# Switching Projectors



## Robert F Jarvis (Aug 1, 2020)

We are going to use two projectors for different cycs during a new show. The animation clips are running on a laptop with MS PowerPoint (works a lot better then anticipated) . But we are having a problem finding a 2nd computer to accommodate the 2nd cyc. As we are using the two cycs at different times it would seem that we could merely remove the HDMI from projector 1 and plug in HMDI from projector 2. But I am nervous that the projector being switched out will report "No HDMI" as the scene changes and then switch off.
So, question: How could I use one computer to feed a PowerPoint presentation to two separate projectors at different times during the show?


----------



## Amiers (Aug 2, 2020)

Active HDMI switcher.

https://www.amazon.com/s?k=active+h...hdmi+&ref=nb_sb_ss_i_3_12&tag=controlbooth-20


----------



## Robert F Jarvis (Aug 2, 2020)

Hmm! OK. I have never used one. So I could send from one computer out to to two projectors. Question is we don't want to see both projectors at the same time (different scenes/cycs) other wise we'll get splash from the unwanted guy. The other question would be that having switched from one projector to the other we need say a black image with a little none black are in it to keep the unwanted projector 'alive'. Does that make sense? If I had the time I would make some sort of mechanical masks to drop in front of the projector's lens. They could run all the time but we could obstruct the lens of the unused projector.


----------



## Amiers (Aug 2, 2020)

Active HMDI switchers will only show whatever output you select. The 2nd projector will need to be on and you will have to set the native splash to black or as you said get a douser. No switch is going to give you true black.
These amazon switchers are cheap. So it’s one of the get what you buy. From the list go with one that lets you pick the output.
Alternatively you could get yourself some semi prograde gear and get a Roland switcher. https://www.bhphotovideo.com/c/prod...6h2vivxZAGS1CwaAq8tEALw_wcB&lsft=BI:514&smp=y

Just comes down to what you want to spend and how comfortable you are trying new things. You could hire someone that does this kind of work and then you don’t need to worry about anything but


----------



## Robert F Jarvis (Aug 2, 2020)

I think I'll send the signal to both projectors and use a douser. Last one I used was a home made contraption. Do they have commercial units that flip a paddle in front of the projector?


----------



## dbaxter (Aug 2, 2020)

Something like this USB to video would give you an output for the second projector. You could run two instances of PowerPoint, one for each. CP Plus does control two video outputs directly.
And, yes, there are commercial dousers. I made mine, however, from a radio controlled car servo and a usb interface from Phidget. There's a video on my YouTube.


----------



## Robert F Jarvis (Aug 2, 2020)

That sounds a bit easier. Hope my computer can run two PowerPoint instances. Must be a lot of work but I'll give it a try. Thanks


----------



## almorton (Aug 2, 2020)

We have some dousers that are dmx controlled and just appear in the lighting plot as a cue to raise or lower the paddle. They're based on a r/c servo.


----------



## microstar (Aug 2, 2020)

Northlight now has a fully-assembled DMX douser for only $150:




__





DMX512 controlled Projector Dowser.




northlightdmx.com





I posted on here somewhere how to make one out of an old CD drive from of a computer.


----------



## Robert F Jarvis (Aug 2, 2020)

That's interesting and a lot better than the prices I saw. My problems looping and fading in SCS disappeared when I updated the version on my computer. It can also send each cue to 1 of 4 'screens' (Projectors) though the old question about the keeping the dormant projector alive remains. It will probably be less expensive to run SCS on two computers and intersperse the images with "Black" slides. I put a tiny little purple circle at the bottom which is enough to keep the projector alive.


----------



## ruinexplorer (Aug 2, 2020)

If you have dousers, you could always send the same signal to both projectors and then have the douser blocking the one you don't want used. Fade through black to give the douser the time to close/open.


----------



## almorton (Aug 3, 2020)

If you're sending a black screen to the projector it shouldn't go into standby, because it will still be getting all the normal signals, just at black. You may still need a douser though, as on a dark stage a black screen isn't _completely_ dark. Depends on your application.


