Any suggestion how to get a good estimation what I need, or even a motor and driver that are not too expensive and definitely strong enough? Also a source to order from Germany?
I plan to control it with an Arduino Nano, no special requirements for the interface, as long as I keep a few pins for sensors (a thermocouple, perhaps later gas sensors ...)
You need to do a torque measurement - weights pan hanging off a string can measure
force, add a side-arm of known length to the axle, and measure the force to pull this
(a pulley for the string may be needed). Calculate the torque from force x length of lever,
double it for a safety margin, that's the basic starting point.
@MarkT
Hm, ok ... I just hoped for something like [stepper motor for 15$] is so strong, it will definitely be enough.
@Chagrin
Well, yeah, I had one of those for playing around about a year ago (died quite fast - either the motor or the driver, dk) and I am quite sure that that one is NOT strong enough. It is surely strong enough to turmn a tin valve, but not the double doored, rubber lipped thing I have to turn. As I said, a rough estimate is opening a PET bottle - at least enough that I thought "Well, thats a bit hard to open".
The 28BYJ-48 steppers contain an internal gearing and will have about as much torque as a smaller NEMA 23 size stepper would. If you're going to buy a stronger stepper, with no gearing, you're looking at something that would weigh around 2kg and then you also would need a driver for it (another $20). Try http://www.stepperonline.com/ to get an idea of torque/size/prices.
You need to get some mechanical advantage to get this thing to pop open. A couple ideas:
Use a 28BYJ-48 stepper with a leadscrew with the nut attached to the control arm of the vent.
A "standard" size RC servo would be $10-$20 and provide around 5kg/cm of torque. Take the whole vent to a hobby store and ask for advice?
Use a DC gear motor with a worm gear and additionally a potentiometer mechanically connected to the control shaft for position feedback. Will also require a motor driver.
Ok, with 2,50$ for a 28BYJ-48, I can't do much wrong. I just ordered one. Any idea what could have happened to my first one? The 4 LEDs on the driver still blink (changing between -x-x and x-x-), but the motor does not move a bit. I used the example sketches from the Arduino IDE.
No guesses on what might have happened to your first stepper. Pretty impossible to tell from this distance.
Version 2 and 3 are pretty much the same thing, but version 2 is in a tidy package. Also, RC servos are limited to ~90 degrees of swing.
You really need to get a good estimate of how much force it takes to break the seal on the vent. MarkT described the basic idea; if it doesn't make sense please ask.
Measuring the torque is not a Problem in principle, I'm a (theoretical) physicist. The only issue is that I will not be at that Location for about a week.
90 degrees is all I want, so for a few bucks, I will go for the package.
Also, I took apart the 28BYJ-48, Still no idea what happend. Even without the whole gearbox, the Motor is only quietly ticking, but not turning. The core doesn't seem to be jammed, though.
You can test for motor damage by measuring the resistance of the coils (should be 130 ohms), and checking for coil continuity or shorts to the frame. You might get lucky, but if the vent seems stiff to you, buying a motor before measuring the torque to open and close it is likely to lead to disappointment.
Since this is a hvac vent check out a forum that deals with controls. A perfect motor, if there is one will work with this vent. Often however, the motors are vacum actuators.
Maybe a bit of topic but anyway:
A much better way to control airflow is controlling fan speed either with a VFD or by voltage reduction (depending on the motor). Uses less energy and gives lower noise.
@OpenMind
I don't really understand what you are saying.
@nilton61
This is the fresh air supply for a fireplace. There is no ventilator As it is in a not too well accessible place, I just want to manually open and close it remotely. In a second step, I might add some controlling using thermocouples in the smoke pipe, but that is future stuff.
As it is in a not too well accessible place, I just want to manually open and close it remotely. In a second step, I might add some controlling using thermocouples in the smoke pipe, but that is future stuff.