Using a call detector circuit schematic, not working

Hi all,
This is the first time I am working from a schematic this complex, so I could use some advice, perhaps, as to what may be going wrong.

I am using the schematic and partslist posted here: **broken link removed**
**broken link removed**
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.

I put the circuit together and can't seem to get it to work. Any ideas of what might be going on here? This are photos of my setup:
**broken link removed**
**broken link removed**

I would suggest the main problem is that any remotely modern phone doesn't generate any magnetic fields that it's supposed to pick.

I'd suspect that it's trying to detect the EMF fields of the vibrating motor. Thus the sensing loop needs to be very close.

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 coil 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.

Just My Take
Ron

Good point. The TA7555 is even worse. 4.5 - 16 V

If you jack up the battery voltage, you need to modify the LED in series with the diode kludge.

KeepItSimpleStupid said:

Good point. The TA7555 is even worse. 4.5 - 16 V

Click to expand...

Then don't use the Japanese IC. It has the same part number as an American Cmos IC but it is not a Cmos IC. It is an ordinary 555 made with bipolar transistors.

The LMC555 made by National Semi is guaranteed to work with a 1.5V supply.