I'm building a table whit lights in it...
and was thinking it would be cool if it lit up when my mobile receives a call.
But how do I detect the mobile magnetic field ???
uC's: Atmega16, 32, 64, 128 and Attiny13
Interests: Small scale robots AND sensor monitoring system
would a long track on the PCB to one of my ADC channels do the job ?
Or do I need some extra protection ?
You might get away with a dipole antenna feeding a diode detector and then use the ADC, but I suspect signal levels will be too low. Try it first.
First, I would confirm that the mobile acknowledges receiving the text message. (I think it does).
Second, search for "power detector" ICs, I think Analog Devices or Maxim.
Work out which cellphone band you want to operate on and make a dipole or folded-dipole antenna to feed into the power detector IC.
This set-up will likely respond to other radio services in the 1-2GHz range, but if you are the strongest signal you should be able to set a threshold on the power detector output so that it will only respond to your cellphone.
What you are after is something similar to a microwave oven leak detector, except NOT operating at 2.45GHz.
Okay thx for the quick reply.
I'll try to search.
Hehe maybe I just should try to write "Cell phone" instead for "mobile phone" on google :D
I found this circuit that looks pretty simple
There are gadgets around, some of them real cheap, with such a function. Most of the time a lamp/LED lighting up, when the phone rings. You could disassemble one and use the circuit inside.
They all work the same way: When the phone is in standby it send short RF-pulses in regular intervals to keep in contact with the cell tower. When there is a call coming in the RF pulse becomes a constant RF signal with a power of a couple of 100mW. It is sufficient to detect the presence of a strong RF-signal in the frequency band the cellphone is using (EU: 900+1800Mhz, US: 1900Mhz).
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