Signals to Photodiode

[AxelD]

Hi,

I have a 555 circuit which generates a 30khz pulse. I use this to flash an IR led.

I am using a photodiode to pick up the IR pulses. Now the problem i have is that when i measure the frequency at the receiver end it is well below the 33khz.

Should this be happening. Could it be that the signal is too small for the multimeter to pick up a correct reading?

Thanks

 

[Nigel Goodwin]

You can't use a multimeter to read that.

 

[AxelD]

Hi Nigel,

I used my multimeter's frequency function to read the frequency from the 555 output so i just assumed i could use it for reading the frequency on the "receiver" side as well.

It must then be that the signal is too small for a reliable reading?

 

[Nigel Goodwin]

Hi Nigel,

I used my multimeter's frequency function to read the frequency from the 555 output so i just assumed i could use it for reading the frequency on the "receiver" side as well.

It must then be that the signal is too small for a reliable reading?

From a photodiode FAR too small, use a scope or amplify it first.

 

[AxelD]

Thank you.