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Electronics => Beginners => Topic started by: Chai on March 17, 2016, 04:51:47 am

Title: 555 discharge pin
Post by: Chai on March 17, 2016, 04:51:47 am
I'm confused why a LOW on the output pin 3 would drive the discharge pin 7 to ground. I thought a low coming from the flipflop/output connected to the base of an NPN would turn off the transistor and disconnect pin 7 from ground. What am I missing here?  :-//
   
Quote
Discharge, The discharge pin is connected directly to the Collector of an internal NPN transistor which is used to “discharge” the timing capacitor to ground when the output at pin 3 switches “LOW”.

(http://www.electronics-tutorials.ws/waveforms/tim37.gif)

http://www.electronics-tutorials.ws/waveforms/555_timer.html (http://www.electronics-tutorials.ws/waveforms/555_timer.html)
Title: Re: 555 discharge pin
Post by: LukeW on March 17, 2016, 06:18:19 am
The output driver section is inverting.
Title: Re: 555 discharge pin
Post by: Chai on March 17, 2016, 06:42:06 am
Hah! Thanks :-+