Some questions before I start soldering this GSM module

Using Arduino General Electronics
1

I bought this module for $2 on aliexpress and I know where to solder the components but I am not quiet sure about the orientation (+/- pole). Bigger image here

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So I got 2 LEDs, 2 Capacitors, 3 resistors and one bigger capacitor. I know how to solder everything but here is what I dont understand:

  1. I think one small smd capacitor is missing, right?
  2. The two LEDs obviously goes to D1 and D2 but how am I supossed to know where the + and - pole on the board is? On the LED a small green dot marks the - pole. Same for the bigger capacitor. Where is +/- on the board?
2

No diagram with the kit showing their location or details of the data connector ?

Have you tried mailing the supplier for the info ?

3

My eyesight is bad, but if D1 and D2 are the LEDs, it looks like the RHS is the negative end, where the white outline is thicker.

Check with your DMM and see if that end connects to GND / 0V. It looks like it does.

Regarding the caps, it does look like one is missing.

I'm surprised you didn't have full info supplied with the kit.

4

you want only 3 capacitors. the C1 and C2 are connected to the same pin.you only need to connect 1 of this at same time.if you can tell the Vcc and the Gnd i can tell you which way the poles of the leds are.

5

There are 3 capacitors and 3 places for caps on the board, what's the issue? The large cap is a
tantalum cap, make sure when you orient it you look up the polarity marking for a tantalum cap,
not an aluminium electrolytic, they are different. Remember the ground-pour on the board usually makes it
easy to work out which is the +ve and -ve end of a component as ground is negative (in modern
logic circuits).

6

MarkT:
There are 3 capacitors and 3 places for caps on the board, what's the issue?

I count 4 - C1, C2, C3 and C4

7

sperera:
the C1 and C2 are connected to the same pin.you only need to connect 1 of this at same time.

Who says? It's common to connect a larger cap and a smaller cap in parallel.

8

Oh yes, C1 was hiding from me(!). I suspect the module already has high-speed decoupling, but
it would be best to have the schematic to hand to figure out the implications.

9

MarkT:
Oh yes, C1 was hiding from me(!). I suspect the module already has high-speed decoupling, but
it would be best to have the schematic to hand to figure out the implications.

I blame my bad eyesight, but I didn't see all four at first either. :smiley:

Really, the instructions/schematic would be handy. I never buy anything without checking on that sort of thing beforehand, along with availability of libraries and further documentation where applicable.