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Master switch wiring

LettersFromFlyoverCountry

LettersFromFlyoverCountry

Well Known Member
Hello, and welcome again, ladies and gentlemen, to another episode of "Ask a Stupid Question."

Our contestant tonight is an RV-7A builder from Minnesota who writes, "I'm using the B&C toggle switch as the master switch." There are four posts but it's unclear to me which wires goes to which post. OP-10 shows a switch that appears to be sideways. Is that a definitive guide to which post to use and, if so, which end is up?"

What a sap this contestant is. He's sure to be this episode's big winner?
 
Im a Nuckoll's fan, but I dont see where the article on switch ratings explains which posts to connect the wires to. I got my info from the chapter on switches in the AeroElectric Connection. Regardless, I know from personal experience that the manufacturer (Carling) of the switches from B&C at one point reversed the position of the posts on their switches. Point being - dont blindly trust ANY source of info on this - test it out with a multimeter to confirm what your diagram says. Its easy and fast, and might save some head scratching later on.

erich
 
Point being - dont blindly trust ANY source of info on this - test it out with a multimeter to confirm what your diagram says. Its easy and fast, and might save some head scratching later on.
Click to expand...

Amen!

Here's a little tip, Bob. Get an inexpensive DMM and a 12v power supply ( a cheap motorcycle batt works fine, charge it occasionally) and test every circuit as you go. Ohm out the wires and switches, and when that circuit is done, power it up and test it. It is way easier to troubleshoot it when it's all exposed, than after it's all laced up and tucked away.

Apologies if you already know this. :)
 
(a stupid followup to my stupid question):

I've seen the multimeter suggestion. But not exactly sure how this is accomplished. I'm using the VP-50 system, the installation instrux for which don't suggest turning it on for a circuit by circuit test.

So if I follow you correctly, you would use a battery or a power supply to energize the circuit and then test it at the other end? Do I follow that correctly?
 
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Beep

For a toggle or rocker switch, if you hold the switch vertically, that is, looking at it with the back facing you, the vertical contact rows will usually belong to one section.

For full size double throw switches, the center contact is usually the common one. For some little ones, it can be on the end but its usually marked.

If your multimeter has a 'diode test' function, select that. Touch the leads together and if you hear a beep indicating continuity, you are ready to go.

Pick a switch contact and connect one probe to it. Poke around with the other probe until you get a beep indicating continuity. That's one closed contact. Throw the switch and see where the the continuity moves. You'll able to determine the common contact on a double-throw switch by finding the one that is part of the connected contact pairs in both switch positions.

By mapping the various combinations you'll have your switch buzzed out in no time.

If your meter does not beep, set it on the lowest resistance (ohms) scale. It will read ---- or some overflow. Touch the probes and it should show close to zero. A beep is better but zero ohms is equivalent for your needs here.

If you don't have an ommeter/continuity tester.. time to go shopping!

BTW: Don't buzz out the switch when its in the circuit. The other stuff connected can throw off the readings.

Have fun.
 
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RE: Master Switch Wiring

Eric,

The article title is a little misleading but if you you would take the time to check out Aero Electric article that I referred too it might be obvious that it does answer most all the points that you raised (and then some). Contact numbering, switch orientation, Micro Switch vs. Carling etc. etc. etc. etc. It answers a lot of basic questions regarding connecting up switches to do what you need the switch to do.

Your advice to test it out with a multimeter is also good assuming you have a multimeter at your disposal.
 
So if I follow you correctly, you would use a battery or a power supply to energize the circuit and then test it at the other end? Do I follow that correctly?
Click to expand...

Yup, that's the concept. The implementation of that concept will vary from circuit to circuit. I'd run power to the VP-50 first. Then, every circuit that is completed (lights, strobes, etc.) can be tested one at a time. Prior to first power application, a circuit should be checked with the DMM to verify proper wiring. Many circuits are going to be polarity critical, the DMM is used to verify correct polarity before losing some expensive smoke. :eek:

To get this concept turned into an intuitive understanding that you can readily use, a local "sparky" would sure come in handy. An hour of his time, showing you the tools of the trade and how to apply them, would be an hour well spent. I would say this is mandatory if you are going to wire your own panel. For example, a couple of alligator clip leads are a necessity, as is knowing how to interpret the DMM. Don't hook up the temporary power supply without an inline fuse appropriate to the circuit under test. There are crimper and connector pin tools you'll need.

Does Nuckoll's book not have a primer on wiring and troubleshooting? I don't have a copy. If not, there has got to be some basic "getting started in electronics" primers out there.

Wiring an airplane is at least as complicated an undertaking as building an engine. Give it the proper due diligence and I'm sure you'll do fine.

Disclaimer: I may have forgotten something important, so I'll leave you with a quote from Rusty in Ocean's Thirteen: "Remember, no matter what, never ever...". :D
 
Ted Johns said:
Does Nuckoll's book not have a primer on wiring and troubleshooting? I don't have a copy. If not, there has got to be some basic "getting started in electronics" primers out there.
Click to expand...

For folks like me -- non engineers -- I think Nuckolls' book is a tough read. I know. I've read it about a dozen times. Part of the reason is it needs a good editor. He'll start on a point and then go off on a tangent and then come back to the point.

Once you understand his writing style, it's a little easier to get the important information and then toss out the superfluous stuff.

But I don't think the book is as good -- or written as concisely -- as, say, his "comic books" on particular issues.

That's not to say it's not a valuable book. It is. Or that he's not an extremely knowledgeable guy. He obviously is. It's that it's difficult to come away with a sense of a step-by-step approach that a lot of us non-engineer types need..

I think appendix schematics are the most valuable. You can look at them and say "now why did he do that" and then go searching through the book looking for some explainer on why he did that. But it's not an easy process, to be sure.

That's why I like the Vertical Power system. Install, plug in your stuff, drink beer.
 
newsum said:
if you you would take the time to check out Aero Electric article that I referred too it might be obvious that it does answer most all the points that you raised (and then some). Contact numbering, switch orientation, Micro Switch vs. Carling etc. etc. etc. etc.
Click to expand...

Yup - my bad. I thought I had reached the end of the article but it continues with copes of pages from the 'Connection that are relevant here. If you have the Carling switches, start with the switch contacts as outlined by Nuckolls but verify with the continuity tester on your multimeter to make sure they havent swapped sides on you, as described in a previous post.

erich
 
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