This is topic Which Motor Relay to use? in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.


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Posted by Bernie Anderson Jr (Member # 410) on 05-15-2011, 04:10 PM:
 
What relay would you recommend as a motor relay to control the Digital sound changeover for a 2 projector booth?

Thanks

Bernie
 

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Posted by Dave Macaulay (Member # 813) on 05-15-2011, 05:13 PM:
 
- coil voltage is whatever your motor voltage is.
- contact rated at a low amperage, 5A is OK. Lower is better, as large amperage contacts can corrode and fail to close with the tiny actual current switched in this application. The P&B KHU-17A11-120 (3A contacts) is good for a 120VAC motor, with the matching socket and a wire retainer. The KRP-14AGA-120 (10A contacts) works OK and also stays in its socket well without a retainer clip.
A socketed relay (with the socket!) makes trouble shooting and replacement easier.
Use shielded wire: shielded pair like the sound reader wire is great - belden 8451 or similar. The conductors can be mighty small (24ga is fine). Connect the shield to chassis ground only at the processor end and insulate it at the relay end, don't connect it to anything at that end.
 

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Posted by Scott Norwood (Member # 30) on 05-17-2011, 11:53 AM:
 
Two semi-related questions:

- is there any advantage two using relays vs. DPST motor switches, with the second pole connected to the processor/DA20 (assuming no automation and only one motor switch per projector)?

- if using relays, what is the preferred place to mount them? On/in the projector base in electrical boxes? In the sound rack? Somewhere else?
 

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Posted by Tony Bandiera Jr (Member # 2365) on 05-17-2011, 12:36 PM:
 
Scott:

1: Yes, a relay provides a very high level of dielectric isolation to keep that pesky 120 volts from the motor away from the sensitive low voltage logic of the motor sense in the processor. DPST switches can and will suffer from contact failures and flashovers (remember you're switching a highly inductive load [motor] which makes for a lot of arcing in the switch) which will fry your very expensive sound processor. So would you rather save your processor or try to save the $10 for a set of relays?

2: Best place will be in the projector bases or in j-boxes near as possible to the motor. (Or if you have wall-mount automation, in the automation can if there is room.) You DO NOT want to run that 120v line from the motor to your sound rack...it is not cost-effective, and you now have a high voltage line with nice spikes on it every time the motor starts/stops mingling with your sound gear.

quote: Dave Macaulay

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contact rated at a low amperage, 5A is OK. Lower is better, as large amperage contacts can corrode and fail to close with the tiny actual current switched in this application. The P&B KHU-17A11-120 (3A contacts) is good for a 120VAC motor, with the matching socket and a wire retainer. The KRP-14AGA-120 (10A contacts) works OK and also stays in its socket well without a retainer clip.

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quote: Tony Bandiera Jr.

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Finally, in a single-projector application, the motor start relay is really not 100% necessary, you can leave the Dolby-supplied jumper in and the Digital will work fine. (If you have no jumper or relay what will happen is if the DD drops out the sound will mute as it will assume there is no film running and thus no SR backup playing.)

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Hey Tony,
Excuse my ignorance, but what is that relay for? I´ve always dealt with single projector systems and, as you´ve mentioned, they come with a factory jumper to the 9 pin connector labeled Motor Start. I have wondered about that before, but never asked anyone.
Thanks,
Andrés
 

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Posted by Louis Bornwasser (Member # 3063) on 05-24-2011, 10:26 AM:
 
I use a simple octal socket & Omron relay from Grainger. What you really need is wiping contacts since the current drain is so low. Louis
 

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Posted by Tony Bandiera Jr (Member # 2365) on 05-24-2011, 02:18 PM:
 
Andres, no need to feel ignorant.

Here is the info from the DA-20 manual on what the motor relays are for:

"Because the data on the Dolby Digital track is normally read in advance of the picture gate, in a two-projector changeover system the DA20 requires signals in advance of a changeover. Motor Start contact closures provide those signals......In a single-projector system, the DA20 requires the MS1 signal to be valid when the projector motor is running in order to allow switching to the analog soundtrack when digital data is not present. If the MS1 signal is not connected to Digital Ground, the DA20 will not switch to analog if the digital signal is unreadable. "

By the same token, in a two-projector system if the proper MS signals are not given the DD will not pick up the incoming reels track in a timely manner, which may result in an extended dropout of sound or erratic switching from digital to analog during changeovers. Also, if the relays aren't present the running projector will not drop to analog if the digital data becomes unreadable.

