using call detector circuit schematic

Posted on Feb 5, 2014

and I think I understand what`s going on. the induction coil senses the magnetic field flux around when the phone calls, boosts the signal, and pulses the LED. These types of circuits were meant to have the phone sitting on the pickup coil. The emf from the bell electromagnets were picked up. As Nigel said they won`t work with modern phones. The c

using call detector circuit schematic
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oil at the input of the circuit is supposed to pickup the radio signal of the cell-phone when it is called and it is transmitting, "I am receiving the ringing". But most RF circuits do not work when made on a breadboard because the tangle of wires are confusing, pickup interference and cause oscillation. The capacitance between rows of contacts is too high. Also the contacts are intermittent. I am going to venture a guess. If you look at the 7555 data sheet they are pretty clear about " Guaranteed Supply Voltage Range. . . . . . . . . 2V to 18V". What they are saying is that the chip will work with a minimum of 2 volts. Some will work at 1. 5 volts while some may not. Given that, I would use a pair of 1. 5 volt cells and try running at about 3 volts as a test. You may need to change a few values of resistors but I would give 3 volts a try. That assumes you are wired correctly. That would be my first guess anyway. AG has a good point with RF but I would try a higher voltage.

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