||Introduction||
I am using a ESP32-WROOM-32 board and I was looking to confirm the method of powering up I was going to use was correct so I don't actually fry my board.
I have around 9 to 10 temperature sensors that I am reading data from. All of these are connected to the 3.3V pin of the board.
I have 1 SD Card module that is writing the data received from the sensors onto the SD Card. This module is connected to the 5V pin on the board.
||Requirements||
Ideally, we are looking to read data with 20 minutes intervals for approximately 10-12 hours. The code works right now with all the sensors. I want to make this remote so I don't have to sit with the board connected to my computer. I am unsure whether or not I could run my board for the duration we would like to run the system for.
||Solutions||
I was looking into options that I can solve my problem with and I found 2 solutions that I could use.
One was to connect a 9V battery to the 5V pin of the board directly and have the default ESP voltage regular to control the voltage. PS: I would have to do that in parallel connection since I already have a module connected to that pin.
Second was to use an external voltage regulator and connect that to the 3.3V pin on the ESP board. With a battery pack connected to the voltage regulator module.
||What I want||
I would like to know based on my uptime requirements, what is the best solution for my case. I was also wondering if I do decide to go with the 2nd solution of providing the board with 3.3V, would I be able to provide 5V to my SD Card Module?
||Extra Information||
This is an image of what my board looks like. There are a few connections missing. Basically, most of the left side pins will be populated.
The reason to show this image is that there are multiple variations of the ESP board and I don't have a designed Vin port in the board unlike Arduino or other boards.
I actually read this on a website and they wrote that the ESP boards have a built in voltage regulator that works out the voltages itself. I haven't used an ESP board before. I used to directly connect the battery pack to the Arduino board.
If I have to use an external voltage regulator, what would you suggest I use, a 3.3V regulator or a 5V regulator?
Some ESP32 based development boards have "Vin" where it is 5V in your board, so that this pin is connected to a linear regulator (AMS1117 in general). I can't say what is yours by the picture of post #1.
the regulator will dissipate the excess input voltage as heat. So, the higher the voltage you apply to "Vin", the less current you can push from the board in order to not exceed its limits. Since 5V is printed in your board I agree with @UKHeliBob and I wouldn´t put anything much higher than that on the pin.
You didn´t tell what are the temperature sensors, but you can find their specs and see their current consumption. Then, multiply it by ten and sum the SD Card to see if the board can handle this value. As an example, DHT11/22 needs 2.5mA while measuring. That means ~25mA for the 10 sensors, plus ~100mA for the SD card, which is ok to feed with 5V or 3V3 pins.
Considering that you´ll need 5V to the SD card, I would use an external 5V voltage regulator to feed the board and the SD card. Then, use 3V3 of the board to feed the temperature sensors.
Easiest way would be using buck converter to step down battery pack voltage to 5V and use that to power both Esp and SD card.
Even some good quality powerbank might work.
You are right, sir. I have seen images where there are ports for Vin on some boards. However, mine does not. This is why I specifically shared the photo of my board so people don't confuse it with other boards.
I was thinking of providing said voltages to the 3.3V pin or the 5V pin. I was just unsure if I could power up the board by supplying external power via those pins. You know like I have been powering up my sensors via those pins. I was unsure if I could revert this by supplying power directly to the pin and powering up the sensors and the board simultaneously.
As for the sensors, I am using MAX6675 thermocouples. I have looked at their datasheet and they are rated 50mA if I am not wrong. So, 6 of these sensors would need about 300mA. We will also be using an I2C 20x4 LCD which needs around 8mA to 10mA. With SD Card included, we would need around 300mA + 10mA + 100mA = 410mA. There are 2 more sensors that we are looking in to include in the circuit as well but we are not sure at the moment. Let's say that I need around 600mA at max, what will be my voltage requirement? (I would be using a voltage regulator within the circuit connected to the 5V pin).
Update:
During the time since I posted here, I did have an idea of using the micro-USB port of the ESP32 board. At the moment, I am connecting the ESP board to my computer via a micro-USB port, my computer is powering up the board and the sensors and letting me push code to the board via that port. I was thinking that I could connect a power bank for example and only utilize the powering up feature through the port. I would cut out all of this complexity, the voltage regulator and stuff, what do you think? Will that work?
I was wondering if I could power up the board using the micro-USB port available on the ESP board instead of going through the hassle? I actually have to go and buy the additional electronic that I need for this.
PS: I have explained a little more if my above post, you can look into that for reference.
I was wondering if I could power up the board using the micro-USB port available on the ESP board instead of going through the hassle? I actually have to go and buy the additional electronic that I need for this.
PS: I have explained a little more if my above post, you can look into that for reference.
You don't have to answer us separately...
Yes, you can power your board from micro-usb as long as it's stable 5V.
Like I wrote before, even good quality powerbank might work.
"Might" because it depends on specific powerbank, some of them expect to charge a battery and shut off when current is too low. You can try, it doesn't hurt.
Ps. it's not good idea to power 500+ mA of sensors from devboard pins. You don't have pins enough in your board anyway, so why not to wire your power supply output to some pin header for distribution?
Okay sir. I am new here so I thought the notification wouldn't reach you unless I reply to you. That's my bad.
I might try out the powerbank option first since it will save me resources and much time.
Additionally, you are right. I should not strain the ESP board too much. However, the thermocouples will actually go onto the 3.3V pin, for which I would need a buck converter since I will be using a 5V power bank.
Should I try out powering the sensors with the ESP board first? What do you suggest?
I'm not saying that you can't do it, make sure that voltage regulator is not heating too much.
I wouldn't expect that your temp sensor modules draw so much (50mA). Do you have some documentation? How are you planning to "split" your 3.3V for all you sensors?
edit:
If you mean SO max 50mA on max6675 datasheet, it means that it's the max current that chip can handle on serial output pin.
The chip shouldn't draw more than 1.5mA
