Got my SX48 Protoboard in and have a few questions.

Comments

• eagletalontim Posts: 1,399

  2009-03-29 04:18 edited 2009-03-29 04:18

  umm. ok. well would anyone happen to have the SX48 component created in ExpressPCB so I could try and mess up, I mean solder as many chips as I can
• Forrest Posts: 1,341

  2009-03-29 04:40 edited 2009-03-29 04:40

  When in doubt, check the datasheet. The datasheet for the LM2940 says 'Designed also for vehicular applications, the LM2940/LM2940C and all regulated circuitry are protected from reverse battery installations or 2-battery jumps...'. The normal input voltage range for the LM2940 is 6.25V to 26V - so I'd say you're OK. Any excess voltage is turned into heat - so if you're pulling a more than 150 mA, it would be smart to install a heat sink on the regulator.
• RobotWorkshop Posts: 2,307

  2009-04-01 05:08 edited 2009-04-01 05:08

  eagletalontim said...
  I noticed that the power in on the Protoboard is only 6 to 9 volts. Since I will be using this in a vehicle application, I need to run it from 12 volts. Should I remove the LM2940 and drop in a 7805 or would that even work? I am also very surprised on how small the SX48 really is. I was expecting it to be a bit larger. Now that I know the size of it, I need to know how to solder one to my own PCB. Are there any specific tools needed to solder that small?

  
  I just use a regular Weller soldering iron to install the SX48 chips and other surface mount components. Since the pitch is fine you'll want to have some solderwick around so you can remove any unwanted solder bridges. If you are going to do your own board you may want to look into getting a solder mask (typically green) coating on the board as this can also help prevent solder bridges. The January 2009 issue of Nuts & Volts has an article about it.
  
  If you want to practice soldering I still have my small SX48 OEM PCB that work well for that. You could just install the parts you need like the CPU and regulator. I've done this on a couple projects lately where I needed a small inexpensive way to mount the chip. In one case I am soldering the wires right to the holes where a 20-pin header would normally go.
  
  Robert
• markaeric Posts: 282

  2009-04-02 02:51 edited 2009-04-02 02:51

  I too just got my sx48 demo board, and yes, it is small.
  
  If you want to practice soldering them, you can find boards that have traces for 48-pin PQFP (the packaging format) on ebay, for example.
  
  Also, you can search youtube for "soldering", "soldering smd", etc. for various methods. The 3 main ones will be:
  
  1. Use a soldering iron (though there will still be various methods)
  2. hot air gun/iron (heats up the entire soldering area with hot air)
  3. Reflow oven (this is typically how production level SMDs are soldered. Many people make their own reflow ovens from old toaster ovens. plenty info available online)
  
  
  
  Just out of curiosity, whatcha building for a car?
• Old_Lady Posts: 20

  2009-04-02 15:13 edited 2009-04-02 15:13

  About soldering that part on:
  You can pay ~$12 here just outside the Boston area and have someone hand assemble that part on your board for you. There are many small assembly houses that specialize in prototype boards... things may be slow with the economy downturn and so you can try to bargain with them for prices. You can contact RapidBoard (www.rapidboard.com) - I mail stuff to them, they assemble it, and then they mail it back to me. They have some folks with very steady hands, apparently.
  
  Good luck!