Hello,
According to the data on the common MQ2 smoke/gas sensor, the heating element consumes 800mW, and takes 5V. In terms of current on the 5V line, does that translate to 0.8W / 5V = 0.16Amps? So the Arduino would have to supply .16A, or 160mA.
When I look at the Uno specs, I'm not sure where it states the 5V current limit. I see this line:
DC Current VCC and GND Pins...... 200.0 mA
But 200mA seems awfully low. Am I reading that correctly? Is VCC the 5V or the 3.3V?
The MQ5 also claims to detect smoke. I haven't been able to find much in the way of sensitivity for either the MQ5 or MQ2 for smoke. Anyone have any advice on which to get for a smoke detector sensor? I'm not using this for safety critical, not replacing my home smoke detector or anything crazy like that
You can power the gas sensor permanently from the +5V pin. The 5V pin can supply enough current However, if you power the Arduino from the barrel jack instead of the +5V pin or USB, watch out for the voltage regulator overheating.
If you want to turn the gas sensor heater on or off under Arduino control, use a transistor, because the current is too much for an Arduino pin.
dc42:
You can power the gas sensor permanently from the +5V pin. The 5V pin can supply enough current However, if you power the Arduino from the barrel jack instead of the +5V pin or USB, watch out for the voltage regulator overheating.
If you want to turn the gas sensor heater on or off under Arduino control, use a transistor, because the current is too much for an Arduino pin.
Oh, so the USB line's 5V is not going through the voltage regulator? Makes sense. Am I doing something wrong if I have the barrel connector powered on at the same time the Uno is plugged into my computer on USB? Aren't the USB 5V and the regulator 5V fighting each other?
For future reference, if I use a limited power USB adapter, would that help protect the 5V from shorting when I do something stupid? So, let's say a 500mA power adapter with a USB female port, and I plug a USB cable into that to power my Uno?
dc42:
You can power the gas sensor permanently from the +5V pin. The 5V pin can supply enough current However, if you power the Arduino from the barrel jack instead of the +5V pin or USB, watch out for the voltage regulator overheating.
If you want to turn the gas sensor heater on or off under Arduino control, use a transistor, because the current is too much for an Arduino pin.
Oh, so the USB line's 5V is not going through the voltage regulator? Makes sense. Am I doing something wrong if I have the barrel connector powered on at the same time the Uno is plugged into my computer on USB? Aren't the USB 5V and the regulator 5V fighting each other?
The arduino board has a auto-voltage selection circuit that if it senses proper voltage range from the external voltage connector (or Vin pin) it turns off a mosfet switching transistor to isolate the board from an attached USB +5vdc voltage source.
For future reference, if I use a limited power USB adapter, would that help protect the 5V from shorting when I do something stupid? So, let's say a 500mA power adapter with a USB female port, and I plug a USB cable into that to power my Uno?
