nema17 dampers
Re: nema17 dampers
I got my Noctua fan today, but I ended up removing it from the enclosure. It doesn't seem to work well in series with the 30mm fan on the e3D. The extruder fan slowed down way too much. Will have to work on a way to wire them directly to 12 volts I guess.
Re: nema17 dampers
There's two independently controllable 24v outputs on the RAMBo (FAN1 & FAN2) ... I'm about 2 dead fans from converting all my shiz to 24v fans across the board, and using the auto-temperature & controller enable features to flip them on or off.
Custom 3D printing for you or your business -- quote [at] pingring.org
Re: nema17 dampers
You wouldn't happen to know what resistor and wattage I would need to put in series with a 12 volt fan to drop that 24 down to 12 would you?insta wrote:There's two independently controllable 24v outputs on the RAMBo (FAN1 & FAN2) ... I'm about 2 dead fans from converting all my shiz to 24v fans across the board, and using the auto-temperature & controller enable features to flip them on or off.
Re: nema17 dampers
The formula for resistance is:
R = E /I
or
voltage / current = Resistance
divide the voltage you want to drop across the resister by the current the fan needs and you will get the resistance value.
example: 12v / 0.1a = 120 ohms
the other thing is the wattage, so we need a higher wattage resistor then is actualy disipated power.
formula for power is:
P = I X E
or
current x voltage = wattage
0.1a * 12v = 1.2W
in this example, you need over a 1.2w resister, id opt for a 2w.
having said all this, the actual current a fan will use is dependent on the backpressure the fan has, it is not a constant current device and will not necessarily run at he current rating on the fan, but a bit less in many applications. so the actual value is less easy to come to but using the rating should get you close enough.
the real way to know the current is to measure it and use that value.
however, if you cant to that, usually fans are pretty resilient and can handle a bit of over voltage if you use the rated value as your calculation.
R = E /I
or
voltage / current = Resistance
divide the voltage you want to drop across the resister by the current the fan needs and you will get the resistance value.
example: 12v / 0.1a = 120 ohms
the other thing is the wattage, so we need a higher wattage resistor then is actualy disipated power.
formula for power is:
P = I X E
or
current x voltage = wattage
0.1a * 12v = 1.2W
in this example, you need over a 1.2w resister, id opt for a 2w.
having said all this, the actual current a fan will use is dependent on the backpressure the fan has, it is not a constant current device and will not necessarily run at he current rating on the fan, but a bit less in many applications. so the actual value is less easy to come to but using the rating should get you close enough.
the real way to know the current is to measure it and use that value.
however, if you cant to that, usually fans are pretty resilient and can handle a bit of over voltage if you use the rated value as your calculation.
M2 - MKS SBase w Smoothieware, GLCD, 24v, Upg Z & extruder stepper - IR bed leveling, Astrosyn dampers X/Y/Z, MIC 6, Zebra, PEI, & glass Build Plates - E3D, V3B Hotends, & more - many other 3d printers - production printing.
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Re: nema17 dampers
I tried to find a few silent 24V fans but I failed. Now I use ordinary noctua fans to a seperate power supply with 10V output. 50mm Noctua for the feeder cooling and 80mm Noctua for the RAMBO Board. The Noctua within the PSU runs with the internal 12V. The fan is noisy with the air pulling outwards but rather silent with the air pulling in.jdacal wrote:I got my Noctua fan today, but I ended up removing it from the enclosure. It doesn't seem to work well in series with the 30mm fan on the e3D. The extruder fan slowed down way too much. Will have to work on a way to wire them directly to 12 volts I guess.
BTW: I ditched the dampers, the cant handle the belt tension, after a few days the belt went really slack and the prints went bad. To many backlash added.
Ingo
Feel free to correct my mistakes. English is not my native language.
Re: nema17 dampers
i've run abut 5 spools though the machine since putting them on, no problems for me so far.
knocks wood.
knocks wood.
M2 - MKS SBase w Smoothieware, GLCD, 24v, Upg Z & extruder stepper - IR bed leveling, Astrosyn dampers X/Y/Z, MIC 6, Zebra, PEI, & glass Build Plates - E3D, V3B Hotends, & more - many other 3d printers - production printing.
Re: nema17 dampers
For the same reason mentioned in the other thread about the 12V vs. 24V fans, I wouldn't use the fans as part of a voltage divider. Although a resistor is a constant load, so you shouldn't have all the issues that can be caused by two fans (both dynamic loads) in series. It's better to attach the midpoint between the fans to a 12V voltage regulator; the regulator gets +24V to ground as input, and keeps both fans at 12V by adjusting for the load difference.jdacal wrote:You wouldn't happen to know what resistor and wattage I would need to put in series with a 12 volt fan to drop that 24 down to 12 would you?
Something like the Fairchild LM7812ACT would do nicely: 12V output, up to 35V input, regulates up to 1A (which is way more than the fans use), and costs $0.71.
Re: nema17 dampers
The main problem was I put the Noctua in series with the 12v 30mm fan that comes with the e3D and the loads were different so it wasn't working out too good. I have two 40mm Noctuas in series now and they seem to be working much better, but will try the regulator when I get time, I still don't think they are working at maximum efficiency.Tim wrote:For the same reason mentioned in the other thread about the 12V vs. 24V fans, I wouldn't use the fans as part of a voltage divider. Although a resistor is a constant load, so you shouldn't have all the issues that can be caused by two fans (both dynamic loads) in series. It's better to attach the midpoint between the fans to a 12V voltage regulator; the regulator gets +24V to ground as input, and keeps both fans at 12V by adjusting for the load difference.jdacal wrote:You wouldn't happen to know what resistor and wattage I would need to put in series with a 12 volt fan to drop that 24 down to 12 would you?
Something like the Fairchild LM7812ACT would do nicely: 12V output, up to 35V input, regulates up to 1A (which is way more than the fans use), and costs $0.71.
Re: nema17 dampers
Three-terminal linear regulators can only source current, so they cannot control the output voltage when it's higher than expected. When the current from the "upper" fan exceeds what the "lower" fan can absorb, the regulator can't hold its output voltage down.Tim wrote:the regulator gets +24V to ground as input, and keeps both fans at 12V
The problem boils down to assuming that digital brushless DC motor controllers inside the fans behave just like 19th Century big-iron DC motors. Interrupting the supply voltage with PWM doesn't produce the expected result, nor does putting the motors in series, because they're not that kind of motor. The digital logic inside the motor requires a constant DC supply, end of story.
If you're going to all the trouble of adding a regulator, rewire the fans so they get the proper voltage and be done with it. Better to use a DC-to-DC converter, though, because a linear regulator operating from twice the fan voltage will dissipate exactly as much power as the fans and will require an absurdly large heatsink for proper operation.
Re: nema17 dampers
Hmm, yes, you're right, I should have looked at the data sheet first. It only provides a current source, so the most it can do in response to an overvoltage is to shut off the current, which won't correct the overvoltage. I was thinking back to something I did on a chip once, controlling an intermediate value on a resistor stack with an amplifier, but that had both source and sink capability. So yes, I guess the only certain fix is to replace the 12V fans with 24V fans in parallel and call it done. Although if the 12V fans are preferred because they're less noisy, then it would be okay to connect them in parallel and drive them both from a single 12V regulator output.ednisley wrote:Three-terminal linear regulators can only source current, so they cannot control the output voltage when it's higher than expected. When the current from the "upper" fan exceeds what the "lower" fan can absorb, the regulator can't hold its output voltage down.
Thanks for the catch, Ed.