I'm doing research into if the Arduino Uno has enough power pin slots to power multiple components, and I'm unsure if it's possible to convert some of the pins from the Digital and Analogue sections to be power/ground. Anyone know>
2 Answers
Only for very light loads (a few mA).
But why would you want to? The number of power pins doesn't dictate the number of devices you can power. Power pins can have as many things connected to one pin as you like. As long as you stay within the board's total power budget you are fine.
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@user32033 This may help you understand more: hackingmajenkoblog.wordpress.com/2017/03/20/…– MajenkoCommented Mar 20, 2017 at 17:29
Yes, for most modules that use modest power, it can be handy to treat modules as shields, in cases where pins can align. You just set each pin on the common 4-pin module connector as needed and plug them in. I've done this several times with DHT22 modules, and it's fun "plug and play"ing on such a low-level.
With an UNO, you get a generous 40ma per output, though I would use a real power rail for anything over 100mw or so.
To make a pin act as VCC:
pinMode(pin, OUTPUT);
digitalWrite(pin, HIGH);
To make a pin act as ground:
pinMode(pin, OUTPUT);
digitalWrite(pin, LOW);
the other advantage to this is being able to switch the module on/off with digitalWrite() (from HIGH to LOW) to save power or reset flaky sensors.
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1But note that the output pins have a not-insignificant impedance of 25ohm, which means that the more you draw from them the lower the voltage will be. Commented Mar 20, 2017 at 21:42
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the dht22 uses less than a ma. All but a couple of the "37 sensor" kit's modules would work with pin power; the relay+buzzers mainly. 25r limits 5v to 200ma, far more than the rated current...– dandavisCommented Mar 20, 2017 at 22:25
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"25r limits 5v to 200ma" No, it means that if you try to draw 200mA you will get 0V. Even just 40mA means a drop of 1V, which will put it out of spec for most 5V or 3.3V devices. Commented Mar 20, 2017 at 22:34
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@IgnacioVazquez-Abrams: sure, but 40ma is far more than most sensors use, a 4v triggers UNO's inputs...– dandavisCommented Mar 20, 2017 at 22:36
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Right, but is far less than, say, a ESP8266 module needs. Commented Mar 20, 2017 at 22:37