How do I stop my UV sensor using the battery through VDD until I want it to? It's connected using TWI headers.

Question

I'm using the nRF52 DevKit with nrf52832 SoC. I connected a UV Sensor through the TWI interface (PINS 26 & 27, as well VDD and GND). 
 However, I fear it's using a lot of battery energy. So, I power down the TWI interface using the nrf_drv_twi_disable() and nrf_drv_twi_uninit() functions until I want to read the sensor. At which time I power it up again. 
 My question is, will calling these functions stop the sensor from using the battery? If not, please suggest how I can stop it from using any battery energy until I want to power it up and use it. 
 Thanks, and I'm looking forward to your response. 
 John

Keith Wakeham · Accepted Answer

Turing off the TWI interface only disables the interface on the nrf52832 chip. It very much depends on how the UV sensor operates to know if it's drawing current. So an evaluation cannot be made unless the type of uv sensor is known. 
 Usually the sensors have a shut down / sleep / low power command to them. This usually drops, but doesn't completely eliminate current draw. In some cases it gets it down to low microamp range. Except in extreme cases of power savings it's usually fine. Find out if it has it and send it before disabling your TWI interface. 
 You can alternatively control it's VDD supply via a fet.

John the novice · Answer

Thank you so much for your response, Keith! 
 The UV sensor I'm using is the VEML6075 https://cdn.sparkfun.com/assets/3/c/3/2/f/veml6075.pdf 
 I'll see if there's a way to put it to sleep. 
 What is a fet?

Keith Wakeham · Answer

The doc indicates that you set SD bit 0 for UV_CONF register to power on or shutdown. This changes consumption from power on (480ua) to shudown (800na, or <1ua). So this should do it. 
 Fet as in MOSFET. Probably a P-Fet high side arrangement to completely shut it down.

How do I stop my UV sensor using the battery through VDD until I want it to? It's connected using TWI headers.

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