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I finished my wiring recently and last night I installed the battery and fired it up for the first time.
Everything works. That’s very exciting!

I have a concern about my master solenoid though, When I switch it off it makes a squeaking noise. Is this supposed to be like this?
I have this solenoid from Spruce: http://www.aircraftspruce.com/catalog/e ... rrelay.php
I have also installed a flyback diode to prevent voltage spikes.

I had another look tonight and it seems the noise is actually coming from the capacitor, not the solenoid. I do believe it is normal for a capacitor to make noise when discharging, not sure if it is supposed to discharge like that at all, but I thought it was more like a popping noise as anyway. Anybody with more knowledge than I have want to comment on the subject?

Capacitors should not pop when discharging check and màke sure all your connections are tight and check the cap for a short

Hey Michael,

The only time I ever heard a capacitor make a noise was real late at night when I soldered one into a TV with reversed polarity.. f@**&in BANG!
I was pretty tired but that woke me up good!

Seriously though, it should not be getting hot enough to vent, which is what it sounds like. I'd be checking if the polarity is correct, if its getting hot under load or when its powered off etc. You could also put a limiting resistor in series with the diode to reduce the back emf current when the solenoid is powered off.

Cheers
Tony

Polarity is definitely correct, it's not getting hot either.
It must be an issue with my wiring setup, I'm new to all this stuff.

I've attached my wiring diagram below. Maybe someone with a little more knowledge than I have can spot the flaw:


I currently don't have the alternator connected as I have not installed my engine yet.

Now, I can get it to make the squealing noise in 2 different ways:
- When I power the master switch on but leave the alternator switch off, then turn the master switch off again.
- Or, when I turn both the master switch and alternator switch on, then turn the master switch off first (no noise yet), but then turn the alternator switch off, I also hear the noise.

Make any sense to anybody?

This might be one path of investigation:

Following Jeff Shultz's Sonex 604 diagram I have wired the alternator to the S704 relay through the N.C. pin which means the alternator is connected to the circuit "by default" when no current is flowing through the coil. the switch has to be closed to disconnect the alternator.
Now I've looked at some other people's diagrams, most people seem to do it the other way around, connecting the alternator to the N.O. pin which means the switch has to be open to disconnect the alternator.

I found this as well: http://www.bandc.biz/pdfs/S704-1_Installation.pdf.
B&C also seems to recommend connecting the alternator through the N.O. switch.
Maybe I should try this and flip the switch around.

Hi Michael,

The s704 relay is usually used with the overvoltage detector from B&C. It is designed to disconnect the regulator output or alternator output in the event of an overvoltage. It crowbars a circuit breaker in the alternator switch cct to de-energise the relay and disconnect.
With your arrangement the relay still provides for an alternator/regulator disconnect, albeit manual. Generally you want stuff to fail open if there is smoke, i.e. not be powered off.
Not sure if you are using 2 separate toggle switches, but the use of the S700-2-10 dual gang switch allows you to power on the master, and connect the battery to the bus independent of the regulator supply in the middle position. With switch in the top position it connects the regulator output to the battery. This also prevents regulator output being applied directly to the bus without the battery in circuit, (some regulators go max output if no battery is in circuit)
Jeff modified his original 2006 aerovee circuit, when he built 1374 http://www.sonex604.com/misc/Sonex1374ElecSys_V1_15Sep13.pdf
This is almost exactly the same as how I've wired mine.

Anyway, I'm wondering if there is something funky with the regulator/rectifier?
I'd disconnect the regulator output and also isolate the rest of the circuitry as well by pulling out the 20A fuse and disconnecting the 4AWG to the starter.
This just leaves you with the 2 relays, the battery and the switches.
Check the operation of the switches and relays first up, and then add each connection back individually and check again.
If all good progressively add the regulator, 20A fuse, starter.

Cheers
Tony

I see, Thanks tony.
I don't have the over voltage protection from B&C, I have a Harley Davidson alternator & regulator on my engine which I believe has this built in but I'll need to confirm this.

