Battery operated: Best way to cut VCC to sensors

Community General Discussion
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I want to control mty BBQ temperature using ESP32 and MAX6675 type k thermocouple sensors and few NTD temperature probes.

I want to extend my battery life for the duration of the cooking , up to 10 hours, by cutting power to the sensors. I want to wake-up them every 2 seconds and shutting them the rest of the time.

I read that I could use a mosfet, but I dont get how to install them using a 3.3v from the dc converter.

Any info or link appreciated

Martin

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The ESP32 consumes far more power than the sensors, so to save the most battery life, investigate deep sleep modes.

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Hello Jremington

For shure I will use the sleep mode for the ESP whenever it is possible. I do plan to have up to 5 temperature probes, some LED, WiFI and/or Bluetooth. I want to operate from a single 18650 battery for an extended period.

Martin

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Keep in mind that you cannot connect output pins on a powered up MCU to an unpowered sensor module, otherwise both can be damaged. At the very least you can expect malfunctions.

That is why most sensors offer sleep modes as well.

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Hi, @arjfca

Will you be using WiFi or a display at the ESP32.

Have you built your project for a proof of concept and measured the current being consumed?
Just a project without any sensor supply disconnection circuitry.

Tom.. :grinning: :+1: :coffee: :australia:

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You could look at this: Adafruit TPL5110 Low Power Timer Breakout : ID 3435 : $4.95 : Adafruit Industries, Unique & fun DIY electronics and kits . I've no personal experience but have seen it recommended in such situations where the application sleeps most of the time but wakes occasionally to take measurements, sends results somewhere then resumes sleep. Is the DC converter you mentioned also powering the ESP32?

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True in general, but for I2C you can use an extended level shifter to allow power down. I have been using the circuit in section 2.3.5 for years with no problem.

Probably not much help for he OP since they are not using I2C.

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8

Sorry for the late reply

I realised that the MAX6675 and ADS1115 won't drain too much current when not in use.

So my interogation will be more about two Wheatstone bridges with 100K resistors that will be use whit an NTC food probe (100k)

After looking at the current consumption of a 100k Bridge with NTC, I realised that it may be not significant since my batterie could deliver 2200 MA

Thanks for your input

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