Hi all, I'm new to this forum.
I've searched this topic extensively thorough the web, but I can't find out a proper how-to guide that explains the nitty gritty details.
It is written that on Arduino One each pin should have a max current of 40mA (30mA better) and that the overall current flowing through the chip at any time should be less than 200mA.
Most websites make an example of a simple circuit with a red led connected to a pin out. A red led consumes 2.0V, using a Resistance of 330Ohm the current flowing through the pin is 10mA. [ = (5.0 - 2.0)/ 330]
Now, what happens for more complex scenarios?
I have some ideas on the matter, but no clue whether I'm doing it right or not.
- 3 leds on 3 different pins each with its own resistance => each consumes 10mA, the total current through the chip is 30mA.
- 2 leds in sequence + 330 ohm resistance => I should compute (5.0 - 2.0 - 2.0) / 330 = 3 mA of current ...is this right? i smell an error here, but dunno. Do I really have to use the remaining voltage or rather the voltage drop to compute the amount of current flowing through the pin?
Now let's go harder.
Leds are rather "easy" to think of once settled up the doubts above. But what happens with with more complex devices?
An IR sensor with 3 connectors, 1 for vin, 1 for gnd and 1 for the sensed data, how many resistor does it need? Should I put one only in front of the vin? should I put one on the sensed data pin too? how do I compute the amount of current/load it imposes on the microchip?
And to make things harder.. how does this story work at all in respect to LCD display? these have something like 8 cables to be connected to the arduino board, some as outputs and other as inputs.. I have an HD44780U, onto its datasheet it's written that it can support from 2.7V to 5.5V of supply and nothing more.. so what resistance should I put and where? and more importantly, how do I compute the amount of current it flows around due to this device being connected to arduino?
I would like to learn how to design these circuits properly with some mathematical background in mind, I am not scared of learning some equation, but I can't find out on my own a proper source for this stuff.
Any so kind to explain me the basic stuff or point me some good reference? Thank you so much.