Routing an overhead Switch to trigger a non FS/PM Function

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jimbo
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Location: Wexford Ireland

Routing an overhead Switch to trigger a non FS/PM Function

Post by jimbo »

Hi Guys,

This might sound mad. I want to use the Equipment Cooling switch to controll Some fans in the PC hardware rack. The idea would be that I cn turn on or off the fans from the flightdeck. The same would go for controlling the Dome and flood lighting which will be mains fed.

Any help would be great.

Regards

James
IBL Signiture Boeing 767 300 Builder.
Skype james.webster4

pcos
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No biggy

Post by pcos »

Short of the Wire gauge.current this should be straight forward I think.
the Cooling Fan switches can be used.
You need to confirm the spec of the fans.. Making sure you are putting a switch in line with the wiring of the fans. Making sure you have the right gauge wire and the right switch capability.. these switches would go in line..
We have done this on computer on/off switches.
We had computers with momentary switches and used momentaries in the overhead to trigger them. Worked well and you could start the sim inside the flightdeck..
PC

jimbo
Posts: 183
Joined: Mon Mar 29, 2004 3:49 pm
Location: Wexford Ireland

Post by jimbo »

Hi PC,

That sounds great. Regarding the momentary switches for pc startup, I might have these on the Auxiliary panel, most likely on the Squib test panel. There are 10 momentarys there.

Can the B-2 knob fit non FDS rotary switches. I would want to run mains through such a switch for flood lighting or is this a bad idea?

James
IBL Signiture Boeing 767 300 Builder.
Skype james.webster4

A320East
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Post by A320East »

James,

For wiring up your fans and lighting that run from the mains voltage you might want to consider using solid state relays (SSR). These are available at industrial electronics distributors and come with a wide varitey of specs for both input and output.

The benefit it that you can use your present low current overhead switches and wiring as the control side of the SSR uses low voltage and low current the same as most of the interface wiring you probably have on the go for annuns and indicators. The output side of the SSR can handle the line voltage and current directly.

An SSR also has the added benefit of providing total isolation from the mains voltage from the rest of your project as they are an "opto coupled" device.
Christopher
"A320East"

vidarf
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Post by vidarf »

As for the PC fans: I recommend to use the black wire. It is the ground wire, and therefore you won't ruin the PSU, motherboard and so on if you get a short-cirquit.

As for the Dome and flood lights: Use 12V equipment. It is not too expensive, and you won't risk legal action should you do something wrong and burn down the house because of your skills as an electrician... And you won't get shocked if you do something you're not supposed to.

I am going to use a 12V LED lamp for the pedestal light located in the trapezoid hole in the overhead. Easy to dim and low temperature.

A320East
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Joined: Fri Nov 03, 2006 5:34 pm
Location: Halifax, NS, Canada

Post by A320East »

Good suggestion Vidarf -

SSR's are very handy and flexible but they do require some basic knowledge and comfort working with mains voltage. Low voltage equipment is a much safer option if you don't posess these skills.
Christopher
"A320East"

jimbo
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Location: Wexford Ireland

Post by jimbo »

Hi guys,

Thanks for all the advice. 12v downlighters would be a safer approach. So if I understand correctly, the black ground wire would be broken by the switch?

James
IBL Signiture Boeing 767 300 Builder.
Skype james.webster4

vidarf
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Post by vidarf »

For the fan, yes. That's how I did it in my home-built "baybus" some years ago (i ran a computer hardware review site), after doing some tests.

pcos
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Chris

Post by pcos »

Chris,
For those that are not "in the know" on relays and how valuable they are in this sort of thing can you give a brief "primer".
(Back in my Car Audio days we lived and breathed these things and they are a perfect resource if the guys understand how they can be used..)
Back to you.
PC

vidarf
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Post by vidarf »

Not to mention that a relay might be used to control a lot of other "interesting" things. You can't use the SYS boards directly, but with a relay you could control a solenoid switch....

jimbo
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Location: Wexford Ireland

Post by jimbo »

Hi guys,

So a relay could trigger a solenoid switch. This could be usefull for the likes of engine starter switches.

James
IBL Signiture Boeing 767 300 Builder.
Skype james.webster4

vidarf
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Post by vidarf »

Yep.
To put it simple: a relay is a electrical operated switch. A low voltage (ie. ~2 volts from the SYS cards) controls the switch, which can control mains voltages. And beyond! :)
There's a lot more to cover on this topic, and I am no expert. So I'll stop right there.

A320East
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Post by A320East »

Hard to know where to start for a primer... there are so many different types of relays.

Most though as Vidarf stated simply use a low voltage and current to energize a solenoid which mechanically closes (or opens) a set (or multiple sets) of contacts. Thus you can control a high voltage / high current load using a much smaller switch thus providing flexibility and convenience for control. A typical small relay has two input connections used for energizing the coil, a set of normally open, and a set of normally closed contacts for the output... thus a relay can be used to switch something off as well! Those having multiple sets of output contacts can be used for driving several separate loads.

Relays come in all sorts of packages from those that look like integrated circuits and mount dirctly to a PC board right up to softball size units which have to be bolted down and can handle hundreds of amps of current! Some PC mount types could be directly driven from the Sys card output of 20 milliamps but these most likely wouldn't handle much current on the output side as the contacts would be pretty small. Still though the output of the sys card could very simply be "buffered" through a drive circuit to switch the relay.

Other types include those that latch (remain on) once initially triggered and time delay types which can be set to stay on for a set period of time once triggered. Some relays will run directly from an AC voltage, others only from DC voltages. The solid state relays (SSR) I mentioned earlier in this post are "electronic relays" that have no moving parts but use transistors, SCR's and Triacs to switch the load voltage. They have the added benefits of being totally silent in operation unlike mechanical types and since the input stage is optically coupled to the output stage provide 100% physical and electrical isolation of the load voltages and currents to whatever is driving them. An SSR used to drive mains (120 volt AC) operated lighting can even be switched on and off many times a second to provide dimming and this is know as phase control. A typical SSR can happily be driven from low current sources such as the Sys cards output, perfect for our applications in simulators and since they usually only have 4 terminals (2 input / 2 output) they are a little easier on the head to understand for beginners, although a little more expensive than their mechanical cousins.

For anyone who wants more info or even help with choosing and using a relay in their sim I'd be happy to answer as I'm sure would many others here. A google search for "relay circuits" will also yield all the information you would possibly need including examples of interface circuits to drive them from different sources.
Christopher
"A320East"

pcos
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Scanning

Post by pcos »

Keep in mind guys that the SYS boards use "Scanning" to handlt input/outputs. Needs to be considered when going this route.
There are other smaller cards around for specific applications like this.
We are looking at a few approaches but want to have the abilit yto cover off the maximum of elements.
the relay idea is perfect when you are doing things in one vltage range but controlling one in another range. Lighting for example... This is outside of the SYS cards and more of a direct connection..
PC

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