Wine powered toilet fan circuit analysis
ฝัง
- เผยแพร่เมื่อ 28 มิ.ย. 2023
- It's a while since I've partaken of wine while making a video, and it definitely adds "something" to the mix. Notably me screwing up the triac connections. No wonder I got tongue twisted during that bit.
MT1 goes to the neutral and MT2 goes to the fan. The gate should be shown on the neutral side too.
I got this fan purely to analyse the humidity monitoring circuitry. These units are built to a price, and that means that they have to use the cheapest humidity sensor possible, which introduces significant design complexities.
This bare HR2902L style humidity sensor uses a conductive membrane that changes resistance with ambient humidity levels. But you can't just measure it as a simple resistor. To avoid electrolytic effects and the risk of changing the characteristics of the sensing layer, it has to be read with AC current with an equal current flow of either polarity. The same technique is also used to avoid electrode corrosion with water purity analysers.
The timing function is much simpler. Just reading a voltage between zero and 5V and then converting that to a scaled value for a counter.
This fan was advertised as having an anti-backdraught shutter. I was hoping for a wax-motor actuated louvre system, but in reality it's a very cheap and nasty floppy plastic flap that will work, but will potentially make flappy noises on a windy day.
The fan also has its own short video due to an oddity that occured while I was experimenting with taming its speed down with a series capacitor. I stepped the capacitor value up progressively and suddenly at 1uF the fan went into turbo mode, and the voltage across it exceeded the mains supply significantly. I reckon I hit a magic ratio between the motor inductance and capacitance that caused an unusual phase addition issue.
If you enjoy these videos you can help support the channel with a dollar for coffee, cookies and random gadgets for disassembly at:- www.bigclive.com/coffee.htm
This also keeps the channel independent of TH-cam's algorithm quirks, allowing it to be a bit more dangerous and naughty.
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It's nice to hear praise for a circuit designer.
And to see a cheapie Chinese product where all of the components make sense and it's not just a bastardized, corners-cut-to-save-money version of someone else's product.
@@tncorgi92🍷🎎
@@tncorgi92you mean my circuit doesn't need a 20 gram weight in there?!?!
Circuit design is really fascinating to me, but it sucks that so many products are horribly made in order to save like 3 cents a unit
Hey Clive! I’ve been watching your videos for a while now. I’m no electrician or any sort, but watching you break open devices and explaining the circuitry is entertaining for me. I enjoy your voice as it is very smooth and easy to listen to. I enjoy it a lot!
When it comes to extracting bumgas from bathrooms, the one brand I think of is VentAxia, mostly because in an episode of Star Trek TNG, they had a species called the Ventaxians, which I can only assume one of the episode writers thought of while taking a dump and saw the fan on the wall... :P
The Bogrollians and Bogbrushians were infuriated they didn't get a mention.
I do wonder though, why these fans don’t have a methane sensor too…
@@demil3618 Because there is very little methane that comes from our digestion to trigger such a thing, a lot of the gas we expel from our rear is just air we've swallowed, followed by hydrogen sulphide (the eggy smell), with a pinch of methane plus some other odourific chemicals that are produced in our gut... :)
Cows on the other hand, they belch the stuff out...
@@twocvbloke I heard stories where people used a cigarette lighter on others to heat their bottoms. Just stories though, never tested it myself 😁
I gave up on VentAxia after having several 4" mixed flow units all fail at around 18 months use in a domestic environment. They were replaced with Manrose units which have lasted for 4+ years so far and were also much cheaper.
That's a clever use of a single pin to both read an analogue input to read one potentiometer and also trigger the resistive humidity sensor 'the right' way. Kudos to the designer of that circuit!
The rule about using AC for the humidity sensor reminds me of lessons at school in how to test the conductivity of solutions. You CAN do this with DC, but should not, for exactly the same reason - it electrolyses the solution. You always connect your conductivity flask to the (low-voltage) AC, otherwise you destroy your sample in the course of testing it.
I have used conductometer but never thought of that!!!!!! Yes DC will have polarization effect and ionic concentration will change over time due to migration.
@@Satyaprakash81102 Same why we use AC no DC in cables. Not about dedlines of dc and ac is meh. But most of the time we use AC as surce/transport of power because ac don't magnetise cables and don't build up antena.
