Preventing a MR from taking off inadvertently

[hover.ch]

Quite often (e.g. using GS simulation mode) I need to power-up my MR in order to do some testing, however, I want to make sure that the aircraft doesn't take off inadvertently. DJI suggests to disconnect the motors / ESCs in such a case, but my motors / ESCs are hard-wired to the power distribution board and I don't want to use an additional switch (for 50A and more). The only workaround for me so far was to remove the propellers, however, that's also suboptimal because you have to re-apply locktite, etc..

Now I had the idea to just create a small jumper-cable with a melting fuse (~2A). In "simulation mode" I would connect the battery via this cable and, in case something goes terribly wrong, the fuse would melt instead of the MR taking off.

That shoudl work reliably or do I miss something?

 

[snurre]

During the situations your refer to I use to feed the copter from a power supply and set the supply's current limiter at about 2A. This would prevent any total bezerk spin-up. Though the motors may still give me a short stab in my face if something went wrong - I try to remember that.
My other, better solution, is to disconnect the wkm power unit from the motor feed cirquit and feed power only to the RX and control avionics.

 

[hover.ch]

I also use a power supply indoors. But when I need to have a valid GPS signal, that's not very comfortable. That's why I came up with the fuse-idea. Disconnecting the WKM power unit is not easily possible, because almost everything is soldered and covered. And for a quick test I don't want to disassemble anything, if possible.

 

[kloner]

if it's torn down and i am diagnosing a problem or a new build, i hit the PC propless. if i'ts just a quickee, i'll just pray

key being never let the radio out of your sight and treat it like a loaded gun. never let anything near the TX period, never be tricky and balance a tx, always set it down in a secure fashion

 

[DucktileMedia]

Or you could make a rig to bolt the Heli down. Or throw a beach towel over the props.

 

[xvin]

Or you could make a rig to bolt the Heli down. Or throw a beach towel over the props.

I have a board with small elastic ties on it. I hook up the skids to the ties. I also use a 1000mah lipo for bench tests.

 

[luismesas]

Take out the propellers

 

[Simon Templar]

I like the towel idea!

What I did was make an umbilical with a toggle switch on it. Plug your battery into one end and the other end to your MR power cable.

When you build it, make it two or three feet long and place the toggle close to the battery end. That way the battery and switch are well away from any props that might inadvertently spin up and you can quickly and easily flip the switch to kill the power.

The switch cost me about $2 at RatShack and the wire, Deans connectors, and heat shrink, were things that were just laying around my bench.


It has saved me once. As I was installing 5.18, two motors suddenly began to spin up. Flipped the switch...problem fixed. No blood, no gore, no trips to hospital.




.....sT

 

[olof]

I just clamp a piece of plywood across the landing gear to my work table. and I have a longish XT60 chord attached to a single lipo when I am working in the assistant. I end up doing this quite a bit to tune the Zenmuse.

There is no way the 800 will fly away with my 200lb table. And if the props start I can just disconnect the lipo (they never have but if they did I am ready). I even start the props this way and add about 15% throttle enough to keep them running and test the response from the sticks. It is a nice way to listen to your motors closely as well.

Where I do this I actually pick up 3-4 GPS satellites (Skylights and big windows I guess). So I can test the whole startup sequence even when it is less than ideal outside like now, heavy snow.

I just updated to WKM 5.20, it seems to have gone very smoothly. No sudden prop starts.

 

[gtranquilla]

I have never had an issue with the MR taking off while in GS simulation mode. But..... I do tie my MR down to the top of a step ladder as a precaution.
I don't believe in using fuses for any object that is designed to fly even for ground testing purposes!!!! Think about it ;-)

 

[chopper]

I built a little wiring harness that allows me to power the FC when doing updates and not power the escs'/motors. Take a look. Its really easy. you just disconnect the 5.5 mm (blue) connector from the PCB (has same 5.5mm connection) and done. no need to remove props etc.. I would assume you could also use this when doing simulations as you don't need to power the esc's, but do need to power the FC.
View attachment 12672

 

[gtranquilla]

Using your idea now..... re: this wiring harness for my RCT800..... nearing completion......Always chose to loop the motor power cables back as you did..... makes a lot of sense....
Snowing again!!!!! Good day for building..... not so good for flying......How is your project coming along?

I built a little wiring harness that allows me to power the FC when doing updates and not power the escs'/motors. Take a look. Its really easy. you just disconnect the 5.5 mm (blue) connector from the PCB (has same 5.5mm connection) and done. no need to remove props etc.. I would assume you could also use this when doing simulations as you don't need to power the esc's, but do need to power the FC.
View attachment 12672

 

[Bartman]

Quite often (e.g. using GS simulation mode) I need to power-up my MR in order to do some testing, however, I want to make sure that the aircraft doesn't take off inadvertently. DJI suggests to disconnect the motors / ESCs in such a case, but my motors / ESCs are hard-wired to the power distribution board and I don't want to use an additional switch (for 50A and more). The only workaround for me so far was to remove the propellers, however, that's also suboptimal because you have to re-apply locktite, etc..

Now I had the idea to just create a small jumper-cable with a melting fuse (~2A). In "simulation mode" I would connect the battery via this cable and, in case something goes terribly wrong, the fuse would melt instead of the MR taking off.

That shoudl work reliably or do I miss something?

Hover.ch

i like your idea, a separate little adapter with an inline fuse would be good for around the shop.

a friend of mine just loosens the prop nuts so the motors and props can spin freely from each other, that way there's no lift if the motors do go nuts and it doesn't take quite as long as fully removing the props.