[HN Gopher] $30 Homebrew Automated Blinds Opener
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$30 Homebrew Automated Blinds Opener
Author : busymom0
Score : 150 points
Date : 2025-05-18 17:05 UTC (5 hours ago)
(HTM) web link (sifter.org)
(TXT) w3m dump (sifter.org)
| allenrb wrote:
| Would measuring motor current be a better way to determine
| torque? Not an expert but seems like you could sense voltage
| across a fairly small shunt to do it.
| 01100011 wrote:
| That's how we did it when I worked on a gate-arm/access control
| system. I'd monitor current and if a spike occurred I'd back
| the arm up because it likely hit something.
| cpgxiii wrote:
| Motor current is a workable, but generally unsatisfactory,
| proxy for torque when using heavily geared motors. Far better
| to measure output torque directly if you can, which is what's
| being done here using what is essentially a series elastic
| mechanism (itself a very common way of implementing torque
| sensing).
|
| To elaborate more, current sensing is only "better" in an ease-
| of-implementation sense, in that a lot of motor drivers already
| have current sensing built in/easily added. For some
| applications this is good-enough, but in terms of estimating
| "real number" torque from current, it can take a lot of work to
| characterize for geared motors.
| buescher wrote:
| Motor current is an excellent way to measure torque and is
| what is done in real-world settings all the time. As a
| hobbyist you might have to settle for relative torque if you
| aren't in a position to characterize a motor or you don't
| have manufacturer's data for it.
| cpgxiii wrote:
| I wouldn't say excellent. Motor current->torque is well
| correlated for motors in isolation, or with very low gear
| ratio. Not so with higher gear ratios. Can the current
| value be used to make control decisions for the motor? Yes.
| Does the current give you torque in Nm? No.
|
| In the robotics world this is sometimes distinguished
| between actuators that report "effort" (i.e. a current-
| derived estimate) and actuators that report torque (i.e.
| actual torque sensing or direct-drive with current
| sensing). Both can be useful, but "effort" is not torque.
| buescher wrote:
| Current will never directly give you torque in Nm which
| is a straw man argument - you will always have to know
| the motor constant, input voltage, coil resistance, and
| gear ratio to back out torque. That's characterizing the
| motor. Yeah, that's a lot of work for a hobbyist, but
| it's not at all unreasonable to consider a motor an
| excellent torque transducer - that's what it _does_.
| cpgxiii wrote:
| If the current->torque behavior of motors with gearboxes
| could be generally well characterized, the entire
| distinct market sector of "cobots" would not exist
| because every industrial robotics vendor would have long
| had good torque modelling on their actuators.
|
| As it stands, Universal Robots (and likely their clones)
| do use current->torque characterization for their
| actuators (which, amusingly, is then stored on a robot-
| specific USB drive or SD card), and their torque sensing
| is shit. Shit enough that for any useful force/torque
| application you still need a separate force/torque
| sensor. Schunk, for some of their electric parallel
| grippers with "force" feedback, only characterizes them
| at a single velocity and there is significant error in
| the force estimate at any other speed. _Good_ current-
| >torque characterization of a complete actuator is so
| difficult that approximately no vendors in the automation
| space are willing to do it.
| Karliss wrote:
| The main keywords here are high gear ratio and cheap
| parts. I am not making universal claims about all use
| cases. For most sane designs, sure electric motors are
| great at converting energy into torque. Normally you
| would want most of the electric energy to be turned into
| useful work. Which implies that electric power directly
| correlates with mechanical power or torque*speed. The
| same can't always be said about gearboxes, especially for
| some of those targeted at hobby/toy use cases with crazy
| gear ratios like 1000:1 or higher. Gear ratio can be so
| high that you will strip the gears or make the shaft
| connection slip long before you can apply sufficient
| torque to slow down the dc motor which is almost free
| spinning and spending most of it's energy to overcome
| friction in first few gearbox stages instead of doing
| useful work. In a toy or hobby project when you want
| something to spin slowly it might not matter that the
| gearbox is <10% efficient if it allows you to reuse same
| cheap brushed DC motor as hundreds of other toys.
