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Thread: Shoot holes in my estop idea

  1. #1
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    Default Shoot holes in my estop idea

    Time for me to work on filing CDRH stuff.

    Want to build an estop system.

    My plans are to mount my FB4 DACs in a box. Each box will contain the FB4 DAC, a 12v PSU, powercon input that powers the 12v PSU for the FB4 and also feeds a PCB with a power cut relay. Ethernet input for estop. Powercon output and DB25 output to the projector.

    I will run 100mbps network. There are two extra pairs of wires not used. On gigabit, each pair goes to magnetics for that networking standard so I will use one lead from one for GND and one for 5v.

    My board (powered by the 12v supply in the DAC box) will have an op-amp and resistor for bringing in 5v and powering the op amp, then the needed crap for a relay that feeds projector.

    I will use high speed photography to measure the output drop on projector when power cut is initiated to show the output loss is super rapid (Lightspace Plutos IIs, it' so quick it's not funny.)

    I know XLaser does something similar but not sure the details. When I was younger we used to dump dual 100mbps ethernet on single cat5 and 100mbps + ISDN PBX phone and other craziness in our nerd house.

    I plan to get auto MDX/MDI switches (low end) and bind all those extra pins together for the stop thing.

    Will keep it isolated to avoid ground loops.

    Any issues that come to mind? Key triggered stop plunger will supply 5vdc.

    Was thinking maybe AC is better due to less line loss?

    Maybe a few boxes for FB3 projectors but really I hate anything that isn't ethernet.
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  2. #2
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    Are you basically saying you are going to have a relay that is powered from 5v?
    Well, after a second look, sounds like 5v just controls your circuit and the circuit controls the relay?
    Any chance the circuit is not failsafe?

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    How about using a opto-isolator to turn your relay on/off? Something like MIDI, however MIDI uses a current loop.

    Also in the switch you will be connecting the estop wires together (bypassing the transformers)? That is what I think you are doing from what you have written.

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    Quote Originally Posted by cfavreau View Post
    How about using a opto-isolator to turn your relay on/off? Something like MIDI, however MIDI uses a current loop.

    Also in the switch you will be connecting the estop wires together (bypassing the transformers)? That is what I think you are doing from what you have written.
    Crap I said op amp I meant opto isolator above. Just that and a 330 ohm resistor or something is what I figure.

    Estop plunger provides power to all devices, then the rest is just receive…. Line voltage drop could be an issue? Dunno.
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    Do the Plutos have any eStop capability already? Sounds like a good plan. I think the only other things would be protection like reverse polarity (diode), overvoltage (zener diode?), a current limiting resistor (I think that is what you described already) and then a pull down on it so that if there is no connection it is off. You could use a differential receiver and I think those are low output if nothing is connected.

  6. #6
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    two twenty ma current loops. One Estop sent out , One Interlock sent back, run it off 12 or better 24V isolated, and use these modern 20 mA led current source chips in a 3 pin package. 3 conductors of an ethernet cable are used.
    Current mode ignores noise in a club, stage, or cell tower environment. Each projector has two optos, one in, one out. socket the optos, use a 9$ isolated psu module for the hot side of the interlock in the projector, so you have 2 to 4 Kilovolt isolation between interlock / estop and projector electronics. standardize it and make it open source.

    Parts cost, dirt cheap...
    Reliability, well industry uses 4-20 mA for safety of life controls for a reason. Distance it can go? What half a mile or more...

    optos are either on or off, and have protection diodes on them to prevent reverse current. The loop has a series diode and a 150 mA fuse to prevent nasties of noobie wiring.

    In theory, you only need 3 wires, to increase simplicity and reliability a bit, I'd use four.

    Steve
    Last edited by mixedgas; 04-26-2023 at 15:04.
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  7. #7
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    Here is the other thread,

    https://photonlexicon.com/forums/sho...able-projector

    At a Vf of 1.6 volts, with a 24V supply, for a typical led in an opto, that is 14 or so projectors on one loop.

    The led current limiter chips are 80 cents each, come in a 3 pin TO82 or similar package.

    If you need to bypass or test the Estop, 9V battery and a 470 ohm resistor is good for 15 hours of use.

    NO current returned to button box = Interlock open. If the Current returned, good to go, interlocks closed and all projectors have power on.
    Current on = estop line enables projector shutter etc. No current =no output. If projectors have a key , it is on ESTOP line inside projector, not on the outside, isolated loop.

    Front to back Isolation is needed in a pro environment, hence the little floating psu brick.

    If you look at the other fellows post, he chose 3 pins on the ethernet connector unlikely to have a conflict. I'd rather use a hirose or mini-xlr rather then ethernet cable for the daisy chain to be professional.

    Current Loops, not voltage loops.

    Easy enough to add another led in series with the loop as a indicator, too.

    I've been wanting to do this for years, with a current loop.

    If you use a set of relay contacts in the projector for the interlock loop, it is even cleaner then the optocoupler route. Relay closed = interlock good in projector.

