Power Switch - Open vs Shorted "Off" State

[dknguyen]

I just have a choice right now between an On-On and On-Off power switch for my RC transmitter I'm planning to build. It just occured to me that if I used the on-on switch, I could wire it so that in the "off" state the + and - terminals of the system were shorted to each other. Is there any benefit to doing this? Drain capacitors and things like that...but would it help otherwise?

EDIT: ANd it just occured to me one consequence of having a shorted "off" state for a battery powered system where the batteries are charged internally...if the battery charging circuitry is wired up to the main circuitry (or is governed by the main MCU) for whatever reason, you could not just have it so all you have to do is plug in the power jack and the batteries automatically charge (like a cellphone or Ipod). It also messes up any supercap or battery-backup systems too, of course...and there could be catastrophic consequences if the battery was plugged in backwards when being replaced if the connectors weren't polarized.

So question still stands I suppose...with the inflexibilities and hazards outlined above...are there any benefits? Or should I just stick with an On-Off switch and keep the potential flexibility of the 3 things above?

 

[kchriste]

I don't think I quite get what you are saying. Do you mean, shortout the power buss of the device when it is switched off? The only reason I could see for doing this is if you needed to be able to cycle the power very quickly and wanted to ensure that the MCU was reset properly.

 

[dknguyen]

I don't think I quite get what you are saying. Do you mean, shortout the power buss of the device when it is switched off? The only reason I could see for doing this is if you needed to be able to cycle the power very quickly and wanted to ensure that the MCU was reset properly.

Yes, that is what I mean.

 

[Sceadwian]

Wouldn't that cause every supply bypass cap in the device to short circuit? This doesn't seem like a good idea. The contacts in the switch could weld from the pulse current, or other weird effects from the large current that would flow.

 

[mbarazeen]

if there is a provision on the switch to make short circuit externally by shorting two pins, then you can connect a resistor instead to limit the quick drain from capacitors.
or use the switch after the power supply so that no big capacitors are short circuited.
the adwantage of using this can be quick response to your switch off, but think is it a mendatory requirement for your application?