How do you build and use a smoke stopper?

Question

What is the right way to build and use a "smoke stopper" device to prevent a short or other improper wiring from damaging your electronics?

Is it different depending on what voltage you are using?

Answer 1

There are different ways, but a common one is to put a light bulb in series with the positive battery lead.

This works because it will allow low currents through to power the flight controller, but if there is a surge in current from a short the bulb will light up and sap away the energy.

You need to make sure you have a light bulb rated for the voltage you intend to put through it - for example if you have a 3V light bulb and use it as a 6S smoke stopper, the filament will melt.

This guide by Joshua Bardwell is great to build a switchable smile stopper: https://youtu.be/I5a0TAmEwLE

Answer 2

There are two problems to mitigate here - incorrect polarity and overcurrent - which have different solutions but can be used together.

To protect against a battery being connected backwards you need to add a diode in series with the battery. This will cause a voltage drop - from 0.7V to 1.4V depending on the diode - and will need to be rated to handle the peak expected current.

To protect against overcurrent you will need a fuse, again rated to be above the maximum expected current. Fuses can come in quick blow or slow blow, depending on how quickly you want the fuse to react to overcurrent.

Answer 3

A small scale power supply with over-current protection also works well.

The type to get are little cheap build yourself units, with a display that allows you to adjust output voltage and display output current.

They can be powered from a lipo.

They are useful for a whole bunch of things, but in the smoke stopper situation they go to max current and that's it. The one I have is limited at about 3A which is similar in protection to a 36W 12V light globe. Obviously, smaller light globes give more protection by blowing up.