What is the acceptance of SMD chips in the community?

[jedynakiewicz]

I would never consider anything other than turned pin, be it for prototype work or product.
The wasted time, damage and cost that has resulted from other types far outways the extra cost.

BeanieBots, thank you. With 8000+ messages on the site I guess that yours is a definitive voice of experience speaking and that is what I was looking for, together with the other helpful replies. In fact do have a proper (earthed) pin-straightener, an antistatic workplace and I have been using turned pin sockets for most of my work. It was really that I was wondering if the extra cost of the turned pin fellows was sensible; you and the others who have replied have convinced me that it is. Looking at these devices again, I note that the inner leaves appear to be gold-plated or perhaps it is just the colour of the spring alloy that is used. Gold plating would, obviously, be a whole lot better in terms of resistance to oxidation etc. Icing on the cake?

 

[nick12ab]

BeanieBots, thank you. With 8000+ messages on the site I guess that yours is a definitive voice of experience speaking and that is what I was looking for, together with the other helpful replies. In fact do have a proper (earthed) pin-straightener, an antistatic workplace and I have been using turned pin sockets for most of my work. It was really that I was wondering if the extra cost of the turned pin fellows was sensible; you and the others who have replied have convinced me that it is. Looking at these devices again, I note that the inner leaves appear to be gold-plated or perhaps it is just the colour of the spring alloy that is used. Gold plating would, obviously, be a whole lot better in terms of resistance to oxidation etc. Icing on the cake?

Maplin claim the following about their range:

A range of high quality 200 insertion turned pin DIL IC sockets, for production and replacement use. Manufactured in UL94-V0 filled polyester with beryllium copper contacts. Suitable for end to end and side to side stacking.

Not really gold!

If the PICAXE isn't expected to need replacement then the best connection comes from just soldering the chip directly to the board - in the rare event that the chip needs replacing it's not difficult as long as you use the right tactic for desoldering and you don't solder it in using lead-free solder. Soldering the chip to the board is my preference for commercial electronics kits even though they come with sockets.

EDIT: 2500 posts!

 

[Dippy]

Bloomin' 'eck, 2500 posts for Nick and he's still too young to drive.
A budding forumholic

I haven't looked at the Maplin offerings Nick but there are plenty of gold plated turned pin IC sockets around.
Just do a search on Farnell, for example.
Don't confuse contact material with plating when you are looking.
(Dippy: 10,000 posts and 10,000 years out of school and in industry.)

Whether to solder or to socket is a judgement call.

 

[BeanieBots]

Whether to solder or to socket is a judgement call.

Absolutely.
For commercial boards it is often more about cost and sockets are hard to justify. For hobby which is often about tinkering, then its hard NOT to justify the extra cost.

If 2500 posts is a budding forumholic, what is 9567 posts? (Lets not mention the +17k posts!)

As for mine being "a definitive voice of experience", just because I've posted frequently doesn't make it any more valid.
However, I DO have a wealth of electronic experience but it is still just an opinion. All the other points raised are perfectly valid.

For what it's worth, for the sake of two resistors + 3-pin header, I strongly recommend ALWAYS fit the download circuit.
Again, some people (esp commercial) would prefer to save the extra few pence.

 

[jedynakiewicz]

Don't confuse contact material with plating when you are looking.

Dippy, you are quite right. I have just checked out the specification of the sockets and the full spec states: "Contact material: Beryllium copper; Contact plating: Gold-on-nickel". The base alloy is the beryllium copper which is then gold-plated over nickel. That seals the deal for me as oxidation of the contacts is eliminated. No wonder problems are avoided with repeated use in prototype boards.

 

[Grogster]

Interesting all the comments about DIL sockets.
I have always used the cheap leaf sockets, and must have used thousands of them now over the years, and I have not had one single one give any problems at all - ever.

I am surprised that the rest of you are having so many issues.

But to be fair, I generally prototype on the breadboard, then when the PCB is ready, I push the IC in and it is there forever unless the chip fails for some reason, so generally speaking, the IC socket is only used with one chip, and that chip is only inserted in the socket once - maybe twice if something kills the chip. Reprogramming etc is done with the chip still in it's socket.