----------



## Robert F Jarvis (Aug 5, 2020)

Not quite right in the case of some projectors. Both our Optoma and ViewSonic seeing a 'black' picture/slide think that means "No signal" and after about 10 minutes turn themselves off. Black means no lamp illumination. Inconvenient to say the least. However, by putting a really, very small circle or square in a bottom corner and coloring it say dark purple so it is not noticeable then the projectors see the none black pixels and stay alive forever!


----------



## jtweigandt (Aug 5, 2020)

I've had a couple viewsonics that time out if the picture doesn't change for a period of like 10 minutes... then up comes the bird splash screen.
So moving from one black screen to the next black screen slide seemed to keep them unobtrusively alive and ready for the real projection.


----------



## Robert F Jarvis (Aug 5, 2020)

See my tip about putting a real small none black pic in your black slide so you don't need to use more than one.


----------



## jtweigandt (Aug 5, 2020)

Robert F Jarvis said:


> See my tip about putting a real small none black pic in your black slide so you don't need to use more than one.


The non black pixel won't help if the projector is timing out because of "no change" in the picture.. which is what our older viewsonics did, Even with a real picture left up.
Maybe a slow blinking non black pixel would work..


----------



## almorton (Aug 5, 2020)

Ah, OK. Our NEC doesn't suffer from either of those problems. As long as it has a signal (even a completely black screen), it stays locked to it. We've had shows where there were long periods of no projection, and it wasn't a problem.


----------



## Ben Stiegler (Aug 5, 2020)

here's another idea. With an HDMI splitter, you can feed both projectors simultaneously. Then look into the PJLink protocol/app ... a middleware tool for controlling projectors. With this, you can usually control lamp on/off remotely ... over IP. so ... dont switch the signal, switch the lamps! 








PJLink Projector Controller | EIKI Projectors

This app can turn on/off and control other functions of your video projector. Every projector that supports the PJLink protocol can be controlled. Get the app Turn your projector on/



www.eiki.com


----------



## theatremgr (Aug 5, 2020)

Our projectors have a built in "dowser" function. That facilitates a blank screen when waiting for a video to be projected. This function is remote controllable.


----------



## Robert F Jarvis (Aug 5, 2020)

Some good ideas here folks. These projectors seem to have personalities/ Switching off because the picture doesn't move seems almost counter intuitive to me. Our ViewSonic will turn off with pure black screen but stay on with a few pixels active. I haven't tested the newer Optoma yet but feeding it a pixilated black screen between videos just in case (time getting short). The real question will be if SCS doesn't keep the unused screen alive between use. Then the only way out I can see is to splash a lot of $ on some dowsers. Ugh!


----------



## Ben Stiegler (Aug 5, 2020)

here's a can of worms: Firmware updates for the projectors. If they have USB or Ethernet ports, they are likely equipped to be updated. Some mfrs (Epson) require you to call the support desk before they will give you a download link. Some update procedures are easy, others are contorted. But every projector I have upgraded over the years has worked better afterwards. So ... have a look. (PS - what model #s are using?)


----------



## DrewE (Aug 5, 2020)

Many, or at least some, projectors that turn themselves off when idle can be configured in their menus to not do that. Probably others cannot be so configured. It's worth consulting the manual and/or scrutinizing the setup menus, in any case.


----------



## ruinexplorer (Aug 5, 2020)

theatremgr said:


> Our projectors have a built in "dowser" function. That facilitates a blank screen when waiting for a video to be projected. This function is remote controllable.


Just to keep terminology correct, a dowser is someone seeking water using a divining rod; a douser is an object that extinguishes light (such as dousing a fire). Though, similar to other words, the longer that these two are misused, they will be correct with time.


----------



## jtweigandt (Aug 6, 2020)

I wondered if the switching off because of no change was to avoid a ghost burn in like you can get on some CRT’s and liquid crystal displays. Even a true LED monitor display could in theory be susceptible to burn in since phosphors age, and change brightness. I don’t know enough about DLP units, but I think they are a liquid crystal variant with a color wheel timed to give you the illusion of the colors.


