SKY Rc switch

[Keith Berriman]

Being a longtime ic flyer and reading about faults that can occur with the on / off switches I have regularly changed mine over the years. Serching web for some new ones this year I came across this electronic unit.

So thought I would ask if anybody has used them ?? And any comments

[Engine Doctor]

Only ever used one that was already fitted to a model I bought. Worked ok . Apparently if they go faulty they will default to on. Not sure if they use any power when turned off or not.

[Keith Berriman]

Thank you for the response I was wandering about power use when not in use so will set up the Meters to check

Have seen where failsafe is power on

[flight1]

I've started using these. had the red one for a year 1/2 and all good. and will be using electronic switches from now on

all have a very small current leakage when off . these types of switches have proved to be very reliable on many devises.

When I have in the past look inside the standard mechanicals rc switch i am not surprised that so many have failures, proberly the biggest cause of crashes next to battery failure not charged (the biggest cause is 'dum thumbs' but no one likes to admint to that, do we?)

[Ron Gray]

I use them on all of my models and haven’t had a problem with any of them (says he tempting fate).

[Frank Skilbeck]

Posted by Keith Berriman on 11/01/2021 11:12:42:

Thank you for the response I was wandering about power use when not in use so will set up the Meters to check

Have seen where failsafe is power on

You'll need a good meter the current in the off position is typically around 2.5 milliamps. I've been using the Multiplex ones for several years, I did have a model with the RC Sky switch, which worked fine, but I sold that model. The thing to remember is to unplug the battery at the end of a days flying.

[Stephen Smith 14]

I have couple of jeti ones, work perfect but don't know about current consumption when off because I always disconnect at the end of a flying session

[Stephen Jones]

I have seen some of the glider guys use magnetic switches.

I have not used any of these or the other just thought i would mention theses too.

Steve.

[Peter Jenkins]

I usually use Powerbox digi switches that rectify a 2S LiPo to 5.9 v. As with all LiPos I always remove the battery at the end of the flying session or when it drops to below 50% capacity so don't worry about the very small drain during the flying session. I've just bought a magnetic switch for a scale model but as I intend to use 2S LiPo for that then again I will be removing the Rx pack at the end of the flying session. A friend uses a magnetic switch and has not had a problem.

OTOH, on a petrol model I have 2 LiFe packs, one for Ignition and the other for the radio, switched by mechanical switches. They are heavy duty ones from Als Hobbies with a tell tale for when they are on. They have not given any problem in the 3 years that I've flown that model. Touch wood!

[FlyinFlynn]

Posted by Frank Skilbeck on 11/01/2021 13:33:48:

Posted by Keith Berriman on 11/01/2021 11:12:42:

Thank you for the response I was wandering about power use when not in use so will set up the Meters to check

Have seen where failsafe is power on

You'll need a good meter the current in the off position is typically around 2.5 milliamps. I've been using the Multiplex ones for several years, I did have a model with the RC Sky switch, which worked fine, but I sold that model. The thing to remember is to unplug the battery at the end of a days flying.

That sounds rather high to me.....quiescent current for a MOSFeT is three fifths of sod all..typically single figure uA, which is an order of magnitude smaller than 2.5mA.... Why is it so high?

[FlyinFlynn]

Posted by Stephen Jones on 11/01/2021 22:28:07:

I have seen some of the glider guys use magnetic switches.

I have not used any of these or the other just thought i would mention theses too.

Steve.

Maybe useable in a glider but a bit dodgy in an arframe that vibrates I would have thought, especially if the magnet is removed for flight so the leaf in the reed switch is relaxed in flight.

[Gary Manuel]

Posted by FlyinFlynn on 12/01/2021 12:08:51:

Posted by Frank Skilbeck on 11/01/2021 13:33:48:

Posted by Keith Berriman on 11/01/2021 11:12:42:

Thank you for the response I was wandering about power use when not in use so will set up the Meters to check

Have seen where failsafe is power on

You'll need a good meter the current in the off position is typically around 2.5 milliamps. I've been using the Multiplex ones for several years, I did have a model with the RC Sky switch, which worked fine, but I sold that model. The thing to remember is to unplug the battery at the end of a days flying.

