T1W3: Starting the Kit

Last class we practiced stripping and soldering wires and soldering components to a circuit board. This class we will start building the Bluetooth radio kit.

The Bluetooth speaker kit has four major steps:

  1. Soldering the LED board

  2. Attaching wires to the speakers and power jack

  3. Assembling the components onto the case panels

  4. Fastening the case panels together to make the enclosure

Here is a link to download the assembly instructions from the kit manufacturer.

Soldering the LED Board

We will build the LED board by inserting electronic components onto the top side of the board with the white labels, and then flipping the board over to solder the lead wires to the round metal pads on the back wiring side. We will solder the shortest components first so we can just rest the circuit board on the components while we solder.

Resistors convert electrical current into a voltage drop, and three different values come with the kit. The resistance values are indicated by color codes painted on the resistor, here is a key to figure out the values - we have 5-band resistors where the fifth band is brown and shows the tolerance is 1%.

Step 1: Solder Resistors R1 & R3

Resistors R1 & R3 have values 20Kohm and color codes RED BLACK BLACK RED (BROWN). Find the two 20Kohm resistors and remove the tape strips from the ends. Then bend the leads of the resistors down in a U shape and insert them into the circut board along the bottom edge. Spread the leads apart slightly to keep them from falling out and then flip the board over and solder the leads to the round circuit pads on the back (wiring) side of the board. When the solder joints look good clip off the leads near the circuit board and save the short bits of wire for Step 4.

Step 2: Solder Resistors R4 & R5

Find two 470 ohm resistors (color code YELLOW PURPLE BLACK BLACK BROWN) and solder them into positions R4 and R5, and clip off the leads on the back.

Step 3: Solder Resistor R2

Find the last resistor with value 2 MegaOhms (color code RED BLACK BLACK YELLOW), solder it into position at R2, and clip off the leads.

Step 4: Solder Jumper Wires J1, J2, J3

We will go out of order a bit from the instructions and solder the three jumper wires J1, J2, and J3 on the top of the circuit board. These wires just make connections in the circuit board that would have been blocked by the other wires or components. Find some short bits of wire clipped off from the resistor leads, and bend them in a U shape about as wide as the lines on the circuit board. Push the wires flat against the board and spread the leads a bit on the other side of the board to hold them in place. The flip the board over and solder the ends of the wire, and clip off any extra length.

Step 5: Solder the IC (Integrated Circuit)

The IC (integrated circuit) that controls the LEDs is the black rectangle with lots of metal leads on the sides. We need to be careful to install this part in the correct orientation, so we will only solder one out of the 16 leads to start. First, make sure all the leads of the IC are straight and lined up with each other - if any wires are sticking out, use the needle nose pliers to carefully bend them back in line with the others. You may also need to bend the ends of the leads together slightly to fit them into the holes on the circuit board - hold the leads against the tabletop and gently bend them all at once in slightly.

Find the notch on the short end of the IC and match it to the notch on the circuit board label. Carefully insert the leads of the IC into the holes in the board, and double check that the notch is on the correct side. Then flip the board over and rest it on the IC to keep it in place. Just solder one corner lead to start with - don't do all of them at once or it will be difficult to fix mistakes!

After soldering just one lead, turn the board over again and make sure the IC hasn't shifted and is flat against the circuit board on all sides. Also check again that the notch on the IC is on the side next to Q1. If needed, you can melt the solder on the one lead and reseat the IC so it's flat, or pull out the IC and fix the orientation. Ask the teacher (Tim) to check your IC before going on to solder the rest of the leads! He can quickly fix any problems if needed.

If it looks good, go ahead and solder the rest of the leads. Try to do this quickly so you don't spend a lot of time heating the IC leads (and cooking them). The leads are short so you don't need to clip the ends off.

After you have soldered all the IC leads, check your connections to make sure you don't have blobs of solder shorting between the leads on the IC. You can fix this by using the solder sucker tool to remove the extra solder - Tim can show you how and help fix problems.

Step 6: Solder the Transistor Q1

The transistor Q1 helps amplify the audio signal from the microphone. It comes in a black D-shaped package with three leads. Align the flat side of the D toward the top of the board and insert the three leads in the holes - you may need to spread the wires slightly to get them to fit. Push the transistor in towards the board, which will spread out the leads on the back side. Then solder and clip the excess length. The leads are close together so be careful not to short out the leads with blobs of solder - check to make sure each lead is separated on the back side of the board.