Arduino Forum

Using Arduino => General Electronics => Topic started by: thegeekway on Feb 03, 2011, 04:52 pm

Title: No pin markings...
Post by: thegeekway on Feb 03, 2011, 04:52 pm
Whats the general process for determaining pin 1.  Its a 74HC4050D with no marking on the body at all, the datasheet has no help and Farnell tech support keeps copy pasting bits of the datasheet ;) (Now they want photos).

Anyone used this part, its a SOIC16 package.

Thanks
Title: Re: No pin markings...
Post by: graynomad on Feb 03, 2011, 04:55 pm
There has to be something, often a painted strip along one end or tiny dimple on one corner.

______
Rob
Title: Re: No pin markings...
Post by: thegeekway on Feb 03, 2011, 04:59 pm
Thats what I thought, but nothing.  Had it under the stereo microscope and can't find anything.  Guess its going to be trial and error.
Title: Re: No pin markings...
Post by: graynomad on Feb 03, 2011, 05:12 pm
Look at the bright side, there are only two options, be thankfull it's not a quad pack.
Title: Re: No pin markings...
Post by: thegeekway on Feb 03, 2011, 05:20 pm
That cheered me up :D  Glad I have the IR station now, last thing I want to do it melt the SD socket and the microswitches. :)
Title: Re: No pin markings...
Post by: johndimo on Feb 03, 2011, 06:56 pm
I've seen lots of SOIC parts that have no painted markings or a dimple on one end on them to denote where pin 1 is.

Look at the plastic body. Look and see if one entire side of it is shaved at a 45 angle.

Typically with parts like this, one side of the chip will be a standard 90 degree, the other at around 45 degree.  The side with the angle in it is how you can tell what it is.
Look at the pic below. See the offset in the marking? That's because of the angle in the body. The marking is centered on the flat area.  The leftmost pin on the side with the angle is pin 1.

(http://i176.photobucket.com/albums/w192/mrtune/PhotoFeb03114956AM.jpg)

Title: Re: No pin markings...
Post by: thegeekway on Feb 03, 2011, 08:53 pm
You are a genius :D

Why dont they put this kind of thing in the datasheets, thankfully I had put it on correctly first time.  Just need to test now.

Thanks!
Title: Re: No pin markings...
Post by: johndimo on Feb 03, 2011, 09:24 pm

You are a genius :D

Why dont they put this kind of thing in the datasheets, thankfully I had put it on correctly first time.  Just need to test now.

Thanks!


No problem. Good luck with the testing! Hope all goes good.
Title: Re: No pin markings...
Post by: Grumpy_Mike on Feb 03, 2011, 11:28 pm
Quote
Why dont they put this kind of thing in the datasheets,

They normally do, it is at the end with the package drawings. You might have an edited data sheet or not the data sheet from the manufacturer of your chip.