Project FINISHED. *DZ
See my last post for the schematic
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Project FINISHED. *DZ
See my last post for the schematic
cant you just cut the power to the QM as well by wiring the DC power thru the switch?
It seems no matter what design i come up with a PS is always needed
for emission indicators,interlock indicators,actuators along with a relay/delay or two
You may want to talk to Bill and see if you can get the digital data to kill the QM.NET and have it send a packet to it? Maybe a close shutter packet which triggers a relay to kill? You could sniff the ethernet traffic using "wireshark" and then reproduce the packets but that really complicates things... Sorry if I am off track!
-Adam
At this point, that is the only way, as the rj45 jack on the qm.net does not allow access to the spare pins.Quote:
Originally Posted by mccarrot
The whole idea of this is to be completely fail safe.. Sending packets is definitely NOT fail safe!!!Quote:
Originally Posted by sugeek
agreed the packet would have to be read and understood to work..
i was thinking about a seperate DC power loop that would run along the Ethernet cable for the QM..
What you do is, you send a stream of packets which are required to keep the shutter open. If one doesn't arrive when it should, you close the shutter.Quote:
Originally Posted by dave
This type of safety system is commonly used in industrial control, and is what I have implemented between my laser and my control booth- if there's no signal positively maintaining communication, it all goes dark, and it does it fast.
Of course, I also have a current loop kill switch just in case.
so i wasn't completely off my rocker...
if you are sending a stream of packets to keep it open.. what is reading the packets.. or does the QM do that?
I have a micro that does it built into my projector. (I don't have a QM.)Quote:
Originally Posted by keeperx
Just in case? Just in case what? ;)Quote:
Originally Posted by heroic
Thank you that makes much more sense!Quote:
Originally Posted by heroic
-Adam
I don't follow the logic here.
Replace a switch and spare conductors of the network cable with 2 microprocessors and IP? Why?!!!!
You are right after thinking about power over ethernet connectors for routers you could have a break out box before the QM.NET going to the projector interlock/shutter circuit. That may be an easy work around.Quote:
Originally Posted by dave
-Adam
That is exactly what I'm doing :)
Just about to get a run of universal boards done up :)
crap, full circle. Well you are right on track sorry.Quote:
Originally Posted by dave
-Adam
The micro's not using IP, it's using USB over an ethernet cable, and it also does fan speed control for the projector enclosure and power sequencing. Using USB, ethernet, or IP is desirable because it can be run through hubs to get desirable features like multi-projector control and longer range. Using a current loop will ultimately limit your range due to the resistance of the line; I can just drop a $25 switch in there and keep going.Quote:
Originally Posted by dave
The microprocessor costs a massive $1.20, you've gotta love living in the future. It needs three external components to do its job. Total cost including the PCB was under $10.
I also have the standard ILDA-style current loop because it seemed churlish to remove a feature I already had just because I'd added a new one :-)
I have changed the schematic and I now will put a AC power relais in the network switch to switch off the QM and the complete laser and a relais in the laser to cut off the power of the laser PSU's
Wat do you think of this solution? Any suggestions?
i like it.. its an ALL STOP.. now you need to add a Shutter button to JUST close the shutter without an ALL STOP.. just a thought..
I dont understand.Quote:
Originally Posted by keeperx
With the RED emergency button you only turn off the lasers, but NOT the galvos, and QM's. similar like a shutter, because according some document from Bill you do not need a mechanical shutter if you can turn off the laser PSU's to kill the light.
The key switch will turn off everything to shut down the QM in case a QM fails (yes you can have problems with qm.nets) or turn off all the equipment
when you want to prevent people to control the laser when you are not arround.
Next week I will make a working Prototype, My keyswitch and emergency switch just arived
One reason for this suggestion may be that one might want to close the shutter before a show to allow the DPSS lasers to warm up some of the lasers take about an 30+ minutes to get to full power. Another reason is that an extra fail-safe is always good. But for a prototype a proof of concept is really satisfying, you can add bells and whistles after :D.Quote:
Originally Posted by mccarrot
Of course post lots of pictures!
