Ne555p

[mjkrams]

How is it going all?

I have just started a project that uses a Texas Instruments NE555P I can't find any pin numbers on it and there is no dimple, how do I find pin one?

Mark K

 

[Gayan Soyza]

Then how do you know that is NE555 can you see the part number?

 

[Speakerguy]

If you can't find pin 1 on a DIP part, quit now

 

[mjkrams]

I can see the part number NE555P under what I presume to be a bach number next to what looks like a little stamp of Texas, there is no dimple as in the example on your jpeg the question is which way is up?


Mark K

 

[mjkrams]

Ill be asking a lot of stupid questions as long as im using this forum Speaker guy, probably just as easy to answer them as take the piss.

 

[Speakerguy]

It is a DIP and not an SOIC, correct? It's just that every DIP I've gotten from TI usually has both the dot at pin 1 and the notch at the top. If it's an SOIC I can see getting confused, if it is that then the side with the beveled edge is the left.

 

[Gayan Soyza]

I can see the part number NE555P under

You mean the part number is under the IC? OMG!!!!!!! If it is mark in up the bottom left hand corner is PIN1.

 

[Speakerguy]

First try a magnifying glass. It could be a paint dot at pin 1 that didn't take too well.

As a funny aside, I was having an incredibly hard time finding pin 1 on a batch of poorly marked SOT-23-6 packaged parts. I broke out a 60x magnifying scope to look at it. I found which corner had the dot, and carefully soldered it on the board in that position. Blew up like 5 of these things and wasted half a day almost. Turns out the microscope was inverting Up was down, left was right, and that pin 1 at the top left was in reality at the bottom right. It's a wonder they kept going up in smoke

 

[mjkrams]

That's answered the question, there is a clear plastic dot in the casting toward one corner that must be pin one. Good, I've learnt something allready. Thanks

 

[Hero999]

Pin one is always on the top left-hand side of the IC when viewing it from the top side, with the legs pointing down. It doesn't matter whethere there's a dimple or not, many ICs don't have a dimple at all.

 

[mjkrams]

That's the problem it's symmetrical, there is no defined left hand corner looking at it from the top, pins down rotate it through 180 deg it looks exactly the same. There is a clear plastic dot toward one corner it is not exactly over a pin and id taken it as a spruce mark from the casting process but I think now it denotes pin one. At the end of the day it is a component worth a dollar, it no doubt will tell me if it's not happy when I liven things up.

Mark K

 

[Roff]

From the datasheet...

 

[Hero999]

That's the problem it's symmetrical, there is no defined left hand corner looking at it from the top, pins down rotate it through 180 deg it looks exactly the same. There is a clear plastic dot toward one corner it is not exactly over a pin and id taken it as a spruce mark from the casting process but I think now it denotes pin one. At the end of the day it is a component worth a dollar, it no doubt will tell me if it's not happy when I liven things up.

Mark K

There should also be a cut out at the top of the package; it's normally U-shaped.

 

[Roff]

There should also be a cut out at the top of the package; it's normally U-shaped.

Not according to the datasheet. See my post, right above yours.

 

[Hero999]

I have never seen a 555 or any 8 pin DIP for that matter without a U-shaped cut-out

 

[Roff]

I have never seen a 555 or any 8 pin DIP for that matter without a U-shaped cut-out

I didn't recall seeing any either, but I guess I had. These were in my stock.

 

[Hero999]

Come to think of it, I've seen an LM741 in the bottom package style.

 

[Nigel Goodwin]

It's a common style, you see all sorts of IC's with just a dimple near pin 1.