On/off switch for brushless motor

[Oldman]

I am building a SPAD biplane which requires a brushless motor (Overlander 2826/18) and corresponding ESC (Overlander XP2 20A). The build instructions do not include any mention of an on/off switch between the ESC and battery (Overlander 1300mAh 7.4V Lipo). I do not want to simply unplug the battery/ESC connector when the system is not in use. Any views? The model is very lightweight and space for components restricted.

 

Many thanks

 

Don

 

[Oldman]

I am building a SPAD biplane which requires a brushless motor (Overlander 2826/18) and corresponding ESC (Overlander XP2 20A). The build instructions do not include any mention of an on/off switch between the ESC and battery (Overlander 1300mAh 7.4V Lipo). I do not want to simply unplug the battery/ESC connector when the system is not in use. Any views? The model is very lightweight and space for components restricted.

 

Many thanks

 

Don

[Engine Doctor]

A simple shorting plug fitted into external fuz will work well.  Xt 60 or whatever size plug you use on the battery. 

I use a smaller version for small rc models made up from servo plug and socket 

[MattyB]

1 hour ago, Oldman said:

I am building a SPAD biplane which requires a brushless motor (Overlander 2826/18) and corresponding ESC (Overlander XP2 20A). The build instructions do not include any mention of an on/off switch between the ESC and battery (Overlander 1300mAh 7.4V Lipo). I do not want to simply unplug the battery/ESC connector when the system is not in use. Any views?

Yes - you don’t store or transport lipo batteries in a model, period. By all means set up a TX throttle cut and (if you are really worried about the model accidentally throttling up in the few seconds between when you plug it in and when you place it on the patch to go fly) a shorting plug, but you should never leave a lipo connected to a powertrain in the pits between flights for multiple reasons (safety, potential for lipo to discharge below a recoverable level etc.).

 

Edited November 27, 2022 by MattyB

[Engine Doctor]

Have you thought about a simple shorting plug for a switch ? A XT60 socket in one of the power leads between the battery and ESC and then use a shorting plug to switch it on . 

[Simon Chaddock]

Don

The conventional wisdom is than a switch can fail. If it fails "on" the motor can start if you accidentally touch the throttle. 

As the Engine Doctor suggests a favoured solution is to use a normal connector as an external plug which when removed breaks the positive side of the circuit. Its removal is also a visible sign of isolation.

You will find that a 20 Amp properly DC rated switch is pretty massive compared to its AC equivalent.

Many clubs insist on a positive battery disconnect before a plane can be returned to the pits.  

[MattyB]

Ps - I actually  have an old foam HK SPAD of a not dissimilar size that runs on 2S 850s on a JST plug. To get it to balance with that very short nose and keep weight down I removed the (moulded in!) steel nose weights, and now install the battery through the prop arc! It’s so small an arming plug isn’t really an option (it would have to be installed further back, affecting the balance), so instead I have configured a fairly complex throttle cut in OpenTX using an unknockable safety switch that requires a sequence of switch movements in a specific time period to a it. It works well, but I accept that some people would not feel confident in such a setup.

 

 

 

Full list of the mods I did are in this thread…

 

https://www.rcgroups.com/forums/showthread.php?1453594-Mini-SPAD-WW-I-biplane-preview-by-HK/page48

Edited November 27, 2022 by MattyB

[MattyB]

Link to Unknockable safety switches setup for OpenTX/EdgeTX…

[Oldman]

Very many thanks.

 

Apologies for my ignorance, but could you expand on "normal connector" and "an external plug", please? Ideally, I would like to mount a connector on the outside of the fuselage to isolate the battery.

 

Don

[EarlyBird]

Welcome to the forum Don. It's a bit confusing to start two topics on the same subject. This is a good answer from the other topic.

 

Steve

[Cuban8]

4 hours ago, Oldman said:

I am building a SPAD biplane which requires a brushless motor (Overlander 2826/18) and corresponding ESC (Overlander XP2 20A). The build instructions do not include any mention of an on/off switch between the ESC and battery (Overlander 1300mAh 7.4V Lipo). I do not want to simply unplug the battery/ESC connector when the system is not in use. Any views? The model is very lightweight and space for components restricted.

