Featured Articles
Announcing Pi
Technical Specifications
Raspberry Pi FAQs
Win a Pi
Raspberry Pi Wishlist
Actions
Forum Thread Details
  • Replies 5 replies
  • Subscribers 663 subscribers
  • Views 485 views
  • Users 0 members are here
Related

Gertboard Assembly - SMD components

royleith

I received my kit a little while ago. I had a problem with component identification. The assembly pdf shows the SMD component labels indicating the product code and component description, but, unfortunately, the kit has a different label system for the component bags that only give the product code.

 

Other folk may find this list a help. I produced it by typing the product numbers into the Element14 search engine and checking the product descriptions and the quantity shipped.

 

SMD

 

100nF capacitors             175-9265

C2, C3, C8, C9, C10, C11, C15, C17, C19, C20

 

22nF capacitors               175-9252

C12, C13

 

10µF capacitors               183-3825

C16

 

10k    resistor                   933-2391

R1, R2, R34

 

0Ω      resistor                  933-3681    (shown as 0Ω in the assembly instructions and the product description)

R4, R24

 

0.1Ω   resistor                   177-9460

R23

 

Resistor Networks

 

5 Pin 1k                            935-6053

RN1, RN2, RN3

 

8 Pin 1k                            935-6517

RN4, RN5, RN6, RN7

 

The other component descriptions are given on the bag labels.

 

A note about the SMD components: The product descriptions show them as the largest 0805 SMD outline, but most of the items dispatched appear to be 0603 or 0402. It should be possible to fit them to the board, but it might be an idea to invest in low cost locking component tweezers to hold them in place during soldering. A pencil tip soldering iron bit (conical and ending in a point) will be essential for such small components.

 

Roy Leith

  • If the components are not the same as described by the Farnell part numbers and some are really 0402 you should take that up with Farnell because it's obviously wrong - hand soldering 0805 parts is quite easy even for beginners but 0402 are annother cup of tea altogether (and they don't fit properly on most 0805 footprints).

     

    Michael Kellett

  • in reply to michaelkellett

    Michael Kellett wrote:

     

    If the components are not the same as described by the Farnell part numbers and some are really 0402 you should take that up with Farnell because it's obviously wrong - hand soldering 0805 parts is quite easy even for beginners but 0402 are annother cup of tea altogether (and they don't fit properly on most 0805 footprints).

     

    Michael Kellett

    Plus, an 0805 can handle a lot more power than an 0402.  If the resistor needs to dissipate that power an undersized package could overheat and fail.

  • in reply to johnbeetem

    I compared them with some other 0805 components and they are the correct size. There were a couple of larger components which mislead me. The pad spacing is fine and the pictures showing the installed SMDs looks right.

     

    The other concern I had was that the circuit diagram shows two 10µF polarised capacitors. I measured the supplied devices and they are a few percent below, but well within tolerance. The board is not marked with capacitor polarity and the capacitors are ceramic rather than electrolytic so all seems to be OK.

     

    Roy Leith

  • in reply to royleith

    Hello Roy,

     

    Did your kit come with a Microchip TC1262-3.3VDBTRTC1262-3.3VDBTR for U1 ?

     

    If it did then a ceramic 10uF capacitor across its output is not ideal:

     

    from the Microchip TC1262-3.3VDBTRTC1262-3.3VDBTR data sheet:

     

    A 1μF (min) capacitor from VOUT to ground is required.

    The output capacitor should have an effective series

    resistance greater than 0.1Ω and less than 5Ω, and a

    resonant frequency above 1MHz. A 1μF capacitor

    should be connected from VIN to GND if there is more

    than 10 inches of wire between the regulator and the

    AC filter capacitor, or if a battery is used as the power

    source. Aluminum electrolytic or tantalum capacitor

    types can be used.

     

     

    It will very likely work OK but it is possible that the regulator will oscillate - I often put a small resistor in series with ceramic caps in this type of location to push the ESR firmly into the regulator's comfort zone.

     

    Michael Kellett

  • in reply to michaelkellett

    Hi Michael,

     

    The kit includes the Microchip TC1262-3.3VDBTRTC1262-3.3VDBTR complete with the Microchip logo. I will take a chance and use a scope to check for stability. I may have some SMD electrolytics that will fit, but that means deducing the polarity - probably not a real challenge, even for me! Alternatively, I might try an SMD pyramid of components. What could possibly go wrong?

     

    Roy Leith