I don't deny the machined sockets are better quality, it's just I have never had any issues at all with the leaf type.
But again - it's probably as the chip is not being removed and replaced...

 

[graynomad]

Thanks nick12ab and srnet for responding to my questions.

Given that UARTs are probably the all time most sort after peripherals on a uC I find it amazing that the Picaxe 40X2 uses a chip with two of them and ignores 1.

Similarly the decision to constrict the I2C and SPI ports to the same pins when there are other options seems strange to say the least.

There may be good reasons to hobbling the chip like this but they escape me. Is it that the hserin/out commands would have had to be modified?

Personally I would think that the change to yell from the rooftops that the new X2 chip has twice as many hardware serial ports would be something worth doing

 

[Grogster]

I agree with that.
I am sure that there must be a good reason, or the PE would allow access to those ports.
I guess it is most likely a compatibility issue with the PE etc.
However, having said that, the PE supports many types of chip, so you would imagine that a compiler for the 40X2 with support for the extra ports would not be impossible.

It's probably a time thing - takes time to write the compiler to allow the extra features. Perhaps it is something that they are working on as we speak...

 

[srnet]

Given that UARTs are probably the all time most sort after peripherals on a uC I find it amazing that the Picaxe 40X2 uses a chip with two of them and ignores 1

The PICAXE 28X2/40X2 uses one of the hardware UARTs, and jolly useful it is too, especially given that functionality added by the background receive.

But as the PICAXE does such a good job with serial out or serial in on just about any available pin, I am not sure how useful a second hardware UART would be.

 

[Grogster]

But as the PICAXE does such a good job with serial out or serial in on just about any available pin, I am not sure how useful a second hardware UART would be.

...an exceptionally good point...

Perhaps more then one I2C port would be more useful then multiple UART's.

 

[srnet]

Perhaps more then one I2C port would be more useful then multiple UART's.

The PICAXEs have SPI and I2C, but if you use the SPI, then you cant directly use I2C on the same port. There are hardware solutions of course, but not for the average constructor I suspect.

Having access to the second SPI\I2C port would help a lot, simpler code and hardware, for those circumstances when you want to mix SPI and I2C devices on the same PICAXE.

I did a 18F25K22 version of one of my locators in Mickrobasic, driving the SPI chip on one SPI\I2C port and an I2C RTC on the other, would be great to be able to do that directly on a 28X2 or 40X2.

 

[graynomad]

Hmm, well at least my interpretation of the various data sheets seems correct. I think the 40X2 design is very lacking in these respects.

Maybe I can design the board for both the 40X2 and the PIC18F45K22 so if you are a PIC expert you can access the features not implemented by Picaxe.

 

[srnet]

Maybe I can design the board for both the 40X2 and the PIC18F45K22 so if you are a PIC expert you can access the features not implemented by Picaxe.

You can, I did it once for a 28X2/18F25K22.

The programming requirements are really quite different though.

 

[SAborn]

I just wonder why you picked the 40x2 chip?
What function is intended that the chip will do?

Often i find the picaxe too slow for a "all in one" chip and use several smaller chips to do what might be done with a larger chip and higher speed.
Using the 40x2 and just doing some simple tasks with it could be like using a sledge hammer to kill an ant.

 

[graynomad]

Yes, presumably I would need to implement both the Picaxe jack and an ICSP header.

From what I can see that's a 6-pin header with

MCLR
VDD
VSS
PGD
PGC
AUX

All except AUX seem obvious, is that used?

 

[graynomad]

I just wonder why you picked the 40x2 chip?

I started with the 28X2 but it's the same price as the 40 so I saw little point in using the smaller chip.

They have exactly the same internals AFAIK but of course the 40 has more IO. They both seem to bring out all the important IO so when run in PIC mode either would suffice I think.

I have a friend using a 40 to do a pretty complex engine monitor in a bus and the extra IO is good for switches, LEDs etc. So the 40 is capable of doing a lot but it can be limited. Part of that is the non-availablity of certain IO as we've been discussing but there is the restriction of the interpreted BASIC as well.

