voltage drop with bh1750fvi ?

[huex]

i create a lightsensor sketch with bh1750fvi, i found when power with CR2032, voltage from 2.9v drop to 2.4 or lower, but bh1750fvi required 2.4V, so sensor node can't continue , but later 3-5 seconds voltage recovery to 2.9v

ATMEGA328P-U-TH+ nrf24l01-smd with Customized PCB, Are there any good suggestions for solving this problem? thanks!

[rozpruwacz]

@huex try with new battery

[huex]

@rozpruwacz yes,but new battery also drop 0.4-0.5v like this ,:disappointed_relieved: , this is new battery offer by Two weeks ago.， use it on si7021 node，work well, so 。。。。

[Yveaux]

@huex said in voltage drop with bh1750fvi ?:

bh1750fvi

Supply current of this sensor is 190uA, sleep current only 1 uA. Are you sure this sensor is put to sleep when not operating it (when your node is sleeping)?
Are you using a GY-30 module? These seem to have a voltage regulator on board to support 5v supply levels. Try to bypass this regulator when powering from batteries.

[huex]

@Yveaux thank you ,

i create a pcb with bh1750fvi chip,

i use multimeter measure bh1750fvi v+ pin and gnd ,when power on battery from 2.9v drop 2.1v ,and 3-5 seconds ,up to 2.9v, use a new battery NANFU cr2032， also 3.1 drop to 2.7v，

sleep all is ok , when sleep 7.3ua

but, when down 2.4v bh1750 no work....so。。。i don't how to do,

[scalz]

@huex
coincell internal resistance is higher than others batteries.
so when your mcu is not sleeping or waking up, you'll get voltage drop (even a few mA drained by mcu will drop voltage like you noticed)

To fix voltage drop and extend lifetime:

• use good brand coincells (significantly better specs and lifetime than nonames)
• add a few(2-3) 100uF close to battery pins for buffering, you can even add one close to the radio module.
• use wait() or sleep() in your sketch before reading your sensor (to allow voltage recover)
• you can also use 1Mhz clock for mcu, to use less power when it's not sleeping
• use a sensor with better voltage range
• and so on..

[huex]

@scalz
ok ,thanks , i follow your suggestion to Give it a try，，thank you ,:+1: