12 ms·

A few years ago, I ordered the cheapest six-axis robotic arm from ebay for about $100 that came with basically no software or motor-driver boards, so I did it a

A few years ago, I ordered the cheapest six-axis robotic arm from ebay for about $100 that came with basically no software or motor-driver boards, so I did it all from scratch with a PCA9685 board, a basic kernel driver and some very hacky scripts from user space. One day I had some friends over for a glass of wine, and wanted to show off my creation. I invited them into my "lab" and placed my wine glass down on the desk so I could type a few commands with both hands. My rudimentary software had some motion smoothing once it was up and running, but upon initialization, if the arm was significantly displaced from where it had been when it was turned off, the PWM board would instruct the motor to immediately "be" in a position that required the arm to travel clear across the desk in effectively as little time as possible. In this case, where it had been previously happened to be where my wine glass was now, and the flimsy aluminum at high speed was enough to shear the stem from the glass and explode the bulb. Luckily the wine didn't get in any sensitive electronics, but I learned a valuable lesson about the difference between messing around with hardware vs software.

its_nikita 5y ago
That's a good story. Yeah I feel like there must be soo many more opportunities to physically damage/harm something from robotics than software alone.
- LeifCarrotson 5y ago
  Anything with an actuator, really. I'm a controls engineer, we work with all kinds of hazards and it's my responsibility to run the risk assessment that makes sure no minimum-wage operator gets harmed because of our machine. People are the squishiest, weakest, most sensitive part of just about any shop, so there's a lot of risks to assess! One key observation, though, when working with code is that the machine becomes so close to predictable that it's more dangerous than if it were unpredictable. A cordless handheld drill is hardly a tool that most people would call 'hazardous'. You turn the trigger, the thing rotates, grab the chuck and you can likely stall it. But that much energy in something driven by code is extremely dangerous, it's waiting for any of who knows how many conditions to take off, a common one is that putting your hands in/on something that seems to be not moving can 'make' a sensor and the machine will take off. There are definitely two kinds of safety domains, one applies to manually operated tools where the operator of, say, a knife is responsible for their own safety - if they cut themselves, they're at fault, not the knifemaker. There's another kind of safety engineering where if the machine takes off 'by itself' while an operator is in the way it's the machine designer's fault for not stopping that from happening, the operator can't be expected to know what's going on. The latter should become more common as computers continue to permeate everything we use - that cordless drill is no longer controlled by the operator with a trigger switch that connects power to a DC motor, it's a brushless motor driver with an analog input sensing the position of the trigger and the EMF of the motor, and the charge state of the batteries, and who knows what else. Bump a sensor and it might take off, you don't know why it does what it does. I'll continue to make my automated cells as safe as I can, but don't trust code that's not so simple you can be confident of how it works.
  - dharmab 5y ago
    > A cordless handheld drill is hardly a tool that most people would call 'hazardous'. You turn the trigger, the thing rotates, grab the chuck and you can likely stall it. But that much energy in something driven by code is extremely dangerous, it's waiting for any of who knows how many conditions to take off, a common one is that putting your hands in/on something that seems to be not moving can 'make' a sensor and the machine will take off. A friend needed a valve cover gasket changed on his Honda, and his wife needed to use the car for her Uber runs that night. He came over and instead of our usual hand tools I put a socket adapter on my 20V drill to speed up disassembly. I handed the drill to him and told him "start on the lowest torque setting, and move up in small steps." I turned around to grab more tools from the toolbox. A minute later, I heard a loud noise. I turned to see the car's windshield cracked and a shocked look on my friend's face. My friend was used to his renter's power drill. He hadn't anticipated how much torque a modern contractor's drill outputs and set the torque to the maximum setting. On the third valve cover bolt, the drill had caught on the bolt head and spun my friend around, smashing the battery into the windshield. There's a piece of paper taped to me toolbox called "List of things <friend's name> may not attempt unsupervised." It gained a couple of entries that day...
    - whatshisface 5y ago
      Why would a drill be engineered to put out more torque than a human holding the handle could be expected to counterbalance?
      - dharmab 5y ago
        For drilling holes in soft materials like drywall and wood, or even softer metals like aluminum. I recently used that drill to drill into a motorcycle engine to remove a stuck rotor cover. Relevant old article: http://www.team.net/mjb/hawg.html http://www.team.net/mjb/hawg.html
      - duskwuff 5y ago
        Powerful electric drills will often come with an extra handle on the side (or a mounting point for one) so that you can brace them with both hands. It's up to the user to set an appropriate torque limit if they're only using one hand.
- rohansingh 5y ago
  Heh, you don't even need proper robotics. Back in 2002, I was getting a package with a brand new Pocket PC (smartphone without the phone, running Windows). And I really wanted to know when it was delivered, but the UPS guy would regularly leave packages on the porch without ringing the bell or anything. This was before you could get delivery alerts or anything like that. But I had a spare laptop with an integrated webcam (wow!), and I'd figured out how to make it run actions on motion detection. My plan was to point the laptop at the door, and eject the CD drive when it detected motion. The tray of the drive would push a water bottle off the table. That would land on a seesaw, which would launch a deck of cards in a hard plastic case at the door and make a very loud noise. It's unclear why I couldn't just play a really sound on the speakers instead. Anyway, I tested the program by standing in front of the laptop and waving my hand. It worked perfectly! The CD tray ejected, and I watched as the water bottle slowly rolled off the table. It dropped onto the seesaw...... and instantly launched a hard plastic deck at my face and got me right between the eyes. Never again have I been in so much pain and also so excited about my code working perfectly at the exact same time.
  - faceplanted 5y ago
    This made me actually laugh out loud, it feels like some of the things I came up with as a teenager wanting to do robotics and automation but having no money or way to purchase things online, water bottles were actually a good way of powering things like opening curtains by dropping them on a string. Also I like that even after you came up with "knock something off the table" you felt you needed a seesaw catapult thing and didn't just knock something off that could make the actual sound like a cake tin or bell or something.
    - rohansingh 5y ago
      > Also I like that even after you came up with "knock something off the table" you felt you needed a seesaw catapult thing and didn't just knock something off that could make the actual sound like a cake tin or bell or something. It totally doesn't make any sense! I think I might have been fascinated with the idea of Rube Goldberg machines or something at the time. Or maybe I thought I could build a "security system" with it? Also it was summer and I was a bored teenager.
isatty 5y ago
I used to do robotics, I can tell you that the fact that it was the cheapest or the most hacky does not matter in the least. Everything can and will go wrong, even the priciest and well documented part. I used to have multiple clamps around the controller, message bus, the firmware and also a physical barrier, and yet would not feel safe with my fingers or person around moving parts.
- AlotOfReading 5y ago
