# Arduino current output [closed]

Simple question: I'm researching before buying. Can any of the Arduino products output current on a 4-20mA scale? I've seen them with Analog inputs but not outputs. And if they do not, are there add on cards/Shields/Modules that you can add to use that as a function?

Thanks a bunch!

• What does "output current" mean? – Milliways Oct 17 '17 at 6:45
• When in doubt, add a MOSFET as a switch to power directly from supply to load, without involving Arduino – user31481 Oct 17 '17 at 7:45
• What are you actually trying to do? Did some device spec say it needs 4-20mA? – gre_gor Oct 17 '17 at 17:27

Assuming a GPIO pins outputs 5V, and you need 20 mA (0.02A), why not use a resistor of 250 ohm?

``````V = I * R <=>
5 = 0.02 * R <=>
R = 5 / 0.02 = 250 ohm
``````

For 4 mA you use a resistor of 5 = 0.004 * R <=> R = 5 / 0.004 = 1,250 ohm

If you want it from the same GPIO pin, you can use also a trick:

• Take a LED from a GPIO which you control by PWM
• Tie a photosensor against the LED and put tape around both the LED and the photosensor
• The photosensor will have a certain resistance (you can control it by the LED)
• Run your circuit needing a current from 4-20mA through that photosensor.

Can any of the Arduino products output current on a 4-20mA scale?

It can be done but with limitations so severe that it may not be a practical solution. Use external circuitry / dedicated chips, however, it is quite doable.