ESP32 Forum

Hello people,
I'm making a wearable device using a vroom 32 and the arduino framework.
I would like to ask some questions about the board but I'm a web developer and I don't have too much knowledge of the mcu jargon so many thing may slip my understanding, so please in your answers, if able tell me what keyword should I look for.

• I can see that even when I have the wifi and bluetooth turned off that the module is getting hot. I have two considerations about this. First of, the device I'm making is going to be wearable and I think that it could potentially cause some discomfort. Secondly, as the device is going to be powered with a LiPo battery, I fear that it could become somewhat dangerous. Now, I've read on the esp32 datasheet that the processor can be used in 2MHz frequency (I suppose the heat is dissipated due the fast nature of the processor) is this really possible? Should it make some difference?
• I want the device, when it is "turned on" to record some events with timestamps. For that I plan to check the time with my phone via the bluetooth and an app. When the device has been used for the spell of time the user needs it, it should fall into sleep mode. Can I keep track of the time when in sleep mode?
• Can I store data to the device (on normal, not sleep mode), along with the timestamps, so I can request them later via bluetooth?

Thank you!

The device can be set to 80MHz (this is an option in the Arduino IDE), which will reduce the temperature (along with the processing speed). Below 80MHz, you are not able to use WiFi/BT. When in deep sleep, the device will use much less power and generate much less heat.
The internal Real Time Clock (RTC) can operate through deep sleep, maintaining time. However, it has a high drift, and should be synchronized against an external time source (NTP) at least once a day. See https://github.com/lbernstone/NTP_sleep
You can store whatever data you want on the device. There is 4-16MB onboard flash, which can be partitioned between applications, and data storage.

Thank you for your answers!
Another question is this:
I need for my project a vibration motor. The vibration motor says that it uses 78mA to operate in its fullest.
The esp32 says that on the 3V pins it can output 50mA. Is that the case, or am I reading something wrong? What could I do to circumvent this issue?

Thank you again

For clarity reasons, I include the table of the vibration motor
Voltage [V] 3
Frame Diameter [mm] 10
Body Length [mm] 3.4
Weight [g] 1.2
Voltage Range [V] 2.5~3.8
Rated Speed [rpm] 12000
Rated Current [mA] 75
Start Voltage [V] 2.3
Start Current [mA] 85
Terminal Resistance [Ohm] 75
Vibration Amplitude [G] 0.8

Just use a small transistor or mosfet to switch the vibration motor. (Also add a flyback diode.)

Yeah, but should I take power from the 3V pin?

terumi wrote: ↑

Tue Sep 08, 2020 7:41 am

Yeah, but should I take power from the 3V pin?

To add to what Ibernstone said about controlling the motor with a mosfet or transistor, you will want to feed the ESP32-WROOM-32 with a stable 3.3v power supply, generally a "LDO" voltage regulator coming from the battery. That being said, you can just directly wire the positive lead of the vibration motor to the batter + terminal, since it's presumably 3.7v, and control the negative terminal of the motor via an N-channel mosfet.

Hope that helps!