Arming switch

[Nick Rigg]

Hi all - is it possible to have a switch that arms the ESC just before you fly? As far as I can see, you need to have everything ready to go, all connections to the RX in place and TX switched on before you connect the battery to the ESC - this is the only way it seems to work correctly. If I use the RX switch after I've connected the battery and ESC it doesn't arm .

Also, I read in a US mag about using the throttle cut feature on their (Futaba) TX to arm (and Disarm) the ESC - anyone know about how this works for arming (I can sort of undersatnd the disarming)

[Former Member]

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[Nick Rigg]

Thanks Eric - having armed the ESC by plugging it all in, I'm wary of nudging the throttle stick be accident - and causing unwanted mayhem as a result. My thought right now is to stretch a rubber band horizontally on the TX and use this to hold down the throttle until I'm ready to fly - maybe others have a better/safer solution

[Tim Mackey]

Some of the brushless ESCs also have arming switches, which supposedly isolates the radio. Ironically, I cut these off, and throw 'em away, preferring instead to leave connection of the flight pack right up to the last seconds before I am ready to fly. IMO the only real safe isolation is with the main battery unplugged, and as far as IC is concerned, the engine  stopped. Simply good discipline and the normal care and respect of the equipment involved is all I rely on, I always put my tr down away from my model and myself, as I connect the flight battery.

[Peter Ford]

. If the model is an IC conversion, its not always easy to connect / disconnect the battery plug.

I have an electric Topgun Spitfire with 2 5S packs (in series!) I have to install these lipos and then bolt the wing on. With a 'live motor' no way!

In this case a quick trip to the local motor spares shop and I had one of these . Its used as an electrics safety isolatorby the racing boys

Looks a bit big, right.. Well for a start, you can cut the 'key' down to a stub, cut a slot and operate it with a screwdriver. You can also remove two of the nuts, at the bottom. Dont forget to buy two suitable ring tags for your wire size.

This switch handles 100AMPS at 12 Volts. I am using it on a 10 S setup with a 2Kilowatt electric motor no problems. The 12 volt rating is a bit conservative IMHO. No connection 'sparks' either

For smaller models I use a Deans shorting plug to make with a socket embedded in the fuselage

You can see the Deans socket here on my electrified Vmar Bulldog. I reinforced it with a ply backplate

My biggest fear is catching my TX neck strap on the throttle stick.

Nick your rubber band idea is a goodun.

[Always broke]

Nick you are correct in thinking you need to fit somthing to disarm your esc.I use the shorted Deans plug on all my large set ups It will take 3kw with no problem and is very easy to install.I fit it in the + cable to the ESC . Costs next to nothing and is totally reliable.I keep it attached to the model with a cable made from closed loop wire so it never gets lost. I only plug it in when I am ready to take off. The hardest bit is mounting the female part securely to the model.I usually mount it to the fire wall in a ply block with epoxy with a small cut out in the cowel .You could use 4mm golds to do it but is more fiddly to make up. Big electrics need to be treated with the greatest respect. A gas engine will stop running but a big electric will not . Try stopping 5 or 6 average electric drills at the same time !!

[Tim Mackey]

Nick Rigg wrote (see)

Thanks Eric - having armed the ESC by plugging it all in, I'm wary of nudging the throttle stick be accident - and causing unwanted mayhem as a result. My thought right now is to stretch a rubber band horizontally on the TX and use this to hold down the throttle until I'm ready to fly - maybe others have a better/safer solution

I only connect the pack when I get to the strip - and then fly immediately. Of all 13 current flying leccy models I have never felt the need for an arming switch - I simply dont connect the pack until absolutely ready to fly, and I dont use a tx neck strap either.

The tx is laid on the ground, throttle stick double checked as low, and I connect up.

Pick up Tx and fly.

As soon as I land the pack is disconnected and then the Tx is switched off.  Simple.

[Always broke]

Hi Timbo

Perhaps not so simple with a big 10S pack in a scale model. Fitting the wing on the strip is not really the best thing to do.Then you have to manhandle the plane with it in an armed state.  Its not a problem with models made for EF that have good access to the batteries.On some of my big models it is nessasary to be infront of the model to connect the cells even though they fit in a top hatch. I do not fancy doing that when it will arm the ESC and could unleash 2 or 3Kw .  Also most of us do use TX straps so you need to think of a safe way of protecting every thing and everyone and an arming connection on the ESC feed is infallible. You can never be to safe with these big setups.

[Peter Ford]

A long time ago I used to work as head of design for a company  that made heavy industrial equipment- sort of giant microwaves.

Previously, switching was done with huge contactors (very big relays, if you like)  My Boss wanted the switching replaced with semiconductor switching- similar to an ESC but good for 12000watts!  When the service manager heard about it he nearly callaed a strike. He wouldnt allow any engineers near the machines unless they were fitted with a conventional isolator switch.

So you see its really about 'elf & safety'.   When large electric models are appearing at model shows, if I were flightline manager, I would want visible proof that the electric stuff was safe untill immediately before 'power up'.  Something similar to the safety tags on ejector seats which have a large red flag or streamer attached to a pin thru the gun 'sear'. Every single mechanic who works on a modern fighter jet has to check the seat is safe, before entering the cockpit. If you think this sounds OTT & dramatic, I'll attach a photo of the scar on my lower forearm caused by a stroppy 35cc petrol engine on my Spinks Acromaster. Thats 13 Stiches,and the blade cut the venous artery. The only other man in sight was a spectator, who, as it happend, was an off duty paramedic-amazing innit. 