-Adam
I have adjusted the schematic a little bit :D.
I think I cannot make a Laser emmision indicator in the Safty switch box, so I made the indicator in the laser.
I also split the 230V equipment shutoff and the switch into 2 parts, so I dont have any high current running trough my switch.
If you are only running 1 QM.net its also possible to work without the network switch, but you will loose the option to power down the QM.
Please tell me wat you think.
If you plug a computer into the switch with your design, you are very likely do do damage. My suggestion would be to connect the 2 wires in each pair together.. Sure, now you can only have 1 switch, but you are a lot less likely to blow anything up.
Is a switch to kill power to the qm.net really necessary?
Why should I damage the PC? the pairs I'm using are the PoE pairs, and can handle upto 48V. When you connect your PC to a PoE switch with 48V on pair 3&4 nothing damages.
When I was toghether with Hugo doing the QLIMAX show with 20 lasers/QM's in a truss due to a strange problem he lost half of the QM's and needed to power down the QM.nets to get them online again.
Hugo is using the same method by switching off the lasers/QM.net with the keyswitch, but hugo got a QM.net in each laser head.
The 1000base-T spec requires 1500 volt isolation on every pin, so yeah, no damage.Quote:
Originally Posted by mccarrot
opps, my bad
I have been thinking about this. Sounds like you know a bit more than I do, so let me know your thoughts.Quote:
Originally Posted by heroic
My understanding, is the network pairs are transformer coupled inside a switch, NIC, etc, right?
Surely putting a dc across the coupling transformer ( like what would potentially happen with the above diagram) is going to result in a dead transformer?
POE uses both conductors of each pair as either positive or negative, I as assuming it was done for this reason..
They're sometimes coupled capacitively and then inductively using pulse transformers; sometimes they're just capacitive.Quote:
Originally Posted by dave
-J.
Quote:
Why should I damage the PC? the pairs I'm using are the PoE pairs, and can handle upto 48V. When you connect your PC to a PoE switch with 48V on pair 3&4 nothing damages.
Be very cautious here, true PoE is negotiated between the end device and the switch supplying the PoE. The port will not be powered until the PoE switch has determined that the device on the end is a PoE device.
PoE can be done in two ways, either across the data pairs (for 1000base-t) or in the spare pairs (for 10/100Base-T)
The cheap (Dlink, Netgear, etc) do a fake PoE by sending 5 or 12 volts down the spare pairs but like Dave suggested they use one pair for the positive and the other pair for the negative. However they still have a disclaimer cautioning the end user over the use of the devices and to ensure that there is one on each end.
Another thing is that 1000Base-T can use all four pairs of the Cat5E cable unlike 100Base-T that only uses two pairs. This will be a problem if you get a gig switch as the spare pairs won’t be spare.
Are you sure this is correct? How would you transfer data if it’s isolated on every pin?Quote:
The 1000base-T spec requires 1500 volt isolation on every pin, so yeah, no damage.
My understanding of how the isolation is achieved is by using a isolation transformer at the connector connected across the individual pairs, and the isolation is between the cable pairs and the electronics.
So I don’t think it would be a good thing to accidently passing constant DC into it.
So by all means do this but just be careful, you really don’t want to blow you NIC up in your laptop before a show
It's AC coupled at a rather high frequency. PoE uses both pairs because cat5 cable's not very thick and high currents tend to both heat it and induce fields which mess up the RF properties of the dielectric.Quote:
Originally Posted by loopee
-J.
Jut looking at a few datasheets, I cant see any AC couplingQuote:
Originally Posted by loopee
http://www.haloelectronics.com/pdf/gigabit.pdf
http://www.midcom-inc.com/Products/L..._1X1_GB_TH.pdf
Maybe im missing something here..
Transformers and capacitors both constitute AC coupling.Quote:
Originally Posted by dave
and putting 12v at 1a across the primary to the transformer is OK? I would have thought the magic smoke would be released?
