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AStoe1
Novice
1,753 Views

Digital sensor has different behavior on battery vs. wall plug

I'm using this sensor:

http://www.seeedstudio.com/wiki/Grove_-_Dust_Sensor Grove - Dust Sensor - Wiki

I discovered something interesting with the dust sensor: I get very different readings and consistency of readings when the board is plugged in via the wall plug vs. my portable cell-phone charger which I use with the breakout board and has always worked fine. I also have a temperature sensor, analog, and its readings are the same with both sources of power, but not the digital dust sensor (plugged into D8, as required in the specs). I get lots of zero readings with the wall charger, and the fluctuation in readings is extreme, but when using the USB-in with my portable charger my readings are more consistent and never show the zeroed-out issue.

This sensor plugs into a digital port so I would not think electricity fluctuation had a role, but obviously is does.

Can anyone advise on why this might be and how to address it?

15 Replies
idata
Community Manager
143 Views

Hello andso,

 

 

According to section 4.12 of the Edison Compute Module Hardware Guide (http://www.intel.com/support/edison/sb/CS-035274.htm http://www.intel.com/support/edison/sb/CS-035274.htm) the max output current of Edison is of 100mA. And according to http://www.seeedstudio.com/wiki/Grove_-_Dust_Sensor http://www.seeedstudio.com/wiki/Grove_-_Dust_Sensor the normal operation current of the sensor is of 90mA. Therefore the power supply you use will indeed impact the operation of the sensor, I mean the less power the PSU provides, the less Edison will be able to provide. The behavior you are seeing could be related to this, what are the specifications of both PSUs?

 

 

Peter.
AStoe1
Novice
143 Views

I am using the power adapter that is included with the Grove Starter Kit. It is rated at output: 12V 2A. Then I'm using a mobile USB charger that is rated at output: 1A - 2.1A (as it is labeled).

idata
Community Manager
143 Views

Do you have access to a multimeter or any other measuring tool? If so, could you verify that both chargers are functioning properly?

 

 

Peter.
AStoe1
Novice
143 Views

I do not have any such item, perhaps I should pick one up.

AStoe1
Novice
143 Views

I'm looking at this multimeter to buy:

https://www.kiwi-electronics.nl/compacte-digitale-multimeter-72-7770?search=multimeter https://www.kiwi-electronics.nl/compacte-digitale-multimeter-72-7770?search=multimeter

However it is unclear to me how I could use it to test a charger that only has a USB port for its output.

Also, the wall plug, which is rated higher output, also seems to definitely provide more juice, because the LCD on the breakout board has much darker pixels when plugged into the wall, so I doubt the wall plug is providing insufficient juice. However, the errors I see are with the wall plug, so is it possible that too much juice is getting delivered to the sensor to cause problems? Or would the board block excess juice?

The other explanation might be that the wall charger is providing the correct amount of juice and that the zero readings that occur every minute or so are in fact correct, and that the more consistent readings with my USB charger are the inaccurate ones. But I doubt this; the dust level in a room doesn't suddenly drop to zero every minute or two when the other readings are thousands of particles per liter.

idata
Community Manager
143 Views

You could measure it through the soldered pins on board by following the Micro USB pinout:

As you mentioned, the wall charger could be providing just enough voltage but it could be lacking current. The opposite case might be happening with the USB charger, who may be providing just enough voltage but is able to provide more current.

 

It would be really helpful if you could measure the actual output of both. Also, do you have access to another wall charger? It'd be interesting to see what happens if we test it, we could check if the readings are congruent with either the current wall charger or the USB charger.

Peter.

idata
Community Manager
143 Views

Hello andsto,

 

 

Are you still having issues when using the wall plug?

 

 

Peter.
AStoe1
Novice
143 Views

Yes, And a friend of mine with identical hardware (edison, board, same sensor, same Grove wall plug) has identical problems: With the wall plug, the sensor frequently reads 0, which is simply incorrect. On a USB battery, it behaves as expected. Same symptoms for both of us.

idata
Community Manager
143 Views

Hello andsto,

 

 

Please let us investigate what could be the issue here. I will post any updates here if I find anything helpful.

 

 

Peter.
idata
Community Manager
143 Views

Hello andsto,

Do you have access to a digital analyzer or an oscilloscope? We would like to check and compare the signals in both scenarios, when the Edison is powered from the wall charger and when it is powered through the USB charger.

Peter.

AStoe1
Novice
143 Views

Hi Peter,

Unfortunately I do not have either of those tools, and I doubt my friend with the same hardware and symptoms has those either.

idata
Community Manager
143 Views

I understand, please let me investigate what could be happening.

 

 

Peter.
idata
Community Manager
143 Views

Hi andsto,

 

 

We tested the sensor with an Arduino expansion board (and on an Arduino Uno) using the sketch provided in the Seeed website and sensor seems to be behaving as expected.