The drawback to using the link (in a single-projector system) is that the system will be in analog instead of muted digital during projector startup.
 

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Posted by Andres Briano (Member # 4621) on 05-24-2011, 02:49 PM:
 
Thanks, man! Understood and learnt!
 

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Posted by Tony Bandiera Jr (Member # 2365) on 05-24-2011, 03:38 PM:
 
You're welcome sir.
 

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Posted by Bernie Anderson Jr (Member # 410) on 02-13-2012, 11:03 PM:
 
Hey Louis,

Which model Omron relay do you use?

Also , for clarity, so I totally understand the operation of the relays, you need two relays, one at each projector motor. When the motor turns on, it closes contacts in the relay telling DD that an incoming reel is about to go on screen. So for those 8 secs that both machines are running right before the changeover, both relays are energized, then when the outgoing machine shuts down, the only relay holding a closure is the incoming machine only. Right?

Thanks
 

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Posted by Louis Bornwasser (Member # 3063) on 02-14-2012, 08:00 AM:
 
That's right. 120volt (motor voltage) Omron octal relay from Grainger.

You will need 4 relays and sockets. The other two follow the picture changeover (120v) for the analog changeover. Louis
 

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Posted by Steve Guttag (Member # 268) on 02-14-2012, 08:49 AM:
 
We've used the Omron LY2-F series for 120V motor systems and one can always double up on the contacts to lower the contact resistance. Likewise, if using the KHAU relays from P&B...double or triple or quadruple up on the contacts to reduce the contact resistance. I've actually had fewer problems with contacts with Omron relays than P&B (especially since the EPA killed off key ingredients in relay contacts like cadmium).
 

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Posted by Sam D. Chavez (Member # 1841) on 02-14-2012, 10:19 AM:
 
As to changeover, I usually use a microswitch inside the Kelmar douser instead of relays. Only one switch is needed, it's cheaper and there is not as much chance of the relay sticking, and if it does, you can mechanically clear it.
 

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Posted by Steve Guttag (Member # 268) on 02-14-2012, 11:53 AM:
 
For changeovers on CP650, I always use "Pulsed" logic as it always is right. For older stuff, I like mechanical latching relays like the KBP series by P&B. For Kinoton, we make our own PCB that monitors the button pushes and then turns that into motor/changover logic in either pulsed or latched.

-Steve
 

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Posted by Bernie Anderson Jr (Member # 410) on 02-14-2012, 01:11 PM:
 
I understand the reason for the use of motor relays for the DA20, but I thought the picture changeover contact happened between the CP65 and the DA20 internally, so when the 65 switched analog from projector 1 to 2 on picture and analog CO it would also send that signal to the DA 20 through pin 25 on J18 confirming it was on the second mahine
 

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Posted by Louis Bornwasser (Member # 3063) on 02-14-2012, 07:50 PM:
 
Bernie; I don't think that is so. I remember analog being entirely seperate. Louis
 

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Posted by Sam D. Chavez (Member # 1841) on 02-14-2012, 08:05 PM:
 
At the risk of being corrected by you know who, the cinema processor requires its own changeover as there is also the analog sound changeover.

In addition, the DA20 properly wired with motor relays will force a changeover to the incoming machine in 8 seconds if it sees the incoming SR.D audio info, or as soon as it "sees" the tail run out of the outgoing machine.

This function takes into account the delay setting of the DA20.
 

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Posted by Steve Guttag (Member # 268) on 02-14-2012, 08:12 PM:
 

 

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Posted by Bernie Anderson Jr (Member # 410) on 02-15-2012, 06:58 AM:
 
I have a latching relay for analog changeover which switches the CP65 from Proj 1 to Proj 2 and back. This is connected to the C/O terminal on the CP65. This does this switching only for analog. Then the motor relays attach to the DA20 motor connector, which tells the DA 20 that another reel is coming on screen in 8 mins. Do I still need a third set of relays to make a proper changeover even with the DA20 connected directly to J18 on the CP65? This is where Im getting confused.
 

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Posted by Scott Norwood (Member # 30) on 02-15-2012, 08:12 AM:
 
No. I just went through this. For motor starts, I used the KHU relays that were mentioned earlier, mounted in sockets in in electrical junction boxes on the projector bases. For analog c/o, I'm using the KB-something latching relay that comes in the relay box for a Kelmar mono system. The automation connector on the DA20 is connected to the DTS automation board, which is connected to the automation connector on the back of the CP65. Everything works fine, although I have not yet gotten to the point of having automated failover from DTS to SRD. DTS does not require any changeover or motor start information.
 

