Thanks for the replies - very helpful!
@dc42 - the X/Z/E steppers are 4 wire, the Y is 6 wire but with 4 wires going into it.
That stepper motor has 3.3 ohms resistance (close!) and 1.2A rated current.
I looked up Nema 17 motors with 48mm body length (the closest they had to 46mm) at https://www.omc-stepperonline.com/nema-17-stepper-motor?mfp=149-step-angle[1.8],183-body-length-mm. the closest they had in resistance were 6.2 ohms for the 0.85A motor, and 1.65 ohms for the 1.68A motor. To a first approximation, for constant body length the rated current should be inversely proportional to the square root of resistance. So a motor with 0.3 ohm phase resistance would have a rated current of 1.22A (based on the 0.85A motor) or 1.25A (based on the 1.68A motor). So I think it's safe to say that the 3 ohm 46mm long motor has a rated current of around 1.2A or a little higher. I suggest running them at between 0.8 and 1.0A.
Awesome, thanks for the detailed help! I'll try that, and leave a thermocouple on the steppers as well as previously suggested. Looking closer at them, I see I was actually wrong about the other ones (so FB poster was definitely incorrect), the Z are actually the same as the Y, and the X is 40mm body with 1.8Ohms (also 6 lead plug, 4 going in). So I guess they chose lower weight, and they compensated by using a higher current model... perhaps! Bit of a head scratcher. Anyway closest on the OMC site is then 42mm body, 1.65Ohms, rated current 1.68A. If I am calculating right they from what you said, mine should be 1.41A in that case. So I'll try it at 1.1A to begin with.
By the way, while I have you - I've gotten tired of naff, noisy 5015's and am thinking of using a 5v radial CPU fan from ebay on the hot end. One I am looking at claims 250ma in the listing but the sticker in the pic says 350ma <sigh> - looks like other CPU fans are all pretty high current, so should make for good part cooling. Would these current levels be OK for the internal 5v on the Maestro though, or would it be better to add in an external 5v supply?
Edited: Just need one fan, not two.
Edit again: For higher current fan, I could create an external circuit taking PWM signal from board, ULN2003LVDR should do the job again, but I'm not so familiar with PWM fans so be nice not to have to!
Are you not able to find a suitable radial fan that runs from your VIN voltage, which I presume is 12V or 24V?
The 5V regulator on the Maestro should be OK up to at least 1A.
I could find them, sure, but I'm thinking good quality CPU fans would be better - if I can get 1A out of the on board regulator, that is great and they should be perfect for the job. Long lasting, quiet, high flow.
Veti last edited by
get a noctua fan for the hotend.
its 0,07 A
Nice but all axial, really needs to be centrifugal for part cooling. I'm curious about dropping a CPU fan in anyway, lots of options there to play with.
Just writing this to add to the knowledge base, in case anyone else wants to try using a CPU fan....
So I tried 25k Hz and it didnt work at all, although I had already tested with an arduino PWM output so knew the fan was good. Hooked up to a 50% duty variable frequency signal generator and it turns out that very low frequencies work best. I settled on just 30Hz. Much above this, maybe 50+hz and the fan starts to make audible tones, getting worst as you get higher, higher still and the airflow will reduce down to nothing. Below 15ish Hz and the airflow starts to oscillate. Now its up and running though, it is perfect for the job - high power, quiet and hopefully extremely reliable. I used one with a part number GC055510VH-A, fits lenovo ideapad B450 etc.
Addendum: My CPU fan seems to have some sort of onboard power management, and reduces its speed either based on time or sensing "blockage" not sure yet. Requires power off/on again to reset back to previous high flow. Most annoying! Not sure why it does this, but others may with to avoid going down this route...
On the other hand, my above PN for the fan is actually wrong, I nearly bought it but then went with ZC0560120VH-6A, which is 4 pin and therefore tacho controlled. Perhaps a 3 pin fan wouldnt be so picky? Assuming it is for PWM and not tacho again... I'll test one. Also possible is that adding a circuit to regularly reset the fan, would be a workaround, although that is probably more hassle than it is worth...
The safe and sure way of making a fan work with PWM when it really doesn't want to is to use an inductor in series with it and a very high PWM frequency. A flyback diode is also needed if the output doesn't have one built in.
Thanks, good to know - although I'm not sure it would work with a 4 pin, as the control circuit probably wants a certain voltage to function? But thinking more about 3 pin cpu fans, I think it should be good. I just bought one to test, at 400ma it pretty much has to be speed controllable, but also the laptop needs to know RPM to monitor for fault. So third wire must be tacho, therefore it "should" be PWM control like standard 5015 fans. If I can get it to work consistently, then it really is an excellent solution. Previous one (280mA) was seriously powerful before the control circuit kicked in, and they are not even expensive.