 

Many thanks

 

Don

Personally, I'd keep it simple and safer and just unplug the battery. Keeping the component count down is more reliable and electrically more efficient as well.  Properly soldered battery/esc connectors shouldn't be difficult to manipulate and get together/apart even in tight installations. Presumably you don't intend to re-charge the battery between flights with the lipo still in the model! 

[Engine Doctor]

1 hour ago, Oldman said:

Very many thanks.

 

Apologies for my ignorance, but could you expand on "normal connector" and "an external plug", please? Ideally, I would like to mount a connector on the outside of the fuselage to isolate the battery.

 

Don

By a " Normal connector" I meant the same connector you use to connect the battery in the model. Beit a Dean's   or one of the XT  range , the XT60 being very popular for average club models.  The female part of the connector can be mounted in the fuselage side flush . The male part is then bridged to act as a shorting plug and when plugged in completes the circuit. After your flight the shorting plug can be quickly and safely removed making the model "safe" from starting unexpectedly.

The male and female description is a bit of a misnomer on the XT connectors as the actual male and female contacts are fitted in the opposites outer caseing . To  clarify I'm describingu the outer plastic parts of the connector in the description .

[Bruce Collinson]

4 Max sell kits of parts for these and knowing George, he will include foolproof wiring instructions too.   I have some but CBA to fit them to my fleet as unplugging the LiPo is relatively easy.

BTC

[Denis Watkins]

This is too big and too heavy, but can you see in your minds eye, a micro version, or solution that satisfies you.

 

[Allan Bennett]

8 hours ago, Oldman said:

. . . . The model is very lightweight and space for components restricted.

 

Many thanks

 

Don

 

There's the main reason to simply rely on unplugging the battery.  As others have said, any switch capable of carrying the current used by even the smallest motor will be far too big for a model aircraft.  I use a 'disarming plug' system, like the one in the previous post except using a Deans plug and socket, on two of my models where it's impossible to disconnect the battery without getting ones hand in the way of the prop.  Otherwise my disarming is done by disconnecting the battery.

[GrumpyGnome]

Out of my 20+ electric models, just one has a switch or arming plug - I just plug/unplug the LiPo & have a throttle active/disactive switch on my tranny......

[Lima Hotel Foxtrot]

19 hours ago, Engine Doctor said:

By a " Normal connector" I meant the same connector you use to connect the battery in the model. Beit a Dean's   or one of the XT  range , the XT60 being very popular for average club models.  The female part of the connector can be mounted in the fuselage side flush . The male part is then bridged to act as a shorting plug and when plugged in completes the circuit. After your flight the shorting plug can be quickly and safely removed making the model "safe" from starting unexpectedly.

The male and female description is a bit of a misnomer on the XT connectors as the actual male and female contacts are fitted in the opposites outer caseing . To  clarify I'm describingu the outer plastic parts of the connector in the description .

In that case, as this is being posed as a safety issue, the male connector/female pins (aka the battery side) should be affixed to the plane and the female connector/male pins should be the arming plug because it's the male connector that isolated the pins from each other in the connector, thus lowering the potential for an unwanted short.

 

Although for what it's worth I regard any of these additional wiring systems as introducing a potential fail point, and good pit drills regarding tx discipline should be followed and are more important than any "solution" that involves fiddling around with extra bits.

[J D 8]

         With my little FF15 I have set up an "arm" switch to allow the throttle to become live just before take off, flight controls can still be tested as soon as battery connected. Futaba T8j

[Engine Doctor]

3 hours ago, Lima Hotel Foxtrot said:

In that case, as this is being posed as a safety issue, the male connector/female pins (aka the battery side) should be affixed to the plane and the female connector/male pins should be the arming plug because it's the male connector that isolated the pins from each other in the connector, thus lowering the potential for an unwanted short.

 

Although for what it's worth I regard any of these additional wiring systems as introducing a potential fail point, and good pit drills regarding tx discipline should be followed and are more important than any "solution" that involves fiddling around with extra bits.

Hi LHF I agree with what you say however if the Male part with the female pins is fitted to the fuselage they will stick out when not in use and be likely knocked . Either way its a compromise but far safer than handling an armed model .