----------



## RonHebbard (Aug 6, 2020)

jtweigandt said:


> I wondered if the switching off because of no change was to avoid a ghost burn in like you can get on some CRT’s and liquid crystal displays. Even a true LED monitor display could in theory be susceptible to burn in since phosphors age, and change brightness. I don’t know enough about DLP units, but I think they are a liquid crystal variant with a color wheel timed to give you the illusion of the colors.


*I have ZERO knowledge of this* BUT I'll paraphrase a post by * @MNicolai* , perhaps a year ago, when I asked a similar question regarding "Burn in" in various types of more "Modern" displays [ Modern compared to conventional CRT's ]: 

I believe *@MNicolai* mentioned MOST more modern displays were constantly (visually unnoticeably) shifting their images by ONE pixel, up/ down / left / and right to minimize the potential effects. 
Perhaps *@MNicolai* would comment on your post. 
Toodleoo! 
Ron Hebbard


----------



## DrewE (Aug 6, 2020)

jtweigandt said:


> I don’t know enough about DLP units, but I think they are a liquid crystal variant with a color wheel timed to give you the illusion of the colors.



DLP systems do (often) have a color wheel, but the DLP device itself is nothing like an LCD panel in its operation. They consist of an array of itsy bitsy mirrors that can be tilted under electronic control. Tilted one way, they reflect the light from the light source through the color wheel and into the lens system; tilted the other way, it's instead directed away to a light trap of some sort. Different brightness levels for the pixels are achieved using PWM or variable duty cycles, I presume. (There are, of course, a couple other ways of getting color: having more than one DLP array, one for each primary, or having an LED or other light source that can change colors rapidly enough.)

Anyhow, it is essentially immune to burn-in; there's no basic mechanism whereby a ghost image would appear. It would be possible for a given pixel's mirror mechanism to break and make a stuck pixel, but that would be pretty much independent of what image is being displayed since it's operating continually regardless--excepting, possibly, pure black and/or pure white pixels.


----------



## jpearson0525 (Aug 6, 2020)

Robert F Jarvis said:


> We are going to use two projectors for different cycs during a new show. The animation clips are running on a laptop with MS PowerPoint (works a lot better then anticipated) . But we are having a problem finding a 2nd computer to accommodate the 2nd cyc. As we are using the two cycs at different times it would seem that we could merely remove the HDMI from projector 1 and plug in HMDI from projector 2. But I am nervous that the projector being switched out will report "No HDMI" as the scene changes and then switch off.
> So, question: How could I use one computer to feed a PowerPoint presentation to two separate projectors at different times during the show?


To Robert, Most laptops can only support one external monitor, so getting a 2nd laptop is the best approach. You will only need it during the rehearsal and show times, not 24x7. If you had the time, a desktop PC could be setup with multiple video cards and support a display and two projectors. But that is a whole new project and will require time and resources to setup. Other Ideas and depending on the amount of power and memory you need on the laptop: Some people have retired desktops or laptops in their garages, Check with your local PC User's group for ideas, A laptop could be rented (or rental donated for an ad in program), If you have a local IT support group in someone's company or school - call them, or finally - who do you know that's going on vacation? Happy hunting.


----------



## jpearson0525 (Aug 6, 2020)

ruinexplorer said:


> Just to keep terminology correct, a dowser is someone seeking water using a divining rod; a douser is an object that extinguishes light (such as dousing a fire). Though, similar to other words, the longer that these two are misused, they will be correct with time.


The douser in projectors is used to blank the screen, but not turn off the lamp. The lamp generally take a while to fully cycle up to full power. The douser (mostly mechanical), lets you turn the light on and off quickly. Check the manual for your model to find out how it interacts with the projection signals. My church projector has a douser, but it required additional controls, so it's not generally used, no blank screens.