I do have the regulator and starter motor disconnected for the moment as I don't have the engine installed yet, the capacitor is there though.
I did a test with the 20A fuse pulled as well, same problem.

In the mean time I have tested flipping the alternator switch around and connecting the regulator to the N.O. pin instead of the N.C. pin.

This has solved the problem but I don't quite understand why. Was the capacitor discharging into the coil of the relay?
Anyway, the way I've got it now is the way others have done this as well I believe but that means that if your battery dies you can't use your alternator to keep power onto your main bus as you need the battery to activate the relay.

All very confusing...

Here's a shot in the dark:

• Master switch open, alternator switch closed
  I believe this would correspond to Master Off, Alternator Off with the way you originally wired the alternator relay.
  
• Master switch closed, alternator switch closed (Master on, alternator off)
  Capacitor begins charging until alternator relay switches to N.O. position.
  
• Master switch open, alternator switch closed (Master off, alternator off)
  Alternator relay switches back to N.C. position. Now the capacitor has a discharge path to ground through the relay coil and alternator switch. The relay opens and closes multiple times as the capacitor discharges to the point it can no longer open the relay.

Wiring the alternator relay to the N.O. position should prevent this scenario as once the circuit opens, there will be no path for the capacitor to discharge through the coil.

If this is the case, then it wasn't the capacitor making the noise, but a strange relay sound caused by it partially actuating multiple times. I can't think of any other scenarios for the capacitor making a noise without involving a short circuit or arcing inside the capacitor, but without the regulator, starter motor, 20A fuse, this is the only explanation that comes to mind, strange as it seems.

Michael,

Let me offer a few suggestions.

Ammeter shunt placement: The ammeter can tell you different things depending on where it's located. You have it placed between teh power bus and battery. This will tell you how much current the power bus is drawing *out of the battery* at any given time. It won't tell you the total draw because the alternator is supplying power to the bus also, and that power doesn't go thru the shunt. Likewise, the starter doesn't go thru the shunt, so you won't see the true demand on the battery when starting. If this is what you want to monitor with the ammeter (the in-flight draw on the battery), then it's ok. If you want total draw by the power bus (from the battery and/or alternator combined), then you'll need to move the shunt. If you want total current flow into or out of the battery at any given time, you'll need to move the shunt.

Alternator Disconnect Relay: The way your diagram shows it, the alternator disconenct relay is always "closed" and the regulator output (alternator) is always tied into the power bus. In fact, once the engine is running, you could turn off the master switch (disconnecting the battery) and the regulator output would continue to keep the panel running. Activating the "Alternator Switch" would disconnect the regulator (alternator) and power would cease to flow into the power bus or battery contactor.

If you reverse the connection of the alternator relay from the "Normally Closed" terminal (what you have now) to the "Normally Open" terminal, the alternator will be disconnected (offline) until you activate the switch. The choice is yours, however, there are a few other considerations. If your regulator goes haywire, gets really hot, and tries to melt down in flight, you'll be able to keep the regulator from pumping in power to your bus by disconnecting the alternator relay, but you'll be unable to stop the regulator from continuing to melt down. This is because the alternator is *always* supplying the regulator with AC current, whether the regulator is connected to anything or not. Moving your alternator disconnect relay to the AC lines coming from the alternator (before the regulator) completely isolates the alternator from the regulator and not just the power bus. It's probably a remote chance or a regulator failure that melts itself down, but this method gives you a chance to stop it in it's tracks.

Squeeling Noise: The noise is possably due to the capacitor discharging into the system. Try disconnecting the capitor from the system and see if the noise goes away. If it does, then that's what making the squeel. One option is to place a small load across the capacitor that will slowly discharge it once the battery (or regulator) have stopped supplying power. I suggest a small resitor (1/4 watt, 10k ohm) or 12v lamp connected to the + and - leads. This will "drain" the capacitor without really affecting the rest of the system while in normal operation.

I hope this makes sense and helps.

Jeff Shultz