The PIC18F45K22 can be bought for < $3 and for that matter the other version of this board I'm working on uses a 32-bit LPC which is also available for < $3. I think we are at the point where it often doesn't matter if you overkill something because everything is so cheap. So you could just use the LPC and be done with it but a lot of people are comfortable with the Picaxe environment.

Also the nature of this system is to distribute processing, for example a daughter board to control 16 or 32 servos can easily be made with a co-processor. This removes a huge load from the Picaxe and might make it more viable for larger jobs.

So I'm keen to have a Picaxe version and if that can also be a PIC18F45K22 version more the better. And if a 40-pin chip costs the same as a 28-pin one then I may as well go the full monty.

 

[srnet]

From what I can see that's a 6-pin header with

MCLR
VDD
VSS
PGD
PGC
AUX

All except AUX seem obvious, is that used?

Thats the PICKIT header layout. AUX is not needed.

Care is necessary with MCLR, that can end up with 12V on it, which you dont want to get back to the rest of the circuit.

 

[Grogster]

Often i find the picaxe too slow for a "all in one" chip and use several smaller chips to do what might be done with a larger chip and higher speed.

Agreed.
I too like the modular approach - several different PICAXE chips, normally talking as need be via SERIN and SEROUT.
Naturally, there are times when you want or need more IO's and ports, but the modular approah does allow true multi-tasking, as you have several different codes running on several different PICAXE chips - a TRUE multi-core system

Coincidentally, I am using the 40X2 in my latest project mainly to get the extra IO's as mentioned by graynomad...

 

[graynomad]

Thats the PICKIT header layout.

Probably as good as any of the ICSP pinouts I suppose.

Care is necessary with MCLR, that can end up with 12V on it,

Noted.

The whole idea of my little design is for a modular approach with stackable boards and/or tiny IO modules. I've been working on this on and off for a long time but keep changing it, I think the basic design is about right now though. I want the system to be usable with any common processor, my favourite is LPCs but I'm also trying to make it usable with AVRs and PICs/Picaxes as well.

 

[hippy]

What the heck happened to posts #60 and #61?

The posts were moving too far off-topic for the thread.

 

[jedynakiewicz]

What the title says, what is the acceptance of SMD chips in the community?

I see that all PICAXEs are now available in SMD packages, are people happy using these on a development board or are DIPs still preferred?

There is at least one obvious benefit to DIPs and that is you can easily replace the chip if you let the smoke out, but does this really happen much? Is it worth the extra PCB real estate for that?

Getting right back to the main theme of this thread, it would be most interesting to hear Techsupplies quantitative sales figures for SMD vs DIP chips; a rough proportion would be a sufficient indicator of an answer to the question but clearly we are talking privileged information here so this might not be so forthcoming. I suspect that the DIPs outnumber SMDs in a very large ratio.

From my point of view, no two projects are the same and I build most of my projects on strip board. The simple ease of the DIL chips is perfect. Having said that, the AXE200/201s are perhaps "SMDs on a development board". I find these are very useful with the regs, resonator and download circuit already on board and then with the pins rearranged more logically than on the 28X2 DIPs. But in the final analysis I am using them as DIPs. So would I like to see other PICs mounted in this useful format? An SMD 40X2 with regs, resonator and download kit on a 40pin DIP (turned pin of course!) would be a most welcome addition to the fold...
As far as the "extra PCB real estate" estate is concerned, this is not often a problem - so for me DIPs and AXE201s rule the day.

 

[Grogster]

Well yes, the use of SMD really comes down to SIZE for me, and I would guess, most others too.
If I can use a standard DIL, then I do, but there are times you want things to be as small and compact as possible, and that is where SMD comes into it's own.

Then, you can always mix the two - I have done that before many times - spread the parts out on both sides of the board. Standard parts on the top, SMD on the bottom.

As mentioned, depends on project and requirements, but what I CAN say at this point, is that I am really pleased there is the freedom of choice in that you can select SMD parts if you need/want to use them, unlike some other alternatives.(BASIC stamp being an example of that).

 

[graynomad]

the use of SMD really comes down to SIZE for me,

Likewise, and as I always like to pack 10 pounds of stuff onto a 5-pound PCB SMDs on both sides are a must.