| Increased torque is partially a side effect of slowing
| down the tiny motor not the primary goal, although at
| those slower speeds you probably want slightly higher
| torque but nowhere near as much as what the gear ratio
| gives in theory. Even some non toy use cases like cheap
| home appliances might occasionally use crappy inefficient
| gearboxes and dumbest electronics possible, especially if
| the 1-3W motor isn't main consumer of power. There might
| not even be motor controller or MCU to monitor the
| current.
|
| It's not always question of lot of work for hobbyist, as
| it is result of using cheap of the shelf parts and
| modules which are optimized with different goal in mind
| and give very poor signal to noise ratio. Doesn't matter
| how much characterization you do if the change in
| temperature, grease viscosity and distribution, plastic
| flex produces higher variance in motor load than any
| force you can apply to final gearbox stage. I guess the
| more careful choice of suitable combination of parts from
| more specialized stores can be considered "lot of work
| for hobbyist" compared to picking first result on amazon
| or whatever you found in your junk bin so your argument
| still stands.
|
| Of course high gear ratio or slow speed doesn't always
| mean inefficient gearboxes. There are solutions for slow
| rotation with or without high gear ratio which are
| reasonably efficient thus allowing to use motor current
| for estimating torque. And any serious or well designed
| equipment will use them. But that usually means more
| complex gearbox, motor controller or purpose built
| electric motors all of which is either more expensive or
| require high MOQ orders from manufacturers.
| numpad0 wrote:
| There was a news story few days ago that Sony is launching
| an Ethernet controlled smart motor with integral reducer
| for robotics applications, and it has encoders on both
| sides of the reducer plus torque on output shaft. There's
| nothing so far on the English side of the public Internet
| about it, at all.
|
| ... so I doubt motor torque be end all be all. Especially
| when Sony does it like that.
| theywillnvrknw wrote:
| Sorry, I had to post this :|
|
| if Apple made window blinds...
|
| https://www.youtube.com/watch?v=Hv6EMd8dlQk
| neilv wrote:
| What are the child safety considerations to be careful of, with
| blinds, and with openers?
|
| (I recall seeing warning stickers and design changes on ordinary
| miniblinds. I suspect that one of the changes involved having
| multiple pull cords be separate and loose, rather than a fastened
| together or a single looped cord. But I'd guess that's not the
| only safety design decision.)
| madaxe_again wrote:
| I think the principle two things are "they can't pull it off
| the wall and onto themselves" and "they can't hang themselves".
|
| With automatic openers you add "they can't get snarled up/lose
| a finger in the mechanism" and "they can't electrocute
| themselves".
|
| I went _extremely_ belt and braces with our blind opener - but
| it is toddler proof. Attached the lower end of the cord to the
| ceiling, attached a pulley that hangs on the cord, hung a 1kg
| weight from it, and used a solenoid from a broken linktap valve
| to pull a pin that allows the weight to fall and pull the cord.
|
| Even with the blinds open the whole assemblage is entirely out
| of her reach, and it goes for the opposite effect to the
| poster's implementation - blinds slam open in about half a
| second with a quiet whirr, as I prefer a jarring wakeup, and my
| wife would sleep through Armageddon. Reset is manual, but
| that's fine, closing them is an optional and trivial activity.
| AStonesThrow wrote:
| What are the safety considerations of smart blinds opening up a
| bedroom at inopportune moments, such as children playing
| outside while you're having sex or changing clothes?
|
| Is there a lockout mode for "I/we are not decent" or do the
| blinds just sort of majestically reveal the bedroom to your
| backyard/parking lot observers like curtains opening on a
| feature film?
| buescher wrote:
| UL 325 covers them and can be read (but not printed or saved)
| on UL's website if you register. More dangerous than you might
| think though the real horror stories are with stage curtains.
