Your question is that the original circuit would shut off when the IR det. sensed. Your first circuit used the transistor as an inverter/driver.

If you tied the collector to + and your led/resistor in the emitter, you have what's called a non-inverting follower/driver. When the IR det. sensed, the led would light. Isn't that what you want?

Rick

Robert Rothe wrote:

> Thanks to all who responded.    Rick, I'm not sure how your original suggestion (Collector to +, LED/RES to Emitter) answers the inversion question -- unless I'm not understanding.  Seems that would just convert the circuit from a common emitter to a common collector circuit.  I'll try it, of course.
>
> If there is a "right" answer, I think it is to either use an PNP or two NPN's.  Ultimately, the signal needs to find it's way into a PIC but I wanted to also provide an accurate visual representation that could exist without the PIC (ie, for a repeater or an extender).
>
> As for the Hex Inverter; if I use one, I'll use it to drive a transistor instead of the LED directly.
>
> Thanks again for the responses.
>
> Rob
>
> -----Original Message-----
> From: rixy04 <rixy04@VVALLEY.COM>
> Sent: Jun 16, 2004 7:40 AM
> To: PICLIST@MITVMA.MIT.EDU
> Subject: Re: [EE:] Two newbie questions on inverting
>
> Matthew Brush wrote:
>
> > Or switch that NPN to a PNP and re-arrange the circuit
> > accordingly.
>
> That's adding more parts.
>
> > Or you could use two NPN transistors.
> >
>
> That's adding more parts.
>
> > Not sure if either of these are the "right" way to do
> > it, but they'll both work fine for an LED.
> >
> > If all you're driving is an LED, I'm sure the inverter
> > IC can handle that.
> >
>
> That's adding more parts.
> Rick
>
> >
> > Cheers.
> >
>
> --

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