Articles, Blog

DIY Temperature Controlled Hot End Cooling Fan

February 12, 2020

One of the most common failure points on a Creality machine is the cooling fan for the hot end. That thing is running
all the time. If powers turned out it’s running even after your print finishes
it’s still running. Now on some printers you can shut it off at a certain
temperature but the Creality Board puts power direct to the fan and it
doesn’t control it by the controller so you can’t control it by firmware unless you
change the motherboard. So I wanted to see if I could create a small little
circuit that I could place right here in the fan wires that would monitor
temperature and turn it on and off based on the temperature and it gave me a
chance to cut a little circuit board on this Bantam tool PCB cutter that they’ve
loaned me to try out. So I did. I made one for my ender three. I’ll show you how I
did it on today’s Filament Friday. Filament Friday is brought to you by
these patreon supporters. Here’s the Creality motherboard. it’s
got three fans connected to it. The hot end fan is connected to power all the
time positive on the Left negative on the right always running. Then there’s two other fans and they’re on these two connectors.
One is the filament cooling fan the other one is electronics fan. These are
controlled by firmware you can turn it on and off. But this hot end fan is what
I want to turn off with temperature so that’s something to focus on. Now some
may think just switch connections but you can’t do that because of you shut
your filament fan off because you don’t want to blow in on the filament, you then
shut off your hot end fan so that’s not an option. So here’s the circuit that we
normally have is 24 volts positive and negative and at the other end you’ve got
the 24 volt fan that cools the hot end. Now normally these are connected.
positive and negative but I want to put a switch between them so first I’ll
connect power all the way across but then on the low side or negative side
I’m going to put a transistor. This will act as a switch to turn it on and off.
Now I got to monitor temperature so I’m gonna put a thermistor, the same one
that’s in the hot end, here from power and then through a adjustable resistor
or a potentiometer and it take that to ground. So this forms a voltage divider
that’s temperature control. Finally I’ll add a resistor for current limiting to
the transistor and that’ll turn the transistor on and off based on
temperature. I measured the current on the fan 33 milliamps typical so a 2N4401 with six hundred milliamps max current can handle this easily and the
gain on it is very very high at that point so a small amount of current
should saturate this easily. I started out with a hundred ohm resistor I’m
gonna change that because I forgot to calculate wattage but it’s a 100K
thermistor, the same ones typically used in a hot end and a 10k potentiometer and
then the 2N4401 transistor. That’s the basic circuit so let me
explain how this works. As the temperature rises at the thermistor the resistance
actually goes down which makes the voltage at this voltage divider go up
and when it goes up it feeds current through the resistor to the transistor
and when it hits a 0.7 volts threshold it turns the transistor on and
when it turns on that grounds the fan so the fan turns on.
Now once the thermistor cools down the voltage here drops which drops the
transistor voltage which makes it turn off so when the transistor turns off it
basically breaks the circuit or the ground circuit so the fan turns off. Very
simple but let’s see if it works. Here’s the setup built on a breadboard. I’ll
heat up the thermistor with my finger and then I’m going to adjust the
potentiometer until the fan turns on. Now let’s heat it up. Now I’ll let go and the
thermistor will start to cool down. The fan stops. I press it to heat it up the
fan turns on. I’ll let go so it cools off and the fan turns off. I did go back and
recalculate this resistor. A 2k resistor will work good that way I can use a
quarter watt resistor. I could have easily built this on a perf board but I
wanted to try out this Bantam Tools PCB milling machine. I could have used any
board layout software. I’m using Express PCB because I know this like the back of
my hand. I could do this in my sleep. I made a bottom layer and then I made a
