Needed: wisdom concerning the use of DIP chip sockets with the Propeller

ElectricAye

Hi all,

I've decided to graduate my Propeller project to a soldered version, so I was wondering if anyone had any comments or suggestions about using a DIP chip socket for the DIP version of the Propeller. I intend on counting pulses at a rate of up to about 1 Mega Hz, so I'm concerned that a DIP socket might have some frequency issues.

thanks,
Mark

Leon

Provided you use turned-pin sockets (I like Swiss-made Preci-Dip ones) you shouldn't have any problems. I use them all the time on my home-made PCBs at much higher frequencies than that. Cheap sockets can be more trouble than they are worth, tracking down intermittent contacts can be maddening. It's one reason why I never use solderless breadboards.

Generally speaking, if connections are short compared to the wavelength of the signal, you don't have to bother about them.

Leon

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Amateur radio callsign: G1HSM
Suzuki SV1000S motorcycle

Post Edited (Leon) : 10/13/2008 3:00:31 PM GMT

Mike Green

A socket lengthens the leads by only 2-3mm. If you're currently using a breadboard, those lead connections are longer. If you're concerned about lead length, you'd need to go to a surface mount package and be very cautious about board layout.

What I'm trying to say is: Pay attention to the physical reality of what you have and what you're proposing and don't get caught up in appearances (and the names of things). You're already using a socket of some sort (a breadboard). Is what you're proposing that much different?

ElectricAye

Thanks, Leon.

And to Mike:

Mike Green said...
Pay attention to the physical reality of what you have and what you're proposing and don't get caught up in appearances (and the names of things). You're already using a socket of some sort (a breadboard). Is what you're proposing that much different?

Yes, that makes a lot of sense. I never thought about it that way before!

Thanks to you, too!

Mark

scanlime

All things considered, 1 MHz is not that fast. At these speeds, you probably don't have to worry much about construction techniques. I could post some atrocious pictures of a wire-wrapped Motorola 68k board I did a while back which ran Linux just fine at 16 MHz [noparse];)[/noparse]

--Micah

Leon

I had a wire-wrapped 68k board running at 12 MHz, with an 8 MHz part. An early example of over-clocking!

Leon

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Amateur radio callsign: G1HSM
Suzuki SV1000S motorcycle

Cluso99

1MHz is no problem. Better to use a decent socket as otherwise you may end up with problems you didn't expect, especially further down the track when the socket starts to corrode. In the late 80's we stopped using sockets in manufacture (100,000 p.a.) and the faulty returns dropped dramatically.

ElectricAye

Micah, Leon, thanks again.


And to Cluso99,

Cluso99 said...
Better to use a decent socket as otherwise you may end up with problems you didn't expect....

What would you say constitutes a "decent socket" - Do I need to use gold contacts or something? My purposes are purely research at this stage, so if my circuit lasts 15-20 months without getting fried, I'll be dancing on air.

thanks,
Mark

Mike Green

Best sockets use what are called "machined socket pins" and these can have either tin or gold plated contact surfaces. Gold is considered best.

RobotWorkshop

ElectricAye said...
I've decided to graduate my Propeller project to a soldered version, so I was wondering if anyone had any comments or suggestions about using a DIP chip socket for the DIP version of the Propeller. I intend on counting pulses at a rate of up to about 1 Mega Hz, so I'm concerned that a DIP socket might have some frequency issues.

If you are only making a few then just go ahead and use the machine pin sockets. On the other hand if you are making a large batch and cost is a sensitive issue there is nothing wrong with using a standard dual-leaf 40-pin DIP socket. They work just fine for most cases. I've used both styles and don't have any issues with regular sockets.

Think about it. Most early systems had CPU's that were 40-pin DIP chips. Almost all of those just used the plain dual leaf sockets. How many TRS-80's, Apple II's, and IBM PC/XT clones are out there that still work fine today? Quite a few. All of them used the regular sockets. A lot of the PC/XT clones ran their 8088 at 10Mhz with the chip in that sockets. When you look at it from that perspective using one for a Propeller and counting pulses at 1Mhz isn't any stretch at all....

Robert

hippy

All the equipment manufactured by a company I worked for a few years ago only ever used standard DIP sockets and that had minimal problems electrically and mechanically. That was stage and theatre equipment which wasn't exactly treated gently in the hands of roadies or in the back of a truck. I only know of one chip which fell out of a socket.