| PSA for hacker news: Safety is the product of a process, not a
| feature, and standards are written in blood. You don't get
| there by surmising, no matter how skilled, clever, or well-
| intentioned you are.
| notpushkin wrote:
| It totally can be saved if you try hard enough (and are not
| afraid of a pretty scary legal warning in the free view
| feature).
|
| If the UL devs read this: if you want to cut your AWS bill,
| perhaps don't send the images as BMP?
| AnotherGoodName wrote:
| Fwiw automated blinds in the bedroom are a 100% no brainer
| benefit. It's wonderful and better than an alarm clock with 0
| mental load (set the times to open close across the week once and
| then never think about them again, you can keep the weekend
| manual if you like).
|
| As in a lot of home automation actually makes things worse.
| Replacing a convenient light switch with an app? 100% terrible
| idea and actually makes things inconvenient, don't automate
| those.
|
| But the blinds, specifically those in your bedroom? Do it! One of
| those life hacks that's really not that expensive and makes your
| life better with 0 cognitive load after initial setup.
| dzhiurgis wrote:
| You are making assumption I want to wake up that early.
|
| Quite opposite - I'm searching for way to completely black out
| the room since kids will wake up with slightest shred of light,
| far before daycare starts. And I'm not even living if far lats.
|
| But yeah I still want them for convenience. Problem is I don't
| want cables dangling around curtains and battery options are
| limited.
| Etheryte wrote:
| This comment makes no sense. You choose when you want your
| automated blinds to open, if you don't want to wake up early,
| just don't set them to open early?
| ranger_danger wrote:
| This comment also makes no sense... they said _completely_
| black out a room, which blinds alone cannot do.
| J_Shelby_J wrote:
| Batteries last more than a year and you can get ones with
| solar panels to recharge them.
| XorNot wrote:
| I just hard wire mine by going through the cornice with a
| flush conduit. It's a good place to put the manual shutoff
| switch as well.
| cortesoft wrote:
| My blinds don't work as an alarm clock for me at all. I sleep
| with a pillow over my eyes, no amount of light is going to wake
| me up.
| sgt wrote:
| That'll just make it too easy for an assassin.
| kulahan wrote:
| I use a silk sleep mask. They're incredible. Added benefit is
| that it helps hold your eyelids closed on days when you're
| not very sleepy. It's also one thing I only do when actually
| attempting to sleep. I swear I get sleepy the second I feel
| that super-light tension on my head
| goda90 wrote:
| I've got Home Assistant set up and the app on my phone. But the
| only light switch I have automated is done with a standalone,
| battery powered timer with a motor to turn a dumb switch on and
| off. It's on my porch light so it turns on and off without me
| needing to be home or paying attention. Only have to override
| it on Halloween and shift it with the seasons.
| WaitWaitWha wrote:
| > As in a lot of home automation actually makes things worse.
| Replacing a convenient light switch with an app? 100% terrible
| idea and actually makes things inconvenient, don't automate
| those.
|
| The key to proper home automation is not to destroy the
| "normal" functions already in place, but to augment them with
| automation.
|
| Smart switches that do not function without connectivity are
| not smart. I discourage new implementation of smart-bulbs too
| as they break the "normal" bulb-switch function. I discourage
| smart plugs for the same reason. Same thing with valves.
| Imagine a valve that cannot be turned on or off manually.
| Horrific.
| AnotherGoodName wrote:
| My own scoreboard is how little i think of it.
|
| An automated porch light that hasn't been touched in 10years
| and blinds that had the schedule setup once and forgotten
| about for 5 years are examples of fantastic automation.
| tasuki wrote:
| > Do it! One of those life hacks that's really not that
| expensive and makes your life better with 0 cognitive load
| after initial setup.