top layer this is just gonna get cut out of a single sided board, so there’s the
full circuit. To get the Gerber’s though I have to go to copper connection. This
is a software you can’t buy any more. ExpressPCB bought em out but I still have
a copy so I can convert my ExpressPCB to Gerber’s so that’s what I did. And
then I can load those Gerber files into the Bantam Tools software. So here’s the
circuit and I can cut the traces, holes and outline with the router so I’m going
to shut off holes and outline and just cut the traces using a point zero zero
five bit. So first it levels itself or zeros itself out, and then it goes to
town cutting the traces. This thing does a beautiful job and then it cuts the
holes. I changed a bit and it actually routers the holes and then it cuts the
outline and the tape holding behind it didn’t hold well enough and the board
went flying. But it came out really good. I like the results. And there’s the top
where I cut. It really thinks it’s copper but it just becomes a silkscreen.
Now I need to install the components. The first thing is a potentiometer. It fit
nicely in the holes the next step is a resistor that installs right above the
potentiometer and then the transistor is right above that. So once I have these in
place I’ve bend the leads so they don’t fall out then I need to install the
temperature sensor. So I just cut the wire stripped them and put them in their
holes and then I put this on my 3d printed vice that I use for holding
circuit boards. This is a Filament Friday from way back. And I just clamp it down
and then I can go to town soldering all these pins. Now I had to be
careful because this is bare copper. I don’t want any shorts anywhere so I
soldered it up, everything looked good and now you just need to clip the leads.
And this thing was done. I like this better than doing a perf board. I’m
gonna install this on my ender 3 Pro so first I took the cover off so I can get
access to the wires and here’s where I’m gonna put it. Right here midway through
the fan wires. So I’ll cut those wires in half and then I’m gonna strip the end of
it so I can insert it into the board. So both sides get stripped and then just
insert them bend them and then I’ll solder them up. So here’s the power lead
coming in power and ground solder those in place and then the fan wires go at
the bottom and then i’ll solder those in place. So this is pretty much assembled
but I have to connect the temperature sensor. So I unscrewed the
temperature sensor screw at the heat block and put my sensor right on top of
the other one then I put the cover back on and then I use some tie straps to just
hold everything in place. Now I need to calibrate it so I set the temperature to
50 degrees and waiting for it to heat up and the fan is spinning but I’m gonna
adjust it so at 50 degrees it stops. So now I’ll run it up to 60 degrees and you
can see once it hits, there’s some hysteresis in this, so once I hit 59 60
it turned on. Now I’ll set it to 28 and you’ll see that once it hits about 50 it turns
off. Now I wanted to actually print something
so I’m gonna print a CHEPCUBE and you can see at about 55 degrees that it turned
on. It printed the CHEPCUBE and when it was done at about 50 degrees it shut off.
It’s great when things work. And milling it on the Bantam tool definitely made it
easier. That was a lot of fun and getting to use the Bantam tool to cut the
circuit board is something I’ve been wanting to do. It’s not an inexpensive
tool but man it is a lot of fun. And it did a great job cutting that circuit
board and it works. When it cools off the fan goes off, when it heats up the fan
goes on. But what I may do in the future is instead of doing this, modify it so
there’s a switch to a relay to shut off the printer when the print is done. That
way it shuts the fan off and everything. That may be a better way to go. I’ve seen
a few people doing that, so that’s something I want to investigate in the
future. So what do you think? Let me know in the comments below. If you like what
I’m doing here maybe click on one of these other videos that are popping up.
If you want to help support the channel patreon is one way or just by through
the affiliate links in the description below, it all helps a lot. And if nothing
else click on that CHEP logo and subscribe. I’ll see you next time right
here at Filament Friday.


