Thread: Developments in Dust Sensor tech

I presume you got it via eBay? If soI would demand a full refund, if they can't pack it properly that is not your fault.
If they refuse, take it up with ebay - they will back you

Thanks Bob, I am aware of that, I am just giving them the option to send me a replacement screen. I bought it from ebay, using the link you posted.
I think if I return the unit, I have to pay the postage to return it to China.

Originally Posted by HardingPens

Thanks Bob, I am aware of that, I am just giving them the option to send me a replacement screen. Otherwise I think I have to pay the postage to return it to China.

Humm . . . . I doubt you should be made to pay for anything that is not your fault. I have not had to pay for return postage on similar situations.

https://www.ebay.ca/itm/292304859123#rpdCntId

The listing says the buyer has to pay return postage. I am not sure if that still applies for a damaged item.

Originally Posted by HardingPens

https://www.ebay.ca/itm/292304859123#rpdCntId

The listing says the buyer has to pay return postage. I am not sure if that still applies for a damaged item.

Check with ebay .

The vendor did the right thing and gave me a full refund today. Thanks for your help Bob.

Sometimes you just have to push them a bit.

Brad are you ordering another or waiting until something else is available?

Pete

This morning when I walked into the shed on the morning I noticed that the dust sensor (Plantower 7003) that sits at about 2.1 m above the floor in the metal working end was reading a constant ~75 ug/m^3 (PM10). The other unusual thing was the PM1, PM2.5 and PM10 values were all very close to each other.

Irrespective I what I do the day before, the usual reading after leaving any dust to settle overnight is under 10 ug/m^3 and it can be as low as 2 ug/m^3. I then took the sensor outside and it still read the same so I thought there must be some smoke about but when I brought down another dust sensor from the house it was reading around 7 ug/m^3.

Tapping the sensor sent the dust values up to the max values (~5000 ug/m^3) and they stayed at these values until I turned the sensor off/on.
On turning back on, sometimes it read all zeros, other times around 75 ug/m^3 and sometimes the 5000 5 ug/m^3 (PM10). It was like it was stuck in those three modes.
After turning it off/on multiple times the sensor now read zero all the time.
I replaced the sensor with a new spare and everything is working again so its not the rest of the particle counter circuit.
Basically I think the old sensor is stuffed.

My initial though is that the sensor had become contaminated with something. That sensor had been in the metal working end of my shed for about 3 months during which I had done quite a bit of metal work. The lathe and mill use a metal coolant lube so the amount of dust these generate is low but they do emit some oil vapour. What does generate a lot of dust is welding/cutting/grinding/sanding. Although I have a welding bay fume hood this does not capture all the dust from angle grinding and cutting. The angle grinder especially throws dust right across the shed. Welding dust capture depends on the size of what is being welded and as I had been welding up a bench from galvanised SHS some welds were done outside the range of capture of the fume hood. I can see some ZnO fumes rise up and travel across the ceiling but eventually these too were extracted over time.

Thinking back on what I had done I think it could have been any of the welding/grinding/cutting. Welding fumes would be my first bet as these are sticky and have probably coated the insides of the sensor, but it could also be a solvent/oil/paint of some kind. Anything sticky that covered the laser or laser sensor could be a problem.

The Mean Time Between Failures for the Plantower 5003/7003 series of sensors is supposed to be 3.5 years and this one was only just over 15 months old although I don't believe they are designed to operate continuously in an aggressive metal working environment.

Anyway fortunately I had a spare sensor but this could serve as useful information for those that have these types of sensors to not leave it running continuously. I'm thinking especially that they may be affected by some finishes etc.

Yeah I mounted mine on the wall, permanently plugged in to a power point, but my shed has a central switch so I just turn everything off when I get out and back on when I get in.

Originally Posted by Spyro

Yeah I mounted mine on the wall, permanently plugged in to a power point, but my shed has a central switch so I just turn everything off when I get out and back on when I get in.

Not a bad idea although its unlikely to become contaminated when you are not there. It's more about what you do while its on. I'm thinking its not a good idea to have it one when any finishes are being applied or large amounts of glue are being used.

Originally Posted by BobL

.....

Basically I think the old sensor is stuffed.

My initial though is that the sensor had become contaminated with something.

......

Thinking back on what I had done I think it could have been any of the welding/grinding/cutting.

Anyway fortunately I had a spare sensor but this could serve as useful information for those that have these types of sensors to not leave it running continuously. I'm thinking especially that they may be affected by some finishes etc.

Good to know, Bob.

Here's a fine dust sensor that has some data storage capability and doesn't cost an arm or leg US($148)
https://www.ebay.com/itm/HT9600-PM2-....c100005.m1851
Screen Shot 2019-05-02 at 7.42.08 am.png

Data storage and averaging is useful because you don't want to or cannot sit and watch a meter while you work.
It also has a recharable battery

If you want to just get instantaneous readings then these are ~US$40
eg https://www.ebay.com/itm/Household-P...sAAOSwCA5cf5xF
You have to provide a USB PS for this one.


Once again all these devices are very sensitive. if you poke it directly under a stream of very fine dust or leave it running for too long (ie weeks) you will kill it.
Best to keep it at least 1 m from a fine dust source and only run it for a few hours at a time in a WW shed.

Originally Posted by NeilS

My cyclone is the Pentz design with a cone ratio of 3:1

Attachment 438737

I had occasion to look inside the drop bag below my filter this last week; the second time in 13 years.

This is what I found....

drop bag dust 2019.jpg

B-all of b-all, and no, I didn't find the 50c piece in the drop bag. that was added for scale.

The telling bit are those few shavings on the right. If you allow the collection bin below your cyclone to overfill your cyclone will inevitably clog up and that will eventually be drawn through the impeller and into your filter/drop bag!

I had it happen once before, probably six years ago, and that time I got half a cup of dust and shavings before I realised what had happened. This time there was hardly enough to cover the bottom of a cup, so I was on to it almost immediately.

As far as I can see, if I don't let the cyclone clog up there is no visible dust or debris coming through to the filter. Of course, it is not the visible dust that is the concern for our health, but from my particle sensor readings that I reported on earlier in this thread I also appear to be avoiding much of the fine particles.

The message for me is to keep an eye on how full my collection bin is below my cyclone.

If you are getting any more than this in the drop bag below your filter then I reckon your cyclone setup is not optimised in some way.

I believe that the 3:1 cone ratio on my cyclone is a significant factor in its efficiency. I say efficient based on two observations:

1. The sensor readings I reported on earlier in this thread, taking into account that the particle sensor I'm using under-reads by 50%
2. How clean all the horizontal surfaces are inside my filter housing, which is a contained area below my workshop floor. Not a scientific observation, but it was an indicator that the dust wasn't completely out off control before I acquired the particle counter and was able to take some measurable readings.

I understand that few home workshops can accommodate a 3:1 cone ratio cyclone, but I'm reporting on my findings here for anyone who is considering a cyclone and has the height to accommodate the 3:1 ratio, which is Bill Pentz' preferred ratio if you can manage it.