@@arned432AC is kinda a giant antenna, losses to the various forms of radiation incurred by AC are a quite significant part of the overall losses in transmission lines especially long ones. There's also plenty of magnetic effects from AC it's how transformers work after all. There's no net magnetism on a DC cable if it's carrying equal current in both directions. (This is true for AC as well but there are generally more conductors in an AC transmission line and they are spaced further apart)
The only real advantages of AC is transformers make voltage conversion easy and the zero crossing can extinguish some small arcs.
These days with semiconductors especially silicon carbide and gallium arsenide MOSFETs the transformer is becoming less of an advantage and more of a liability even at the transmission line voltage level. Lots of new high power long run transmission lines are DC because ultimately it's cheaper and they lose less power.
@@zyeborm AC is not antenna , but AC in a conductor can radiate because of mathematics. And if a conductor is designed for its resonance then it can emit radiation. In case of 50 Hz it's small but in HF and UHF region it's high. DC can also loss due to corona effect which is breakdown of insulator or dielectric and effect is more severe. A moving electrical charge creates magnetic field. so both AC and DC produce magnetic field. AC has an oscillating magnetic field and DC has a fixed magnetic field. A change in magnetic field strength induces current in a conductor and thus AC induces current in a not electrically connected but magnetically connected conductor of a transformer. But DC has no such effect.
Thanks a lot for the explanation on the humidity sensor.
I used to work for an Agricultural Research Centre and developed a low cost green-house control system (controlling A/C, windows, shades, fans, watering, mist generator, etc.) for use in green houses on remote islands, with off the shelf parts. I used the DHT11. I know, they aren't really good (but good enough for the purpose), but I designed the circuit in a way, that the sensors can be easily replaced by the farmers themselves.
This gave me a new idea to (maybe) redesign with different parts.
I enjoyed the wine-induced slight extra sprinkling of chaos; cheers to you, sir.
You've extracted all you can from that. I'm feeling refreshed with knowledge if not flushed with success. Consider me a fan.
That's a clever and clean little circuit! I love how it's running and measuring the humidity sensor!
All I saw was "wine powered toilet fan" and I knew who this would be. 😆 Love your work, your insights, and the insatiable curiosity and wonder you contribute to this platform, BigClive. :)
A few tricks and a nice design to make the cheapest humid fart extractor possible.
Seems that it can last a very long time too. It's pleasing to see a nice product nowadays.
Fascinating teardown 👍 A friend introduced me to Humidistat fans like this in the mid 2000s - I installed a Manrose 4" into a bathroom purely in humidity mode - it worked brilliantly and had a knob to adjust the trigger point. Unfortunately Manrose then seemed to copy this style of design with their newer ones as I bought a couple of their new low power, super quite 5W fans with humidity and timer - the circuit board looks very similar but had a larger MCU - they never, ever, worked consistently with humidity - they'd either run non-stop or at times the bathroom would be like a steam room and they wouldn't come on - completely bizarre regardless of the tweaking on the pots. In the end the bearings became too noisy - they were supposedly DC fans - I've replaced them with some "smart" fans from Greenwood which monitor the humidity constantly and look for steady peaks in humidity to avoid false triggers - they are always-on at low speed and then jump up to high - again not perfect when humidity is already high but far better than the Manrose ones!
By far the best teardown I've seen. I've created an HR202 humidity sensor library for arduino + simple schematics to run it with AC inspired on this circuit, requiring only an 100k resistor plus 1uF capacitor.
This is just like Opera, I'm getting one word in 10, I have no idea what's going on, but it's beautiful.
I always wished we could get the UK-style toilet fans in the USA. The ones here generally are junk. 100watts, loud, and absolutely no time-delay. The place I stayed in the UK had a 4" fan, DC motor, very quiet and efficient, and the delay-off is genius.
Good circuit. I do like squeezing the most functionality out of a microcontroller, and this circuit has some great tricks like that.
Fascinating and well-made video, Clive. I definitely learned some interesting design techniques from this one. Thanks!
Excellent! I enjoyed the video. The 3 Pin Humidity sensors you refer to at the end of the video are indeed the DHT11 and DHT22 models (there's an AM2302 also that uses the same protocol). There are better options out there, but those sensors are more complicated, using I2C for communication.
The new DHT20 in the series now uses I2C.
