Accidental Battery Polarity Reversal?

[FiveseveN]

That would make it a reverse polarity indicator that offers no protection though. Think it through.

[GibsonGM]

This ^

Reversed LED will flash and then burn open upon reverse current, so there's no protection.

With a limiting resistor, it will remain lit, but is now just part of the reverse circuit that is now killing opamps etc.  The CLR still allows for other low-R pathways to gnd to exist.

A reversed 'power diode' that can handle the current on its own will turn on when hit w/rev. polarity and offer such a low resistance ('on' diodes have almost none) that virtually all power is shunted to ground thru it, saving following circuitry...a short if you will...

[Phend]

First thing I solder is a diode across the battery and a 47uf electro cap in parallel with it. Wither the circuit calls for it or not.

[antonis]

I guess you've never heard of current limiting resistors?

It reminds me something but it's blurry enough..

P.S.
A CLR in series with an LED,  both serving as reverse polarity shunt diode configuration,  DON'T short power supply..!!
(voltage across CLR+LED remains undamped..)

edit: Didn't realize your objection is already vitiated above..

[Sooner Boomer]

If it's a critical bit of kit, and there's a good chance some thumb-fingered booger-eater will connect it backwards, I stick an appropriatly sized bridge rectifier in the power circuit. The +/- pins on the rectifier go to the power in of the circuit, and the AC pins go to whatever power in leads - battery clip, etc. I've done this with a lot of test equipment, and almost every pice of test kit that can be used on a car.

[antonis]

I stick an appropriatly sized bridge rectifier in the power circuit. The +/- pins on the rectifier go to the power in of the circuit, and the AC pins go to whatever power in leads - battery clip, etc.

Good for either polarity power supply connection but bad both for 2 X diode forward voltage drop and 1 X diode forward voltage drop circuit ground offset..
(welcome ground loop..)

[Phend]

Like to add this to the topic,

[antonis]

https://www.diystompboxes.com/smfforum/index.php?topic=120494.0

[amptramp]

You could always follow the NASA NHB 5300.4 soldering spec but it is designed for the lightest weight and therefore, the least solder usage:

http://everyspec.com/NASA/NASA-General/NHB_5300--4(3A-1)_7148/

We had three women doing all our soldering back when I worked on spacecraft and their work was something I couldn't believe a human could do.  Our parts reliability man called me over one day and asked what I thought of the soldering on a particular board.  I looked at it and said it looked like a lot of dry and insufficient solder connections.  He told me to look at it under an eye loupe.  He said it was the best soldering I would ever see in my life.  He was right.  That was in 1976 and I still haven't seen anything as good.  The board had flatpack digital IC's on it with gullwing leads and the solder fillet went halfway up the vertical part of the leads everywhere.  All of the connections were good but never excessive and this is important when you are lifting something into synchronous orbit.

[Phend]

Where does the diode across + and - method of protection fall in the various ways of doing this ?
Why would this be best ?

[GibsonGM]

Where does the diode across + and - method of protection fall in the various ways of doing this ?
Why would this be best ?

Yes...is a 5 cent diode a better choice than a more expensive mosfet + zener?  For the 'sensitivity' of most things I build (opamps, FETs, few special ICs) I've always used a power diode and been done with it. 

I can see adding the mosfet for a complicated and time-consuming build you'd be hard pressed to even debug, like a delay...I'd rather add a few more parts/use more space than see major work turn to blue smoke.

[antonis]

Ron, I think you've mixed threads up..
https://www.diystompboxes.com/smfforum/index.php?topic=129035.0

[amptramp]

So it would appear.