    Steve
    Last edited by mixedgas; 04-26-2023 at 15:20.
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  8. #8
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    Quote Originally Posted by telmnstr View Post
    Time for me to work on filing CDRH stuff.

    Want to build an estop system.

    My plans are to mount my FB4 DACs in a box. Each box will contain the FB4 DAC, a 12v PSU, powercon input that powers the 12v PSU for the FB4 and also feeds a PCB with a power cut relay. Ethernet input for estop. Powercon output and DB25 output to the projector.

    I will run 100mbps network. There are two extra pairs of wires not used. On gigabit, each pair goes to magnetics for that networking standard so I will use one lead from one for GND and one for 5v.

    My board (powered by the 12v supply in the DAC box) will have an op-amp and resistor for bringing in 5v and powering the op amp, then the needed crap for a relay that feeds projector.

    I will use high speed photography to measure the output drop on projector when power cut is initiated to show the output loss is super rapid (Lightspace Plutos IIs, it' so quick it's not funny.)

    I know XLaser does something similar but not sure the details. When I was younger we used to dump dual 100mbps ethernet on single cat5 and 100mbps + ISDN PBX phone and other craziness in our nerd house.

    I plan to get auto MDX/MDI switches (low end) and bind all those extra pins together for the stop thing.

    Will keep it isolated to avoid ground loops.

    Any issues that come to mind? Key triggered stop plunger will supply 5vdc.

    Was thinking maybe AC is better due to less line loss?

    Maybe a few boxes for FB3 projectors but really I hate anything that isn't ethernet.
    a large heavy plate in front of the projector suspended by a string backed by a steel plate. A sharp knife mounted so all you do is hit a button and the string is cut. No power full proof. Yes I’m kidding

    - - - Updated - - -

    Quote Originally Posted by telmnstr View Post
    Time for me to work on filing CDRH stuff.

    Want to build an estop system.

    My plans are to mount my FB4 DACs in a box. Each box will contain the FB4 DAC, a 12v PSU, powercon input that powers the 12v PSU for the FB4 and also feeds a PCB with a power cut relay. Ethernet input for estop. Powercon output and DB25 output to the projector.

    I will run 100mbps network. There are two extra pairs of wires not used. On gigabit, each pair goes to magnetics for that networking standard so I will use one lead from one for GND and one for 5v.

    My board (powered by the 12v supply in the DAC box) will have an op-amp and resistor for bringing in 5v and powering the op amp, then the needed crap for a relay that feeds projector.

    I will use high speed photography to measure the output drop on projector when power cut is initiated to show the output loss is super rapid (Lightspace Plutos IIs, it' so quick it's not funny.)

    I know XLaser does something similar but not sure the details. When I was younger we used to dump dual 100mbps ethernet on single cat5 and 100mbps + ISDN PBX phone and other craziness in our nerd house.

    I plan to get auto MDX/MDI switches (low end) and bind all those extra pins together for the stop thing.

    Will keep it isolated to avoid ground loops.

    Any issues that come to mind? Key triggered stop plunger will supply 5vdc.

    Was thinking maybe AC is better due to less line loss?

    Maybe a few boxes for FB3 projectors but really I hate anything that isn't ethernet.
    a large heavy plate in front of the projector suspended by a string backed by a steel plate. A sharp knife mounted so all you do is hit a button and the string is cut. No power full proof. Yes I’m kidding

  9. #9
    mixedgas's Avatar
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    He said shoot holes, not Guillotine..
    Steve

    Quote
    a large heavy plate in front of the projector suspended by a string backed by a steel plate. A sharp knife mounted so all you do is hit a button and the string is cut. No power full proof. Yes I’m kidding[/QUOTE]
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  10. #10
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    Sorry I'm so late to this party...
    Quote Originally Posted by telmnstr View Post
    Estop plunger provides power to all devices
    2 Caveats:

    1) You need 2 separate attenuation methods that are both activated by your e-stop. However, interrupting the AC power supply to the projector is not an approved attenuation method. You are allowed to interrupt the DC supply to the laser diode drivers, however. Other options include a shutter, and crowbarring the modulation inputs to ground.

    2) The e-stop circuit needs a separate "start" switch that is separate from the mushroom switch, such that even when all interlock conditions have been satisfied and the e-stop switch has been reset, the circuit will remain in the shutdown state until commanded to restart by the operator. (This prevents unintentional projector restarts following a momentary loss of power, or momentary connectivity loss through the cabling of the interlock circuit.)

    Number 2 is the tough one. To be compliant, you must be able to unplug any cable (control, data, power, e-stop), anywhere between front of house and the projector, and the projector must immediately shut off, *AND*, when the cable is plugged back in, the projector must remain in the shutdown state until the "start" button is pressed again.

    Essentially, this means you need a latching relay inside each projector.

    Adam

    PS: If you are only doing this for a class 3B laser, you can ignore #2, but if you're going to use this on any class 4 lasers, then #2 applies.

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