The following circuits are presented in a logical order (unlike the way they were designed) from initial power-up to the frills tacked onto the end of the project. A less organized and more stream of consciousness version of the Mark II design can be found here, this is the sanitized and organized version. Some general changes since the Mark I include the switch to 9 volt operation (so I can just use a
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single battery which fits in the 9V battery compartment of the box I decided to use) and the switch to a TLC3704 voltage comparator chip (a very low power CMOS version of an LM339) instead of a LM324 op-amp. One of the (obvious once I finally thought of it) improvements over the Mark I was the change to actually disconnect the batteries when I don`t have the phone in the system, thus saving lots of battery power while I`m not at home and the phone isn`t in the Mark II. To prevent accidental triggering of the detector during the initial power-up period when capacitors are charging and the photo resistor is stabilizing, I needed to make sure nothing drastic happens for a few seconds after the power comes on. This circuit does that by holding the 555 timer reset pin low while powering up. The Mark I and Mark II both operate by noticing when the phone display lights up (which happens on incoming calls). The circuits are fairly similar in both, but I`m using the TLC3704 chip now, and one important change was the addition of resistor R8 to provide some hysteresis in the circuit so it doesn`t accidentally trigger after the photo resistor has already been lit up and is now going back to dark. (I also needed to tweak R8 a little - after everythng was together I found the detector failed intermittently and decided I was getting a little too much feedback. The 390K value here is the final version and works much better than the initial...
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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