I'm using a DFRobot Firebeetle 2 (ESP32-WROOM-32E) and have been using the 3.3v pin to connect various components. However, I have a water level sensor which needs 5v (one of the boards with copper traces used to detect water). The Firebeetle has a VCC pin which supplies 5v when connected to USB or 3.7v when connected to a Li-ion battery, but I don't think this is regulated. I've looked at the schematic, but to be honest it's too advanced for me; I'm only just starting out. The schematic of my board can be found here: https://dfimg.dfrobot.com/nobody/wiki/fd28d987619c16281bdc4f40990e5a1c.PDF
The manufacturer's wiki also states the following:
GND: common ground for all power and logic
VCC: positive voltage of USB/li-ion battery input(5V-output USB voltage when powered by USB; 3.7V-Output battery voltage when powered by Li-ion battery)
3V3: output of 3.3 voltage regulator, can provide 500mA peak current
My question is, can I just hook the water level sensor up to the VCC pin or do I need do anything differently due to the presumably unregulated power? (or for any other reason). I'm using USB to power the board. I'd also like to move my piezo buzzer from 3.3v to 5v to try to get a little more volume.
The water sensor came with an Elegoo Uno R3 starter kit and the board isn't branded. The 'so called' data sheet that came with the kit doesn't give much info. It's more of a tutorial than a data sheet, but I've attached it anyway. Water Level Detection Sensor.pdf (183.6 KB)
I've just noticed that the images in the PDF show 'Funduino' on the board which isn't on my board so I can try to find something for that online.
@jim-p So, does regulated just mean it's definitely 3.3v or definitely 5v etc? and unregulated an be a range like 4.75v to 5.25v? If that's the case, how do you calculate the resistance required if the voltage could vary?
It is UN-REGULATED
If you are using USB to power the board, then Vcc will be whatever the USB voltage is. Somewhere between 5.25V and 4.75V
That's 5V +/-5%. Most devices specified for 5V can tolerate a +/-5% variance.
No need for a resistor
Ok, thank you. I've just looked for more info on the 'funduino' water sensor and although I can't find a data sheet, I found some sites and videos suggesting it will work with 3.3v, so I hooked it up to my UNO and tried 5v then 3.3v and it worked on both. So I clearly did something wrong when I hooked it up to the ESP. I'll have another go with 3.3v on the ESP first and try 5v if I don't have success.
I havent used one of those sensors but I'd not be happy with it. The "water" could have almost any restiivity and you may get corrosion and electrolysis. Also if the "water" isnt isolated it could form a connection to something else.
Thanks for the advice. I plan to use the sensor in a drip tray which sits underneath a wall mounted air-con in the server room at work. It has leaked once in the past but there shouldn't be water in there for any extended period of time. It's an aluminium tray and if I was to guess, I'd say it's probably about 2 inches deep and maybe 2-3mm thick (I'm not at work to check). What would you recommend I use to detect a leak?
You need a pair of electrodes that will detect when there is water between them.
The Al tray needs to be electrically isolated as eg if it was at mains live potential it would fry anything you connected to it. I'd guess that wouldnt be a problem.
If it was you could insulate it externally (or put a plastic tray inside.)
You could use my soil moisture detector circuit to detect the water.
maybe tilt the tray so the water would gather at one end?