|
| I'd love to, actually. But where do I even start? How to choose
| the solution? I have some old blinds which leak a lot of light
| and wouldn't mind replacing them. Guess my only hard
| requirement is for the blinds not to connect to the internet.
| J_Shelby_J wrote:
| I just want to share that these are by far the best home
| automation you can have. I love my smart lights, hacked together
| smart humidifier, smart fans (the vornado dc fans with outlet
| switches), intake air pump, and air quality monitoring.
|
| But nothing has the quality of life impact of smart blinds. It's
| the best, and probably only, way to reliably keep your sleep
| schedule in sync. Smart lightbulbs - four of the brightest you
| can buy - are nothing compared to a window on a cloudy day.
| threatofrain wrote:
| Could we hear more about your home automation stack? I'm
| looking to get into this myself.
| joshvm wrote:
| Can't speak for OP, but just get Home Assistant running and
| play around. It'll work in Docker in anything, but it's a
| good use for an old Raspberry Pi. There isn't much more of a
| stack than that, and HA is by far the most polished OSS
| solution.
|
| It's got some sharp edges - every time I've done a major
| auto-update it's broken something critical. You can run it
| alongside other controllers like the Hue Bridge, which is
| nice to have as a backup (since 90% of what most people
| connect is smart lighting). Probably the most useful simple
| automation I have is an motion activated dim light in the
| bathroom at night, but that's using Hue.
|
| Then look at ESPHome, which is an ecosystem for making your
| own DIY sensors and controllers that can feed into HA. For
| example we have a Sensirion air quality sensor that triggers
| a smart switch connected to a fan if the particulate level
| gets high when cooking. You can go a very long way with
| on/off to control non-smart devices, and your sensors don't
| need to be particularly accurate (like absolute PM2.5) as
| long as the conditon you trigger on is repeatable.
|
| The only thing to think about is what hardware ecosystem
| makes sense for you. For example there's at least four
| different competing standards for connectivity (WiFi, Zigbee,
| Z-Wave, Matter/Thread, etc). So getting a Zigbee dongle isn't
| a bad idea because then you can connect any IKEA or Hue
| device (among others).
| Larrikin wrote:
| Home Assistant is nice for this crowd in that you can
| actually use a real programming language to do the
| automations. I went with PyScript but NodeRed is very
| popular as well. No need for YAML
| J_Shelby_J wrote:
| Same. I use the hue automations to handle the lights. HA is
| for everything else.
|
| The hue motion sensors pay for themselves pretty quickly.
| asdefghyk wrote:
| RE ".....if the particulate level gets high when cooking
| ....." What is the particale counter level you use ? The
| number ? Just curious.
| J_Shelby_J wrote:
| The home assistant $100 stand alone device. Pretty seamless
| user experience. On par with what you would expect for a
| consumer device as far as UX. Maybe could be a bit more
| polished but you can do pretty much anything with it as far
| extending the ecosystem. My only complaint is that writing
| automations in untyped yaml sucks. Fortunately, if you dump
| the docs in an LLM it can one shot most things - if you're
| trying to do something the gui automation tool doesn't
| support.
|
| The rest is zigbee and zwave switches and sensors. You can
| get cheap ones from ikea. You can get nicer ones from Zooz. I
| like Apollo for air quality sensors. The humidifier is the
| German brand Ventura. Zero maintenance. But it's not smart so
| I got a power outlet that reports power usage. When it runs
| out of water the humidifier shuts off and the power goes to
| zero, so I have an automation that detects that and sends a
| message via the HA app.
|
| Living in California and having fans move air around from
| cool rooms to warmer rooms has cut our AC bill significantly
| as a dc fan is a fraction of power consumption of a whole
| house AC. And also co2 levels stay much lower. Last week I
| set up my window fan to blow air in whenever it's cooler
| outside then inside.
| seanalltogether wrote:
| Automated blinds can also have a good effect on temperature
| control. In the summer you can have your south facing blinds
| automatically close when you leave the house to block out the
| sun.
