Choosing a substitute electronic part

Choosing substitute electronic components is a common snag for beginners. What do you do if you can’t get the exact part used in a project? Part finder posed this question about the USB IR Toy:

This component is hard to find from my local store: D1, Small signal diode (DO323, BAS16HT1G, Rectifier 85V/0.2A Small Signal Diode).

Can I replace it for example with [this]?

What are the important values?

We didn’t give a particularly helpful reply, but Brian Willoughby picked up the slack with this fantastic description of how to pick a substitute part:

The most important value is the DO323, a.k.a. SOD-323. As Ian says, you can’t easily squeeze a different shape onto the PCB.

What I always do is hit Mouser. Start with a search for BAS16HT1G, and when you click on the Mouser part #, you’ll be given the opportunity to search for similar replacements. In this case, Mouser uses SOD-323 as the package / case. You can basically turn off the checkbox for everything else, because you don’t care about brand or other overly specific values. In the results that appear after clicking “Show Similar,” I tend to sort by price and then start narrowing down the options. Mouser finds about 425 options that would fit the PCB.

The actual selection process can be a little tricky. I recommend keeping a browser window open on the original part, and then use it as a guide to narrow things down in the search results. For example, after selecting general purpose diodes in the search results, I see recovery times of 4 ns, 6 ns, and 50 ns. Since the original part is 6 ns, I just select 4 ns and 6 ns to weed out the slower 50 ns diodes, just in case speed is important. Meanwhile, the lowest voltage is 70V and the smallest current is 150mA, so probably anything will do. If you’re concerned, then start specifying more values to narrow the results.

You’ll note that there is a 1N4148 in SOD-323 as part of the results.

If you want to speed up the process, the Mouser part # page for the original part will update the number of similar parts Found as you check or uncheck different specifications, so you can quickly experiment with how precise you want the match.

Great description of a tricky process, thanks Brian!

CC-BY-SA image by sparr0.

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  1. HI, how and where one can search a substitute component . For example , I need the substitute part for93LC46 eight pin . Please, what part you suggest to replace the mentioned component? Can you e-mail me the necessary part number with some pin out explanation? Thank you in advance. .

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