Esc power safety switch?

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ShowMaster
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Esc power safety switch?

Post by ShowMaster » Wed Apr 16, 2014 11:47 pm

Having recently taken a friend to the ER to have many many stitches to close the large DEEP prop cuts in his arm from hitting his throttle on the bench, I had this power safety sw idea.

Before we bring up a safety tx switch mode or inline lipo plug, let me share my idea. The tx safety sw is a good one if your tx has FW to allow it, his didn't! Any inline lipo master plug is a good idea if you don't want to work on servo trims or direction adjustments.
There are pre made switch setups that go between the BEC and rec but they kill the receiver and servo action as well as carry all the servo current required. You can disconnect one or more motor leads if easy to do but most don't!
Or,
How about adding an arming switch in series with the esc pulse lead? Usually a yellow, brown, or white lead.
This is very low current requirement, most if not all modern esc's have a power safety function in its FW that kills the motor if the pulses are missing.
This in combination with the tx safety switch mode if it's available, would be a safer setup. One can work all servos but not have motor control until all switches are in the run position.
Basically you would set your plane on the ground and arm the throttle to esc path switch. After that arm the tx switch.
Some esc's have this switch installed but not many. As I see it, if the missing throttle pulse does disarm the motor circuit due to power esc's power safety feature, this is a good bench mode!
It happened so fast and thanks to Quick Clot a fellow flyer had with him, not a lot of blood! He's on blood thinners. We were lucky!
Ok, will my idea work? I can't fully bench test it for a few days.
SM


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Re: Esc power safety switch?

Post by gohsthb » Thu Apr 17, 2014 3:04 am

Of course this would need to be tested with the particular esc. I think you are right most modern escs won't arm unless there is a signal to it first. I think some testing will need to be done to make sure this works as planned. Install a switch in the signal line to the esc. Then with that switch off and the tx on, plug in the battery. Check that the motor doesn't arm. Typically they will beep. Then check that the throttle stick doesn't work by moving the stick up and down. After that checks out then turn the switch on, and check that it does arm and work normally. Now turn the esc switch back off to check that the esc doesn't start up again. Rearm the esc, start the motor at, let's say, 25% throttle. Now turn off the esc switch again, make sure the motor stops. I think this covers the possible combinations that could occur.
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Re: Esc power safety switch?

Post by ShowMaster » Thu Apr 17, 2014 6:28 am

Thanks for replying. Yes I'll be really checking it all out. I've seen several bad cuts lately. One person severed an artery and was pumping blood. Fortunately 2 EMT's were watching on their lunch break and were in there truck 50 ft away.
So many uninformed electric flyers thinking it's not going to start up at the wrong time. Many have failsafe and don't set it or know how. They turn their tx off and all he'll breaks lose!
I'm defiantly going to see what I can come up with that any dummy can do to be safe. Of course if it costs $1 it'll probably not be used ha ha.



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Re: Esc power safety switch?

Post by Kilrah » Thu Apr 17, 2014 7:10 am

Yes, better to test it thoroughly with every different ESC you install it on.
I would not be surprised if at the moment where you cut the switch the motor briefly starts due to the "broken" pulse.

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Re: Esc power safety switch?

Post by Bill » Thu Apr 17, 2014 11:06 am

Without the FW your idea is very sensible.
But thanks to the er9x software it is simple to set up a switch to cut the throttle, something I didn't bother to do until about three weeks ago bending down to pick up my plane, the throttle lever was caught by the neck-strap :oops: I was lucky it only slashed my sleeve open not my arm, now after landing and before take off I use the switch to make sure that it doesn't happen again.
One lady flyer I know uses the failsafe set to cut the throttle and switches off before handling the model this also seems a sensible thing to do (only on modern 2.4 of course)!
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Esc power safety switch?

Post by Daedalus66 » Thu Apr 17, 2014 11:41 am

Bill wrote: One lady flyer I know uses the failsafe set to cut the throttle and switches off before handling the model this also seems a sensible thing to do (only on modern 2.4 of course)!
In the early days of Spektrum 2.4 (2006), a big thing was made of the "safety" of the new system, in that supposedly all you had to do to make it "safe" was to turn off the transmitter. We don't see that advice any more, presumably because too often people fail to set the failsafe correctly.

I should be clear that I don't use or advocate this approach. I'm of the "Tx on first, off last" school. I use a sticky safety switch on the Tx.
Last edited by Daedalus66 on Thu Apr 17, 2014 1:28 pm, edited 2 times in total.

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Re: Esc power safety switch?

Post by jhsa » Thu Apr 17, 2014 12:19 pm

That goes against all the safety rules I've learnt. Never ever switch the tx off before the plane :o
Just program a good sticky throttle cut. If the tx can't do it, don't use it. Or use it on really small models that can't hurt you or others.
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Esc power safety switch?

Post by Daedalus66 » Thu Apr 17, 2014 1:29 pm

I amended my post to make clear I'm not advocating the early Spektrum approach. In fact, I'm not sure Spektrum ever recommended it. But it seemed like every article on the new fangled 2.4 radio talked about turning off the transmitter as safety measure.

