Power a Projector with a relay module?

[jborden5]

I recently powered a rented projector with a Sensor relay module. The person picking up the projector noticed this and was very upset, warning me that I had better hope the projector was not damaged. I'm thinking that power from the relay supplies nice, clean, ample power which would be no worse than a wall plug. Who do you think is right, and why?

 

[rochem]

My guess is that the person picking up the projector has been warned numerous times about the dangers of just parking a dimmer at full, and didn't realize or understand what a relay module is or how it works. There is no problem whatsoever with powering something like that off of a relay module - if anything, the power will be cleaner than what you'd get out of a wall socket.

 

[MNicolai]

A dimmer is a no-no, but a relay will only give you the same quality of power as you'd get out of a normal wall receptacle. It's effectively the same as the switch on a surge protector or circuit breaker, except it can be remotely switched on and off by the wizardry of electronics.

Anyone who tells you power from a relay would be bad for any a projector doesn't understand what a relay is.

 

[ruinexplorer]

The concern that I would have is that you are not going through the proper power down sequence by switching power off at the rack as opposed to using the projector cycle.

 

[MNicolai]

The solution is when you power down, let the projector's lamp go out and let it cool down before you kill the relay.

 

[museav]

They were right to be upset. A relay is probably okay for switching power but you don't turn projectors on and off by switching the power. For one thing, the projector usually won't turn on when power is applied, you need to apply power and then send an 'on' command to the projector. But as ruinexplorer noted, more important is that killing the power without letting the projector cycle through its shutdown process is a good way to quickly kill lamps and the light engine.

If you have to turn on the projector after power is applied and then turn the projector off and wait before cutting power, then what's the point of switching the power?

 

[MNicolai]

If you have to turn on the projector after power is applied and then turn the projector off and wait before cutting power, then what's the point of switching the power?

(I presume) The point is not having a CC20 module around to constantly power the circuit and therefore having to use an R20AF module as a fall back. Using power that's closer is preferable than running 150' of cable to the nearest 5-15 receptacle and then having to tape cables down in the wing. At that point, it's more likely someone will kick a power cable out of the wall than it is the relay for the project gets turned off.

 

[ruinexplorer]

If you have to turn on the projector after power is applied and then turn the projector off and wait before cutting power, then what's the point of switching the power?

In temporary set-ups, sometimes that's the only available way to get proper power to a location, especially if you want clean(er) power (some ballrooms I do not trust the power drop that engineering provides).

Since some projectors can be set to turn on when given power, there would probably be just concern on the part of the owner that the intent of the user was to establish the projector that way and control the on/off by the relay instead of using the power cycle of the projector itself.

 

[museav]

Powering it from an always on relay controlled circuit is different than using the relay to try to turn the projector on and off, which is why I specifically referenced "switching the power". Unless you are trying to prevent people from being able to use the projector, I don't see a reason to switch the power to the projector.

It is definitely possible that someone could accidentally disconnect the power from a wall outlet, but if the projector is not a part of the standard configuration then it seems that you could also have scenes programmed that could be triggered but that have that circuit off. And that is also the other side, imagine maintenance staff hitting 'all off' for the lights one evening and then the next day someone trying to use the projector without realizing that the ciruit powering it had been turned off.

So the issue seems to be why the projector was powered off a relay module and whether the circuit was left on or was used to switch the projector power. That then could affect whether the projector owner had good reason to assume whether the situation related to possibly damaging the projector. But it doesn't seem unreasonable for the projector owner to assume the switched power may have been used, intentionally or unintentionally, to turn off the power to the projector without it properly cycling and it would seem to be up to you to allay their concern.

 

[porkchop]

Wow, didn't take long for this thread to get overly complicated/derailed.....
I believe that the purpose of relay modules is to supply non dimmed power to devices like moving lights and projectors. So I would say the person that yelled at you either didn't realize it was on a relay module, or they have been warned that power from dimmers parked at full is bad and don't realize relay modules exist.

 

[museav]

Wow, didn't take long for this thread to get overly complicated/derailed.....
I believe that the purpose of relay modules is to supply non dimmed power to devices like moving lights and projectors. So I would say the person that yelled at you either didn't realize it was on a relay module, or they have been warned that power from dimmers parked at full is bad and don't realize relay modules exist.

The conversation is not at all overly complicated or derailed, but some do seem to be missing that the issue is the switched aspect and not the "non-dimmed" aspect. Something like http://www.etcconnect.com/docs/docs_downloads/datashts/7050L1018_SR_Constant_Mod_Spec_Sht_vF.pdf is what would usually be used for non-dimmed, unswitched loads while a relay module like http://www.etcconnect.com/docs/docs_downloads/datashts/7050L1025_SR_Relay_Dimmer_Mod_Spec_Sht_vF.pdf is normally used for non-dimmed, on/off switched loads.

They may not have had an unswitched circuit available for the projector and thus used the relay switched circuit. Since a relay module allows switching the related circuit on and off via the dimming system, the projector owner would seem to have a reasonable concern that could have been used to switch off the power to the projector before the projector properly cycled. If the power to the projector was never turned off or at least not until after it was verified the projector had properly shut down then explaining that may alleviate their concern, however if the relay module was used to turn off the projector then their concern is valid.

 

[ruinexplorer]

Well put, and my sentiments exactly.

 

[jborden5]

I posted the original question, and I thank all of you for your thoughtful advice. To clear up some missing details in my particular scenario, the relay module was used for the sole purpose of getting sufficient power to the projectors. Nearby wall plugs were tried first and tripped a building breaker. The relay module was parked and left "on" at the dimmer rack which can not be overridden by any other control command and is completely inaccessible to button happy janitors and kids.

The rental guy was concerned about the quality of the power, though he claimed to know the difference between a relay and a dimmer at full. I think he was worried that the banks of dimmers on the same power feed would somehow inject noise into the relay power. I guess that this is the issue I am trying to resolve in my head, because in my view, properly installed and amply powered dimmer racks will provide acceptable power however it is doled out. I have also powered fog machines and moving lights from a parked relay with no difficulty. Am I missing something?

 

[DuckJordan]

Just make sure its a relay and not a dimmer. The chopped sinewave of a dimmer will wreak havoc on motors and balasts as well as some CPU type devices. The difference between a wall circuit and a relay is that instead of a hard switch you can turn the relay off with dmx