Seeking quiet electric motor

Dear Lazyweb,

My curtain automation is very loud. The idea was for it to open the curtains in the morning as a gentle reminder that the Sun exists and I should get out of bed, but the reality is that the noise rather than the light wakes me up most days.

As far as I can tell, most of the noise is coming from the motor itself rather than from the gearing or the curtain track, so I'd like to replace the motor with one that is quieter. It couldn't hurt to have one that was more powerful as well, since this one is clearly straining a bit toward the end of the cycle.

What am I looking for? I don't know how to shop for these things or how any of this is specified.

The existing motor is about 1" in diameter, and the replacement would need to be very close to the same size. You can see it in the photos. It's 12VDC now but with a little hassle I could run it on something else.

I may try building a padded box over the whole contraption, but that doesn't strike me as a very promising approach.


Victory! My curtain is now insanely quiet. Thanks to several of the suggestions here, it was a multi-pronged approach that did not involve replacing the motor at all.

  1. I opened up the box housing the motor and gearbox (pictured above) and packed it full of clay (Sculpey).

  2. I built a cardboard box to hang on the wall around that contraption, with just two holes at the top for the pulley ropes to penetrate. I lined the inside of it with PC-case sound-foam, and lined the outside with two layers of 1/8" mass-loaded vinyl. At that point, the motor was almost inaudible. The box isn't pretty, but it's hidden behind the curtain, so it's invisible.

  3. I then moved on to the next-noisiest thing, and lubed up the curtain track and its wheels with aerosol Tri-Flow.

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41 Responses:

  1. Wobin says:

    Maybe change the mechanism to a weight and pulley system, that silently uses a weight to draw the curtains open, and the engine to draw the weight back up at night when noise isn't an issue =)

    • jwz says:

      Sure, that sounds easy. I'll just re-engineer the whole thing from scratch instead of doing what I asked about, swapping out a single component.

      • Wobin says:


        Ask lazyweb, complain about solution. I figured that if you went to all the trouble to develop an automated system, you'd not be concerned about thinking outside the box to solve the problem in a different way.

        I'll let the engineers respond with an actual answer.

        • jwz says:

          Oh, there was a solution I was complaining about? I must have missed that part, because I thought I was making fun of your non-solution to a question I didn't ask.

          *click* Next caller, you're on the air!

  2. Joerg says:

    Approach 1: replace to motor. This is going to be rather difficult and will probably involve some trial and error, since you'll typically not know in advance how noisy the new one is. Brushless DC motors will generally be better, coreless ones even more so. But they can be prohibitively expensive. Otherwise a good start would be here or here. Mounting it may be a pita.
    Approach 2: silence the existing motor. Oftentimes the motor's vibration is amplified by cheap, puny casing, mounts or other parts around the motor itself. Smothering all that in pouring resin (after carefully sealing any openings in the motor, obviously) or stuff like Sugru (which I haven't used personally, yet) may help. That's the route I'd try first.

    • I 2nd this, finding the right motor, with the right spline or gear end, and the righ mounting holes and the right torque i suspect is way beyond your limited patience. not to mention after all that if its still just as noisy you have gained nothing.

      Your friend when soundproofing is mass, i would cover the motor holes with tape and then fill the block with plasticine clay (modeling clay). and then put rubber washers anywhere where it mounts to reduce noise conduction.

  3. Derek says:

    We use these in our lab:

    Might take a long time to open the curtains though.

  4. demcanulty says:

    It's probably too big for your casing, and switching to AC would probably require a couple other new components, but I seem to recall that mirrorball motors are pretty hefty and quiet.

  5. demcanulty says:

    Oh right, 1", well, maybe scratch that idea.

  6. Mattbot says:

    Motor torque is rated by the weight the motor can lift at a given distance from the rotor, usually expressed in pounds and feet but you might see it speced out as grams and centimeters. Lifting power drops off the further away from the rotor. If you can figure out the weight required to pull your curtains, you should be able to match it to a motor. Gear boxes can help with torque as well but it looks like you've got limited working space. Motor noise can be compensated for with the application of stereo volume.

  7. John Morton says:

    How does the current system figure out when to shut off the motor? Is it a function of the motor, gear box or some other circuitry? (I seem to recall you dumped much of the original controller.)

    • jwz says:

      It's mechanical: as the rubber wheel that pulls the curtain string turns, it also turns a wheel on the front which has adjustable stops attached to it. Eventually one of the stops bumps a 2-position switch, which is a sensor. This is how the original system worked, and I gutted it and kept just the motor, the gear chain after the motor, and the front sensor switch.

      • John Morton says:

        So it's fundamentally just counting wheel turns. I was considering scratch building a curtain controller using something like a Raspberry Pi for the electronics. Sounds like it'd just down to making a reasonable selection of motor and gearing now. Will talk to the engineers at work this afternoon.

