Polarity Protection Diode

[M. Spencer]

In many of these layouts the polarity protection diode is a 1n5817. I am starting to run out of them but have more 1n4004s than I can ever use; are the 4004s useful to replace the 5817 as polarity protection diodes?

Follow up question, what parameters should I have looked up on the data sheets to answer my own question?

[Travis]

The 1N4004 will work fine, the main downside is that the 400x types can have thick leads that are difficult to fit into the board

Since we're using series polarity protection, you're looking for a diode with the lowest voltage drop possible. I bought a bunch of 5818 from Tayda for cheap since I use them a lot

[IvIark]

The other problem with the 1N400x diodes is that when it's series protection the voltage drop with them will be around 0.7V instead of maybe 0.4V with the 1N5817, so it takes more away from the supply.  That is the main reason I used the 5817's in so many layouts.  

If the protection is parallel then the voltage drop isn't an issue.  But the downside is the diode will blow up if you reverse the polarity and take out your board

[M. Spencer]

Thanks guys! I have some other diodes in some quantity, looks like I'm off to data sheet land to see their various voltage drop specs.

[Beaker]

I use 1N5818 too.

When I bought them, 1N5818s were stupid cheap compared to 1N5817s for some reason, so I was able to order 200 1N5818 for the price of 50 1N5817.

[Frank_NH]

I found a good source for 1N5817s on eBay and picked some up recently.  1N5818s have a slightly higher voltage drop, but then if you miss the higher input voltage, you can just use one of those 9.6V Boss wall warts .