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Facts for beginners using A Arduino

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be80be

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There a lot of people would have you to think that the ATmega328P can source and sink 40mA. a pin

First off it's Absolute Maximum Rating is 40mA but this is basically a one pin per port, Not all 23 I/O

And the chip can only sink or source 200mA from gnd and VCC

A port can only sink or source 100mA

What this means is don't use more then a port can output when figuring you hardware

Like if you need to drive a relay use a 2n3904 or a 2n7000 with base or gate resistors and a kickback diode

Light a led use a resistor need more power use a driver 2n3904 or a 2n7000 for small loads up to 200mA and look up better options for bigger loads.
 
There a lot of people would have you to think that the ATmega328P can source and sink 40mA. a pin

First off it's Absolute Maximum Rating is 40mA but this is basically a one pin per port, Not all 23 I/O

And the chip can only sink or source 200mA from gnd and VCC

A port can only sink or source 100mA

What this means is don't use more then a port can output when figuring you hardware

Like if you need to drive a relay use a 2n3904 or a 2n7000 with base or gate resistors and a kickback diode

Light a led use a resistor need more power use a driver 2n3904 or a 2n7000 for small loads up to 200mA and look up better options for bigger loads.

It's all ports, the sum of the current cannot exceed 150mA, not 100mA per port.
A PN2222 or 2N2222 is also a good transistor to use as a driver, or ULN2803 8 channel drivers (built in resistors for 5V operation).

2N7000s are FETs, finicky, and blow up very easy, not recommended by me.
 
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