Choosing circuit protection diodes?

[sengo]

hey everyone,

I have a mess of diodes I ordered a while ago from the Electronics Goldmine or Jameco (I don't remember which), and I was wondering if any of them could be used as circuit protection diodes in case someone connects the battery the wrong way? How can I tell, by looking at them or finding their datasheet, if they will work? From what I understand you can't use the glass ones, but i have a number of black plastic ones with thicker-than-usual leads. Will these be okay to use?

Thanks,

Nick

[petemoore]

How can I tell, by looking at them or finding their datasheet, if they will work? From what I understand you can't use the glass ones, but i have a number of black plastic ones with thicker-than-usual leads. Will these be okay to use?
  Have any numbers on them ?
  Do one measure one Si diode drop ?
  What happens if you reverse connect a battery to it?  [just kidding, unless you were thinking you want to..one or the other will probably start heating up faster..
  Leads are kinda thick, but yes.

[brett]

What's written on them?
1Nsomething?
PS Me, I use the diode *in series* with the circuit, rather than in parallel.  I figure it's easier to stop the reverse current than try to divert it.

[sengo]

There are many varieties,

1N5260
1N5944
1N4741
1N526
1N5991
1N755


There are also a ton of glass ones, and several I can't actually identify, as well as some SMD diodes.

Any of these look good? If I find the data sheets for them is there a particular value I can look for to identify suitable diodes in the future?

PS Me, I use the diode *in series* with the circuit, rather than in parallel.  I figure it's easier to stop the reverse current than try to divert it.

I was actually wondering why people don't just do that instead. Unfortunately I've already designed and etched the PCB, so for now it's too late to place it in series.

Nick

[Paul Perry (Frostwave)]

The downside of putting the diode in series, is that you will lose .6V or so of the supply voltage.
But normally that should not matter.

Downside of just having a diode across the input, is that 1. it will probably burn out & then where are you? and 2. your unit might burn out before it does. Can't see it, myself.

Best of all worlds: series diode, then a reversed diode to ground AFTER the series diode.
And if you make the second diode say a 10V zener.. BOMB PROOF.