PDA

View Full Version : Electromagnetic release switch?



dave4002000
12-04-2007, 09:56 PM
Hey guys, i'm brand new to this site and have a question about electromagnetic release switches.

I've seen the videos on the PM site with the engine start and A/T switches. I have looked high and low for info on how do make something like that work, but for the life of me, i can't find anything about it.

Does anyone have any info on how to set that up? (or a link to a company that sells the e-mag switches)

I can understand how the A/T switch works, because the button on the throttles can control the release of the switch. But i'm kinda confused as to the engine start switch. Does that get an input from the software? Or is there some kind of timer function on it, so once you turn it to "start", it will wait a few seconds before releasing?

Any info you guys can give me is greatly appreciated!

Thanks,
~Dave Stankiewicz

Mike.Powell
12-05-2007, 12:03 AM
Dave,

There are several types of these switches. They variously go by the names "magnetically maintained", "magnetically held" and "magnetically latched" switches. Honeywell/Micro Switch makes toggle versions. I believe Eaton makes a rotary type. Fundamentally, these are switches that can be held in a spring-return momentary position by a magnetic solenoid. Cut power to the solenoid and the spring pops the switch out of the momentary position.

In an engine start application, the switch is put into the start position and the starter motor begins to spin the turbine (actually this has been used on piston engines as well). When the engine passes a threshold RPM the starter switch is automatically released. Alternatively, if the threshold is not reached within a certain amount of time, the switch is released.

Magnetically held toggle switches show up on Ebay from time to time. A very few (one, maybe?) magnetically held rotary switches have as well. A year ago or so, someone posted on Avsim details of his DIY version rotary eng start switch.

As far as making a physical magnetically held switch work with a sim, it will depend on the sim and the aircraft model. You will need both an input and an output. The input communicates the switch position to the sim application while the ouput will be used to power the solenoid. If the A/C model includes the proper variable for the solenoid, use it to drive the output. Otherwise you'll have to write some additional code to infer or simulate its position to drive the output. If you're using FS9 you need FSUIPC to get access to the sim variables. If using FSX, use SimConnect.

Michael Carter
12-05-2007, 12:18 AM
The Sperry SP-50 and -150 autopilot system control head uses two solenoid held toggle switches, two magnetically held toggles, and one magnetically held rotary switch.

When 28VDC power is interupted from the AP disconnect on the yoke all switches are released. That is a normally closed pushbutton switch.

You can find solenoids on a google search. They can be used to imitate a magnetically held switch if you can't find any at a reasonable price. You probably won't because as Mike said, they are scarce.

Gsey
12-05-2007, 12:27 AM
Great price. Snap one up. Holds with only 12v
http://cgi.ebay.com/ebaymotors/Aircraft-Aerospace-Cockpit-Toggle-Switch-Honeywell-OK_W0QQcmdZViewItemQQcategoryZ26439QQihZ003QQitemZ4633668588QQrdZ1QQsspagenameZWDVW


http://www.flamecorp.com/pdf_files/ettoggle_7.pdf

Phidgets software and relay card to control it.

Sorry for not giving more info right now, but I have to go.

Gary

Michael Carter
12-05-2007, 12:31 AM
Exact same toggles on the Sperry control heads right down to the wiring schematic on the case and the color.

dnoize
12-05-2007, 04:46 AM
I can understand how the A/T switch works, because the button on the throttles can control the release of the switch. But i'm kinda confused as to the engine start switch. Does that get an input from the software? Or is there some kind of timer function on it, so once you turn it to "start", it will wait a few seconds before releasing?




here is some nice info on constructing your own engine start switches:

http://www.hanskrohn.com/BuildingTips/EngStartSwitch/EngineStartSwitch.htm

Stef

737NUT
12-05-2007, 07:57 AM
Great price. Snap one up. Holds with only 12v
http://cgi.ebay.com/ebaymotors/Aircraft-Aerospace-Cockpit-Toggle-Switch-Honeywell-OK_W0QQcmdZViewItemQQcategoryZ26439QQihZ003QQitemZ4633668588QQrdZ1QQsspagenameZWDVW


http://www.flamecorp.com/pdf_files/ettoggle_7.pdf

Phidgets software and relay card to control it.

Sorry for not giving more info right now, but I have to go.

Gary

WOW!!!!!!!!!! 70.00!!!!

Glad i saved 3 for future use in my sim. I paid 30.00 for 3 of mine!

I think some of these reseller's are a little out of the loop expecting these kind of prices on a used non-airworthy part! Problem is, simmers with more cash than brains are driving the prices up! :(
Rob

Gsey
12-05-2007, 07:02 PM
No simmer is driving the price of these up. Just because you were able to be at the right place at the right time doesnt mean every simmer is going to be as lucky. Ive been lucky with plenty of purchases Ive made but never will you here me say that some of us guys have no brains just because we are willing to pay alittle bit more to get items that are hard to come by if you dont have the right contacts. What you said stands true for alot of sellers and thats why you will see most items that are way overpriced on the market for quite some time. $70 for an used electromagnetic switch isnt bad at all considering the list price for these things.


Gary

Michael Carter
12-05-2007, 07:18 PM
And their rarity on the consumer market.

My Sperry AP is an example of a great price on a rare item. Never have seen another Mk IV since purchasing mine. Took a month to pay for it but it was worth every penny.