the state of a latch and turn on an LED without requiring actual physical human contact. The pad may be insulated. A range of 12mm is easily obtained and sensitivity is adjustable. Central is the 74HC02 CMOS NOR Gate IC. The gate input capacitance is typically only 3pF. To enable a suff
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icient voltage to change states reliably a 100M bias resistor is recommended. I had to check to see if such a resistor is easily available ” yes, it is available from DigiKey at a cost is only $0. 52. Or you can fabricate a resistor via series 10 or 22M resistors ” that is what I did to obtain 50M. The low sides` of these resistors are tied to a bias potentiometer so that the static gate input voltage may be set very close to the threshold. Sensitivity is also increased by reducing Vcc to 2. 7V (minimum specified operating voltage is 2. 0V). I was able to obtain a range of about 16mm using a 50M resistor and paperclip non-contact pad. ` I also experimented with the CD4011 NOR gate ”it worked reasonably well, but it has higher gate input capacitance (5pF) and minimum operating voltage is also higher at 3. 0V. A 2N7000 N-Channel MOSFET (Q1) drives a 20mA ultrabright white LED. Note that the gate output voltage may be insufficient to fully turn on the transistor because the maximum Vgs threshold voltage is 3V. Fortunately, most run close to the typical 2. 1V. In case one does not work, try another device. The pads may also be insulated or placed on the back side of a thin board such as a canvas painting etc ”this is the initial application. Another possibility would be an anti-theft deterrent/alarm that would be easily turned on, but not easily turned off. A sensitive coil 6V relay with back diode may also be driven by Q1 ”...
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.....
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