 

 

The board was powered using an external power supply (12V-1Amp) and Micro-USB (5V-.5Amp). Following the instructions provided in the website, the sensor preheated for 3 minutes when used for the first time. According to the website http://www.seeedstudio.com/wiki/Grove_-_Dust_Sensor getting readings of zero is an expected behavior.

 

 

The dust sensor is not very sensitive to low particle levels, so in order to make this sensor more sensitive you could use a fan and a 10kΩ resistor between pin 5 and ground.

 

 

All this information can be found in the website, I encourage you to take a closer look at the sensor's documentation. If you are still experiencing issues with the sensor, could you please provide us with the code you're using, the expansion board you're using and how you are wiring the sensor? Please be as detailed as possible, every detail will be of much help.

 

 

-Peter.
AStoe1
Novice
143 Views

Hi Peter, thanks for looking into this! Just to clarify, you received the same dust sensor readings with the power adapter as with a USB battery charger? For us, the power adapter readings are similar to what you report, but with 2 different batteries on 2 different rigs, the behavior of the sensor is very different. The batteries have ample power (I have one that powers an iPad Pro and is rated at 1-2.1 A) and other sensors such as the temperature sensor do not change behavior between power adapter and battery.

idata
Community Manager
143 Views

Hi andsto,

 

 

There are zero readings on both tests, I'm not sure if this is what you are referring to. Below are the details on what we used for the test and how the test was performed. It might not be the optimal environment as is only running for a short period of time and the dust sensor was just sitting on the desk. Also, we had to change the program language from Arduino to C++ since the board cannot output data to the IDE's serial monitor when powered via USB (with USB battery charger).

 

Is this what you are referring to? If it isn't, could you please share the details of your setup (wiring, source code, which expansion board is being used, etc.) so we can try to replicate his issue.

 

 

First test:

 

1. Edison Kit for Arduino

 

2. Board powered using external power supply (Output: 12V-1.25A)

 

3. Running cpp example provided in the IoT Developer Zone website: https://software.intel.com/en-us/iot/hardware/sensors/ppd42ns-dust-sensor

 

4. Program ran for about ~5 minutes.

 

5. Dust sensor draws about ~73.3 mA

 

6. These are the output results of the test:

 

root@edison:~# ./dust

 

This program will give readings every 30 seconds until you stop it

 

Low pulse occupancy: 322448

 

Ratio: 1.07483

 

Concentration: 556.506

 

Low pulse occupancy: 0

 

Ratio: 0

 

Concentration: 0.62

 

Low pulse occupancy: 0

 

Ratio: 0

 

Concentration: 0.62

 

Low pulse occupancy: 627830

 

Ratio: 2.09277

 

Concentration: 1082.3

 

Low pulse occupancy: 1009112

 

Ratio: 3.36371

 

Concentration: 1748.62

 

Low pulse occupancy: 183355

 

Ratio: 0.611184

 

Concentration: 317.267

 

Low pulse occupancy: 288224

 

Ratio: 0.960747

 

Concentration: 497.676

 

Low pulse occupancy: 315229

 

Ratio: 1.05076

 

Concentration: 544.098

 

Low pulse occupancy: 164195

 

Ratio: 0.54732

 

Concentration: 284.268

 

Low pulse occupancy: 303456

 

Ratio: 1.01152

 

Concentration: 523.862

 

 

Second test:

 

1. Edison Kit for Arduino

 

2. Board powered using USB Battery charger with 3000mAh capacity (Output: 5V-1A)

 

3. Running cpp example provided in the IoT Developer Zone website: https://software.intel.com/en-us/iot/hardware/sensors/ppd42ns-dust-sensor

 

4. Program ran for about ~5 minutes.

 

5. Dust sensor draws about ~67.5 mA

 

6. These are the output results of the test:

 

root@edison:~# ./dust

 

This program will give readings every 30 seconds until you stop it

 

Low pulse occupancy: 2664415

 

Ratio: 8.88139

 

Concentration: 5089.81

 

Low pulse occupancy: 422081

 

Ratio: 1.40694

 

Concentration: 727.769

 

Low pulse occupancy: 3105354

 

Ratio: 10.3512

 

Concentration: 6196.08

 

Low pulse occupancy: 1350245

 

Ratio: 4.50082

 

Concentration: 2364.36

 

Low pulse occupancy: 0

 

Ratio: 0

 

Concentration: 0.62

 

Low pulse occupancy: 0

 

Ratio: 0

 

Concentration: 0.62

 

Low pulse occupancy: 1299530

 

Ratio: 4.33177

 

Concentration: 2271.25

 

Low pulse occupancy: 680652

 

Ratio: 2.26884

 

Concentration: 1173.7

 

Low pulse occupancy: 217609

 

Ratio: 0.725365

 

Concentration: 376.23

 

Low pulse occupancy: 0

 

Ratio: 0

 

Concentration: 0.62

 

 

-Peter.
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