Safer breadboard power supply

[phector2004]

Hi everyone,

Just wondering if there's a way to limit the current going to a breadboard. I do my best to prevent shorting on the board, yet almost started a fire last week when I left my project to grab a bite. Even though I had disconnected the battery, the red lead somehow made its way to the audio jack sleeve. Came back to find a burning hot battery and yanked it out of the board right away. It's voltage dropped from 8.75V to 5.6 while I was gone 

What would be best way to limit the current in case of a short?

A 9V regulator and a 12V adapter?
A resettable fuse?
A low current slow-blow fuse?

[ayayay!]

Other than rigging something up to disco your circuit when you stand up, a-la riding lawn mower seat, I don't see much you can do.

Look, you're prototyping.  You'll have to start thinking safety first.   

[phector2004]

I actually get off the John Deere to push it when it gets stuck in the mud 
Can't do that with the new ones!

[blooze_man]

The easiest thing to do would be to just disconnect both battery leads and move it away from the breadboard.

[R.G.]

Just wondering if there's a way to limit the current going to a breadboard.

Lots of ways. Some of them even practical and efficient. 

What would be best way to limit the current in case of a short?
A 9V regulator and a 12V adapter?

This one gets my vote, particularly if you use the 78L09 or LM317L regulators which are internally limited to about 100-150ma without any other messing with them.

A resettable fuse?

Maybe. It's hard to get them small enough, though. And tolerance is a huge issue.

A low current slow-blow fuse?

I would not.  You'd have to replace a fuse every time, wonder why it blew, and in general fuss with the uncertainty of what current it blows at, not a trivial thing to do.

Things you didn't mention include active current clamps made from a couple of transistors.

Try the 78L09 or LM317L.

[phector2004]

Thanks, R.G!

I figured it was the simplest "safe" option.

The easiest thing to do would be to just disconnect both battery leads and move it away from the breadboard.

I do do that when I'm not tinkering, but when you're debugging a circuit on the breadboard and put it in the wrong hole, you sometimes don't notice wires overheating till they stink up the room! I've already cooked an LED and a jumper from shorts, as well as my battery last week. I'm trying to keep it to a minimum!

[spargo]

I don't use batteries, just a 9V DC adapter.  I believe it has built in protection for shorts, etc.  Just in case, I simply unplug it when I leave.