That sounds rather high to me.....quiescent current for a MOSFeT is three fifths of sod all..typically single figure uA, which is an order of magnitude smaller than 2.5mA.... Why is it so high?

"LIPO" LED lit whenever power is applied (as per photo at top)?

Edited By Gary Manuel on 12/01/2021 12:59:41

[Alan Gorham_]

They don't use reed switches, they use hall effect, solid state devices.

Edited By Alan Gorham_ on 12/01/2021 12:51:58

[Frank Skilbeck]

Posted by FlyinFlynn on 12/01/2021 12:08:51:

Posted by Frank Skilbeck on 11/01/2021 13:33:48:

Posted by Keith Berriman on 11/01/2021 11:12:42:

You'll need a good meter the current in the off position is typically around 2.5 milliamps. I've been using the Multiplex ones for several years, I did have a model with the RC Sky switch, which worked fine, but I sold that model. The thing to remember is to unplug the battery at the end of a days flying.

That sounds rather high to me.....quiescent current for a MOSFeT is three fifths of sod all..typically single figure uA, which is an order of magnitude smaller than 2.5mA.... Why is it so high?

That is the number quoted on the Multiplex data sheet for when the switch is in the off position, so it is for the complete unit not just the Mosfet. The Multiplex switches are slightly different as they use a 3 position mechanical switch to switch between the on and off positions and if the mechanical switch goes faulty the safety switch remains in it's current state. The Jeti magnetic ones state 160 uA.

Edited By Frank Skilbeck on 12/01/2021 18:53:20

[FlyinFlynn]

Posted by Alan Gorham_ on 12/01/2021 12:51:40:

They don't use reed switches, they use hall effect, solid state devices.

Edited By Alan Gorham_ on 12/01/2021 12:51:58

Ah!........Thanks...didn't think of hall effect as they are not really switches, they are variable devices and as such, have leakage and on resistances - neither of which is particularly desirable in a switch environment.

Edited By FlyinFlynn on 13/01/2021 11:09:53

[Keith Berriman]

So I have had delivery of three Hitec heavy duty switches my preferred option in the various makes and one SKY unit. Will be in the hanger later to see how they will fit and how the new switch on one model will work with cabling etc.

Many Thanks for all your responses and comments what a great site this is to get support in this lock down period

[FlyinFlynn]

Posted by Frank Skilbeck on 12/01/2021 18:47:52:

Posted by FlyinFlynn on 12/01/2021 12:08:51:

Posted by Frank Skilbeck on 11/01/2021 13:33:48:

Posted by Keith Berriman on 11/01/2021 11:12:42:

You'll need a good meter the current in the off position is typically around 2.5 milliamps. I've been using the Multiplex ones for several years, I did have a model with the RC Sky switch, which worked fine, but I sold that model. The thing to remember is to unplug the battery at the end of a days flying.

That sounds rather high to me.....quiescent current for a MOSFeT is three fifths of sod all..typically single figure uA, which is an order of magnitude smaller than 2.5mA.... Why is it so high?

That is the number quoted on the Multiplex data sheet for when the switch is in the off position, so it is for the complete unit not just the Mosfet. The Multiplex switches are slightly different as they use a 3 position mechanical switch to switch between the on and off positions and if the mechanical switch goes faulty the safety switch remains in it's current state. The Jeti magnetic ones state 160 uA.

Edited By Frank Skilbeck on 12/01/2021 18:53:20

Thanks...that explains it.....

[Phil Green]

Posted by Engine Doctor on 11/01/2021 11:04:57:

Apparently if they go faulty they will default to on.

This is a misunderstood generalisation - a powerFET as a device in isolation will usually fail short (ie 'on' ) but the switch unit as a whole could have other failure modes, the gate control circuitry could fail or become erratic with water ingress, the power button could fail (is it a dimple contact or capacitive proximity?), and of course wiring, plugs & sockets could fail or oxidise - my point is that 'default to on' applies only to the FET itself - other fault modes could switch the FET off or otherwise break the circuit.

