[mythtv-users] Simple transmitter-is it safe?

Chris Osgood mythtv at functionalfuture.com
Mon Jan 5 13:53:40 EST 2004

I'm using the same transmitter. (IR LED + diode + 220 Ohm resistor)

The suggested 1k resistor was too much for my modern serial port as it
only does like +/-5V in the first place.

With no resistor I get a range of over 8 feet (as far as I could easily

With the 220 Ohm resistor I get a range of about 2-3 feet which is all I
need since it's stuck on the front of my cable box.

Note that I've found the range can vary drastically depending on how good
the receiving device is.

Works great so far.

// Chris

On Mon, 5 Jan 2004 steve at nexusuk.org wrote:

> On Mon, 5 Jan 2004, Stuart Felenstein wrote:
> > Reading the lirc documentation on the simple transmitter, seems to
> > suggest the serial port may not be safe.
> > Any comments on this , as I know people have built them?
> > Did you go with the suggested options for eitehr a bigger resistor or
> > amplifier circuit?
> I assume you're talking about an IR transmitter?  I built both the
> homebrew transmitter and receiver as shown on the LIRC site and it works
> fine.  The RS232 specs provide very a very robust electrical specification
> for the port and it's well buffered so I can't imagine you would blow it
> by just sticking an LED across it.
> --
>  - Steve                                             http://www.nexusuk.org/
>      Servatis a periculum, servatis a maleficum - Whisper, Evanescence

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