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Some basic help please

  • Thread starter Kamus of Kadizhar
  • Start date
K

Kamus of Kadizhar

Jan 1, 1970
0
I've build a couple of the IR receivers shown here
http://www.lirc.org/receivers.html but now I'd like to get a little
fancier.

Mostly, I'd like to add 2 LEDs, one that turns on when the serial port is
activated, and the other when the receiver gets a signal.

I located some 5V LEDs (they have an internal resistor, pretty neat) and
tried to add them in a way that makes sense to me.

Since the voltage regulator provides a nice steady 5V, I connected one LED
across pins 2 and 1 of the TSOP. That works fine; the LED comes on when
the circuit is energized.

The signal received LED is a bit more problematic; the TSOP holds pin 3
high when inactive, and drops pin 3 to ground when a signal is received,
an LED across pins 2 and 3 should work. But when I try that, I get a
latching effect - once the LED comes on, sometimes it latches and stays
on. The circuit won't receive any more signals either. I thought perhaps
the LED, being so close, might be sending enough IR out to mess with the
receiver, but adding shielding did not help.

I thought this might be some excessive current drain, so I disconnected
the LED between pins 1 and 2, but the latching effect stayed.

I played around with it a bit, but then decided I did not know enough
about this sort of stuff.

So, any suggestions for modifying the circuit to add a power on and signal
LED?

FWIW, the 5V LEDs are Chicago Miniature part no. 4302Hn-5V or 12V, and
they come in different colors (the n is the color code, 1 for red, 5 for
green.)

TIA,

Yan
 
Kamus said:
I've build a couple of the IR receivers shown here
http://www.lirc.org/receivers.html but now I'd like to get a little
fancier.

Mostly, I'd like to add 2 LEDs, one that turns on when the serial port is
activated, and the other when the receiver gets a signal.

I located some 5V LEDs (they have an internal resistor, pretty neat) and
tried to add them in a way that makes sense to me.

Since the voltage regulator provides a nice steady 5V, I connected one LED
across pins 2 and 1 of the TSOP. That works fine; the LED comes on when
the circuit is energized.

The signal received LED is a bit more problematic; the TSOP holds pin 3
high when inactive, and drops pin 3 to ground when a signal is received,
an LED across pins 2 and 3 should work. But when I try that, I get a
latching effect - once the LED comes on, sometimes it latches and stays
on. The circuit won't receive any more signals either. I thought perhaps
the LED, being so close, might be sending enough IR out to mess with the
receiver, but adding shielding did not help.

I thought this might be some excessive current drain, so I disconnected
the LED between pins 1 and 2, but the latching effect stayed.

I played around with it a bit, but then decided I did not know enough
about this sort of stuff.

So, any suggestions for modifying the circuit to add a power on and signal
LED?

FWIW, the 5V LEDs are Chicago Miniature part no. 4302Hn-5V or 12V, and
they come in different colors (the n is the color code, 1 for red, 5 for
green.)

TIA,

Yan

Can you still measure 5V across the regulator output when it's in the
latched state?

This guy http://www.electronics-lab.com/projects/pc/019/ went to the
elaborate length of having a seperate battery for the activity LED.

You might be able to get more power by using both RTS and DTR if both
are asserted.
 
K

Kamus of Kadizhar

Jan 1, 1970
0
Can you still measure 5V across the regulator output when it's in the
latched state?

I didn't measure that. I'll put together another one to test on a less
valuable machine (just in case I fry the serial port....) :)
This guy http://www.electronics-lab.com/projects/pc/019/ went to the
elaborate length of having a seperate battery for the activity LED.

That just seems too clunky for my taste.... I wonder why he didn't power
it off DTR with a voltage regulator? How much current can a serial port
supply, anyway? I guess I could also go to the trouble of pulling 5VDC
off a USB port, which may be the way to go - eliminate the voltage
regulator altogether.

--Yan
 
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