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Bi-stable solenoid

D

Dozer

Member
I have an idea to use a Blue-system bi-stable solenoid https://www.bluesea.com/products/category/20/95/Solenoids/ML-Solenoids

From my point of view, a bi-stable solenoid is much safer device compared to a regular solenoid. It doesn't consume any power. it will keep contacts connected even if the coil will fail. I mean - if you started the engine on the ground then you should worry about this solenoid during the flight.

Am I wrong?

Here is a manual
https://d2pyqm2yd3fw2i.cloudfront.net/files/resources/instructions/990180170-006.pdf
 
I looked at it from a "packaging" standpoint. It would solve some space problems. I wondered the same as you and actually asked someone to confirm. Looks good on paper but there's no fail-safe position/action. While chances are remote, this could cause issues. The 0.13 contact amps on the L series is way do-able.
 
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If the battery contactor fails during flight, the pilot probably won't even know it because
the battery does not power the aircraft electrical system, the alternator does.
it will keep contacts connected even if the coil will fail
Click to expand...
That is dangerous. The pilot should have the ability to shut off all sources of
electrical power as close to the source as possible.
 
Cockpit electrical fire.

Consider actions if you have it latched "ON" and need it "OFF"

I like the silver contacts!
 
Mich48041 said:
If the battery contactor fails during flight, the pilot probably won't even know it because
the battery does not power the aircraft electrical system, the alternator does.
Click to expand...

Mostly true but the pilot would still know it. The battery acts like a huge capacitor on the output of the alternator. If you remove the battery from the system while the engine is running most voltage regulators will spike the voltage and damage a lot of equipment on the airplane.
 
rvbuilder2002 said:
Mostly true but the pilot would still know it. The battery acts like a huge capacitor on the output of the alternator. If you remove the battery from the system while the engine is running most voltage regulators will spike the voltage and damage a lot of equipment on the airplane.
Click to expand...

Then why is the alternator connected to the switched (cold) side of the master?

It will be disconnected from the battery if the master is switched off.
 
gasman said:
It will be disconnected from the battery if the master is switched off.
Click to expand...

That's why the common Cessna split-rocker master switch won't let you do that. SteinAir also sells a progressive toggle switch that acts the same way. There's no reason to set it up any other way because an alternator won't work properly without a battery acting as an "accumulator".
 
Then if you are running P mags and shut off the master to test the p mags, you risk a spike in the system if you are using a single toggle switch for the master, and you failed to take the alternator off line first??
 
gasman said:
Then if you are running P mags and shut off the master to test the p mags, you risk a spike in the system if you are using a single toggle switch for the master, and you failed to take the alternator off line first??
Click to expand...

That is not the proper way to test a P mag. They are supposed to be wired through a separate switch breaker which you cycle during the ignition check. You’re not turning off the aircraft master switch or alternator for that check. And it has already mentioned by someone else most alternator systems including the electrical drawings from vans are designed such that if you turn the master off without turning the alternator off it kills the alternator also. This is to prevent the problem that I already described.
 
rvbuilder2002 said:
…..And it has already mentioned by someone else most alternator systems including the electrical drawings from vans are designed such that if you turn the master off without turning the alternator off it kills the alternator also. This is to prevent the problem that I already described.
Click to expand...
That’s easily done with an electrically held contactor. Going to take some thought with a latching contactor….

We used to use a lot of latching relays in industrial and lighting control applications as multi location control was much simpler wiring. However, solid state control interfaces and the fact that latching relays were a lot more expensive led to more wide spread use of electrically held products. If anyone cares…..

You might check with Blue Sea to see if they tested for G loading on either product, plus orientation and application of force. Probably not an issue but I would want to know.

The standard cheap contactor Vans uses has withstood the test of time….
 
disconnect battery with alternator on

rvbuilder2002 said:
… The battery acts like a huge capacitor on the output of the alternator. If you remove the battery from the system while the engine is running most voltage regulators will spike the voltage and damage a lot of equipment on the airplane.
Click to expand...

An anecdotal example if an inadvertent test of disconnecting battery with alternator on… B&C wound field vacuum pad alternator, SDS EFI+I, glass panel… no damage. https://vansairforce.net/community/showpost.php?p=1573832&postcount=28
 
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