| Spivak wrote:
| So that's a funny thing, your blinds are on the inside of
| your house so the sun energy is hitting them and dissipating
| from there. Hopefully your blinds are white and reflecting
| more of it out than the other surfaces it would otherwise
| hit. But if you want to make a real temperature difference
| you need blinds on the other side of the insulated box
| otherwise known as an awning.
| blacksmith_tb wrote:
| The only tricky part being that it's desirable to limit the
| amount of sun shining into the house in the warmer months,
| but not the cooler ones. Awnings that fold or are otherwise
| removable are a reasonable solution, there are also
| sunshades which mount outside, and also use a spinning rod
| to raise and lower (if the electronics and motor here could
| be weatherproofed a little they might be quite usable).
| asdefghyk wrote:
| Having the blind close to the window and covering at
| least a extra 6 inches or 15 cm band around edge of
| window significantly reduces light spillage into the
| room, when the blind is down, in my experience.
| foobarian wrote:
| The blinds shown under this article are pretty ordinary vinyl
| type blinds that leak a ton of light. I wish I could find
| blinds thick enough to behave like cardboard over windows, that
| could also be opened on a daily cadence.
|
| At this point I gave up on blinds and put a shirt over my eyes
| to sleep. I thought about just covering the windows permanently
| but I don't relish that idea.
| zymhan wrote:
| Curtains.
| ojame wrote:
| Not sure what country you're from, but "blockout blinds" are
| likely what you're looking for. They blockout (essentially)
| all light and are operated like normal blinds.
| danielheath wrote:
| Have never seen blockout blinds which stop enough light
| during the day - they leak enough to be comparable to a
| reading lamp, since outdoors is so bright.
| sokka_h2otribe wrote:
| Mounted internal to the window frame, not external, works
| better for me. Internal can ride tighter to the window,
| so light can't go out the edges. With external frame
| mounting, you need much wider shades.
|
| If the fabric itself isn't blocking light... You need
| better material. I have only ever had problem with light
| leakage in the edges, not in the fabric material.
|
| I believe 'blackout thermal shades' is what to look for.
| danielheath wrote:
| You can get very nice sleep masks (padded, shaped to your
| head, etc) for under $30 online (or much less pleasant ones
| for a few dollars).
| TheKnack wrote:
| I have these on all of my blinds and they are amazing. You can
| sometimes get them on sale for $50-60 each. They come with a
| solar panel that keeps them charged. You can add a hub that makes
| them work with HomeKit.
|
| https://us.switch-bot.com/products/switchbot-blind-tilt
| xyst wrote:
| Person just wanted to automate a few "dumb" appliances but ended
| up building his own system (software and hardware) to do this.
|
| I wish I had time to bike shed like this. Just learning,
| tinkering, and enjoying life.
| asimpletune wrote:
| Does anyone know if something like this already exists for the
| heavy duty, built-in shutters they have in Italy? The kind that
| close and form a barrier over the window and are operated with a
| flat roll of fabric from inside.
| notpushkin wrote:
| I've seen those somewhere in the Southeast Asia so I think I've
| got what you're saying. The challenge would be to replace the
| stopper you currently have (because it's hard to work around it
| with a motor) and replace it with something you can activate
| electrically.
| patrickk wrote:
| They also have them in Germany. I used to have the manual "flat
| roll of fabric" in the past, and upgraded the entire rollers in
| the house to electric ones (I don't know if it's possible to
| only upgrade the fabric roll -> electric switch without
| upgrading the entire shutter).
|
| After you have electric-controlled rollers, you can control
| them via any automation you want by installing a "Shelly Plus
| 2PM" device behind each switch.
|
| I connect the Shellys to home assistant, and from there,
| trigger all the rollers to go down a certain number of minutes
| after sunset. They all rise at a certain time in the morning.
| You can always trigger them manually too, of course. ChatGPT
| can spit out very complex YAML for HA if you want to make life
| easier, your only limit is your imagination.
