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Emergency Stop Switch - Wiring?

Discussion in 'DIY Motion Simulator Building Q&A / FAQ' started by boosted-lt1, Feb 11, 2014.

  1. boosted-lt1

    boosted-lt1 Member

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    Hey All,

    Just getting into my first sim (2DOF platform) and had a question on how to wire the stop button properly. Below is a wiring diagram created to show a single DOF. This will be mirrored obviously for the second motor, with the stop button wired to shut off both motors on a single switch. I'm pretty sure that current supply to the controller/motor should not be wired directly to the switch (most of these switches seem to be low amperage) so I need some help understanding.

    wiring.JPG

    Thanks
  2. SeatTime

    SeatTime Well-Known Member

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    Most of the emergency stop buttons are designed to work on 240V AC with current ratings lower than what would be required for the DC circuit. So it would make sense to wire it in on the AC side of the power supply. You would need to be careful in doing this, as the voltages involved can be lethal if you get it wrong.
  3. eaorobbie

    eaorobbie Well-Known Member Staff Member SimTools Developer Gold Contributor

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    I use this one from Jaycar , designed for 240v but quite fine on my DC battery system that will produce more amps than a pc power supply, one side of the switch is normally open and the other is normally closed. So test with a mutimeter to find the right side to use so the circuit is open when the switch is closed as in no power to the jrks.

    http://www.jaycar.com.au/productView.asp?ID=SP0786

    Wired like this.
    12v battery.jpg

    Beware earth runing to the switchs is to aid the lights in the switchs, ones without an internal led dont need the earth.
    The above circuit the Estop will kill power to both jrks but not the fans, as I like to leave them on for a little while to aid in the better cooling of the Jrks.
  4. SeatTime

    SeatTime Well-Known Member

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    Just be aware that the ratings and design of DC switches (that handle a few amps) are quite different to AC switches, so a AC switch used in DC circuit will have a shorter life. While working as an electrician in a dockyard which used many DC machines many moons ago, I've actually seen DC switches fuse close due to arcing. Basically if a switch is used in a DC circuit & is opened under load, an arc will be produced lasting longer than an arc caused by an AC voltage (since the DC voltage is constant - not alternating through zero). This longer arc can causes significant damage to the switch contacts. DC switches are designed to handle this arcing with different designed contacts(even having items called 'quenching coils' to blow out the arc on high current applications) while AC switches do not. If a switch is used in a DC circuit that has an inductive load (motors), the arcing across the switch contacts will be worse due to the "Back EMF" created by the inductor as it's magnetic field decays. Not saying what you have won't work, but it will have a shorter life if used with a bit of current flowing through it (possibly 80 AMPS peak in this case), so only use it in anger when necessary.

    .
    • Informative Informative x 2
  5. boosted-lt1

    boosted-lt1 Member

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    Thanks guys, good info. Messing with wall voltage kinda gives me the willies. I may try to see if I can locate a DC switch that can take the amps.

    Is there another way to do this with a relay? (sorry, I have much to learn on the electronics side)

    Thanks!
  6. SeatTime

    SeatTime Well-Known Member

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  7. eaorobbie

    eaorobbie Well-Known Member Staff Member SimTools Developer Gold Contributor

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    Ah in 4 years of using them never had an arc out or a switch bugger up.
    With the Jrks lucky to record a 45 amp draw and that's only milli seconds.
    They will draw a constant 12 amps thou. Switchs are rated at 240v 15amps or 125vdc at 10 amps, so at 12v think Im covered.
  8. boosted-lt1

    boosted-lt1 Member

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    I think I'll use a relay to turn the sim on and off in the cockpit. Amazon has 80amp continuous duty relays for $15-20 USD. I will run one relay per DOF even though 80 amp per motor is overkill, they seem to be common.

    I've updated my wiring diagram, can you guys take a look please? Here are acouple of things I like about this idea.
    1. No AC Voltage in the cockpit
    2. No High-Amp DC Voltage in the cockpit (Since the Stop Switch is 12v but low amp)
    3. Longer life of the Stop Switch (Figure with the cost of the 2 relays you could just plan to replace the switch as needed. Probablly not a huge issue as eaorobbie mentioned)
    4. Since the switch is now on a low-amp circiut (only for turning the relay on and off) I don't need to run 10AWG gauge wire all the way to the cockpit and back. This keeps the feed wire to the motor controller as short as possible, which is a good thing!
    Wiring Diagram_2-14-14.JPG
    • Agree Agree x 1
  9. eaorobbie

    eaorobbie Well-Known Member Staff Member SimTools Developer Gold Contributor

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    To me overkill never had an issue, but to play safe yes looks good mate.
  10. fusednova

    fusednova Member SimAxe Beta Tester Gold Contributor

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    Not sure if I should create a new thread but consolidation of info seems to help future searches...

    I'm also looking at emergency off switches. Is there a reason not to use the power supply on/off function wired to an emergency switch like this one:

    I'm thinking of wiring the 2 power buttons to one switch.
  11. AceOfSpies

    AceOfSpies Living the Dream!