[Lima Hotel Foxtrot]

5 hours ago, Engine Doctor said:

Hi LHF I agree with what you say however if the Male part with the female pins is fitted to the fuselage they will stick out when not in use and be likely knocked . Either way its a compromise but far safer than handling an armed model.

None if this us a new idea, so I suspect there is an off-the-shelf solution to fitting a plug securely in the plane without it getting in the way. 

 

A powered up model is only as safe as the person handling it, no amount of switch combo or electrical doohickys will prevent an incident if the flyer is acting like a bag of mince and not paying attention to the fundamentals

of safety. The likelihood of an electrical component going haywire on its own is vanishingly small. Yes it happens, but not as often as human error on the field happens. 

[Peter Jenkins]

Jeti do make switches that can be operated by either a magnet or the radio to connect and disconnect the main battery in electric models.  This one copes with 100 A and weighs 110 g but the price is steep - £175!  See this link.  You can buy a complete model for that!  They also sell a 200 A version and you could probably buy 2 models for that.  The point is, they do exist.

[Engine Doctor]

15 hours ago, Lima Hotel Foxtrot said:

None if this us a new idea, so I suspect there is an off-the-shelf solution to fitting a plug securely in the plane without it getting in the way. 

 

A powered up model is only as safe as the person handling it, no amount of switch combo or electrical doohickys will prevent an incident if the flyer is acting like a bag of mince and not paying attention to the fundamentals

of safety. The likelihood of an electrical component going haywire on its own is vanishingly small. Yes it happens, but not as often as human error on the field happens. 

 Your  statement  that it's  not a new idea to you or me and thousands of others is correct however it's obviously new to the OP so why is trying to pass on some help without him spending a fortune so outrageous? And the OP did ask for any views . Why the argument?

Shure no amount of safety devices will prevent a "flyer is acting like a bag of mince and not paying attention to the fundamentals" from having an accident.

As for your suggestion that an electrical component going haywire being vanishing small : there are probably a  small number of folk that have the scars or injuries and wouldn't agree. Electronics are made in the millions and not individually tested so a simple safety solution is IMHO better than a box of electronic gizmos costing a fortune,  Why re-invent the wheel ?

[Peter Jenkins]

As for your suggestion that an electrical component going haywire being vanishing small : there are probably a  small number of folk that have the scars or injuries and wouldn't agree. Electronics are made in the millions and not individually tested so a simple safety solution is IMHO better than a box of electronic gizmos costing a fortune,  

 

ED is quite right.  Also, there is the software to be considered.  In full size aviation when safety critical functions are being performed using software you usually required four systems with a voting facility to determine the correct course of action.  You can lose one system but if you lose 2 systems the voting system doesn't work any more.  With our software, it is not developed to the same stringent rules otherwise we wouldn't be able to afford the products.  So, LFH's point is not strictly correct for 2 reasons.  I never take any liberties with my electric motors and always assume that there might be a sudden application of full power due to a gremlin.  That way, I've kept my fingers still attached to my hands.

[Andy48]

On 28/11/2022 at 14:15, Engine Doctor said:

Hi LHF I agree with what you say however if the Male part with the female pins is fitted to the fuselage they will stick out when not in use and be likely knocked . Either way its a compromise but far safer than handling an armed model .

No they don't. The outer shroud of an XT60 protects the pins, and if the outer shroud edge is flush with the fuselage, there is no way the pins can get knocked without causing serious hanger rash elsewhere.

 

[Andy48]

On 28/11/2022 at 10:33, Lima Hotel Foxtrot said:

In that case, as this is being posed as a safety issue, the male connector/female pins (aka the battery side) should be affixed to the plane and the female connector/male pins should be the arming plug because it's the male connector that isolated the pins from each other in the connector, thus lowering the potential for an unwanted short.

 

Not in the case of an XT60. As the outer shroud is on the plug with the pins on it (male plug, convention is it goes by the pins not the shroud), that is the sensible one to fit to the fuselage. The way I use the arming plug is to fit the battery in the pits, and walk out to the flight line before inserting the arming plug. Thus the chance of a short is very, very small indeed, especially considering that the end of the pins is below the level of the shroud.  If you wanted to make it 100% secure, you could insert an unconnected female socket with a cover into the male side of the arming plug.