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Re: Esc power safety switch?

Post by Bill » Thu Apr 17, 2014 1:48 pm

Yes I agree a safety switch is the best idea but turning off the transmitter does work if you set the failsafe correctly (for those poor souls without openRC software).
The safety rule about not switching off the the transmitter is ingrained in us from the 27 35 36 72 76 MHz days.
Some of the early sets would even destroy their servos if that happened! Happy days (not)!
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Re: Esc power safety switch?

Post by ShowMaster » Thu Apr 17, 2014 3:20 pm

Sadly the new flyers at open fields, not private, don't seek help from we experienced flyers with prop close calls scars or stories. They aren't required to take any advice or safety course to fly. Most don't set failsafe or have it. I see many that turn the receiver on first and tx last, tx off first, receiver last!
Those I teach RC flying to get that lesson many times during the training. The scary part is when the plane in on an elevated bench top face high to their children they bring along to help "daddy" fly.
I jump on that right away but I do get some flack at times.
I just hate to see the blood and deep cut wounds. It makes me woozy!

As great as any tx safety switch setup is, it's still done via an rf link that can fail or swamp.
I can't save them all but maybe if everyone reading this could test and report on their brand esc's action with switching the signal wire off and on, it would help sort out the better brands to own.
Maybe I could get Bruce of modelRCreviews to do a video on it? He does bother some but his videos are popular. Maybe Scott Page since his videos are well done and popular?

Finally, one could Install a switch in just one motor lead but the current rating would/could be prohibitive? Maybe an external deans for under 40A!
Again the idea is to allow full functioning servos and receiver but kill the motor until your ready.
I have bench time this weekend so I'll see what I find out.
I'm also working on getting my clubs to stock some Quick Clot in the electric areas first aid kit. It sure stopped the bleeding instantly. We usually have guest club speakers on RC gear. I'm going to see if I can get a EMT to speak on how to stop a serious bleed out cut while waiting for help. I've seen too many serious electric related injuries this last year to do nothing!
Btw, the #1 daily ER room visit the ER DR told me, is bullet holes in the hands!
I'm glad we're flying planes ha ha!
He guessed RC prop right off when he saw my friends arm. The ER room is 4 mikes from our field, a clue to his guess.

SM


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Re: Esc power safety switch?

Post by jhsa » Thu Apr 17, 2014 3:37 pm

I wouldn't count on Bruce that much. I asked him once to make a video on safety. Didn't even get an answer. I think he is too busy at the moment trying to get permission to fly again..

Joao

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Re: Esc power safety switch?

Post by ShowMaster » Thu Apr 17, 2014 3:50 pm

Maybe Scott then.
Yes, Bruce's topics seem to jump around a lot. He needs a director and producer to keep him focused I think.



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Re: Esc power safety switch?

Post by Bill » Thu Apr 17, 2014 4:39 pm

Safety is not just an electric issue at public flying fields you get people tuning their IC engines with their eyes inches from the prop and other acts of moronicy are seen every day including buzzing other idiots who are walking dogs across designated flying areas, launching downwind, landing straight towards other people etc etc.
Mind you even at private club sites you get problems we had the retards from the local fox-hunt ride over our carefully mown and rolled strip when the imbecile in charge red faced and shouting at us that we shouldn't be there at that time of day (it was the day the clocks went back and he hadn't put his back)!
So slightly deferring to us by not riding over us in the pits area they tore up the strip as an act of dominance over the insolent peasants who dared to point out the time change!
To paraphrase Kings 2 para 20 In life we are in the midst of morons :x
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Re: Esc power safety switch?

Post by jhsa » Thu Apr 17, 2014 5:42 pm

Here the hunters took our club to court.. apparently because of the noise. Of course they didn't win but now we have limitations. we must log every IC flying and only allowed until 8pm week days and saturdays, and only 120 minutes of motor run time on sundays and holidays.. It's not bad I would say. But I think that the main reason is that they can't go there shooting the animals.. And we can call the police if we see them there or driving with the cars on the runway.. I heard that people at our field already experienced some dangerous situations with the hunters shooting on the fields next to ours..
at the end of our runway (doesn't belong to us) there's a kind of wooden shelter that they use to hide after leaving some food outside. Then just wait for the rabbits and deer :(
But to go there they must drive on our runway. And they are not allowed ;) :D :P
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Re: Esc power safety switch?

Post by ShowMaster » Thu Apr 17, 2014 8:16 pm

I've flown at a field with a shotgun club at one end of the runway approach. A large wall it there. The giant sign on it says" don't fly beyond this wall"! Some do and learn why the signs there! The planes seem to explode in the air?
SM


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Re: Esc power safety switch?

Post by jhsa » Thu Apr 17, 2014 9:27 pm

And no one had the idea yet of teaching them that they shouldn't shoot at the planes? You can put some stuff on the plane that would make them think twice before shooting at an aircraft again :D
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Re: Esc power safety switch?

Post by ShowMaster » Thu Apr 17, 2014 10:28 pm

When asked, no gun owner there knows who did it, you'd think the boom would be a clue ha ha.


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Re: Esc power safety switch?