  • Reply George Brooke February 7, 2020 at 10:13 pm

    Is the electronics fan on a separate wire to the other fan? Surely it would be more ideal to leave that on all the time since its inside a box and then firmware control the hotend fan. Not sure though

  • Reply Brian Popilek February 7, 2020 at 10:23 pm

    I’ve been waiting for more electronics projects on here. I love that it is a simple solution that costs literally pennies to implement. Nicely done Chuck!

  • Reply dev deque February 7, 2020 at 10:24 pm

    Did you look into tapping into the existing temp sensor? (putting your custom PCB with the mainboard housing etc)

  • Reply Calvin Witt February 7, 2020 at 10:24 pm

    I love how simple it is and yet effective it is. Also, a great way to show other hobbies working together!

  • Reply Patrick's WorkShop February 7, 2020 at 10:24 pm

    this would be a great idea to be built into the machine motherboard from the factory I was wondering how many hours the fan would work for running nonstop

  • Reply Paul Cumber February 7, 2020 at 10:26 pm

    that is cool stuff

  • Reply Roberto Correia February 7, 2020 at 10:30 pm

    If you can change firmware, use the EXTRUDER_AUTO_FAN on Marlin. It's more simple… Don't forget to use a transistor too (but the circuit it's much more simple and the firmware control when turn on or off the fan)

  • Reply Job91 February 7, 2020 at 10:30 pm

    when mine broke I injected tough grease in the metal bushing. It has been going strong for atleast 8 more months

  • Reply Aaron Shepherd February 7, 2020 at 10:33 pm

    Pretty ingenious idea, well done!

  • Reply Joe Garmer February 7, 2020 at 10:33 pm

    great video Chep i have had my cr10 fan fail and my Tevo Tornado fan fail and it seems its more about the guard collecting lint and plastic then stopping the fan spinning and it burns up. I snipped the guard off with diagonal cutters. Also I wonder if a video on how to mill a pcb on a 3018 cnc at 169 bucks would be a more realistic project since the bantam is 3000 dollars thanks for all your great work. I use my vise all the time to solder I scaled it up to 150% when i printed it. great tool

  • Reply Martin Hendriks February 7, 2020 at 10:35 pm

    Yeah, its a very expensive fan controller this way

  • Reply Peter Obermeier February 7, 2020 at 10:37 pm

    In one of your previous videos you explained to replace this fan with a silent Noctua fan and you added a voltage regulator to get 12V for the fan. I thought that is a good idea to use a Noctua fan, but did not want that voltage regulator, so I replaced the control board fan with a Noctua 12V as well and connected both in series which is working fine. I guess you want to give us ideas how to reduce the fan noise and let us decide which solution is best, but I am interested to hear your experience, because I cannot try all solutions. What is the best solution for noise reduction? Thank you for this video!

  • Reply Mario Makers Reus February 7, 2020 at 10:39 pm


  • Reply One Razz February 7, 2020 at 10:43 pm

    Very good video.I'm a retired tech and love watching circuit work and mods. Hmm Maybe I should stream when I'm working on stuff or just a simple repair. I'm still trying to collect my gear to do such repairs properly again. the darn house fire took everything. But I'm slowly collecting it back.Can't be with out my tools a Tech never dies just his tools do. I enjoyed the video very much and nice work solving a problem .

  • Reply Asger Vestbjerg February 7, 2020 at 10:53 pm

    Great work/design 👍
    Thanks for sharing 👍😀

  • Reply Lathan Montgomery February 7, 2020 at 11:00 pm

    Nice. I haven't checked the specs on the transistor you used so I can't tell, but does it fail on or off if it can't read the temp? Nothing worse than a dead thermistor causing a fire.

  • Reply TheMidnightSmith February 7, 2020 at 11:04 pm

    Chuck just flexed all over with that in depth electrical knowledge lol. I love it!

  • Reply joe zenkus February 7, 2020 at 11:05 pm

    please sell this as a kit!

  • Reply CAPTAINCOOK February 7, 2020 at 11:11 pm

    Great Chuck, Would be great for those overnight prints 👍

  • Reply r2a3867 February 7, 2020 at 11:13 pm

    @CHEP, with regards to the relay idea, if you're going to do that don't attach it to an OctoPi host, there's a grounding issue in the Creality mainboard that can run the entire printer off the 5V rail for some reason, burned out both my Pi and printer's USB links doing that by accident, and it also totals the SD card slot on the printer when that happens, so make sure you isolate things if doing anything along those lines.

  • Reply Terry Clair February 7, 2020 at 11:28 pm

    Great job Chuck!

  • Reply Richard Lebow February 7, 2020 at 11:30 pm

    Great Idea!!

  • Reply Arek R. February 7, 2020 at 11:37 pm

    Would be good if 3D printer companies would start using 4-pin style fans which have PWM input.
    You can cut it down to only 4 cables and you have precise control over both fans.

  • Reply ChaosBlades February 7, 2020 at 11:38 pm

    If you do a relay PLEASE don't use a 10A relay like I have seen everyone else do. That is not enough for the ender 3 as it can pull up too 15A. This is a fire hazard. KNACRO has 30A relays that switch at 5v, 12v, and 24v.

