Shop OBEX P1 Docs P2 Docs Learn Events
A few questions about the Propeller and a product I sell. — Parallax Forums

A few questions about the Propeller and a product I sell.

eagletalontimeagletalontim Posts: 1,399
edited 2011-06-05 00:44 in Propeller 1
I had designed a product which I sell using the SX28 chip but now that it is at EOL, I am needing to redesign all over again. The main concern I have is the size of the Prop DIP. The Prop chip is almost as big as the board I am currently using. I have seen the 44 pin surface mount chip which is way smaller and am wondering if it is even possible to hand solder all the leads without burning out the chip.

Another question I have is...Is there a pre-manufactured IC chip that can read a square wave RPM signal from a vehicle and output a readable signal for the Propeller? I would like to offer an extra plug and play device that connects to the product currently using the SX chip and having a small box that just plugs in would be great!

And last but not least.. Is there a difference in current handling between the small surface mount components and through hole components like resistors, diodes, transistors, and caps? I know they are still 1/2 watt, but I worry about heat. The current design has no heat and is very reliable / stable. Two years and counting on my current design thanks to some on this forum! :)

Thanks for any help!!

Comments

  • LeonLeon Posts: 7,620
    edited 2011-06-04 08:29
    I don't have any problems hand-soldering QFP parts. I drag-solder the leads using my Metcal system with a mini-hoof cartridge.

    You need to calculate the power used by resistors, before switching to surface-mount parts, if you are worried about power ratings. They can't handle anything like the same dissipation. It depends on the size, of course. I mainly use 0805 parts - 0.1W.
  • Duane DegnDuane Degn Posts: 10,588
    edited 2011-06-04 09:08
    I've also hand soldered many (well, half a dozen or so) QFP Propeller chips. My new favorite method is to hold the chip in place with some tape (I use that yellow thermal tape) while I solder a few pins.

    Most of the pins have solder bridges after the first pass with the solder and soldering iron. The trick that makes hand soldering possible is cleaning up the extra solder with solder wick.

    I haven't damaged any chips I've soldered. I just use lead solder. I suppose lead free solder might need more heat but I still doubt you'd damage the chips.

    Duane
  • smbakersmbaker Posts: 164
    edited 2011-06-04 09:27
    I've soldered a few QFP44s using a cheap pneumatic solder paste dispenser (ebay, $100 - $200) and a cheap hot air iron. Every so often I might still bridge a pin, but it's easily cleaned up with desoldering wick. It's a toss-up now on whether I prefer through-hole or SMT components.

    I hear the real way to do this effectively is with a stencil and a toaster oven, although I've not tried that technique.
  • Duane DegnDuane Degn Posts: 10,588
    edited 2011-06-04 09:34
    I've also seen electric hot plates used to for smt soldering.

    I almost exclusively use smt resistors. They are so nice and small; the 0603 size fit nicely between 0.1" holes. I just use my normal soldering iron.
  • eagletalontimeagletalontim Posts: 1,399
    edited 2011-06-04 11:32
    Thanks for all the input! I am really wanting to try out the SM components, but the boards are so expensive in small quantity for R & D. I currently use expressPCB and they have good prices for larger quantities. I have also tried making my own with a laser printer and a clothes iron. It works, but is not reliable for small traces. Out of curiosity, is there a socket that the Prop can fit in?
  • LeonLeon Posts: 7,620
    edited 2011-06-04 11:46
    QFP sockets are available, but they are very expensive. I've made surface-mount boards for the Propeller at home, it wasn't difficult.
  • LawsonLawson Posts: 870
    edited 2011-06-04 12:19
    I just followed the sparkfun tutorials for my first attempts at surface mount soldering. I've since had a lot of practice. I now consider 0805 passives and SOIC to be easy. I can do 0402 in a pinch, and 1/2mm pitch IC can be done reliably with solder wick.

    For one or two of a board I really like www.batchpcb.com prices and quality are great though it takes a while for boards to arrive. I use www.4pcb.com BareBones deal for when I need prototypes fast. (the 4pcb deal always costs >$60) The 4pcb "$33 each" deal is also nice for small production runs if you panelise and cut apart the circuits yourself.

    Lawson
  • PublisonPublison Posts: 12,366
    edited 2011-06-04 14:21
    Check out this item available at Parallax:

    http://www.parallax.com/Store/Microcontrollers/PropellerDevelopmentBoards/tabid/514/CategoryID/73/List/0/SortField/0/Level/a/ProductID/568/Default.aspx

    I soldered the entire board together in 1 hour, no errors. It will give you confidence for SMD devices. I now solder 0805 and 0602 and QFP components all the time.

    A good soldering iron or station is a must.



    eagletalontim wrote: »
    Thanks for all the input! I am really wanting to try out the SM components, but the boards are so expensive in small quantity for R & D. I currently use expressPCB and they have good prices for larger quantities. I have also tried making my own with a laser printer and a clothes iron. It works, but is not reliable for small traces. Out of curiosity, is there a socket that the Prop can fit in?
  • HollyMinkowskiHollyMinkowski Posts: 1,398
    edited 2011-06-04 15:16
    eagletalontim wrote: »
    wondering if it is even possible to hand solder all the leads without burning out the chip.

    read a square wave RPM signal from a vehicle and output a readable signal for the Propeller?