  Yep. When I have to work with robots, it's from a distance and with as much safety equipment as possible. I've seen too many physical, hardware, and software failures to risk anything I care about. Hearing protection is also important. A hundred pounds or more of metal slamming into itself at high speed makes a deafening sound.
  - _pmf_ 5y ago
    Every hardware demonstration is like the board room scene from Robocop: https://www.youtube.com/watch?v=ZFvqDaFpXeM https://www.youtube.com/watch?v=ZFvqDaFpXeM
    - deleted 5y ago
      [deleted]
  - faeyanpiraat 5y ago
    I’ve read a story somewhere, that someone trying to fix something in the toilet had to be in a position close to the toilet, then the lid accidentally fallen shut and the guy had his hearing damaged because the toilet bowl somehow concentrated the noise in one point where his head was. It’s weird how even ordinary things can be dangerously loud.
    - softblush 5y ago
      https://threadreaderapp.com/thread/979583605637877760.html https://threadreaderapp.com/thread/979583605637877760.html
lathiat 5y ago
The "Stuff Made Here" youtube channel was dealing with this recently when making a chainsaw robot. As you can imagine, it was kindof important. He ended up with a combination of a flashing "armed" light and an e-stop switch. https://www.youtube.com/watch?v=ix68oRfI5Gw&t=732s https://www.youtube.com/watch?v=ix68oRfI5Gw&t=732s (12m12s)
0xfaded 5y ago
We had a scary and quite overspec'd arm acquired cheaply in the early history of a startup. We we're able to control it via the serial interface, but similarly to you we had no documentation and everything had been reverse engineered. The thing was surrounded by e-stops.
lloeki 5y ago
> messing around with hardware vs software. Back when I was doing some hands-on practical training in electric engineering school, we had to design a control circuit on some breadboard, the kind that in high school would lit a couple of leds, and maybe make a light fade, but here it was driving a big-ass train engine boxed in a 1.5m x 1.5m x 3m steel cage, right next to the bench where we pieced the control device together, barely arms length away. While conceptually the same, "theory" vs "practice" and "command" vs "power" suddenly takes a whole new meaning where you're suddenly pushing several orders of magnitude more power than a puny 9V battery could. The buzzing of a hundred amps ready to flow inches away was chillingly ominous. You get a strange urge to triple check, quad check even, design and calculations before flicking the switch. As we all successfully started up our bench, the rumbling of a dozen of these bare protomachines revving up in a hangar was eerie. The thought of them sucking in such an amount of overall power from the grid dizzying. I rarely get cold-sweat and goose bumps, but this was one of these days.
cmenge 5y ago
Something similar happened to me when I remote-controlled a buddy's computer. This was I guess in the early 2000s when disc drives were still a thing. Opening the drive knocked over a glass of wine and caused quite a mess... Noone hurt, but also spilled wine.
Mauricebranagh 5y ago
I remember in college (mech ENG BTECH) I had a coursemate who's day job was a programmer on the CNC side. She mentioned that this had happened to a v high end CNC machine the cutting tool after a power cut went straight to the home position very $$$$$$$ At my place we had a computer controlled wave tank and as the guy I shared an office with said you could program the ram to go full travel in zero time which would have flooded the lab.
xnx 5y ago
> I learned a valuable lesson about the difference between messing around with hardware vs software. Tesla Autopilot developers should read this.
Agentlien 5y ago
At my first job we once developed our own controllers with haptic feedback for our surgical training simulation. It was amazing how realistic the feel was. The motors were quite powerful and there were a few close calls which really made you think. It used to twitch violently as it was calibrating on initializing. Once, it reset and did that while testing. Luckily the person holding it managed to get his hands out of the handles on time. Another tim the tip of one instrument had broken off and during initialization there was an error in the force applied in the direction along the shaft. It flew out like a rocket.