Post by ShowMaster » Wed Apr 23, 2014 3:59 pm

I'm hopefully getting some bench time to look into an esc safety mod.
No luck finding any esc schematics so far.
My ideas are the so far,
Add a switch to the esc signal input line. If this line is left floating will it be a time bomb? What if I force it high or low with this safety switch? If the input stage isn't cap coupled this could work to bias the input hard off. If it does have a series cap it would at least not be a floating antenna lead?

How about using a switch or resistor or cap or diode, to short 2 motor leads together, or to ground? This should confuse the esc's CPU to not allow a full power run up?

The idea here is to be able to use the receiver and servos but kill or confuse the motor. At the same time everything else works.
I've had the obvious answers from flying buddies,
Take the prop off, disconnect a motor lead. I think we all agree that this is not done because of the lazy mode we get into!
My friend didn't do it because he was only making a "minor adjustment".
Several others this week have been rushed to the ER with arm and hand/finger cuts I was told at last nights club meeting. I think we're going to stock "Quick Clot" at the field now.

Windy today so bench time.
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Re: Esc power safety switch?

Post by Bill » Wed Apr 23, 2014 4:16 pm

A 1k resistor connected to ground on the other side of the of a single pole switch one way connects to the signal to the esc, the other side to the 1k connected to ground. The other options don't sound too healthy. :shock:
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Re: Esc power safety switch?

Post by Kilrah » Wed Apr 23, 2014 4:22 pm

Any ESC should already have a pull-up or pull-down as they're supposed to be immune to an unconnected input.

And no, don't short motor wires, I've already seen several Chinese ESCs burn themselves up if the motor was blocked.

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Re: Esc power safety switch?

Post by ShowMaster » Wed Apr 23, 2014 4:37 pm

Thanks for the tips. I'm in favor of the signal short to ground on the esc side.
A SPDT switch I'm thinking. Of course much bench testing.



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Re: Esc power safety switch?

Post by jhsa » Wed Apr 23, 2014 5:52 pm

If I'm not mistaken most ESCs won't start the motor if they don't have a "VALID" PWM signal at the input... Floating is NOT a valid PWM signal.. Even if there are some voltages on the wire, it's not a valid pulse.

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Re: Esc power safety switch?

Post by SkyNorth » Wed Apr 23, 2014 8:04 pm

How about something like this?
ESC_Safe.JPG
-Brent

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Re: Esc power safety switch?

Post by Kilrah » Wed Apr 23, 2014 8:30 pm

This looks like it can be armed, but not disarmed, right?
I think easily disarming is a must too, as following the laziness theorem the target users won't be the type to open their plane and disconnect the battery to disarm.
But at the same time it must not be too easy to disarm in case "something" causes a spurious press, so like 2-3 seconds press might be needed.

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Re: Esc power safety switch?

Post by SkyNorth » Wed Apr 23, 2014 9:11 pm

Yes , once the scr is latched , you would need to remove the power, to reset it.

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Re: Esc power safety switch?

Post by jhsa » Wed Apr 23, 2014 9:18 pm

it sounds like a job for a little Attiny45/85 ;)
You could program a "press and hold to arm", as well as the same (using the same button) to disarm. The other advantages? smaller to build and probably less components. :)

João

EDIT: Actually it could start already with motor disarmed when connecting the battery. you would have to press and hold the button to arm the motor before flight :). Couldn't be safer ;)
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Re: Esc power safety switch?

Post by SkyNorth » Wed Apr 23, 2014 10:06 pm

Adding a push button across the scr , would allow you to disarm it.

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Re: Esc power safety switch?

Post by ReSt » Wed Apr 23, 2014 10:08 pm

I really believe this is a question of the specific receiver and the ESC.

I just did a short bench test of three different ESC connected to the FlySky 3 CH receiver
In no case did the motor run when the radio was powered off.
Neither when power to the receiver end ESC was connected with powered off radio, nor when the radio was powered off after the motor had been armed and had run.

So to my impression, my cheap chinese no name ESCs are safe (for flying electric gliders).

Reinhard

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Re: Esc power safety switch?

Post by ShowMaster » Thu Apr 24, 2014 1:54 am

Same here. My test was to first have the system ready to fly. Then I broke the sec speed control signal wire. I of course couldn't run the motor. I raised the throttle and reconnected the signal lead. It required me to go to full low throttle before I could arm it. I broke the signal connection while the motor was running. The motor stopped in 2 seconds. I reconnected the signal wire and I had to go to low throttle to rearm the motor on control. From our tests, I think adding a good switch in the esc signal lead is the simplest and cheapest way to go.
Now to make a few betas up and pass them around at the field.
SM


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Re: Esc power safety switch?

Post by jhsa » Thu Apr 24, 2014 6:49 am

SkyNorth wrote:Adding a push button across the scr , would allow you to disarm it.
You're right, but it would be one more button. ;)

If it works with just one switch, couldn't be easier. The problem is that you might forget to disarm the ESC when powering off the model after flight. And then next time you might think you're safe but you aren't. With the attiny idea, the ESC would be always disarmed on start up, requiring a long press on a push button to arm it.

Joao

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