  • Reply xchgre February 7, 2020 at 11:43 pm

    Awesome! I was doing this in the manual, with an on/off button

  • Reply Damion Rushton February 7, 2020 at 11:46 pm

    What was the value of the pot when you calibrated it? Hence only 2 resistors would be needed instead of a pot. Thanks CHEP, great idea 👍

  • Reply Chris J February 8, 2020 at 12:07 am

    Neat idea! I’m annoyed that the fan runs constantly.

  • Reply David Keogh February 8, 2020 at 12:26 am

    The part cooling fan is PWM right? In theory you could change marlin to output clocked pulses so you could decode them with a little microcontroller and drive a bunch of fans. Complete overkill!

  • Reply Kymo Sabe February 8, 2020 at 12:35 am

    Thank you CHEP. Simple and neat. You may want consider adding a diode to protect the transistor.

  • Reply electronron1 February 8, 2020 at 12:36 am

    Great Idea.
    I think I'm going to try this with parts I have laying around. I'll probably try using a 2N2222 and I have a bunch of 5K thermistors so my series resistance POT will be smaller but it won't cost me anything to try it out.

  • Reply Vincent Fischer February 8, 2020 at 12:42 am

    great idea and execution! could you measure the resistance please that you dialed in at the poti?

  • Reply Gustavo Arenas February 8, 2020 at 1:01 am

    An absolute genius!!!

  • Reply YB 44 February 8, 2020 at 1:03 am

    It would be great if the printer turned itself off after finishing a print in the middle of the night.

  • Reply Aneudi Madera February 8, 2020 at 1:15 am

    Awesome, I was thinking about the way to make a little interface board to make easy changes of thermistor, fans and heating element in the printhead without routing the cables to the motherboard. Something like geeetech a10.

  • Reply Bradley Lauver February 8, 2020 at 1:18 am

    Awesome video! The fan on the underside that cools the main circuit board seems to only run when the heating elements are on. Why can you not just connect the two fans in parallel? That way, when the heating elements are turned off, both fans shut down.

  • Reply TootEmCarMan February 8, 2020 at 1:19 am

    You should make a good few more PCB's, I recon they would sell well!

  • Reply ifell3 February 8, 2020 at 1:24 am

    Good project but wouldn't a KSD9700 bimetallic temperature switch be easier? Though you would have to get it close to your hot end being a little bigger.

  • Reply MC's Creations February 8, 2020 at 1:47 am

    Fantastic work, man! 😃
    Really interesting tool to make PCBs!

  • Reply RED apple February 8, 2020 at 1:47 am

    This turned into a Great Scott video.

  • Reply John Sullivan February 8, 2020 at 1:59 am

    great job

  • Reply iDig3D February 8, 2020 at 2:19 am

    Very cool! Fantastic project. Thanks for sharing.

  • Reply Parts Dave February 8, 2020 at 2:21 am

    Nice to see you doing something different. Very informative!!!!!

  • Reply Trevor Ward February 8, 2020 at 2:40 am

    That's a great idea Chuck! Great video

  • Reply sekazi February 8, 2020 at 2:52 am

    Could you technically jump off the hotend thermistor instead of using another? Also us with a SKR E3 Mini would we be able to put the fan on one of the unused 2 pin connectors? Specifically the probe and e0 stop and use it as a controllable fan through firmware?

  • Reply CityBoi FPV February 8, 2020 at 2:57 am

    How many people will never do this just because their afraid to solder… Lmao..! Smh.
    Great mod though..!

  • Reply Kevin Hoskins February 8, 2020 at 3:37 am

    Did you use a low-side switch versus a high-side switch because the thermistor is a negative coefficient device?

  • Reply Demons Headshot February 8, 2020 at 4:41 am

    hey chep hopefully its the right place to ask here but can you tell me how to increase the nozzle temperature of my longer lk4 pro printer? Its been doing me really good but I wanted to print PC and Nylon with it, any idea on how to do it because I can't exactly find any information on it, thanks.

  • Reply Timsalsanights aka The Caffeine Racer February 8, 2020 at 6:25 am

    I found a circuit that Cuts power to machine after the print finishes be so useful stuck a video on my channel might be worthy of a filament Friday video was super easy to fit. Love ur work

  • Reply sharkbytecomputer February 8, 2020 at 6:30 am

    ATX psu controlled by a pi is a great option, and the 5v standby line works for powering the pi. take your transistor to switch the signal line, and as an added bonus, set it up to kill power if it detects printer throwing any runaway errors.

