I currently have 2 Atlas Scientific sensors running on a Wemos D1 pro and transferring data via MQTT. All is well so far but after investigating the components in more detail I have a concern.
The “datasheet” for the Wemos can be found HERE
I am running each sensor via pins D1 and D2 using I2C.
I am powering the Wemos via a power supply to the Wemos 5V pin. I have experimented with using both 3.3V power and 5V power to this pin and both seem to work well.
Two main questions.
I’m very confused on what the 5V pin actually is? Is this where I am supposed to apply power to the Wemos via an external power supply? Or is this a 5V OUT pin that supplies power to OTHER devices when the Wemos is powered via the USB? If this is the case, is the only way the Wemos is actually supposed to be powered is through the mini usb jack?
I’m concerned about amps. My power supply shows about 100mA used on startup (I’m guessing this is when the Wemos is working to make an internet connection) and then between 45mA and 55mA after settling and the sensors taking their readings.
The datasheet for the EC sensor states a max operating amp draw of 35mA and the PH sensor datasheet states a max amp draw of 18.3mA.
The Wemos GPIO pins are rated for a max amp draw of 12mA??? However, I’m really confused. To my best understanding, I’m only using the GPIO pins for the I2C communication. My guess is that these pins are working in the acceptable range (less than 12mA) because things appear to be running smoothly? Thus, I’m sort of back to my first question. Does the 12mA max draw also apply to the 5V Wemos pin? If it does not, what is the max rating for this pin?
I’m really a novice here, and although things are working now, I’d like to understand if I’m putting the components in a less than desirable position (operating them at too high an amp draw). Thanks for taking the time to read this. Any and all help is GREATLY appreciated.