| lultimouomo wrote:
| Yes, the keyword you are looking for is "tapparella
| motorizzata".
| tayo42 wrote:
| I need to figure something like this out. My bedroom has this
| arch window about 3-4ft wide that's over 10ft high that I've
| permanently blacked out so I can sleep in. I'd love an easy way
| to open it and get light in the day though.
| ge96 wrote:
| Funny I used that white magnetic encoder and now I see it
| everywhere
| vanschelven wrote:
| I wondered what an "homebrew automated" was and by which
| mechanism it could blind the person who opened it...
| ThrowawayTestr wrote:
| I love the choice of enclose.
| KennyBlanken wrote:
| "I doubled up the relays feeding the main motor and the heating
| coil, which gives a lot more headroom on the amperage"
|
| ...That's not how that works. One of the relays is going to close
| first, and those set of contacts will take all the load.
| Similarly, one set is going to bear all the drama from breaking
| the connection (and with the motor, there's inductive kickback.)
|
| The correct way to do this is to look up the motor rating for
| your relay and then size accordingly, not to do dumb shit like
| "oh I'll just double up these two relays."
|
| Of course he fucks up and uses a resistor from mains to logic,
| too. Mains and logic should never, ever, _ever_ come anywhere
| near each other. They 're supposed to be physically isolated on a
| PCB, cutouts in the board, even.
|
| Don't fuck with mains / appliances / HVAC / household water
| supply if you don't know what you're doing. This guy has no
| fucking idea what he's doing, and some winter day he's going to
| come home to a house that's 100 degrees inside and a flooded
| first floor (notice he didn't connect the water leak sensor?)
|
| Home insurance is scummy, annoying, difficult and weasely in the
| best of circumstances. The second they figure out you had some
| chewing gum and duct tape hodgepodge running your dishwasher and
| that's what caused the flood, they will not only refuse to pay,
| they'll cancel your coverage on the spot.
|
| Then you find out the joys of not having home insurance coverage
| on a house with a mortgage.
|
| Edit: Holy christ I missed this part: "It seemed to be due to the
| push-on jumper cables either becoming too loose after years of
| jiggling or perhaps oxidizing and self-insulating a bit."
|
| That is how you start a fire, people.
| robocat wrote:
| > Don't fuck with mains / appliances / HVAC / household water
| supply if you don't know what you're doing. This guy has no
| fucking idea what he's doing
|
| A little OTT. How do people learn to maintain their house or
| learn to hack improvements? Should we all have your expertise?
| Perhaps you think paying a qualified installer would be better?
|
| Any work on your home or car or whatever runs risks. Making
| mistakes is often an important part of learning (and can be
| expensive). Being a Swiss watch isn't a good compromise.
|
| It is great that you share your knowledge: good feedback is
| difficult to get.
| shepherdjerred wrote:
| For roller shades, I've had success with Ryse SmartShade [0] +
| their WiFi hub + Home Assistant.
|
| Setup was not straightforward at all, and I have 10 windows, but
| it was worth it in the end.
|
| You can write automations in YAML (or TypeScript with [1]), and
| your blinds can also be controllable with Siri or whatever voice
| assistant you like.
|
| [0]: https://www.helloryse.com/products/rysesmartshade
|
| [1]: https://docs.digital-alchemy.app/
| duxup wrote:
| I have a south side back of house open kitchen / dining / living
| room on my house. 11 Windows.
|
| I have consumer model power roller shades. I love them. If you
| have a room that gets lots of sun / you like the views, being
| able to hit a button and open it's an amazing quality of life
| thing.
| js373054 wrote:
| If you want something less jank I suggest this
| https://www.thingiverse.com/thing:2071225
|
| 3d printed gear box with a servo that sits inline with the shaft.
| Invisible outside of the blinds if you route the cables
| correctly.
|
| I controll mine with esphome and home assistant rock solid for
| years
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