  8. Tom says:

    You need some mechanical grease and cotton balls.

  9. I strongly suspect you have a gearmotor. This is a unit that includes both a motor and gearing. Motors on their own do not really make noise. The noise comes from gears or driver electronics (the latter emitting a high-frequency squeal, the former being more rumbly at one or more frequencies). So, the first problem if you need to find a motor that requires about the same voltage and current (amps), and is at least as powerful. Without changing the inputs (volts and amps) you can get more power (torque, usually newton-meters) by sacrificing speed (rpm).

    So, you'll need to figure out those aspects of your current motor, which is hard. Then you need to find a more quiet gearmotor which meets those requirements, which is almost as hard. Yes, this sucks. Your gearmotor will probably be more quiet if it has a higher rated lifespan (vibration being noisy and bad for longevity) and if it has plastic gears (which clank around less, but also reduce lifespan).

    Option B is to build a foam-filled box around the box that holds the motor. This is undoubtedly easier.

    Option C is to open the box up and hot glue/caulk down everything that isn't supposed to move.

    Technically, you can do any combination of A (replace the motor), B and/or C.

    • moof says:

      Figure 8 of the patent he cites shows at least three sets of reduction gears.

    • jwz says:

      You really think there are gears inside this thing? Because the rotating post coming out the other end of the motor drives a larger set of step-down gears that actually rotate things. Those, presumably, are the gears referred to by the patent.

      I haven't pulled it all apart to re-check, but I seem to recall from the first time around that the motor had no markings on it of any kind. I wish I knew what it was.

      • the motor by its self can you freely spin the shaft with your fingers? if so does the back end shaft rotate at same speed, if yes then no there are no gears, if its kinda stiff and you hear a whine, then yes, it has a small sun and planet gear reduction going on.

      • Hrm, so there's visible gears on the other side? Interesting. I'm guessing they're what's actually making the noise (unless it's both external gears and a gearmotor). You might try pulling the motor out of its case and running the motor alone (give some resistance with your fingers), and manually turning the external gears. Might help you figure out where the noise was actually coming from. I'm still thinking option B + option C are the sweet spot in terms of PITA vs sound reduction.

        • jwz says:

          I don't remember whether the motor with nothing else attached turned freely, but I do recall that the motor with nothing else attached was fucking loud. The external-to-the-motor gears are big and fill most of the other side of the box.

          • Was it loud (is it loud) in a mechanical things sense, or a high-frequency electronics (dying CRT monitor) sense?

            If you're set on replacing the motor, you're going to have to measure the RPM, voltage and current draw, and torque of the motor, then buy a similarly sized and specced motor that's relatively expensive, which should be quiet.

            ... you did contact the manufacturer, right?

          • hattifattener says:

            Interesting, in my experience it's usually the geartrain that makes all the noise in things like that (and it's sometimes integrated into the same case as the motor proper), but it sounds like it isn't in yours. If you literally do just need a quiet motor and not a quiet motor+gearhead, that's a lot easier. You could try buying a few appropriately-sized surplus motors from AS&S (per Helyx below) and using the quietest one. Physically mounting the new motor always entails more around-fuckery than I'd like though.

  10. I know you use the curtain automation for more than just waking, but I wanted to chime in on the waking part. I've been using a Philips Wake-Up Light for about a year now. There are some UI bits that are irritating (buttons that are impossible to tell apart by feel; buttons so stiff the whole unit sometimes slides away from me when I try to push them; it only has one stored light level, so you can't adjust lamp mode intensity without also changing the wake-up intensity), but the gradual light increase part is very effective for a gentle wake-up regardless of the color of the sky. When something caused the light to stop lighting (even after replacing the bulb), they shipped me a new one. There's been some model churn since I got mine; I have no experience with the laying-down cone style.

  11. Joe Loughry says:

    Just don't fall into the trap of thinking 'I'll use a stepper motor'. Mathematically alluring creatures, these little babies seduce programmers with the promise of 'turn exactly three hundred degrees clockwise and stop, then hold position'. But stepper motors are trickier than that. They have pitiful torque, and they like to run hot (100 degrees C is not unusual, so bolt that motor to a heavy piece of metal). H-bridges are prone to minor explosions and electrical fires. Fun!

    Agreed that looks like a PM gearmotor. Try the local RC hobby shop and see what they have in the way of electric airplane motors. That's probably going to be a pretty close size match with much higher reliability and low acoustical noise.

    • Logan Bowers says:

      Funny, I was about to suggest "use a stepper motor". Driver chips like the A3992 are quite nice because you can shift along torque-heat tradeoff with software. I built out a driver board for my RepRap specifically so I could get torque when I wanted it, and a cool motor the rest of the time. There's a small amount of (programmable) high frequency noise from the PWM current limiting, but jwz is old, so he probably can't hear it anyways.