  • Reply Michael Lubecke February 8, 2020 at 7:06 am

    Brilliant!! I really like this >… I would love to see the power killed after print has finished as well. Thank you!

  • Reply Tantrum Design Studio February 8, 2020 at 7:13 am

    Will chep make a kit out of this, preferably with the fan installed?

  • Reply 3D Printing Nerd February 8, 2020 at 7:39 am

    Chuck, this is fantastic. Great use of the Bantam machine, and you just showcased what could easily be A). an official upgrade from Creality and/or B). a product you can sell. Well done, brother.

  • Reply HappyandAtheist February 8, 2020 at 8:29 am

    now that's clever , well done SIr 🙂

  • Reply Viktor Solenoid February 8, 2020 at 8:32 am


  • Reply HappyandAtheist February 8, 2020 at 8:38 am

    I have ordered all the bits from alie express to covert ny CR10s to a water cooled hot end. Sadly it has been delayed due to the situation in china but I am looking forward to doing this upgrade 🙂

  • Reply the German 3D Printing Nerd February 8, 2020 at 8:41 am

    now that's clever , well done SIr 🙂

  • Reply A Al-Jahwari February 8, 2020 at 10:00 am

    Well done. Can i use a mechanical temperature switch like the one used in some smps? I think It will be easier to install.

  • Reply Andreas N February 8, 2020 at 10:06 am

    Could you do me a favor and messerue the resistance of the potentiometer? Then I just could use a normal resistor .

  • Reply TheSirBlackbird February 8, 2020 at 10:49 am

    Excellent 🙂

  • Reply official_gymkhanaschoitl February 8, 2020 at 11:25 am

    Always looking forward for your next video. You sometimes make Videos about stuff that ran through my mind for several months. Like this. Another one is auto power-off after print is finished with SKR Mini

  • Reply Toni Ryan February 8, 2020 at 12:57 pm

    Personally I would have wired the electronics fan to the hotend fan terminals and let it run all the time then modify the firmware so that the electronics fan controls the hotend fan. Add you auto-temp circuit into the electronics fan inside the box.

  • Reply Mark Ferrick February 8, 2020 at 1:01 pm

    Nice video, great little mod. Thank you.

  • Reply id February 8, 2020 at 1:23 pm

    that's a cool mod!

  • Reply Jose Baars February 8, 2020 at 2:19 pm

    So, if there is already a temparature sensor in, this should be easily modifyable in software; is this just missing in the Ender-3 firmware?

  • Reply Angel D. Mercedes February 8, 2020 at 2:29 pm

    This is honestly a pretty cool and simple mod to do if you don't have an extra port to control fans. I like the fact that this functionality is already included in Marlin. I use a MKS 1.4 on my FT5 and I took the extra hotend port and use it for the case and hotend heatsink fans. It makes so much difference. Marlin also can allow you to use a free pin on your motherboard to connect the gate of a mosfet to and control your fans that way too.

  • Reply Scott Beasley February 8, 2020 at 2:43 pm

    Great idea and super video! The Bantam is nice, but wow the price! I have a 3018 CNC that cuts PCB nicely. Having one for small projects like this is so convenient. Keep up the good work.

  • Reply Guido Mersmann February 8, 2020 at 2:45 pm

    Cool solution. I have a Raspberry pi connected to each printer and it turns the printer off after 15 minutes of inactivity and if the temperature gets below 50•C.

  • Reply reasonablebeing February 8, 2020 at 3:10 pm

    Great project and video! I would like to see the auto shutoff project as well. It would save some electricity after a print is finished and the hot end has cooled. Another idea you sparked is the need to know when the bed is cool enough for a print to release. I might consider a variation of this circuit with a tone or buzzer that goes off when the bed is cool.

  • Reply WFOrider February 8, 2020 at 4:10 pm

    Look at you go! Nice work

  • Reply Spartacusse February 8, 2020 at 4:18 pm

    Love the idea, but I would run the wires and put the board on the other end, next to the main board.