    Is there a difference in current handling between the small surface mount components and through hole components

    Yes you can hand solder the sm Propeller chip...but why? Get a hot air station..they are really
    inexpensive now. It will only take you an hour or so to get good at soldering a prop to a board. You
    will always be glad you got a hot air station as they are so useful. If you need help finding a bargain
    just ask here...60.00 USD should buy you one, 20.00 USD more for one with a soldering iron attached.

    The Prop should have no problem at all detecting and counting a square wave signal, I guess RPM
    means revolutions/min ? I see no need for an extra IC to do this. The prop has 8 processors so you
    can dedicate one to simply counting the square wave and placing the results into ram for the other
    processors to read. Once this is done you don't need to think about it any more, the count will always
    be there in ram waiting to be used.

    The sm Prop is rated the same as the DIP part is.

    As for the other parts why not just stay with through hole parts for them?
    Just get a new board made that has pads for the sm prop and holes for
    regular resistors, caps..etc

    See this thread for info on getting new boards made up for about 1.40 USD
    and that includes shipping :-)

    http://forums.parallax.com/showthread.php?131974-Really-really-really-cheap-PC-boards!

    Oh, I find it easiest to solder the large ICs to the board first.
    After you have through hole parts on the board it's much harder
    to solder something like a sm prop close to them. When your
    boards come in just solder a prop on each of them and then it will
    be easy to add the other parts later.
  • zoopydogsitzoopydogsit Posts: 174
    edited 2011-06-04 16:29
    I do all my prototyping using smd. I wouldn't go back to through hole. I hand solder with a cheap 15w iron with a filed tip. I use a big magnifying glass (getting older). I have not killed any smd component. I've found the qfp44 prop to be easy to solder, the trick is in validation testing. I use 2 tests, meter adjacent pins for shorts, then meter pin to pin for connectivity. Testing will quickly identify soldering faults, and save you a lot of troubleshooting time/effort.

    For dev work, consider breadboarding the dip40 prop.

    Enjoy :-)
  • eagletalontimeagletalontim Posts: 1,399
    edited 2011-06-04 22:14
    That was one thing I was wondering about was the wattage of the soldering iron. I have a 40 watt which can solder quickly with high heat, then a 15 watt for low heat, but it takes longer to get the solder to flow, and I have a soldering station that has adjustable temperature. The problem with a hot air station is your are heating the entire area up including the chip....I figure if you are not fast enough, you will burn up every chip until you get it right. I just don't have that kind of money :p


    *Edit*
    Interesting enough, both of my vendors I use to order parts through don't offer surface mount components....any suggestions?
  • smbakersmbaker Posts: 164
    edited 2011-06-04 23:22
    eagletalontim wrote: »
    The problem with a hot air station is your are heating the entire area up including the chip....I figure if you are not fast enough, you will burn up every chip until you get it right. I just don't have that kind of money :p

    I use an aoyue 852++, a cheap chinese hot air iron, and the only problem I ever had with burning up anything was soldering plastic SMD header sockets for an xbee. I now use through-hole sockets, the SMD sockets were way too much trouble. Traditional SMD devices (ICs, resistors, etc) are no problem whatsoever. You'd have to be fairly negligent to seriously damage a component or delaminate a board.

    Using the small tip, you get pretty good control of where the heat is going. Generally you have controls for both air flow and temperature.

    For easy practice, grab old computer PCBs from your junk bin. My initial learning experiences involved destroying and putting back together some old netgear ethernet cards. Every computer guy has a pile of obsolete expansion cards.

    Another real handy thing to have is an inexpensive stereomicroscope (for example, amscope.com). Such a thing has come in handy for inspecting both through-hole and especially SMD work, as my eyes continue to age. I look back fondly at the days when I could solder boards with no magnifier, just looking at them...

    EDIT - for vendors, I often use jameco, digikey, or newark. I find Jameco's catalogs to be just the right balance to get a good overview of components available without getting into too much detail or an overwhelming selection of the parts. All three of them have decent website search capabilities to find what you need.
  • HollyMinkowskiHollyMinkowski Posts: 1,398
    edited 2011-06-05 00:03
    eagletalontim wrote: »
    The problem with a hot air station is your are heating the entire area up including the chip....I figure if you are not fast enough, you will burn up every chip until you get it right. I just don't have that kind of money :p

    That's what everyone, including me, thinks before they get a hot air station
    and get some practice time. Solder the sm chip onto the boards first is what
    I recommend.

    For parts I recommend buying from ebay sellers in Thailand, ML China, Tiawan
    or Hong Kong. I just got a sack of 500 3.6V Zeners (thru hole) for 9.90 USD
    and that included shipping. If I bought them local here in Israel it would have cost
    several times that much. I really didn't need 500 but it was so cheap and I figured
    I would need them someday.

    One really nice place to get parts is www.taydaelectronics.com -- great prices, fast
    and cheap shipping and they take paypal. SM resistors are less than a penny and
    thru hole are one penny each...for example. When buying in bulk you can do better
    from ebay sellers but Tayda is great for buying smaller quantities.. I buy 3v3 regulators
    there for .18ea for the TO-92 type and .24ea for the 1.5amp LM317T (I use these for
    3v3)

    If you post a list of the components used on your board maybe I can direct you to
    some good sources for those parts...many others here on the forum are also great
    bargain hunters and may know good sources.
  • LeonLeon Posts: 7,620
    edited 2011-06-05 00:44
    50W is better than 15W for surface-mount soldering, because the parts are heated for less time.

    A hot air rework system doesn't heat the whole area, the tips are fitted with shields that stop adjacent parts from being unsoldered.
Sign In or Register to comment.