Some of the transformers have a capacitor (or two) in series with them. Others have a choke to block DC.Quote:
Originally Posted by dave
Can you post a link to a datasheet? Im interested to get a better grasp of all of this..Quote:
Originally Posted by heroic
The datasheet you posted with the ethernet transformers in it shows the choke DC blocking scheme. Capacitors are separate components, you can see them on a lot of ethernet cards. Usually large polystyrene or ceramic types.Quote:
Originally Posted by dave
This page has a nice explanation of the behaviour of capacitors in these situations, and why 8B10B and MLT-3 coding is important to gigE.
http://www.sigcon.com/Pubs/news/7_09.htm
Ethernet transceivers must be DC isolated because of ground lift problems; moreover, it is possible to connect a structured wiring plant's ethernet ports to a telephone system by mistake. When this happens, it's important that not even the 120 volt AC of a ringing POTS line will kill the ethernet transceiver on the other end; remember that ethernet interfaces used to be really expensive (I remember paying $1600 for one, not too long ago) and you'll realize why they're so well protected.
Chokes block AC. Don't they? I'm sure that's what i learned in school!!
Regardless. I would prefer to implement the most risk free solution.. And running 2 different potentials down different conductors of the same pair is not risk free in my mind.
Uh, yes they do. Not quite sure what I was thinking. (The chokes in these transformers are intended to improve common-mode noise rejection. The capacitor coupling is external to the magnetics.)Quote:
Originally Posted by dave
I'd just use the PoE pinout myself.Quote:
Regardless. I would prefer to implement the most risk free solution.. And running 2 different potentials down different conductors of the same pair is not risk free in my mind.
Ok thanks for the info, to be sure I now have devided the Key and Kill switch over different pairs:
1 Data pair 1
2 Data pair 1
3 Data pair 2
4 KILL switch
5 KEY switch
6 Data pair 2
7 KILL switch
8 KEY switch
Revision 2.2 of the Laser safety stop.
So how are you going to wire up the kill switch for additional projectors, you’re going to have to loop in and out of every switch port and either always use all switch ports or some kind of loop plug
The other issue is that you'll potentially will be passing 24 volts DC along 600 meters of Cat5 cabling (based on the 6 port switch you have shown) and will have considerable volt drop across that length of cable.
This also then leads to the blown Christmas tree bulb syndrome of trying to identify which link is a fault when you have a dodgy cable
Another issue is, are you going to standardise the projectors all to be the same, each with a connection to the 24volt power supply of the scanners?
Don’t think the power supplies will appreciate that, and also Power hum here we come!
So why not put the key switch and emergency stop inline and use the single power supply of the switch/hub and parallel the blue and brown conductors to minimise the volt drop, then use one relay in the projector to control the lasers and the QM.net board and Shutter.
However I do think that by the time you get to five relays (and medium sized ones at that) the voltage drop is going to be an issue unless you use something like opto couplers to control them.
One more suggestion would be to combine the safety stop box and switch into one unit
Good Day,
Not trying to get off track, just a idea/question. PoE may actually be good solution if you get a switch with PoE support then get rid of the AC portion there and it would open up another set of fun stuff... If we want to go down that road I can babble more.
-Adam
PoE uses phantom power so you will not lose a data pair.
Quote:
PoE uses phantom power so you will not lose a data pair.
Not always the case, some vendors have a pre-standard prior to 802.11af that only uses the spare pairs that are not used for data transmission.
All the devices that have pre-standard PoE are only 100Base-T devices
Cisco’s current line of PoE switches will support both standards for legacy product support and I don’t think they are the only ones.
However in this case it’s not doing PoE, it’s purely putting 12V and 24V down the spare un-used pairs
yeah i was talking EEE 802.3-2008
but since POE can handle 48v at 400mA steady with like 15W burst (i think that right) then powering the dac over ethernet should work just fine..
maybe pangolin should think about adding that to the dac so its plug and play...
quote=loopee So how are you going to wire up the kill switch for additional projectors, you’re going to have to loop in and out of every switch port and either always use all switch ports or some kind of loop plug
MCCarrot:
I allready have a switch build in a box and on the box there are also Neutrik RJ45 connectors, those connectors are very strong. From Neutrik plug I wire pair 1 & 2 to the switch and all blues and browns to each other.
