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Old 10-25-2019, 03:30 PM
transientair transientair is offline
Join Date: Apr 2012
Location: Oregon
Posts: 36
Default Push Button Start and Mag Toggle Switches

I know that this topic has been addressed before, but I'll be the first to admit that when it comes to wiring, I start scratching my head near immediately. So the searches I've done (Google and VAF) have offered some diagrams, but nothing I've been able to successfully figure out.

I have a push button start and two toggle switches (NKK S-6AL) and I'd like to wire them in such a way that with both switches up, the right mag (non-impulse coupling) grounds. I'll have two conventional mags.

From what I understand, this should be possible with the switches I have.

But as soon as I look at all of the connections on the back of these switches, my brains turn to water.

Does anybody have a kindergarten-level explanation or drawing that would help?

Thanks all

Last edited by transientair : 12-25-2019 at 11:32 PM.
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Old 10-25-2019, 05:24 PM
BobTurner BobTurner is offline
Join Date: Dec 2011
Location: Livermore, CA
Posts: 7,857

Originally Posted by transientair View Post
I have a push button start and two toggle switches (NKK S-6AL) and I'd like to wire them in such a way that with both switches up, the right mag (non-impulse coupling) grounds. I'll have two conventional mags.
Having both switches up but the right mag grounded would be unconventional. You don?t want your switches ?lying? to you. Here?s what most would do:
Notice each mag switch is really two switches (?double pole, double throw?). Pick one switch on the left mag switch. Bring the left P lead to the center connection. Use an ohmmeter to see which connection (top or bottom in the photo) is connected to the center terminal, when the switch is down (off). Connect that terminal to ground, leave the other one unconnected. Repeat for the right switch. Now look at the two remaining switches. On the right mag switch, bring a wire connected (fuse or CB) to 12 volts to the terminal next to the grounded one. Connect a short wire from the middle terminal, over to the left switch, but to the terminal opposite the one connected to ground. Connect a wire from the middle terminal, to the starter switch. And from the opposite terminal on the starter switch, to the start relay. Now, 12 volts will flow to the starter switch only when the left mag switch is up (on), and the right mag is off. After start, turn the right mag on (up).
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Old 10-25-2019, 06:05 PM
LeonardWestermeyer LeonardWestermeyer is offline
Join Date: Dec 2016
Location: Spokane, Washington
Posts: 27
Default Clarification

Trying to understand your instructions:

When you say to connect a short wire from the middle of the second right mag switch to the terminal of the second left mag switch ?opposite the grounded terminal? do you mean the terminal on the second left mag switch which is connected to the middle when the switch is ?on?? This confused me because the ?off? terminal of the second left mag switch is not connected to anything according to your instructions. Only the first switch on the left and right mag is grounded.

Thanks for the clarification!

Leonard Westermeyer
Newman Lake, WA
RV-7A waiting for an engine
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Old 10-25-2019, 06:49 PM
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scrollF4 scrollF4 is offline
Moderator, Asst. Line Boy
Join Date: Jan 2010
Location: Flower Mound, TX
Posts: 1,632
Default Try one of these

I installed an ElectroAir electronic ignition switch panel:

Looks fantastic, performs exactly the way you want it to. I just covered over the ElectroAir label with my own label. Be careful with the wiring: You'll have to invert one of the switches for it to work properly with your mags.

It costs. But I love the professional non-home-rolled look it gives that corner of my panel.

Sid "Scroll" Mayeux, Col, USAF (ret)
52F NW Regional/Aero Valley Airport, Roanoke TX (home of DR's Van Cave)
"KELLI GIRL" N260KM RV-7A tipper
Catch her on YouTube's "Because I Fly!" channel

Exemption waived.
Proud and grateful 2021 -=VAF=- Contributor

PS: I am not an influencer. I have no influence. Just ask my kids.
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Old 10-25-2019, 06:53 PM
BobTurner BobTurner is offline
Join Date: Dec 2011
Location: Livermore, CA
Posts: 7,857

I think you got it. Use an ohmmeter. The wire which is going to go to the 12 volts should flow thru the mag switches when the right mag is off (down) and the left mag is on(up), and on to the start switch. All 4 center terminals should have a wire on them. Of the remaining 8 terminals, 4 are not connected. Draw out a schematic, it should be clearer.
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Old 10-25-2019, 07:16 PM
Mich48041 Mich48041 is offline
Join Date: Apr 2008
Location: Riley TWP MI
Posts: 3,234