----------



## ruinexplorer (Aug 6, 2020)

jpearson0525 said:


> The douser in projectors is used to blank the screen, but not turn off the lamp. The lamp generally take a while to fully cycle up to full power. The douser (mostly mechanical), lets you turn the light on and off quickly. Check the manual for your model to find out how it interacts with the projection signals. My church projector has a douser, but it required additional controls, so it's not generally used, no blank screens.


Yes, internal dousers will be put in place between the optics of a projector, blocking the light from exiting. In addition, the projector will mute the signal (video black) to prevent more light from escaping. If the projector has a solid state light source such as LED or Laser, it may also douse the light source. For lamped projectors, turning them on and off causes stress on the lamp, shortening the life. Some of the external dousers that are commercially available also have DMX control.


----------



## FMEng (Aug 6, 2020)

A black video with a slowly moving, single pixel is probably all it would take. I'll bet a quick internet search would turn one up for free.


----------



## macsound (Aug 10, 2020)

Like a 1 pixel screen saver. I can imagine some nerd making one of these in the 90s


----------



## Ben Stiegler (Aug 12, 2020)

jpearson0525 said:


> To Robert, Most laptops can only support one external monitor, so getting a 2nd laptop is the best approach. You will only need it during the rehearsal and show times, not 24x7. If you had the time, a desktop PC could be setup with multiple video cards and support a display and two projectors. But that is a whole new project and will require time and resources to setup. Other Ideas and depending on the amount of power and memory you need on the laptop: Some people have retired desktops or laptops in their garages, Check with your local PC User's group for ideas, A laptop could be rented (or rental donated for an ad in program), If you have a local IT support group in someone's company or school - call them, or finally - who do you know that's going on vacation? Happy hunting.


My dell laptop dock happily supports 2 external monitors and takes way less space and complexity than running 2 PCs. There are also USB to video adapters


----------



## dbaxter (Aug 12, 2020)

Once upon a time, we did not recommend using the 2nd laptop output for use in show projections with our software. However, in the last several years, processing speed has improved relative to video rates and the 'skipping' problem seems to have gone away in new vintage laptops. So, yes, that second output or usb adapter is an option.


----------



## EdSavoie (Aug 12, 2020)

jpearson0525 said:


> To Robert, Most laptops can only support one external monitor, so getting a 2nd laptop is the best approach. You will only need it during the rehearsal and show times, not 24x7. If you had the time, a desktop PC could be setup with multiple video cards and support a display and two projectors. But that is a whole new project and will require time and resources to setup. Other Ideas and depending on the amount of power and memory you need on the laptop: Some people have retired desktops or laptops in their garages, Check with your local PC User's group for ideas, A laptop could be rented (or rental donated for an ad in program), If you have a local IT support group in someone's company or school - call them, or finally - who do you know that's going on vacation? Happy hunting.



I'm late to the party, but a run-of-the-mill intel laptop from 2013 onwards should support three total displays through the integrated graphics. it's up to the laptop maker if they actually give you more than one output port, but anything from that era onwards (probably a VGA + HDMI for older laptops) should be able to run both outputs simultaniously.

There are also USB video adaptors, but short of modern HDMI / DP over USB Type C, which are just redirecting internal graphics to that port, one should pick a deity and pray when going that route.


----------



## EdSavoie (Aug 12, 2020)

FMEng said:


> A black video with a slowly moving, single pixel is probably all it would take. I'll bet a quick internet search would turn one up for free.



Have a little fun with it!
(i've lightened the pipes a bit for visual purposes, but there's a very good chance this would be imperceptible on the projection screen anyways)

[The old windows "pipes" screensaver, with a custom texture]


----------



## Robert F Jarvis (Sep 22, 2020)

To put this to bed now, the show went off without a hitch using SCS and two projectors. Right at the last minute the director wanted something that was going to the rear projector changed to the front. It took about 5 seconds to make the change! Just in case, we put up a black picture with that small purple circle bottom left and had no instances of projectors going off. Thanks for all the help and advice. With Covid we could only have 50% seated and sold out so quickly that we put on three extra matinees and sold those out too! News went around town pretty quickly and a lot of the success was due I believe to those animated backgrounds supporting a great cast.


----------

