The receiver has two 3.4 kHz single pole highpass filters in series.

Update: What is the frequency of the transmitter?

ak

Hi

Schematic for Transmitter is in post #9 on this thread , don't know what the frequency of it is though ! .

 

hi spike,
This is your TX in LTSpice simulation.

The ON period of the LED.s is ~ 100uSec.

I have assumed a 9v supply.

Eric

 

5.8 kHz is less than one octave above 3.8 kHz so there is some signal attenuation in the filters. If the range is not what you need, some receiver components can be adjusted.

ak

 

Hello,

Also the light emitter must be modulated.
A constant light source will not work.

Bertus

Petkan:
Very appropriate suggestion (to modulate the transmitting LED) as to suppress effect of background light changes.
To improve robustness people even tune the receiver (i.e. make it narrow frequency band) to the light modulating frequency.

 

Hi All

I would just like to say a BIG thank you to everyone who has helped me with this project ( and others ) , I would of been at a loss without all your help .

again thank you

spike

 

Hi again

Just a quicky on this project , could I use a 2N3904 Transistor in place of the BC547 ! , and why the Base on the BC and a Gate on the 2N ! .

BC547 -
Voltage rating: 50V
Maximum current: 0.1A
Power rating: 0.5W
Frequency range: 300 MHz

2N3904 -
Voltage rating: 60 V
Maximum current: 0.1 A
Power rating: 0.625
Frequency range: >250 MHz
Amplification (B): >100

cheers

spike

 

hi spike,
The 2N3904 will be OK.
I don't understand what you mean.? and why the Base on the BC and a Gate on the 2N ! .

E

 

Hi

Sorry confused the BC547 Transistor for a PNP , apologies .

cheers and thanks for your reply

ps: eric where in Yorkshire did you come from ! .