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#1
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I need a kill switch
For those times when my robot or joysticks goes out of control I need a kill switch which disables all input to the motors ASAP.
I would like to find a way to do this where I press the trigger button to stop all motor activity and then resume once the button is pressed again. Has anyone done this before in code or does anyone have any ideas on how to do this? Please advice Thanks Last edited by Japper : 23-01-2007 at 05:18. Reason: Sorry, I forgot to subscribe to instant notification |
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#2
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Re: I need a kill switch
If the RC doesn't see the OI, it should set all PWMs to 127, and SPIKES to OFF turning off all motors. You can build a competition port dongle that allows you to disable the robot.
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#3
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Re: I need a kill switch
You can write a little checker at the beginning of your While loop that checks to see if the trigger is depressed. If it is, you can have it go off to a section of code that turns off the motors. If you want a system where click once disables and click again enables, then you need something to keep track of how many times the trigger has been pressed and released.
What software are you using? If you need more help, let me know, Jacob |
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#4
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Re: I need a kill switch
If you wanted to write it in code you could do
PHP Code:
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#5
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Re: I need a kill switch
Quote:
I would definitely suggest using the dongle. It's the safest approach. However, a programatic approach would be a fine addition if that's how you roll (so to speak). Good luck this year! |
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#6
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Re: I need a kill switch
Simple answer...Build the dongle linked above. ALL TEAMS should have at least one!
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#7
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Re: I need a kill switch
Quote:
On S.P.A.M. it is REQUIRED for safety. No-one tests or drives a 'bot without one. ...and no-one drives or operates a robot while also holding the dongle. Like Al said ... see intellic7's post Eric |
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#8
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Re: I need a kill switch
Build a dongle and wire it to an E-STOP button.
Make your dongle part of your OI board so it goes with it every where. Rockwell Automation has them. Either 22.5 mm or 30 mm. Twist and release style. Our button is 60mm in size, so it's pretty big. |
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#9
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Re: I need a kill switch
we have a "competition" box with a disable switch and an auton switch on it and its been used more then a few times...
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#10
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Re: I need a kill switch
Quote:
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#11
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Re: I need a kill switch
This cannot be stressed enough, I have enough scars to make the point very obvious, BUILD A DONGLE! OR BUY ONE! Just get one, its not worth your hands/toes/knees/eyes/someone elses one of those/ to save the time/money on making a dongle, and a programming solution is a terrible thing to trigger accidentally during a match.
Right here is a top quality one you can buy: http://andymark.biz/am-0016.html Or just use the above link to make one, its worth it, I promise. And all of my sore bones/joints and scars also promise. |
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#12
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Re: I need a kill switch
Two tricks that also help:
1) Pull the breakers from your drive circuit. This disables the drive motors and allows you to isolate the lifts, compressor, pneumatics and actuators for testing. 2) Put your robot (securely) up on blocks so the wheels don't touch the ground. That way you can spin your wheels and do all your testing without the robot driving all over the place. Both of these techniques are handy if you have limited space (say, you're hooked up to a programming cable, or maybe working in a 10' x 10' pit area) but don't provide that full-motion feeling that you may be looking for. For that, the dongle is most useful. (But if you're ever stuck, just unplug the OI. Not good practice to do it that way all the time, but it works in a pinch.) Jason |
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#13
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Re: I need a kill switch
It works, but I believe it's worse than "not good practice". It's definitely bad practice. Unplugging the OI leaves the RC running for about a half second before it decides it has lost communication and shuts its outputs off. The switch on a competition port dongle disables it now. That extra half second can make a real difference, safety-wise. It's also a whole lot faster to slap a big red emergency stop button than it is to find, grab, and yank (with a real chance of damaging) the OI power cord.
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#14
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Re: I need a kill switch
I like to always relate what I can to the students.
In the real world, automation "safety" requires the use of hardware interlocks. No software code or programming must be used or act as a safety device. All safety devices must be hardwired through a safety circuit. Depending on the hazard different categories of safety must be achieved. Category 4 is a redundant hardware safety circuit with safety monitoring relays that monitor the safety circuit of an automated machine. These safety circuits are important and not controlled by any software code. Here is a great article online that references real world safety circuits. The dongle is a hardwire safety, er uh…as close as we can get to hardwire….anyway… hopefully you’ve got enough information to decide what’s right. Article: http://www.roboticsonline.com/public...ils.cfm?id=938 |
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#15
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Re: I need a kill switch
Quote:
For a future redesign of the control system, I would like to see it require an external connection in order to enable the robot. That would be much more fail-safe than the present scheme. |
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