Detailed and witty overview, what more could anyone ask for. It's probably best to avoid drinking upside-down resistors.
Seeing the bare humidity sensor reminded me of VCRs of 30 years ago. They used them to detect humidity near the drum and prevent the tape lacing up and getting stuck / torn.
Ah yes, the old "dew sensor". Fun memories working on those machines...
@@springpan Ever have to fight with a faulty infrared "tape in" sensor? 🤣
@@dashcamandy2242 I used to wrap the LED sensor post in the middle of the cassette with electrical tape during troubleshoot, but no, I never found many that failed.
These circuits are super cool, they even have them built into the light switch here in the states. Super nice to not have to manually turn it on/off
It still blows my mind that a simple extractor fan now has more computing power than the computer that I sawed up for 6 months for.
Does it? Then how many times your old computer is a common Wi-Fi light bulb, with a superior 32-bit ESP8266 chip running at ten times the clock of the fan's 8-bit STM chip?
I think your computer is probably fairly safe in this case, stm8s are in general 8 bit 16mhz kinda deals with a few kB of ram and storage.
286 is probably going to outrun this by quite a margin.
Even a z80 with its 16 bit instructions would probably give these a run for their money in terms of raw compute 😊
@@rexsceleratorum1632 wi-fi light bulb..? Now that is something I will never get my head around. We have perfectly good light switches here.
@@TestGearJunkie.Some people are to lazy or find them cool. Turning on a lamp using a app is for some people the future but also the past of their privacy! I personally only use 2 cloud based things the rest is local control
@@TestGearJunkie. China churns out the processor and wifi combined for 1.5 USD a piece, so don't blame me for buying them and flashing them with ESPHome to control some lights.
Very clever circuit design.
Learned a lot, ty.
Wine makes engineering easier and more fun. Got it!
The AC driving reminds me of LCD's which are the same. Adafruit (and plenty of other vendors) sell what they call a Liquid Crystal Light Valve or a Shutter Glass. It's a postage-stamp sized single pixel LCD, which at rest is transparent, but if 5V is applied across its two terminals in either direction, it will go black. The little trick to keep in mind though is that if you apply long-term DC to them, they will have migration in the liquid crystals and fail. When I drive these I just connect them to two Arduino outputs. To make it go black I drive one high and the other low, and while it's darkened, I toggle both pins, effectively creating an AC drive signal across the two pins. It works quite well.
Yes, LCD (ie watches) have always been H driven and would be silly having a series capacitor for each segment
A humidity sensor , finally something I know a lot about. Quite the circuit there. Thank you
Very interesting! Great video! Thanks Big Clive 🙂
Always learn something from your videos, I didn't know about driving the humidity sensor with AC, probably explains why my arduino sensor failed!
I'm planning some humidity sensing myself and this sure comes in handy. Now I know what to look for.
The extractor fan at my last house was a 240V motor with two pull cords that toggled a switch, one side for on, the other side for off. Old school tech. LOL.
took me a minute to realise that the analysis was powered by wine rather than the circuit
Very interesting. Thanks Big Clive.
Very interesting and simple circuit thanks Clive very intriguing 😊
Great video Clive! Always interesting to see clever little hacks to get more out of a circuit.
Isn't it incredible how often the mere act of thinking "I'd better be careful not to..." instantly results in the outcome you wanted to avoid? I'm sure there must be some quantum mechanics explanation...either that or the universe just loves messing with engineers :D
Very nice, clear, clever autopsy, thanks!
Thanks I enjoyed the wine - Good chat too
I'm glad you're doing this. I have an Expelair toilet fan that's operated by a PIR. They don't seem to last more than a couple of years and has been replaced under warranty several times.
I hope this video shows its weakness, I haven't watched it yet as you can guess
It would be interesting to see which part fails. I don't see a snubber across the triac and there seems to be limited protection for the micro to incoming switch or PIR spikes, though analyses with a scope would be required to see if these were potential issues.
Never doubt the wine my friend!
Very clever circuits! Yes, using AC is required on these humidity sensors, though one place I worked used DC and got away with it for inexpensive devices. They probably didn't stay in calibration for years like the fan would. We also used AC for fluid conductivity measurements for the same reason (this being a much more expensive device.)
Was wondering what a "wine powered toilet fan circuit analysis" was until I realized that it was a wine-powered circuit analysis of a toilet fan, not a circuit analysis of a wine powered toilet fan!
