I'm working through the Beginning Arduino book and while I have a fair bit of programming experience, I have no electronics experience. Which leads to 2 questions on project 13 (Chapter 4, for me page 90) with the LED and piezo sounder.
The LED is connected to pin 9 and then directly to ground. Why is there no resistor in there? Wouldn't that present a danger of blowing the LED?
Why IS there a 1M resistor in parallel with the sounder?
This is one of the few projects that don't have a hardware overview so generally I can see why the layout would work but the missing/extra/misplaced resistor I can't figure out.
perrien:
I'm working through the Beginning Arduino book and while I have a fair bit of programming experience, I have no electronics experience. Which leads to 2 questions on project 13 (Chapter 4, for me page 90) with the LED and piezo sounder.
The LED is connected to pin 9 and then directly to ground. Why is there no resistor in there? Wouldn't that present a danger of blowing the LED?
Absolutely should have a resistor. Might not be the best for the LED, but worse, might damage the microcontroller if it draws too much current.
Why IS there a 1M resistor in parallel with the sounder?
Not entirely sure on this one. If the piezo unit were a purely capacitive load, it could generate some high current spikes. But I'm not sure that is the case. Anyone else?