its_nikita 5y ago

That's a good story. Yeah I feel like there must be soo many more opportunities to physically damage/harm something from robotics than software alone.

LeifCarrotson 5y ago
Anything with an actuator, really. I'm a controls engineer, we work with all kinds of hazards and it's my responsibility to run the risk assessment that makes sure no minimum-wage operator gets harmed because of our machine. People are the squishiest, weakest, most sensitive part of just about any shop, so there's a lot of risks to assess! One key observation, though, when working with code is that the machine becomes so close to predictable that it's more dangerous than if it were unpredictable. A cordless handheld drill is hardly a tool that most people would call 'hazardous'. You turn the trigger, the thing rotates, grab the chuck and you can likely stall it. But that much energy in something driven by code is extremely dangerous, it's waiting for any of who knows how many conditions to take off, a common one is that putting your hands in/on something that seems to be not moving can 'make' a sensor and the machine will take off. There are definitely two kinds of safety domains, one applies to manually operated tools where the operator of, say, a knife is responsible for their own safety - if they cut themselves, they're at fault, not the knifemaker. There's another kind of safety engineering where if the machine takes off 'by itself' while an operator is in the way it's the machine designer's fault for not stopping that from happening, the operator can't be expected to know what's going on. The latter should become more common as computers continue to permeate everything we use - that cordless drill is no longer controlled by the operator with a trigger switch that connects power to a DC motor, it's a brushless motor driver with an analog input sensing the position of the trigger and the EMF of the motor, and the charge state of the batteries, and who knows what else. Bump a sensor and it might take off, you don't know why it does what it does. I'll continue to make my automated cells as safe as I can, but don't trust code that's not so simple you can be confident of how it works.
- dharmab 5y ago
  > A cordless handheld drill is hardly a tool that most people would call 'hazardous'. You turn the trigger, the thing rotates, grab the chuck and you can likely stall it. But that much energy in something driven by code is extremely dangerous, it's waiting for any of who knows how many conditions to take off, a common one is that putting your hands in/on something that seems to be not moving can 'make' a sensor and the machine will take off. A friend needed a valve cover gasket changed on his Honda, and his wife needed to use the car for her Uber runs that night. He came over and instead of our usual hand tools I put a socket adapter on my 20V drill to speed up disassembly. I handed the drill to him and told him "start on the lowest torque setting, and move up in small steps." I turned around to grab more tools from the toolbox. A minute later, I heard a loud noise. I turned to see the car's windshield cracked and a shocked look on my friend's face. My friend was used to his renter's power drill. He hadn't anticipated how much torque a modern contractor's drill outputs and set the torque to the maximum setting. On the third valve cover bolt, the drill had caught on the bolt head and spun my friend around, smashing the battery into the windshield. There's a piece of paper taped to me toolbox called "List of things <friend's name> may not attempt unsupervised." It gained a couple of entries that day...
  - whatshisface 5y ago
    Why would a drill be engineered to put out more torque than a human holding the handle could be expected to counterbalance?
    - dharmab 5y ago
      For drilling holes in soft materials like drywall and wood, or even softer metals like aluminum. I recently used that drill to drill into a motorcycle engine to remove a stuck rotor cover. Relevant old article: http://www.team.net/mjb/hawg.html http://www.team.net/mjb/hawg.html
    - duskwuff 5y ago
      Powerful electric drills will often come with an extra handle on the side (or a mounting point for one) so that you can brace them with both hands. It's up to the user to set an appropriate torque limit if they're only using one hand.
rohansingh 5y ago
Heh, you don't even need proper robotics. Back in 2002, I was getting a package with a brand new Pocket PC (smartphone without the phone, running Windows). And I really wanted to know when it was delivered, but the UPS guy would regularly leave packages on the porch without ringing the bell or anything. This was before you could get delivery alerts or anything like that. But I had a spare laptop with an integrated webcam (wow!), and I'd figured out how to make it run actions on motion detection. My plan was to point the laptop at the door, and eject the CD drive when it detected motion. The tray of the drive would push a water bottle off the table. That would land on a seesaw, which would launch a deck of cards in a hard plastic case at the door and make a very loud noise. It's unclear why I couldn't just play a really sound on the speakers instead. Anyway, I tested the program by standing in front of the laptop and waving my hand. It worked perfectly! The CD tray ejected, and I watched as the water bottle slowly rolled off the table. It dropped onto the seesaw...... and instantly launched a hard plastic deck at my face and got me right between the eyes. Never again have I been in so much pain and also so excited about my code working perfectly at the exact same time.
- faceplanted 5y ago
  This made me actually laugh out loud, it feels like some of the things I came up with as a teenager wanting to do robotics and automation but having no money or way to purchase things online, water bottles were actually a good way of powering things like opening curtains by dropping them on a string. Also I like that even after you came up with "knock something off the table" you felt you needed a seesaw catapult thing and didn't just knock something off that could make the actual sound like a cake tin or bell or something.
  - rohansingh 5y ago
    > Also I like that even after you came up with "knock something off the table" you felt you needed a seesaw catapult thing and didn't just knock something off that could make the actual sound like a cake tin or bell or something. It totally doesn't make any sense! I think I might have been fascinated with the idea of Rube Goldberg machines or something at the time. Or maybe I thought I could build a "security system" with it? Also it was summer and I was a bored teenager.

isatty 5y ago

I used to do robotics, I can tell you that the fact that it was the cheapest or the most hacky does not matter in the least. Everything can and will go wrong, even the priciest and well documented part. I used to have multiple clamps around the controller, message bus, the firmware and also a physical barrier, and yet would not feel safe with my fingers or person around moving parts.

