I thought maybe the spools that were sitting on my AMS Lite were getting “wet” after being on there a month (PLA Basic). So I got a Sunlu S4 dryer (in case i need to print from it in future summer months). After running one session, the humidity in the dryer in the “maintain” mode was listed at 32% even though room RH is 10%, so i thought, nice, it squeezed some moisture out. But then I was doing another set of spools and dropped in the second RH meter in the dryer.
Anyone know where the S4 senses RH that is displayed on the screen?
The RH meter I got off Amazon says my room is 10%, the meter I put inside the dryer with some filament also says 10% after being in there for 30 min.
Yet the Sunlu dryer says 21%, significant difference.
Your answer lies in your photo. RH is function of how much water vapor the air at a specific temperature can hold. In your case, the sensors show a 10c temperature difference.
However, in the case of your circular hygrometer, it looks like the humidity sensor has failed. the 10% reading is indicative of a failed sensor. I recently found out why. These sensors have a coating on them. If they were mishandled(someone touched them during manufacturing) or somehow the chemical coating was worn off, they will stop reading accurately and eventually fail.
I had both the Creality Pi and Sunlu S2 in my office with the intent to determined which one I was going to keep. The Sunlu S2 failed in an epic way. One in particular was that both dryers did record RH very accurately. You can find that report in this link Sunlu S2 VS Creality Space PI Bake-Off Review
Here’s an example of what I mean. I took multiple sample readings inside the containers and the temp sensors were wildly off. The Creality was the least of the worse but Sunlu was laughable.
Sunlu clearly does not know how to design a dryer. I mean sure, force enough hot air over anything and it will dry, but as a piece of instrumentation? Well… let’s just say this, if they made cooking ovens and I was in competition for Baking, I wouldn’t trust what was on the dial. In a word, their products suck. The S2 was returned to Amazon.
What this shows you is that when you see a YouTuber try to sell you on the notion that this drier does the job, you’ll know their full of Sh*t and really didn’t test it properly. So now you can ask the question, what else are they wrong about?
The dead horse I will continue to beat; trust no one–not even me–verify everything for yourself. But make sure your testing methodology itself isn’t flawed. Drying a wet sponge like I see so many YouTubers do as a dryer test only shows that anything wet, heated enough will dry. However, what we really want to know is if the plastic inside is dry.
Here’s my dream dryer specs:
The humidity and temp sensors should be inside the chamber not inside the electronics enclosure like all dryers today are. This will allow for “Truer” readings.
There should be three sensors throughout the chamber and an average should be taken.
The drier should have a scale baked into the mechanism to allow for weighing moisture. This is the only truly valid test of how much moisture was in the spool.
The drier should have a USB interface with application software to log and record drying and allow one to maintain a database of filament weights and moisture.
For a single spool, the drier should be under $70.
It should be a square box, not this fancy sh*t that requires half a desk space to open the chamber but looks pretty.
The display should be backlit and stay on.
The touch screen should be solid capacitive outside the dryer container so one gets the same touch experience as one might on the a phone. “ALL” of these driers apparently are using the same Sh*tty Chinese maker for their touch displays and in my testing, it was clear that none of them worked well.
I think my room is just very dry, if i breathe on the hygrometers the go up. 10% is the minimum spec, so maybe just bottomed out, but now that you mention it, they are not reading higher, so maybe they were “stuck” at 10% somehow.
Thanks for the detailed reply though. I think the S4 will dry filament, i just dont think ill trust the readings too much. Im sure its 50c somewhere in there, just not the air temp.
As an S4 owner, I don’t rely on the temperature or humidity readings.
When I received the S4, I checked the actual temperatures, sadly “accurate” is not the word I can use to describe the S4.
What I can say is, if I dry filament for 6 hours, before printing it prints better. Once the print is finished I store it in the standard cereal box that many people use.
10% RH is possible during the winter but it is painfully dry. If you set the Sunlu to not be heating and open up the flaps what does it read the room RH as?
What did you measure the ‘actual’ temperature with in your S4?