      Granted, it would add 1,000 lines of code, and increase the part-count by 20 or so...

      Alternatively, if speed is not important, get a low-torque motor out of an, e.g., tape player or VCR. They will be very quiet and spin relatively slowly. You then need to couple it to a reduction gear, maybe you can find something suitable on alltronics ( Your blinds will open very, very slowly, but it should be pretty quiet.

    • Tim says:

      But stepper motors are trickier than that. They have pitiful torque,

      You're using the wrong stepper motor.

      and they like to run hot (100 degrees C is not unusual, so bolt that motor to a heavy piece of metal).

      Sure, if you make a habit of slamming full drive current through one of the windings when you've stopped the motor, 24/7. For an application like jwz's? Don't do that, that's stupid. A stepper driven for literally about 1 minute per day to open curtains in the morning and close them in the evening will not burst into flames.

      H-bridges are prone to minor explosions and electrical fires. Fun!

      No, they aren't. Not if you're competent at selecting appropriate components. Also, H-bridges are a generic circuit which is not inherently linked to steppers. You can use them to drive DC motors too. In fact, there's a pretty good chance the motor drive circuit jwz's already using is a H-bridge since it has 4 relays...

      All that silly fearmongering and you never mentioned what is by far the most appropriate reason for jwz to not re-engineer that box around a stepper motor: NOISE. Unless you use a (hilariously expensive and inappropriate for this application) microstepping controller, one of the common consequences of using a device with (usually) 200 discrete steps per revolution is lots of vibration. Especially at slower step rates. Not everything with a stepper is bound to be noisy, but hobby projects frequently are...

      • While what you said is true, I don't think it's applicable to the situation. AFAIK, jwz is not interested in "electromechanical designer" as his 3rd career, or even as a hobby.

        • Tim says:

          To clarify, I didn't think jwz would be interested in that much electromechanical hacking either. I just got irritated at someone being Wrong On The Internet.

  12. Helyx says:

    I've had good luck with American Science & Surplus,
    Most of their motors have all kinds of specs listed with them, and I know their customer service is good. You could probably call and see how loud X motor is.
    At least if you wanted to go with the original solution.

  13. Max says:

    Have you tried emailing the Add A Motor people? They might just point you at their more expensive curtain system, but they also might tell you something interesting.

  14. jwz says:

    Ok, well, I took the cheeseball way out and opened up both sides of the box and packed the interior with clay (Sculpey). Since it only operates for a minute at a time, hours apart, hopefully it won't overheat. Then I wrapped a tube of PC-case soundproofing foam around the whole thing. It's hidden by the curtain, so that jankiness isn't visible.

    It seems to have helped... At least, now it sounds like the rail is a more prominent part of the sound than the motor, so that's progress.

    Of course while doing this I managed to break the push-button for manually operating it, so now it can only be operated via ethernet. This is why I can't have nice things.

    • Steen says:

      "I have to ssh into my curtain now" is a sentence it turns out I have been looking forward to hearing.

      • jwz says:

        SSH? Luxury!

        % telnet curtain 10001
        Connected to (
        Escape character is '^]'.
        telnet> Connection closed.

        • Tim says:

          I just had to see if that FQDN resolved.

          $ ping
          PING ( 56 data bytes
          Request timeout for icmp_seq 0
          Request timeout for icmp_seq 1

          Oh, jwz. Why do you have to torment us like this? Making your curtain visible in the public DNS with a private non-routable IP address? My heart is broken.

    • Adolf Osborne says:

      I'm late to this party, but glad you got your motor noise more-or-less sorted. I wouldn't worry too much about heat with clay; it always seems a bit cool to the touch, which at least means its better at heat conduction than air alone, and you've got plenty of thermal mass.

      For the rail noise (it rides on ball bearings and stuff, yes?), assuming that the thing is still well-greased from the factory: A very mild damping fluid might actually keep things both lubricated and quiet.

      This is the stuff that makes good SLR lenses feel sexy to turn and allows tonearms to drop as if gravity applies differently to them than it does other things.

      ISTR that it is also used for center differentials for AWD cars, so someone is making serious quantities of the stuff...

      Or, if the track is not greased anymore (the grease has gone to glue, or you detect none at all), try Tri-Flow. Any reasonable bike shop has it for sale, commonly either in aerosol or a small squeeze bottle with a dropper on it. It fixes things, including noisy/sticky things, and things covered in ancient grease (without even cleaning the grease out first), and those things tend to stay fixed for far longer than anyone would ever reasonably expect. (And please do not be tempted to use WD-40, which exists only to make you buy more WD-40...)

  15. Proplas Int says:

    We're engineers in Burnley specialising in electrical motors and circuits, if you don't want to replace the motor, your casing could be an issue in this case!