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$30 Homebrew Automated Blinds Opener (2024)

sifter.org

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Re: $30 Homebrew Automated Blinds Opener (2024)

#11

Post by buescher »

neilv wrote: post #4

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.)

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.

Re: $30 Homebrew Automated Blinds Opener (2024)

#12

Post by rapestinians »

neilv wrote: post #4

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.)

[flagged]

Re: $30 Homebrew Automated Blinds Opener (2024)

#13

Post by buescher »

cpgxiii wrote: post #6
allenrb wrote: post #2

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.

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 moto…

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.

Re: $30 Homebrew Automated Blinds Opener (2024)

#14

Post by cpgxiii »

buescher wrote: post #13
cpgxiii wrote: post #6

Earlier quoted context omitted.

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 moto…

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.

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.

Re: $30 Homebrew Automated Blinds Opener (2024)

#16

Post by buescher »

cpgxiii wrote: post #14
buescher wrote: post #13

Earlier quoted context omitted.

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.

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 r…

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.

Re: $30 Homebrew Automated Blinds Opener (2024)

#18

Post by notpushkin »

buescher wrote: post #11
neilv wrote: post #4

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.)

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.

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?

Re: $30 Homebrew Automated Blinds Opener (2024)

#19

Post by threatofrain »

J_Shelby_J wrote: post #8

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 brigh…

Could we hear more about your home automation stack? I'm looking to get into this myself.

Re: $30 Homebrew Automated Blinds Opener (2024)

#20

Post by seanalltogether »

J_Shelby_J wrote: post #8

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 brigh…

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.
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