AlotOfReading 5y ago
Yep. When I have to work with robots, it's from a distance and with as much safety equipment as possible. I've seen too many physical, hardware, and software failures to risk anything I care about. Hearing protection is also important. A hundred pounds or more of metal slamming into itself at high speed makes a deafening sound.
- _pmf_ 5y ago
  Every hardware demonstration is like the board room scene from Robocop: https://www.youtube.com/watch?v=ZFvqDaFpXeM https://www.youtube.com/watch?v=ZFvqDaFpXeM
  - deleted 5y ago
    [deleted]
- faeyanpiraat 5y ago
  I’ve read a story somewhere, that someone trying to fix something in the toilet had to be in a position close to the toilet, then the lid accidentally fallen shut and the guy had his hearing damaged because the toilet bowl somehow concentrated the noise in one point where his head was. It’s weird how even ordinary things can be dangerously loud.
  - softblush 5y ago
    https://threadreaderapp.com/thread/979583605637877760.html https://threadreaderapp.com/thread/979583605637877760.html

lathiat 5y ago

The "Stuff Made Here" youtube channel was dealing with this recently when making a chainsaw robot. As you can imagine, it was kindof important. He ended up with a combination of a flashing "armed" light and an e-stop switch. https://www.youtube.com/watch?v=ix68oRfI5Gw&t=732s https://www.youtube.com/watch?v=ix68oRfI5Gw&t=732s (12m12s)

0xfaded 5y ago

We had a scary and quite overspec'd arm acquired cheaply in the early history of a startup. We we're able to control it via the serial interface, but similarly to you we had no documentation and everything had been reverse engineered. The thing was surrounded by e-stops.

lloeki 5y ago

> messing around with hardware vs software. Back when I was doing some hands-on practical training in electric engineering school, we had to design a control circuit on some breadboard, the kind that in high school would lit a couple of leds, and maybe make a light fade, but here it was driving a big-ass train engine boxed in a 1.5m x 1.5m x 3m steel cage, right next to the bench where we pieced the control device together, barely arms length away. While conceptually the same, "theory" vs "practice" and "command" vs "power" suddenly takes a whole new meaning where you're suddenly pushing several orders of magnitude more power than a puny 9V battery could. The buzzing of a hundred amps ready to flow inches away was chillingly ominous. You get a strange urge to triple check, quad check even, design and calculations before flicking the switch. As we all successfully started up our bench, the rumbling of a dozen of these bare protomachines revving up in a hangar was eerie. The thought of them sucking in such an amount of overall power from the grid dizzying. I rarely get cold-sweat and goose bumps, but this was one of these days.

cmenge 5y ago

Something similar happened to me when I remote-controlled a buddy's computer. This was I guess in the early 2000s when disc drives were still a thing. Opening the drive knocked over a glass of wine and caused quite a mess... Noone hurt, but also spilled wine.

Mauricebranagh 5y ago

I remember in college (mech ENG BTECH) I had a coursemate who's day job was a programmer on the CNC side. She mentioned that this had happened to a v high end CNC machine the cutting tool after a power cut went straight to the home position very $$$$$$$ At my place we had a computer controlled wave tank and as the guy I shared an office with said you could program the ram to go full travel in zero time which would have flooded the lab.

xnx 5y ago

> I learned a valuable lesson about the difference between messing around with hardware vs software. Tesla Autopilot developers should read this.

Agentlien 5y ago

At my first job we once developed our own controllers with haptic feedback for our surgical training simulation. It was amazing how realistic the feel was. The motors were quite powerful and there were a few close calls which really made you think. It used to twitch violently as it was calibrating on initializing. Once, it reset and did that while testing. Luckily the person holding it managed to get his hands out of the handles on time. Another tim the tip of one instrument had broken off and during initialization there was an error in the force applied in the direction along the shaft. It flew out like a rocket.