Clive, don't ditch the fan, just repurpose it for use when soldering. Looks like a decent exhaust fan and no need for a timer in that application...inside or out of a box.....of which I think out of mostly😉
It's not getting ditched. Although its original intended application is now being handled by a computer style fan. I thought this one was going to have a thermally actuated shutter, but instead it's just floppy plastic flaps.
Thanks, great explanation
Having just installed a timer for that type of fan here in the US, I'm happy they have those as standard, and a bit bummed that we don't here.
Thanks Clive, interesting indeed.
I’ve been obsessed with wind power lately and read the title “Wind powered toilet.” 😂
Nice to hear about a toilet fan ,I've been one for many years but thought I was on my own. If only I could find a human toilet fan😢
I'd get banned by TH-cam for writing the name, but there are websites for human toilets and their fans.
Is it only for fans ?
Then i probably know what you think of 😅
You can never have enough wine and long as you are having a good time.
Our fart fans in the US usually have their own switch, and if they have a humidity sensor, it is usually part of the switch as well.
Fans that come on automatically when the lights are turned on and stay on when the lights are switched off are usually only found in public bathrooms.
Some people I talk to prefer the DHT22 and BME280 although they cost a bit more. I've used BME280 and the DHT11. The DHT11 seems good enough accept when I need pressure too.
Never knew how those humidity sensors worked before!
Loved this one Clive. Very good. I still find it hard to believe those little to92 triacs can cope with mains switching, I'm still remembering the massive packages back in the 70s... PS. Your 39k resistor was found on the top deck of a 432 bus, without a ticket of course.
Remember that it doesn’t have to carry much current and only switches on zero crossings. Having to switch with voltage across four layer devices means huge current spikes. That’s why those old tangled puck devices were invented. The main terminals had lots of surface area which coupled nicely to heat sinks and in some cases water cooling systems.
I think Clive should do an episode covering four layer devices in general, why different types exist and what they can and can’t do. When I was first introduced to them in the early 70s they struck me as black magic.
@@markfergerson2145 Yes that would be excellent. Thanks Mark.😸
I reside in a humid swamp-like part of Ireland, and sadly these kind of fans are just not good enough in colder wetter months.
I learnt Arduino code purely so i could make a much more intelligent and logic based fan controller that essentially gives a constant on and off cycle all day (to stop mold) and ramps up in shower humidity etc, or if ambient is over a set amount. I also use a much more stout industry rated fan, overapecced so it won't fail in a couple of years. Hopefully.
It's massively humid on the Isle of Man too. I recently set up an experimental computer style fan that vents air out the house and into a ventilated underfloor area at the back. Just that small airflow has improved the air greatly, reducing the musty smell of an old home. I might try the same as an attic mounted filtered positive pressure fan.
Small smd parts should come with parachute and personal locator beacons for just this reason...!
Clive. If you had drunk more wine then there's a chance of you trying to use your multimeter to get a reading from a photo again. 🥴👍
Your theory about breaking the live and switched live sounds right.
That would explain the ubiquitous "wide switch" (they are chunky) three pole isolator usually above bathroom doorways in newer builds. I think it's a standard in the regs these days.
Also says "three pole isolator" on them and often has a fan symbol, though I've never taken one apart (yet) or lived in a house that had them so can't comment on genuine function of the internals.
Switched a few off in hotels late in the evening though, noisy buggers: I'm trying to sleep!!
Edit: the only thing I'm editing is this bit, after some love back from the man himself (fourth or fifth time now, which feels like a badge of honour): a big thanks to Clive for the effort and amusement he's provided over the years. Cinderella you shall drink for free and indeed most heartedly at the ball this evening, not 100% on the pumpkin taxi though.. hard to come by!
I went on google bard, and asked it to analyse a fan circuit in the style of Big Clive. It said:
"Introduction
Today, we're going to be analyzing a fan circuit. This is a relatively simple circuit, but it's a good way to learn about the basics of fan control.
The circuit consists of a power supply, a microcontroller, a relay, and a fan. The power supply provides the power for the circuit, the microcontroller controls the relay, and the relay controls the fan.
Analysis
The power supply is a simple 12-volt supply. It provides the power for the entire circuit. The microcontroller is a small chip that controls the relay. The relay is a switch that turns the fan on and off. The fan is a simple 12-volt fan.