  • Reply Sebastian Bruer February 8, 2020 at 4:53 pm

    Awesome! 🙂 Educational as always!

  • Reply Perspectologist February 8, 2020 at 6:59 pm

    I enjoyed the electronics project. Thanks.

  • Reply NASEEM AKHTER February 8, 2020 at 8:26 pm

    Thanks bro

  • Reply Kotisko Miau February 8, 2020 at 10:13 pm

    Chep it is great idea and good joob!!! Thanks!!!

  • Reply thenakedcableguy February 8, 2020 at 10:43 pm

    Very helpful as always.

  • Reply wolffin100 February 9, 2020 at 12:10 am

    Ok Chep I need one of these , you should market this 👍👍. Love your videos

  • Reply Chris Whitney February 9, 2020 at 12:58 am

    Nice job, I will make one myself. thank you!

  • Reply Ryan Zaragoza February 9, 2020 at 1:18 am

    Is there anything wrong with connecting the hotend fan to the electronics fan connection and the electronics fan to the hotend fan terminal?

  • Reply shenqiangshou February 9, 2020 at 3:52 am

    Practical, well explained, easy to follow electronics projects and 3d printing, bravo! Do more of these videos!

  • Reply GoatZilla February 9, 2020 at 5:26 am

    Just use a bimetal switch

  • Reply Skelet Umart February 9, 2020 at 6:41 am

    пожалуйста расскажи про настройки гравёра для плат. у меня без проблем получается сверлить и фрезеровать. но как только я начинаю гравировать дорожки у меня ломается инструмент.

  • Reply Vladimir security February 9, 2020 at 5:07 pm

    Можно не париться, купить плату skr 1.4 turbo и в прошивке марлин настроить эту функцию!!!!

  • Reply Bernard Tarver February 9, 2020 at 5:25 pm

    FWIW, I'm using Aus3D fan extender boards that allow control of 2-4 fans, based on pin assignment, motor movement (controller board cooling), and hot end temp.

  • Reply thenakedcableguy February 9, 2020 at 5:49 pm

    Just a quick question.
    If I turn up the speed of my ender 3 during a print, do I need to increase flow to match it or does it compensate for the increased speed?

  • Reply lez briddon February 9, 2020 at 6:08 pm

    is the fan ok with a ramping up voltage to start, personally i'd have liked a bit of switch on hysteresis to give it a kick

  • Reply Felipe Goncalves February 9, 2020 at 8:40 pm

    Awesome Project !!!! Thanks .

  • Reply spooner Fpv February 9, 2020 at 11:03 pm

    Brilliant Chep

  • Reply Spenat1k February 10, 2020 at 4:57 am

    Good idea but that place you choose… You shoud do this right next to board and no need to cut fan wires

  • Reply Ron DLH February 10, 2020 at 6:59 pm

    Quite nice, you also could use a temperature switch, they are available for a wide range of temperatures. It will just switch on at a given temperature. The switch temperature you use is not very important because your hotend is at room temperature or above 150 degrees. In between it only spends a few seconds. Another alternative is to use an external MOSFET and hook in it up to an availabe IO pin. You would need to compile Marlin for this to work.

  • Reply Richard Burguillos February 10, 2020 at 7:25 pm

    Great mod! Like that circuit board machine. Thanks for sharing the fun.

  • Reply Thomas Hessel February 11, 2020 at 4:21 am

    Awesome Chep, would love something like this. Thoughts on taking orders and selling them?

  • Reply RomanoProductions February 11, 2020 at 12:45 pm

    Obligatory comment for mighty CHEP

  • Reply Victor Ramamoorthy February 11, 2020 at 5:21 pm

    To reduce the hysteresis, you can add another transistor (as a Darlington stage) to get a boost in the gain.

  • Reply A_Disciple February 11, 2020 at 6:37 pm

    I started hearing a weird noise in the motherboard housing like a buzzing noise. I opened it up and it seems the cooling fan doesn't want to spin up. The fan will cut down to like 1/4 speed and buzz. If i slap the mother board housing with my hand a few times then it will spin up and the noise stops. I checked all my connections and they are ok. Do you think the fan needs to be replaced or is this a mother board issue?


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