Dear Alice,
1) What is the comm speed are you using?
2) Which polarity of the RS232 voltage the 2n2222 is switching for bit
'1'? up or down?, it must be down, from zero to -12Volts.
3) I understand you are not using any modulation signal, just pure bit 1
= IR tx led solid irradiation, right?
4) What is the distance from TX ro RX led?
I recommend start this tests in a closed very short distance TX-RX (less
than 2 inches), inside a tube or pipe, to avoid external interferences.
Note that IR can travel through several materials, even black or solid
colors for IR is just as clear as pure glass... :) Once you have this
"close test" working fine, go for taking them apart and them you will
deal with bigger distances... I bet you would end up using 30-50kHz
modulation pulses for distances bigger than 1 meter. Remember that
Radio-Shack or Digikey has ready to use IR modules that nicelly remove
the modulation and delivery pure digital ones and zeros. You just need
to modulate the TX led and data with 30-50kHz.
Wagner
Alice Campbell wrote:
{Quote hidden}>
> Hi all,
> ive just spent the weekend trying to build an infrared comm link
> between the pic and the serial port. The reciever end is a
> radioshack photodiode that switches the base of a 2n2222
> transistor which runs through a diode to the rs232 Rx line. The
> problem is that the computer cant decode the characters. it gets the
> right number of gibberishes, in the right order, though. i think
> that the resistor is too sloppy to give clean voltage transitiions.
> i looked in catalogs and cant find a shottky device with less than 14
> pins, and i only need to clean up one signal, and hopefully cram
> everything into a d-9 case. Does anyone have any sound advice on how
> to produce cleaner levels for the port using just a few parts? or is
> sending ir ascii a hopeless approach?
> thanks,
> alice