The circuit works by the microcontroller sending a signal to the relay. When the signal is received, the relay closes, which turns the fan on. When the signal is removed, the relay opens, which turns the fan off.
Conclusion
This is a relatively simple circuit, but it's a good way to learn about the basics of fan control. The circuit is easy to understand and build, and it can be used to control a variety of fans.
Bonus
Here are some additional things to consider when analyzing a fan circuit:
The type of fan: The type of fan will determine the power requirements of the circuit. For example, a high-power fan will require a larger power supply.
The speed control: The circuit can be modified to include a speed control. This will allow you to adjust the speed of the fan.
The safety features: The circuit should include safety features to prevent the fan from overheating or being damaged. For example, the circuit could include a fuse or a thermal fuse.
Outro
That's all for today's analysis of a fan circuit. Thanks for watching!"
Not a bad analysis, but Clive's job appears to be safe at least for now.
That's surprisingly good. It gets the modular approach and actually seems to present it in my style. I wonder if it's a generic style it uses or if it has an actual understanding of my video presentation style.
Very generic response...it did not...(because it could not) know the type of power the fan required......
I thought you were gonna look at one of the fans from an integrated blower that fancy Japanese toilets and bidets are equipped with.
For a subsequent video may I propose that you look at the circuitry on a $600+ bidet toilet seat to see what makes it tick? the ones with built in seat warmers are neat-o!
also I don't know if it means anything to you but because of you going over the circuit boards and going over the logic involved I realized my years of training in formal logic might actually prove useful. I'm applying to a computer engineering program next year after I beef up my maths this year. thanks man
Clive, sometimes, as with this circuit, I would love to see some ‘scope traces to show what is going on with that sensing system. It’s very clever but trying to describe it is not like seeing the behaviour directly.
Awesome Video big clive
I guess the humidity sensor can be read by measuring the charge/discharge time from pulse to read between the two pins, maybe to a comparator type input. It's similar to the RCtime function in PICBasic, but using two pins instead of one. This would make sense with the large RC values. Neat little circuit!
Interesting how the sensors are so common over there. As a landlord, I install humidity sensitive switches for the fan so it is automatic, typically they are all manual in the US. One switch for the light, one switch for the fan.
I love it. I'd like something similar to kick on my shower fan when I forget (the switch is blocked by a glass door when I'm showering) and to goose the thermostat so the A/C can replace that conditioned air I'm dumping outside with freshly dehumidified outside air from its make-up intake. (living with extreme outside humidity changes one's goals a bit)
Two in a week? This must be Clive’s summer festival fan zone.
Aye - you sound a bit pissed! But I tell you what, even with wine onboard, you manage to explain fairly involved circuitry very well. Nice, and thanks.
Future video idea: Take a usb charging and disable the data transfer lines, making it charging only. This would be done for security reasons.
Maybe it would make a nice short video or something? Cheers! 🍻🖖🏻
I perfer to use external diodes to clamp the inputs, the esd diodes on the inputs are in my experience on very robust. Best to know what the characteristics are of the components in your design.
Not really an esd diode unless they have specified it as such. Most often they will be a body diode that's part of the chip fabrication process. Many manufacturers will specify allowable current through them and such which should count as specified really. Also with 2 meg of electron sieving going on I get 0.1 milliamps that's pretty low really.
@@zyeborm I was also going to say that using the body or esd diodes can also lead to device latch ups in strange ways. which is why for a few extra pence i can have a well defined part.
Currently supping a dangerous mix of vodka, rum and ginger beer... Bring on the wine powered toilet fan!
Love this
With all of the pinged surface mount components, you might be well-stocked during the next component shortage. The trick will simply be to screen them out of the vacuum cleaner.
Might be in your beard😂
Had several failures with low-voltage fans where the regulator electrolytic fails causing the controller to now be driven from half-cycle AC (albeit zener clamped). The step down transformer for the LV fan then burns out causing an expensive failure. So if you have an LV fan controller, replace the supply electrolytic as soon as possible to prevent expensive failures. Lost 2 transformers before I discovered this.
You got me with that headline! lol
I've had SMD resistors go missing before, only to find them weeks later still stuck to my soldering iron, somehow surviving many cleanings and other soldering work.
