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05-24-2017, 01:18 PM
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Join Date: Sep 2013
Location: Buda, TX
Posts: 56
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Your circuit operates on the positive side of the master relay. Most are wired with the master switch shorting the negative side to ground:
http://www.aircraftspruce.com/catalo...-03161draw.pdf
They are wired that way to prevent the possibility of the unfused master power switch leads shorting to ground. With the ground side being switched, the worst a short will cause is for the master relay will turn on unexpectedly. If you use your circuit, you should at least redesign it to work on the negative side of the relay.
For ground testing, I'm just using a 13.8V supply connected directly to the battery through an Anderson Powerpole connector. It powers everything and acts as a float charger if (when) I forget and leave the master switch on. Alternately, you could plug the power supply into a power outlet (power inlet in this case), and never turn the power switch on.
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05-24-2017, 01:29 PM
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Join Date: Jul 2007
Location: Taylorsville, Ga
Posts: 798
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Or buy yourself an iFly740 , it powers up with the master switch and powers down when the master is turned off . Never had a problem since its been on a ram mount there in front of the pilot. And the secondary benefit is that its an excellent VFR gps and includes wx and traffic with a bit extra.
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DRRhodes
2020 VAF Supporter
RV9 N908DR
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05-24-2017, 02:36 PM
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Join Date: Sep 2012
Location: Omaha, NE (KMLE)
Posts: 2,247
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The solution I have seen before (other than leaving the strobes on, good idea there) is a simple low-voltage alarm. If the master is on and the bus voltage falls below, say, 13V or thereabouts, you get a light and beeper. It will be off any time the engine is running, and on when the master is ON but the engine is not running.
Of course you don't want to listen to it whine and complain when you first turn the master on. A simple timer will take care of that -- longer than your usual engine start, shorter than it will take you to close up and leave the hangar. It's not completely foolproof, but you'd have to work to accidentally leave the master on.
Hacking one up with a couple of chips (555 and maybe an op-amp or a couple of transistors) would be an interesting evening's project, but writing the code, schematic and PCB layout to do it with a single $1 PIC took me all of an hour or so. I included a provision for a blinky LED, a piezo beeper (some of which are QUITE loud and annoying), and a mute switch that will mute the beeping but not shut off the blinking LED. What I had in mind was a momentary pushbutton with an LED, to provide mute and test functions.
__________________
Dale
Omaha, NE
RV-12 # 222 N980KM "Screamin' Canary" (bought flying)
Fisher Celebrity (under construction)
Previous RV-7 project (sold)
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05-24-2017, 07:23 PM
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Join Date: Jan 2006
Posts: 6
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I have the avionics cooling fan energized with the master...can't hear it in-flight, but would notice after shut-down if the master were left on. Strobes, as discussed is a great idea. I'd be careful about putting some tricky "system" into that circuit.
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05-24-2017, 07:40 PM
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Join Date: Feb 2005
Location: Shawnee, Kansas
Posts: 804
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Quote:
Originally Posted by GeraldC
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That's an easy and wise swap. Thanks!
__________________
Bruce Meacham
Building RV-4A 18ZM
Built/Own RV-4 254MM
First RV RV-3 3456B
VAF annual donation on autopay
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05-24-2017, 07:52 PM
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Join Date: Sep 2013
Location: Ooltewah, TN.
Posts: 580
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Quote:
Originally Posted by krw5927
I'm imagining a simple piezo buzzer mounted out of sight behind the panel, and powered by the master bus through the normally-closed side of a standard oil pressure switch.
Same principle as the "Low Oil Pressure" annunciator light in common use. A light can be easy to miss. An annoyingly loud buzzing noise, not so much.
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This is the best solution in my opinion. Super simple, and works well.
Similarly, in a club I was in, we had in our checklist to always leave the rotating beacon ON in our 172. If you left the master switch on, you'd immediately see and hear the beacon when you got out of the airplane. It worked perfectly and we had zero dead batteries on the club plane after adding that one item to the "securing aircraft" checklist.
__________________
Lynn Dixon
RV-7 Slider -
Tail kit Completed - March 2017
Wing Kit Started - June 2017
My Build Log: http://www.theskunkwerx.com
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05-24-2017, 08:33 PM
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Join Date: Mar 2008
Location: Reno NV
Posts: 542
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Best master switch saver?
Guys: I solved the problem with the oil pressure switch, available in the aviation isle of your favorite auto parts store, that turns all the red lights and symbols on when you turn the car ignition switch on before starting. I installed the switch on the block Vans supplies to mount oil, fuel and vacuum lines and pressure switches. At the oil pressure line and switch I mounted the no oil pressure switch that is normally closed at no pressure and normally open with 3 psi or more oil pressure. I used it as a ground by running a hot wire from the master switch to a radio shack "bing bong" noise maker then to the no oil pressure ground. Shut down the engine, wait for the oil pressure to drop below 3 psi and presto, the loudest most irritating noise you can imagine until the master switch is turned off. No more $50 battery jumps. Dan from Reno
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05-24-2017, 09:14 PM
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Join Date: Dec 2009
Location: Boulder, CO
Posts: 4,435
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Seems that it would get annoying if you're working on something that needs electrical power in the hangar. And if you put a disabling switch in that device, that'll be the one time you leave the master on.
Or am I missing something?
Dave
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05-24-2017, 10:01 PM
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Join Date: Sep 2012
Location: Omaha, NE (KMLE)
Posts: 2,247
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Quote:
Originally Posted by David Paule
Seems that it would get annoying if you're working on something that needs electrical power in the hangar. And if you put a disabling switch in that device, that'll be the one time you leave the master on.
Or am I missing something?
Dave
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You're right. Great point. I just added a few lines of code to beep every couple of minutes even when muted, just so you don't outsmart yourself while working in the hangar.
__________________
Dale
Omaha, NE
RV-12 # 222 N980KM "Screamin' Canary" (bought flying)
Fisher Celebrity (under construction)
Previous RV-7 project (sold)
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05-24-2017, 11:58 PM
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Join Date: Dec 2014
Location: San Diego, CA
Posts: 135
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Check list prior to leaving hangar
Car Keys
Plane Keys
Cold one for the road
Lights off
Alarm Set
Door locked
Check....
__________________
Mark
RV-3 restoring
Stearman - N2S-5 completed/flying
L3 building for San Diego Air and Space Museum
Misc. others...
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