The other issue is that you'll potentially will be passing 24 volts DC along 600 meters of Cat5 cabling (based on the 6 port switch you have shown) and will have considerable volt drop across that length of cable.
From your laptop/safety to the switch on the stage can be maximum 100 meter.
On stage you can again put your lasers again 100 meters away from your witch. So the theoretical max lenght will be 200 meters. But I have never seen a Stage 200meter width. you???
This also then leads to the blown Christmas tree bulb syndrome of trying to identify which link is a fault when you have a dodgy cable
No. Or you have 2 wires to your projector, cat5 for QM.net and another cable for the safety switch or you have only 1 cable you can break. so you need to bring 2 different spare cables instead of 1.
Another issue is, are you going to standardise the projectors all to be the same, each with a connection to the 24volt power supply of the scanners?
Don’t think the power supplies will appreciate that, and also Power hum here we come!
Hmmm yes, this is something we have to think about...
So why not put the key switch and emergency stop inline and use the single power supply of the switch/hub and parallel the blue and brown conductors to minimise the volt drop, then use one relay in the projector to control the lasers and the QM.net board and Shutter.
Then you can not setup and test all the QM's and Lasers without laseroutput. and also when I turnoff the QM together with my lasers I get a very short output of laserbeams from my projectors, so it's always good to turn off your lasers first before you switch off your QM.net
However I do think that by the time you get to five relays (and medium sized ones at that) the voltage drop is going to be an issue unless you use something like opto couplers to control them.
The standard 24V DIN rails relais I now have are 600ohm, Cat5 got max 0,188 ohm/meter resistance, so with Worstcase 200 meter cable the DC resistance is max 75Ohm. With 75 ohms you have 2.6V voltage drop, but with allot more relais you defenitly wil have a problem, so I think it's better to use Electronic relais instead, to keep the current as low as possible.
One more suggestion would be to combine the safety stop box and switch into one unit
And wire Multiple wires from the safety to the projectors? If you are at a rave and the stage is 100 meter away from the point you are controlling you have to Carry allot of Cat5 with you instead of just 1 cable to the swith on stage close to the lasers.
Excuse me guys, couple of sanity checks here...
Firstly, proper (when i say proper I mean enterprise grade) POE switches will negotiate with the device at the other end before applying full power... I don't think it is a suitable solution here...
Secondly, regarding the talk around using complicated IP based or "packet stream" techniques to determine whether the switch is depressed or not..
Well, as our esteemed colleauge Mr.Benner has asserted multiple times (and i have to agree with him), safety systems should be as risk free as possible.
Forget about using anything "digital or uProc based" to turn a shutter on or off - there is enough digital shit in your controller, enough complicated shit in your projector (scanners, alignment, etc), that there are multiple single points of failure that can result in a dangerous laser emission.
Surely the point of the whole safety shutter emergency switch thing is to provide a rock solid, simple, reliable, fool proof means of dropping a shutter in front of a laser beam...
So why would we do anything more complicated than sending a voltage down a couple of spare conductors in a fast ethernet link to lift a shutter??
Unless the real goal of this excercise is to extend penis sizes... but i thought thats what building bigger and better laser projectors than everyone else was about :P
I was assuming a power injector and an extractor in example: [device]->ethernet->[PoE injector]->[kill switch]->[PoE decoupler]< 1.power 2. ethernetQuote:
Originally Posted by aijii
Thus turn the kill switch it cuts the power to the switch... (but you are right it should also close the shutter) Alot of people here don't think they need a shutter due to the wiring paper by bill suggesting that you can kill the lasers too (I think of this as an in addition to closing the shutter), but people think DPSS lasers don't need them.
I think I am done here!
Adam
You have shutters for 5V 12V and 24V, for the diagram it doesn't matter if you use a relais or a shutter in the projector. But then there is a new problem, the 24V shutters take 85mA. so when you connect a couple of lasers to the safety stop the voltage drop will be too high.
Revision 2.4