Always Broke is right, Timbo, Should be one safe rule, in watever form that might be, for everyone

      

[Tim Mackey]

I agree that in certain models due to layout, connection of the pack immediately prior to flight is difficult, and in these cases a suitable isolator is therefore a good idea.... I wasnt advocating that they were a "bad" idea - but also still feel that in the majority of cases, they are un-necessary and another PPOF.

As for having 1x  standard "safe" rule then that is a little impractical if expected to be across the board for every electric model as there is no way an isolator switch would be feasible on a very light weight foamy.

I think we are both right

[Former Member]

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[Always broke]

Eric Bray wrote (see)

Having a 'Deans' plug on the fuselage side is ok, to a point, but what happens if it should happen to fall out? The pins are not very long. No electrics! If you just break the power to one of the three motor leads of a brushless, is the motor still live, or is it safe?

For a small model, I'm with Timbo, plug in just before flight. For a big model where access is awkward, how about a knife-switch under a 'natural' hatch somewhere? If the hatch is open, the switch is open too, and the weapon is definately 'dead'!

If you have a Deans plug that falls out then it is not a DEANS plug and socket. Proper ones are not going to fall out under any circumstances ,in fact they are tight to connect and tight to take apart, it is just not going to happen and has worked for me for many years. .But as you say you can use anything that will handle the current in my case about 100 amps .Also in the models I am referring to the radio is supplied from a separate source. Also you would not fit it in the motor leads but in the lead from the battery to the ESC thus not arming the ESC.. As Timbo says there is no single safe rule and there are many different ways to achieve the same thing, everyone has a different view ,the main thing is that it is safe. In my models up to 6s none of this is a problem as I can connect the battery  just before I am ready to take off. But it is a different story on my 10s and 12s models where they are connected in the pits.

[Chris Card]

Interesting thread guys.  I can see how a Deans shorting plug will be helpful in most instances where the flightpack isn't easily accessible and I wouldn't worry about the Deans falling out - have you ever had one fall out!

A deans in line between battery and motor won't let you carry out field charges through it though as the ESC will still be in circuit.  With A123 packs accepting 10A charge rates I really want to be able to land, remove arming plug then charge the pack inside the plane through the arming connection.  I think for this I will need a 4 pin connector, ie. break both negative and positive connection from battery to ESC.  Does anyone know of one which is rated up to 100A?. 

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[Paul Adams]

There is no reason why you could not wire a separate charging socket across the battery, but I would use different socket to the shorting plug or put them well apart, as plugging in the shorting plug into the charging socket would short out the batteries............Paul

[Former Member]

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[inspector9566]

how about using deans shorting plug to disable the esc and then wire in two surface mounted 4mm banana sockets under a convienently placed hatch for charging an easy option that i might go with unless anybody else can improve on this idea.

[Peter Ford]

Not quite sure what you mean by disabling the ESC. Perhaps you are suggesting grounding the signal line from the reciever?

The 'elf & safety' argument is that an 'Air Gap' be required in the power supply wiring to be absolutely certain that no catastrophic failure in the ESC Thyristor system can inadvertantly pass power to the motor.

I appreciate that even a big hefty switch can fail although much more unlikely than any semiconductor circuit.

[Always broke]

I have a system in a model that has a 2mm female gold and a 4mm female gold socket flush mounted for charging. This makes sure you connect it up the correct way round. I then have the deans to isolate the esc as before. works really well for me. unplug the deans , plug in the charging cable and away you go.

You could use a Mini deans for the charging as that would work really well. It would flush mount the same as the big one.

[inspector9566]

good call on the mini deans for charging but that would mean another lead, using 4mm bullet connectors means you shoud already have the leads made up ready for use

[Chris Card]

I like that idea Always Broke, the mini deans would be a neat solution.  Are they rated for up to 10A?

[Always broke]

Take 10A easy.

It would take out connecting the charger up the wrong way round  or any thing silly like that.

You can get them on fle bay

[Chris Bott - Moderator]

I use a Deans shorting plug to arm big scale models.

To charge I have a single 2mm socket near to it.
My +ve charge lead uses 1 connection on the deans - the battry side. (I cant plug that in wrong as the deans only goes in 1 way.
My -ve charge lead goes into the 2mm  socket.

 Also means I cant possibly charge with the arming plug in.

[Always broke]

Good Set up. Simple and efective .

[Chris Card]

Excellent idea Chris, some really useful thoughts emerging in this thread!

[Geoff Goodwin]

As some-one who has just started in Electric power this has been a most informative thread on the one bit I have hated about electrics so far - i.e. Going live (armed) before you can finish rigging.

I'm not sure if you can upload images to the forum, but would be interested to see how the solutions referred to look in practice.

It got me thinking about a small arming hatch that could be as small as a tube with bullet type connections inside and a cap to close off the hatch - naturally you would need some cable slack to allow sliding out to connect / disconnect. Is there any reason why this would not work or otherwise not a wise move?