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Posted by Tony Bandiera Jr (Member # 2365) on 02-15-2012, 01:34 PM:
 

quote: Bernie Anderson Jr

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I have a latching relay for analog changeover which switches the CP65 from Proj 1 to Proj 2 and back. This is connected to the C/O terminal on the CP65.

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Bernie, no you do not need a third relay, and in fact you can parallel the c/o terminals on the DA 20 and CP 65 with no ill effects. Match the lines c/o to c/o and ground to ground.

See how easy it is?
 

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Posted by Bernie Anderson Jr (Member # 410) on 02-15-2012, 05:50 PM:
 
thanks, that's what I thought

Bernie
 

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Posted by Bernie Anderson Jr (Member # 410) on 02-16-2012, 01:23 PM:
 
What should the front panel LEDs on DA 20 display as it switches reels? If Proj 1 is running and Proj 2's motor starts, should the Motor LED only be lit? Or motor2 and Proj2 both be lit before the picture changeover?

Right now, when the motor starts on Proj 2, both lights for Proj2 and Motor 2 come on, although the CP65 is still on analog Proj 1.
 

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Posted by Tony Bandiera Jr (Member # 2365) on 02-18-2012, 12:53 AM:
 
That sounds like either a control line problem (does the Proj 2 LED stay on all the time?) or a possible problem with the CAT 611A card. (BTW, you should have a CAT 611A card there were issues with the original 611 IIRC.)

If you tied the c/o lines as I suggested make sure they aren't crossed as that might cause issues. (Br SURE that the c/o connection on both the CP65 AND the DA20 are connected to each other and that the E connections are connected to each other. If you accidentally crossed them up the DA20 could be thinking that it is in Proj 2 because it is grounded at the cp65 end.)

Read page 110 of the DA20 manual here on F-T.

EDIT: Do you have a 25 pin cable connected between the CP65 and the DA20? It handles all functions including c/o signals.

Also make sure your CAT611A CP Type switch is set to "2" (auto digital).
 

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Posted by Bernie Anderson Jr (Member # 410) on 02-19-2012, 09:18 AM:
 
I think everything is working correctly, but it leads me to another questions: Does the the dolby digital changeover happen regardless of what projector the CP 65 says its on? I'm also trying to time the digital sound changeover to the timing of the automation. Is there a way to change the delay from the time the DA gets the motor start closure to the time the picture changes over?
 

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Posted by Louis Bornwasser (Member # 3063) on 02-19-2012, 10:26 AM:
 
The motor start means for the digital part of the processor to setart looking for the digital code. When it sees it, it will changeover. No need to think in terms of the picture changeover.

Really there is no need for the flat ribbon cable on the DA-20 except to allow reversion to analog if needed. Changeover on analog is seperate from digital changeover.

Same goes for the CP-500 and 650. Louis
 

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Posted by Steve Guttag (Member # 268) on 02-19-2012, 11:27 AM:
 
Not entirely.

There is a buffer in the Dolby Digital system and the motor relays tell the digital processor which soundhead to look at. The way it is supposed to work is to start filling the buffer with the incoming projector and make the switch when the host processor signals that changeover has been made. However...if the buffer runs out of the outgoing projector info, it will have to make the changeover anyway.

-Steve
 

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Posted by Bernie Anderson Jr (Member # 410) on 02-19-2012, 12:18 PM:
 
I think what I was hearing was this, I had a leader on a trailer reel that came off of a feature with DD encoded on it. The projector would change over to this reel and it would pick up the DD code on the leader and play it before the splice to the first trailer.

So if I'm going to do something like this, use leaders that don't have DD encoded on it, except where I'm running a feature and then even then it must be the correct leader.

Is there a way to set the buffer?
 

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Posted by Brad Miller (Member # 2) on 02-19-2012, 12:33 PM:
 
Yup that is what will happen and no the buffer is hard coded. I believe the buffer time is 7.7 seconds, but Steve will correct that if I am wrong.
 

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Posted by Steve Guttag (Member # 268) on 02-19-2012, 04:06 PM:
 
It has changed over time (or there has been changes). There is also splice cache such that during the reel the DA20/CP500D/CP650 will store up the information that occurs around the reel change to deal with the area right around the splice.

-Steve
 

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