Question: What happens to the simple air sensor when the battery pack runs low?

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stevie asked on May 20, 2019 18:10
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Interested in thinking about things that can happen in demoing/using a simple air sensor.



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I recently heard from a community member that "we had another embarrassing moment when the “power bar” battery apparently didn’t have enough energy, as no change from green was seen even with high particulate levels :("

Anyone else experience this or have thoughts as to why this happened?

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@OrionAllgaier were you there for this? can you shed some more light on what happened?

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Hi Stevie, I was was there for that. To the best of my memory the simple air sensor turned on and displayed white light compared to the normal green, yellow, and/or red. Once the battery pack was plugged in and charged the sensor functioned properly again.


Wow, I wouldn't have guessed that it'd show green with low power (i.e. no reading from the sensor, i'd imagine), so hearing that it turned white instead is really helpful. I wonder if we should generally say "if you see it turn white, that's an error"?

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Wow amazing article dear, I found what I was looking for, thanks for sharing this information


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I haven't seen this happen in part because it runs a /long/ time on a battery, but I have seen it when running on a solar panel without enough sunlight. It would fail and reboot every second or so, so the light would blink. 

Recently we changed the firmware so that it waits 2-3 seconds to start up. The idea was that it'd try to run for 2-3 seconds, before turning the light on, so that it could "test" whether there's enough power. And if there was, it'd start showing a light. Otherwise, it'd just stay dark (although you may see some of the really tiny lights blinking as it boots up). 

That way, if power is too low, it wouldn't annoyingly blink a lot, but rather would reboot over and over but never get to the point where the light goes on. We're still testing how well this works. 

On Mon, May 20, 2019 at 2:10 PM \<notifications@publiclab.org> wrote:

Public Lab contributor stevie just posted a new research note entitled ' What happens to the simple air sensor when the battery pack runs low?':

Read and respond to the post here: https://publiclab.org/notes/stevie/05-20-2019/what-happens-to-the-simple-air-sensor-when-the-battery-pack-runs-low


Interested in thinking about things that can happen in demoing/using a simple air sensor.


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Thanks @Warren (and @Stevie) for this info. Recently I fully charged the battery bar but after plugging in the "traffic light" sensor, the display stayed white even with high generated PM2.5 levels.

Your ability to create a light and small Plantronics sensor-battery combination is nonetheless very interesting: if the sensor could also write data to an SD card (as it does in PurpleAir SD models), I would like to know how much this all weighs and contact my two drone pilot colleagues. If feasible, I think it would be fascinating to measure PM levels at different altitudes and positions relative to a frac sand mine.


Hi, @crispinpierce - can you check that the white connecter is fully inserted? I noticed the white light happens also when that cable comes loose. If that still doesn't work, please post a photo and we can help you debug or we can swap you for a new one.

We can add an SD card logger for about $15, i believe. It does add complexity and some weight, although nowhere near the weight of the battery, which is the main contributor to weight.

We have also brainstormed some cheaper/lighter options for logging without an SD card, but it's not clear if they'd meet your needs: https://publiclab.org/notes/warren/04-02-2019/can-we-log-data-on-an-arduino-without-an-sd-card

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Hi @Warren, Thanks so much for the quick follow up. Here are photos of the unit fully plugged together, showing white after several minutes of warm up (was expecting green) and after corn starch particulate generation (was expecting red).

65246806_382598882375726_7248456081704222720_n.jpg

65094784_359901081573530_3138598203964784640_n.jpg

(I'm not sure if images are uploading after drag-and-drop.)

I would be VERY interested in a Plantronics/battery bar/SD card unit we could load on a drone (if the SD card portion were lighter than the battery bar, I'm sure this can work). We can certainly afford the cost you suggest.

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Hi @crispinpierce - that's great to hear about your interest in the SD card logging. I'll see what we can get together.

The images showed up perfectly, and the ribbon cable looks OK. I wonder if, without a housing, it's just gotten bumped around a bit. If you want to send it back to us at:

Public Lab 55 Cromwell St 1C Providence, RI 02907

We can replace it or fix it. Thanks!


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