They're probably very good, and better than traditional switches, but they're being touted as 'failure proof' which they're certainly not

Cheers
Phil

 

Edited By Phil Green on 13/01/2021 12:12:58

[Gary Manuel]

Posted by Phil Green on 13/01/2021 12:12:35:

Posted by Engine Doctor on 11/01/2021 11:04:57:

Apparently if they go faulty they will default to on.

This is a misunderstood generalisation - a powerFET as a device in isolation will usually fail short (ie 'on' ) but the switch unit as a whole could have other failure modes, the gate control circuitry could fail or become erratic with water ingress, the power button could fail (is it a dimple contact or capacitive proximity?), and of course wiring, plugs & sockets could fail or oxidise - my point is that 'default to on' applies only to the FET itself - other fault modes could switch the FET off or otherwise break the circuit.

They're probably very good, and better than traditional switches, but they're being touted as 'failure proof' which they're certainly not

Cheers
Phil

 

Edited By Phil Green on 13/01/2021 12:12:58

I agree absolutely.

The true test of a failsafe switch would be, what happens when I unplug it from the receiver? If the power to the receiver passes through the switch and is lost when the switch is unplugged, it's not a failsafe arrangement.

The only true failsafe switches that I am aware of is the "PowerSafe" ones supplied with some of the high end receivers supplied by Spektrum / JR, though I'm sure that other brands have similar products. With these receivers, power is connected directly to the receiver, rather than via the switch. The only current passing through the failsafe switch is used the power the receiver OFF when the switch contact is made. Unplugging the switch, turns the receiver ON.

This definition of failsafe assumes that "safe" means working, rather than safe because it has no power to it!

 

Edited By Gary Manuel on 13/01/2021 12:29:15

[Bob Cotsford]

Surely all that you are doing is to move the power FET and control electronics to inside the receiver? It is still subject to the same failure modes as the self contained 'failover' switches sold by Mpx, HK and others. All that has happened is that the control switch is on a pigtail to plug in.

No power supply can be truly failsafe unless it's part of a redundant supply circuit, can it?

Edited By Bob Cotsford on 13/01/2021 15:52:01

[Frank Skilbeck]

The way these electronic switches work is that they have to see a positive change to change state. On the MPX units the mechanical switch is actually a 2 way switch with the switch connecting the centre wire to either of the outer two wires, one connection will trigger the switch to the on condition, this will not change until the other connection is made to trigger the off condition. So if the switch has to positively change to operate the FET and if doesn't make good contact the condition will not change. The Jeti switches are similar except use a hall sensor and magnet to change the FET state.

On a MPX system, if the switch was on and you cut the wire to the remote activation switch the main power would stay on, if it was off when you cut it, it would stay off.

They are probably not infallible, but a step up from a mechanical switch which may be affected by vibration or over time could see an increase in resistance.

[Gary Manuel]

Posted by Bob Cotsford on 13/01/2021 15:51:07:

Surely all that you are doing is to move the power FET and control electronics to inside the receiver? It is still subject to the same failure modes as the self contained 'failover' switches sold by Mpx, HK and others. All that has happened is that the control switch is on a pigtail to plug in.

No power supply can be truly failsafe unless it's part of a redundant supply circuit, can it?

Edited By Bob Cotsford on 13/01/2021 15:52:01

The SKYRc switches are rated at 10A and carry the full load of the receiver and servos. The PowerSafe switches only carry the current required to switch the FET on and off.

Yes, the same failure modes exist, but the physical switch and the plugs are the most likely failure points. If either of these fail on the PowerSafe system, the receiver switches ON (assuming no other faults).

[Piers Bowlan]

So the $1m dollar question is, are they an improvement on an ordinary switch and is there any point buying them?

[Bob Cotsford]

Posted by Piers Bowlan on 14/01/2021 19:08:51:

So the $1m dollar question is, are they an improvement on an ordinary switch and is there any point buying them?

I used to use the HK dual failover switches which look to be the same sort of thing only in a dual package. I went off mechanical switches especially on IC powered models after a mysterious loss of control occurrence or two and having other switches go high resistance. In my opinion yes, they are an improvement.

[Gary Manuel]

I would say that it is worth while using these as a FET is generally going to be more reliable than a metal to metal switch contact, particularly some of the cheap slider switches I've seen.