The NuTone heat-vent-light I installed last fall didn't have a humidity sensor or a timer. It did have a thermostat, but that's just there to turn the vent on to cool the box if the 250 watt heat lamp gets the box hot. I thought it was odd that they put a thermal fuse in the electrical connection box. A lot of people were complaining that the thermal fuse caused the unit to prematurely fail (within a month), so I removed it. I can see maybe see why you'd want to put a thermal fuse where a 1500 watt heater was used, but this is just a glorified light socket. Also, it has never been practice to put a thermal fuse in an electrical box even when the box is plastic.
It's not unusual for thermal fuses to be a last resort if things are getting too hot. If a unit is left on it can gradually approach the temperature it trips at.
It's better to replace the thermal fuse if it fails as a safety precaution. It may be that the unit is not designed to be left on for long periods of time.
The thermal fuse protects for the case the fan is out of order.
It wasn't protecting the fan. The thermal fuse was placed in line with the power leads just to protect the wire connections. It looked like an after thought. There is nothing in the National Electric Code about there needing to be a thermal fuse in junction boxes which what this isolated part of the housing is. I wouldn't doubt they'll start putting thermal fusing in every receptacle in switch down the line, if that's what you're getting at.
@@CG-rr6yx It wasn't anywhere near the fan. It wasn't anywhere near the light sockets. It was in the junction box.
@@robertgaines-tulsa A thermal fuse can fail without obvious reasons if it is put to repeated cycles that do not cross the rated limit but are rather close.
Worth mentioning is also that heating / lighting enclosures installed on / in the ceiling are subject to heat accumulation due to air convection currents.
The junction box, which I understand is part of the casing, likely gets heated high enough to be a good place for a thermal protection device.
With heating on, thermostat failing and fan jammed (both because of dust and grime collected in months of good service) a thermal fuse is a last line of defense.
I am a big fan
me too .. but my link to a giant wind blower got removed.
Here in Australia I've never seen an exhaust fan with a run on feature that lets it keep running after you turn the switch off, less still have I seen one with a humidity sensor.
The bathrooms in Canada have an exhaust fan in the ceiling and it is on a manual switch next to the light switch.
Tooooooo much wine, Clive! ( :P ) The chip you can't identify offhand is quite visibly labeled LM393 in the video.
As for the temp/humidity sensors... there are two. The DHT11 is the cheaper of the two, and is notorious for having tolerances so wide that it's essentially a vestigial circuitry element in each and every potential use case. The DHT22 is fully twice the price of its cheaper cousin, but actually sports reasonable accuracy. Both use a horrible proprietary protocol that is notorious both for the fact that Arduinos inevitably have to bitbang comms with them, and for the fact that, in the best of circumstances, an Arduino is only just barely fast enough to actually manage some vague semblance of coherent communications because of the required bus speeds. Both sensors have a thusly well-earned reputation for being incredibly awful to work with.
Well, good news because their newer DHT20 is now I2C
Did you use that 39k resistor in your wine to slow down the alcohol intake speed into the bloodstream?
Smells good 👍🙃
Very clever design and a very good video too!
However, those fans are often out-dumbed by the bathroom user. They would shut the bathroom door tight af, to prevent any smelly leakage. The little fan now tries to draw a vaccum, since there is no airflow and the stink will linger longer.
From the title for a moment, I thought the fart remover was powered by wine.
I just want a fan with three features - a delay start, an off delay and a humidity sensor. I can pick any two of those. Apparently a fan with all three features doesn't exist.
Of course there is a 'smart' extractor fan that can be controlled with a smartphone app though. Extractor fans should not need an internet connection lmao. What a time to be alive.
Those three features in a fan would be quite specialist.
When you realize Big Clive can explain things better than you even after a bottle of 🍷🤣
Excellent video Big Clive. A big shout out to the circuit designer as well!
👍
humidity sensor is for when you dont have it behind a switch. it will turn on when it smells moisture. I have one with light sensor and moisture. so when it sees light or motion it turns on also
Oh, not literally in the toilet, but the vent fan for the bathroom.
My mind was in the toilet I guess. :P
I've got a cheapo eBay indoor temperature and humidity sensor and I've never really trusted the humidity readings. The air vents were also tiny little things, so the first thing I did was drill some big holes in the case.