The reason I ask is I measured the air temp in my own S4 by sticking the temperature probe from my multimeter through one of the PTFE tube openings, and the reading I got agreed with the S4 screen within a couple of degrees. I was frankly surprised as I expected it to be way off.
The reason I checked temperature was that I had a self printed PLA spool deform inside the S4.
I tested four different locations with a HOBO UX120-006M Analog Data Logger.
Temp’ probe cables were fed in the top of one side of the S4, I taped the lid on that side of the S4.
There were four spools in the S4.
Probe positions were:
A bottom internal corner (back left),
close to the back of the S4 display (looks like the input sensing area for the S4 display),
between spools on one side (on dessicant box) and
taped under one of the lids.
Generally the display on the S4 showed 49-51C, average 50C, I did not watch this for the whole test period.
I logged the following peak temperatures:
48C
54C
59C
55C
I don’t check temperatures all the time, but I won’t use self printed PLA spools in the S4.
FYI the 70C setting for PETG doesn’t get to 70C in my S4.
I really wish there was a standing ovation emoticon but this is the best I could find.
I applaud your technique and thoroughness. This is the kind of thing this community needs more of, less opinion and more science.
I know I harp on the notion that one must try at all possible to distinguish what one “read on the Internet” versus what one observed using empirical measurements like you are doing. In other words, if someone represents their findings as data gathered, they need to bring their receipts.
The thing I want to be clear on is that I have no complaints about the Sunlu S4, I mainly use PLA, PETG and TPU.
Delivery of the S4 was quick, it improved my filament printing, it allows me to have some control over humidity. The only thing that I would change is having an option to rotate spools while drying, but on the rare occasion that I print direct from the S4, the spools rotate anyway.
I went out and got my Govee Hygrometer from my green house and let it sit two hours in the S4 with the lid open, here are the results.
As you can see from it, S4 has 21c with 31% RH, the Govee has 20.1c with 36% RH, so definitely a discrepency. I do trust the Govee more.
What i dont trust is either of the cheap circle hygrometers i got off Amazon. You get what you payfor I suppose. Temperature they seem to track closely, but RH is all over between the two (one reading 10% which is low limit, the other 23% sitting next to it). If i breath on them, the RH changes, so its detecting something, but yeah, worthless.
I do agree on the S4 for drying though, it holds 4 spools, does a timed dry at a specified temperature, and while the air temp might not match the display temp, it does seem to work for drying the filament, and technically I could print from inside it if needed.
I found the video from BigCliveDotCom that explains why these moisture sensors go bad so frequently.
The TL;DR version is that Amphenol the maker of the sensor states that these should only be driven by AC current, something that many designs simply do not do. If one drives it with DC–which requires fewer components–the sensor becomes polarized if DC current is applied. Which would explain why all those cheap Chinese hygrometers fail over time. He also explains what kind of mishandling can cause damage.
Near as I can tell, this is the only sensor being used on the market. It was invented by Telaire which Amphenol acquired in 2013.
Yes, I do mean the dryer market. The package does not matter whether its through hole or SMD. Sometimes what might appear to be a SMD device is in fact just a packaged through hole circuit card. But if you can take a photo of the element, it would be helpful.
The driest place is María Elena Sur. Located in the Yungay region, in the Atacama desert (in Chile), the MES is the driest point on planet Earth. With a mean atmospheric relative humidity (RH) of 17,3% and a RH in the soil with a constant 14% at a depth of one meter.
RH really depends on the temperature, hence, “Relative” humidity.
Relative to the temperature.
WIKI Humidity - Wikipedia
The RH data logger that I have has a reported range down to 5%.
The manual details temperature range and pollutants : Using the RH sensor
In order to take humidity measurements, the temperature sensor must be used in conjunction with the RH sensor. Conditions outside the recommended range may offset the RH signal. Vapors may also affect the RH sensor. The diffusion of chemicals into the sensor may cause a shift in both offset and sensitivity. High levels of pollutants may cause permanent damage to the sensor.
In a word, their products suck. The S2 was returned to Amazon.
