ON/OFF Switch

[Wogboy]

Newbie question:

I'm currently installing radio gear into an electric motor glider I've scratch built. The speed controller I have does not have an on/off switch, but I would like to be able to turn the radio gear on/off without doing this with the battery connectors, as well as a safety precaution in case I need to turn off the motor in a hurry. If I put the switch (standard receiver-style on/off switch) between the battery and speed controller, will the switch be able to handle the current at high loads? I'm using a 1450mAh lipo with a small brushless motor. The speed control has no specs on it, but I'm guessing it's low around 10-15A. Using BEC too.

Cheers,

Darren

[Malc C]

Its not clear from your post what you actually want to do

If you simply want to switch off the supply from the battery to the reciver so that you turn on the transmitter, then throw the switch on the model and go fly, then a simple toggle / slide switch in line with one wire from the battery will do

Surely your esc will allow you to control the speed so why would you need have a switch in the motor feed ?

Most reciver operated switches (ie that can be controlled from the transmitter) often have limited current outputs, as they tend to be used for switching LEDs, however its a simple case to use a FET to switch higher motor loads.

[Chippie]

One to ponder.....What happens if the switch fails in flight?

[Malc C]

:) :) it either glides off into the sunset, or glides like a brick to the ground :eek:

[Acetronics]

Hi, Wogboy

Did you try an automotive fuse ( U shape ) on its socket ... ??? ( from auto accessoiries shop !!! )

We use it for our low power 7 cells championships ( here a compulsory 30A fuse limits costs ...)

Alain

[Miami Mike]

Unless you want to use the method that Acetronics suggested above, which is fine, you should cut the red lead of the three-wire cable going between the ESC and receiver, and put the switch in there. That's essentially the way that ESC's with on/off switches are normally wired.

[Wogboy]

No I haven't tried an automotive fuse, where is it placed - across 2 of the motor wires?

[Andrew McGregor]

No, in the positive lead to the ESC.

[Terry S]

In line with one of the battery leads for full protection or one motor lead as an arming switch only. There is a risk if you fit in in the battery lead and use BEC that it may blow and your radio will go dead. I would choose a size 3 times the current you expect to draw with your motor as a good safty margin in this case.

Terry

[vintage1]

A switch that will take full motor current will be excessively heavy and lossy. As will a blade fuse in series with one lead of the pack, but its less lossy and heavy than a switch.

If the requirement is merely to render the motor inoperable then a light weight switch in series with the positive wire from he ESC to the reciever wil nearly alwys do the trick.

[Wogboy]

Thanks for all the help and ideas guys

[jeffs555]

I have used small slide switches in all my helicopters and planes, and have not had a problem.(knock on wood) I wire the switch in series with the positive battery wire. The helis draw 10 amps or more. Don't know what the switches are rated for, but I am sure it is not over 3 amps. The thing is that switches are rated for the current they will switch. Once they are closed, they will usually handle a lot more current. Since the throttle is off when I throw the switch, it is only switching very low current. I have checked the switches under full power, and they don't even get warm. I have had several battery connectors fail, but have never had a switch fail. Again, this is just my experience, and Murphy will probably smite me for talking about it.

[Miami Mike]

I have checked the switches under full power, and they don't even get warm.What you could eventually get is a sort of avalanche effect. Heat generated by the slight resistance between the contacts can begin to erode the connection, which will increase the resistance and therefore the heat, causing it to eventually fail. It might just be a matter of time.

[jeffs555]

Possibly, but like I said, I have all my planes and helis wired this way. Some of them have been flying for 5 years and the switches show no sign of increased resistance, voltage drop or heat. This was not the case with some of the cheaper battery connectors which exhibited exactly the symptoms you describe in less than a year. I went to Deans connectors and no problems since.

Having a switch in the main battery lead is just so convenient that for me it is worth the very slight risk of inflight failure.