Quote:
Originally Posted by Geo
What i see......
555 works at 44Khz.
Problem is around the BC548.
BC548 with 290uH and 16.8 nf parallel to coil is tuned at 72.1 Khz...
The 68 Ohm resistor is so low compared with the Z of the tuned circuit, so i believe that the capacitor 100nf who is connected at the collector of the bc548 must calculated as a 100nF parallel to the other 2 capacitors (16.8nF). So with inductance 290uh and 116.8 nf capacitance the transistor is tuned at 27.34 Khz.
So we have 3 different frequences that don't match....
Your opinion???  |
FG90 is a broadband receiver.
It also works on MHZ frequency of garage door openers.
Maybe it does not matter if the transmitter circuit is efficient or not.
For a hand-held version which can make an FG90 to beep from 2 meters distance, I think you do not need a 555 for oscillator, and do not need a ferrite.
The battery can be a computer cmos battery at 1.5 volts.
So the hand-held version can be much smaller... the size of a coin.
Best wishes,
J_P