Dust sensor throwing different values on change of usb cable

Praveena
Posts: 4
Joined: Wed Sep 26, 2018 6:07 am

Dust sensor throwing different values on change of usb cable

Postby Praveena » Wed Sep 26, 2018 6:20 am

Hello,

I have a dust sensor from Honeywell [https://sensing.honeywell.com/honeywell ... 0-e-en.pdf][ and which is connected to Vin(5v) of esp32 dev board. The problem I am facing is sensor throwing different values when I change USB cable which I use to power on esp32. Different cable is giving me different values but sensor works fine when I use it with Arduini uno.
I also use esp32 WIFI and BLE which are switched on all the time.
Can someone please explain to me what am I missing here?

chegewara
Posts: 1234
Joined: Wed Jun 14, 2017 9:00 pm

Re: Dust sensor throwing different values on change of usb cable

Postby chegewara » Wed Sep 26, 2018 6:58 am

According to datasheet this sensor requires only 80mA, it is not much. But using ble + wifi, especially during initialization, is using more. Usually its causing brownout. Could you try to test it without wifi and ble?

Praveena
Posts: 4
Joined: Wed Sep 26, 2018 6:07 am

Re: Dust sensor throwing different values on change of usb cable

Postby Praveena » Wed Sep 26, 2018 7:11 am

I tried without wifi and BLE on but the same issue. Brownout issue is another issue I am facing but not that frequent but when that happens device goes to a reboot loop.

ESP_Sprite
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Joined: Thu Nov 26, 2015 4:08 am

Re: Dust sensor throwing different values on change of usb cable

Postby ESP_Sprite » Wed Sep 26, 2018 8:40 am

The fact that you have brownouts indicates that you have a power supply setup that has voltage sag when some current is drawn, possibly because of thin USB cables. This may also affect the output of your dust sensor. Can you try to see if supplying external voltage to the board, e.g. by using a lab power supply, solves this issue?

costaud
Posts: 55
Joined: Wed Dec 30, 2015 5:09 pm

Re: Dust sensor throwing different values on change of usb cable

Postby costaud » Wed Sep 26, 2018 8:40 am

I think you can connect a oscilloscope to check the voltage of the 5V pin.
When RF circuit is working, it might take more current.

Praveena
Posts: 4
Joined: Wed Sep 26, 2018 6:07 am

Re: Dust sensor throwing different values on change of usb cable

Postby Praveena » Wed Sep 26, 2018 8:49 am

ESP_Sprite wrote:The fact that you have brownouts indicates that you have a power supply setup that has voltage sag when some current is drawn, possibly because of thin USB cables. This may also affect the output of your dust sensor. Can you try to see if supplying external voltage to the board, e.g. by using a lab power supply, solves this issue?
I don't have a lab power supply at home but I tried few android mobile chargers. I have the android chargers(all are 2A) from XIOMI, LENOVO, SONY and I get a perfect reading with SONY charger and weird reading from the other two.

Praveena
Posts: 4
Joined: Wed Sep 26, 2018 6:07 am

Re: Dust sensor throwing different values on change of usb cable

Postby Praveena » Wed Sep 26, 2018 8:50 am

costaud wrote:I think you can connect a oscilloscope to check the voltage of the 5V pin.
When RF circuit is working, it might take more current.
I checked in my multimeter and in all cables it hovers between 4.6V and 4.7V

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