Re: Urgent - Time to kill, want to build IR Extender

[Nigel Orr <nigel@xxxxxxx>]

NOTE:  I misremembered the circuit when posting previously- if nothing is
connected to the input, the LED _will_ stay on.  When the TSOP is
connected, it's internal pullup resistor should provide enough current to
set pin 4 low and turn the LED off.

At 11:14 02/11/00 +0000, you wrote:
>I have double checked the circuit, and I was missing the connection
from pin
>6 on the 555N, however after adding that the transmitter circuit is now
on
>continuously even without the connection from the receiver.

Remove T2 for now, so you've just got the visible LED.  And pull out T1, so
the 'reset if low' pin is connected to +12V through a resistor, and not to
anything else.  The LED should now be on.  Take out the 10k resistor (I'm
assuming you have this in plugboard, this is why I suggested it!!), and
connect it between pin 4 and 0V instead- the LED should now be off.  If it
isn't, there's a fault with the 555 timer circuit.

If that works, plug T1 back in.  If you now connect the 'input' end (the
end that _isn't_ connected to T1) of R7 to +12V, the LED should be off, if
you disconnect it, or connect it to 0V, the LED should be on.

Let me know what happens then- direct emails are probably easier at this
stage?

>I can only
>assume something is shorting. but can't see any problem. The only part
of
>the diagram I am not so sure about is circle by pin 4, what does that
mean ?

You can ignore that- (it just means that the timer stops running when pin 4
is low, instead of when it is high).

Nigel


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