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    Hi @fusednova, no reason not to use that switch, as long as it is rated for the voltage and total current used. Remember to earth all metalwork on your rig.

    Mike :thumbs
  12. boosted-lt1

    boosted-lt1 Member

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    You should be okay using the switch to turn on/off the power supply itself as you mention. I'm still planning to wire mine using a relay so the switch will stop the controllers only, killing motion. The power supplies would still be on to run fans, etc. I think this one comes down to preference.

    Scott
  13. fusednova

    fusednova Member SimAxe Beta Tester Gold Contributor

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    Thanks guys! I imagine a mechanical failure can get quite dangerous....
  14. Nick Moxley

    Nick Moxley Well-Known Member

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    Quite dangerous if the finger's are in the wrong place at the right time. I never had one at first and had a couple "oh shi*" moments.....Now with a kill switch no more worries.
  15. WhiteGoblin

    WhiteGoblin Member

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    Quick question here. Looking at the diagram is there any reason to not wire the kill switch on the negative side, just before the circuit completes to the PSU? I was under the impression that switches were safer that way, and the AMPS would be less, correct? I understand things like the fans would also be killed with the wiring diagram posted above, but let's assume the fan wiring bypasses the kill switch. Thoughts?
  16. Alexey

    Alexey Well-Known Member

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    I've put my safety switch in between the 240v ac socket and the IEC input for the power supplies. This is the furthest point back and kills everything. You have to think about what can fail and protect against it. For instance what if your power supplies fail internally and you only have the safety switch breaking power to the motor drivers? Before I condone people breaking into AC power cables, I would only suggest you place a safety switch on the input power line if you know EXACTLY what you are doing as it can be dangerous if done incorrectly. Fuses can be used to protect motor drivers and other sensitive electronics.
    • Agree Agree x 1
  17. SeatTime

    SeatTime Well-Known Member

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    I am only interested in stopping the motors, as I also use it to stop the sim while in use for many other reasons so do not want to shut everything else down as it can cause issues, so only use a high current 12v relay which just cuts the DC to the motors. My emergency and limit switches are all wired through the control side of the relays (one for each motor). My AC side is suitably protected for failure by the power supplies fuses and the power outlets circuit breaker. I have not had one blow up yet :).
  18. Martin van Hagen

    Martin van Hagen not trying brings you nothing! SimAxe Beta Tester Gold Contributor

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    When incorporating a safety system, or Emergency ShutDown system (ESHD), it is important to look at various factors in order to ensure a dangerous situation or further damage is prevented.

    There are two types of emergencies concerning simulators:
    A) mechanical emergencies; (1) a control failure that caused the servo motors to move uncontrollably which will lead to mechanical damage of equipment; (2) some situation where a person, or pet, gets pinched between a linkage or hinge.
    B) electrical emergencies; (1) a component failure causing an overload; (2) a short circuit that caused or potentially lead to a fire; (3) electrocution.

    Either or the energy feeding the simulator needs to be shutdown. To ensure this happens safely we should incorporate the "fail safe" principal. This entails that at initiating the ESHD button or any component failure of the ESHD system the simulator stalls to operate any further. To achieve this a seperate safety system (low voltage circuit) should be incorporated in the supplies feeding the dangerous part driving the simulator. A good practice is to built a standalone system using a separate power supply and incorporate Normally Close Shutdown button(s) (NCb) in ESHD circuit energizing the Normally Open relay(s) (NOr) in the primairy voltage to your power supply (supplies). Why NCb's and NOr's? To ensure that when a ESHD is initiated the relays will be de-energized and disconnect the feeding power or any component would fail the design will cause a shutdown. To reset ESHD circuit you can make it als complex as you like, however less is often more, but when using the correct ESHD buttons they will be of the latching type and can be reset by either turning, pulling the "mushroom" knob.

    This set-up will function within any system where using DC or AC voltages of any level. When using a DC set-up you will need to ensure that relay contacts and wire gauges are correctly rated. A contact rated for 240 VAC / 5A will endure a nominal current of 5 Ampère and guarantee electrical isolation up to 240 VAC. A contact rated for 24 VDC / 25 A will endure a nominal current of 25 Ampère and guarantee electrical isolation up to 24 VDC. The characteristic of the load behind the switching element is important for lifespan and in, our corner of the world, often inductive DC loads. This can lead to "welding" the contacts together and no longer be able to isolate the power when required. To extend the live span of the contacts surge protection can be incorporated, however this will be another component that could introduce an unsafe situation. Best is to test your ESHD system regularly to ensure the safety of you and those who are in close vacinity of the simulator. Better safe then sorry!
    • Informative Informative x 1
    Last edited: Jul 27, 2015
  19. Sebj

    Sebj Active Member

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    Hi @boosted-lt1 Where did you source the fuse block single feed unit?
  20. Sebj

    Sebj Active Member

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    @boosted-lt1 , where do you have the 35Amp switch mounted?

    Could you post a couple pictures of your wiring work?
    Last edited: Oct 30, 2015