A wine powered fan!?!?!? Makes a change from boring old electric fans, I suppose. ;-)
Interesting circuit ^^ And yes, those cheap but "safe" humidity/temp sensors are called DHT11, but they're not that accurate. The "better" version is the DHT22 (or AM2302) that comes in a 4-pin package (+V, data, GND, GND). The DHT22 is a bit slower (you should only probe it every 3+ seconds while the DHT11 can be probed every 2+ seconds) and can apparently "glitch/freeze" sometimes and has to be disconnected from power in that case. You should also use a resistor (5-10k) to pull the data pin high. I've experimented with a DHT22 a few times so far, and it works well, but I guess the values should be calibrated and not used "raw" since it consistently read a temperature that was 1-2°C higher than what all other thermometers in my room measured...
Accuracy of humidity isn't particularly important when you're just making a decision on whether to turn a bathroom extractor fan on or not. You just want it on when it's high and off once it's not.
They have a new I2C module called DHT20, might want to look into that one
Had no idea what a toilet fan is until starting to watch the video. Was hoping it was something new, odd, or crazy but nope ... its just what we here in the United States call an exhaust fan
Still an interesting video though :o)
Ace 👍👍
I wish we had units like this in the US....
Yes, DHT11. They're ubiquitous and cheap, but not that accurate when it comes to humidity measurement..
The DHT22 is much better and also much more expensive. Works really well with Arduino remote sensors and since they are only powered on for 2 -3 seconds every hour or so you don't need to worry about electromigration.
I would love to see the wave forms.
By the way the reason for sensing AC line is because the capacitive drop power supply cannot supply enough current to drive the triac continously. The fire the triac around the zero crossing point and then turn off the drive to conserve power.
I know this is odd but what style/tip pen do you use? I have bought a few similar to it based on what I can see but don't seem right. I have been sketching some schematics and tried to find it. I have to use a very fine felt or other non ball point pen because my handwriting is bad and I assume it's because I am left handed most ball points that work fine for right handed people don't work for me.
It's a Pilot V-sign. Refilled with printer ink.
I find Jelly pens work better then ball points.
Hi Clive,
I just started getting into SDR shortwave radios dongles for the computer and would love to see some videos on your take on them.
Here in the Colorado rockies we call it a fart fan lol😂
Clive, does the fan come with an optional shutter/damper to block outside wind as an option?
It came with a floppy plastic flap to block air from blowing in, but I was hoping for a thermally actuated set of shutters.
By interesting coincidence, I was asked to look at a faulty dehumidifier that used one of those sensors just the other week. I incorrectly assumed it was a One-Wire device like the DHT-11/22/etc. This explains why it was labeled on the PCB as if it was a resistor.
I have the control board sitting on my bench (the dehumidifier was a goner). Now I'm sort of curious to try and mess with the sensor.
Thank you for the informative video. Two small remarks, if you let me. You flipped the triac on the schematic, and I guess the op-amp is an lm393 comparator, I can clearly see the second 3.
You're right. I have flipped the triac.
Interesting control circuit, novel way to drive the humidity sensor without using an H-bridge.
I'm surprised UK exhaust fans do not have a damper flap to keep warn air from exiting when the fan is not running, On this side of the pond there are dampers both on the fan itself and the weather hood on the outside of the building.
There is no difference between both sides of the pond in that regards. That fan is not meant to be installed like that!
The fan itself is installed in the (bath)room (usually in the false ceiling, over the shower or close to it). And it is hooked up to a duct via the roof/attic. It is THERE that those flaps/dampers are installed, not on the fan itself!
Aka: this is not a fan to be installed directly in the OUTER wall of your (bath)room. You should never do that (unless it is especially meant for it of course, but those will indeed almost always have such flaps, an insect mesh, etc)
Note that this was also mentioned/drawn in the manual of the fan, btw. You can get a glimpse of the installation drawing when Clive shows the manual.
If you look how the fan is laying on Clive's desk: the side that is clearly meant to be connected to a duct is in plain view. The other side, which is touching his desk, is the side which is meant to face your (bath)room. So, he has the fan laying upsidedown so to speak. Aka: this is NOT a fan which is meant to be installed without any ducting.
It does have a horrible floppy plastic diaphragm. I was hoping for a solid thermally actuated shutter.
The TRIAC only needs short pulses to fire, which can be provided by the decoupling capacitor.