15465Re: Point me into the right direction please.
- Feb 1, 2005--- In Electronics_101@yahoogroups.com, "Roy J. Tellason"
> On Tuesday 01 February 2005 02:31 am, rtstofer wrote:circuits
> > Take your LED flasher example. You can look for 555 timer
> > on the internet. A single 555 will make one LED flash. Whatshould
> > the second do? Turn on when the first turns off? Well, anysingle
> > transistor inverter will do that. Voila' Two flashing LEDs.the
> Even that's making things too complicated...
> > Start simple, get one LED to flash using the 555. Then, get a
> > 2N2222 transistor or most any NPN device. Connect the emitter to
> > ground, connect a 1K ohm resistor between your power supply and
> > anode of the LED (the long lead) and connect the cathode of theLED
> > (the lead near the flatted edge) to the collector lead of thewon't
> > transistor. Now, connect a 1K resistor between the output of the
> > 555 and the base of the 2N2222. That's it. A simple inverter.
> > Assuming you have a 5V power supply the LED will light up. It
> > be very bright because the 1K resistor in series with the LED istoo
> > large. But, it will work.output of
> Nah. If you wire up one LED and resistor so that it's on when the
> the 555 is grounded, then wire up another one so that it's onwhen the
> output is high, you don't need the transistor inverter!I knew somebody would come back with that. And, of course, it is
true because of the active pull-up of the 555. It won't work for
every device but it will work for the 555.
The thing is, building the inverter is worth the effort.
- << Previous post in topic Next post in topic >>