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Topic: Resistor on pin 1 needed? (Read 623 times) previous topic - next topic

robstokes

I've just built an arduino clone using a atmega328 chip.
It seems to work just fine without a resistor on pin 1.

I was under the impression it would continually reset without it?

or have I just gotten the wrong end of the stick....?

Nick Gammon

I believe there is a weak internal pull-up on pin 1.
Please post technical questions on the forum, not by personal message. Thanks!

More info:
http://www.gammon.com.au/electronics

CrossRoads

Previous discussions have gone ovef erratic behavior without the external pullup.
Atmel Application notes seem to suggest having one, especially with DTR cap, external reset switch connected.
Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

Osgeld

I have personally had zero problems with it while tinkering around, but I have never left it out on something that's going further than a evening on the breadboard, as I have been able to reset the chip by waving my finger over it once before
http://arduino.cc/forum/index.php?action=unread;boards=2,3,4,5,67,6,7,8,9,10,11,66,12,13,15,14,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,86,87,89,1;ALL

Grumpy_Mike

Yes it will work without it but not reliably. That means under all conditions of noise and temprature.

smeezekitty

The internal pull up is very weak. I built an attiny13 project and without and external pullup resistor, it occasionally resets by itself.
Avoid throwing electronics out as you or someone else might need them for parts or use.
Solid state rectifiers are the only REAL rectifiers.
Resistors for LEDS!

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