Here is a picture showing how to connect the wires.
Without having the parts in hand, I had to make assumptions.
I know that is risky.
I assume that the top of the picture is up.
Anyone feel free to correct me if wrong.
Joe Gores
RV-12 Flying
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Old 10-25-2019, 07:27 PM
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Mark33 Mark33 is offline
Join Date: May 2010
Location: Baton Rouge, La.
Posts: 757

Hi Cody,

I?ll send you a PM with my email attached and if you?ll send me a return email I?ll attach a simple, easy to understand circuit schematic of a DPDT toggle switch. The one I?ll send you is for a Honeywell toggle switch, but I?m sure all DPDT switches work the same. One thing to keep in mind when trying to figure out which terminal is hot at any particular time is to think about the switch as actually being two separate switches in one. What I mean by that is to picture each three rows of terminals as two totally separate switches from one another. So for example, if you were to connect a hot wire to the center terminal (common) on a particular row, you would only have power to the top and bottom terminals (depending on the position of the switch) on that one row of three. The other row of three terminals wouldn?t have any power going to any of them. To have power going to that row of three you?d have to put a jumper wire going over to the other side. That?s what makes a DPDT switch so useful. You just have to decide which terminal(s) you want powered (or no) in any particular position. Once again, just think about the switch actually being two separate switches in one. It takes a little while to wrap your head around what you want the switch to do in a particular position and what terminal(s) you want hot and that?ll tell you where to bring the power in to and then where to put your jumper wire to power the other row of terminals. Once you study it a little bit, it becomes clear.
Mark H.
RV-7- IO-360, EFII, Whirl Wind C/S, (Built and sold)
RV-4- O-320, Catto three blade, P-Mags (Sold)
RV-8- IO-360, Hartzell C/S (Flying)
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Old 10-25-2019, 07:55 PM
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wjb wjb is offline
Join Date: Nov 2012
Location: Half Moon Bay, CA
Posts: 1,120

Here's a schematic version of what I did. Left on-start (up); right off-start (down) .. that permits the pushbutton starter to activate the starter contactor. Once started, flip the right to the on (run) position.

Bill Bencze
N430WB RV-7 @KHAF, Flying 100+ hrs
VAF 2021 donation happily made

Last edited by wjb : 10-25-2019 at 07:59 PM.
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Old 10-25-2019, 10:15 PM
scsmith scsmith is offline
Join Date: Jan 2008
Location: Ashland, OR
Posts: 2,971

I was thinking that one of the good features of the push-button start is the capability to crank the engine independently from whether either or both of the mags are 'on'. This puts the onus on the pilot to select left mag only to start, then select the right mag once the engine starts. But it enables engine cranking with both mags off - that can be handy.

Question for Bill -- if I understand your schematic, you are 'grounding' your mags into the shield conductors of the leads. But I don't see where the shields are connected to real ground.

Also, is there a special reason for putting the momentary contact start switch between the two mag switches? Or could it be 'upstream' of both mag switches?
Steve Smith
Aeronautical Engineer
RV-8 N825RV
IO-360 A1A
WW 200RV
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Last edited by scsmith : 10-25-2019 at 10:19 PM.
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Old 10-26-2019, 02:03 AM
paul330 paul330 is offline
Join Date: Feb 2007
Location: Mpumalanga, South Africa
Posts: 1,065

If you want to be able to crank the engine:

L1 Common - Ground
L1 Up ON - Not Connected
L1 Down ON - L Mag P-Lead

L2 Common - Not Connected
L2 Up ON - Not Connected
L2 Down ON - Not Connected

R1 Common - Ground
R1 Up ON - Not Connected
R1 Down ON - R Mag P-Lead

R2 Common - 12V Supply
R2 Up ON - Not Connected
R2 Down ON - To Starter Button

Starter Button Supply - From Right Mag
Starter Button Load - To Starter Relay

Disadvantage is that if you forget to put on the left mag for start .... well, it won't start! Also the Start Button is "Live" with the mags off so "Curious" fingers could cause issues ......

The ground does not have to go to the shield - it's just a schematic...... You can ground at any convenient point.

Note that on most double throw switches, the "live" terminal is normally opposite the switch position. So up powers the bottom terminal and vv.

If you choose this route, you could simplify things by changing the left switch to a SPST (OFF-ON) with OFF being UP. Right switch could be a DPST (OFF-ON) with OFF UP.
One side GND/P-lead and other side 12v/Starter Button
Mercy Air, White River FAWV
RV-10 ZU-IIZ - "Zeus"
Building Bearhawk Bravo - RV-18 not available
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