Skip to main content

Power up

Work in Progress
These docs are still a work-in-progress and may not be fully baked just yet! Please contact me if any of it seems very wrong or needs extra clarification.
tip

SPST switches have very short legs and won't stay in the PCB as you flip it over, making them tricky to solder. You can use a bit of tape to hold them in place as you solder. See the general tips section for other advice.

info

There are three SPST switches in this kit: one with its slider at a right angle to its pins and two with their slider vertically above the pins. For this step, we want the right-angle one.

Steps​

  1. Prep wire
    1. The 9v battery snap connects to two separate wires. Twist them together so they're easier to manage.
      9v battery snap with wires
    2. They're also longer then needed. Cut them in half (or, minimally, 2" on the battery snap side and 1" on the other side) and save the unused section for later. cutting battery snap wires
  2. Feed the battery snap's wires up through the relief hole by BT1, then, on the PCB bottom, solder its wires into place: red for + and black for -.
    battery wires through relief hole battery wires soldered to PCB
  3. Solder the right-angled SPDT switch to SW3. Its slider/actuator will stick off the left edge of the PCB.
    SPDT switch soldered to PCB switch actuator on PCB edge
  4. Connect a 9v battery.
    Connect 9v battery

Notice how you inserted components into the PCB's top and soldered on the bottom. This is standard for all the components on this board.

Test​

okay

It's okay to skip the multimeter test if you don't have one. Just keep in mind that if the next step's test doesn't pass, it may be a battery/power problem.

Use a multimeter to measure the voltage across any/all of these empty chip pins as you toggle SW3.

  • U2: 16 and 8
    multimeter test point 1
  • U3: 16 and 8
    multimeter test point 2
  • U1: 14 and 7
    multimeter test point 3

The multimeter should measure around 9v (more or less, depending on the type of battery) when SW3 is up and 0v when it's down.

Not working as expected? Check the PCB troubleshooting section. Otherwise, continue.

How it works​

info

As you solder, the schematic will grow with all the new parts you've added. It's a humble start. See if you can follow along!

Schematic symbols rarely match their physical components. You can think of them as shorthand "source of truth" for a circuit, like what sheet music is to a musical performance. Schematics tell us how to make the circuit, not what it will look like. The more schematics you read, the more they'll make sense.

Here's what you just made:

Power up schematic

  • BT1 is the 9v battery. Its negative terminal connects to GND (ground).
  • SW2 is a Single Pole Double Throw (SPDT) switch. Its pole is the diagonal line in the middle that moves between pins 1 and 2 (the throws) as the switch slides. Its pin 2 is fixed and connects to the battery's positive terminal.
  • In switch parlance, "open" means unconnected and "closed" means connected.
  • You'll see VCC and GND labels throughout the schematic, and they'll all refer to the same common connections: GND will always connect to the 9v's negative terminal, but VCC will only be the 9v's positive terminal when SW3 is closed.
  • The "x" on SW3's pin 3 means it's unconnected.

Consider:

  • If you were to explain this step to someone else, what would you say? How would it differ what you read?
  • If you drew a picture, what would it look like? Would it be more like the soldered PCB or the schematic?
  • What would you prefer as the receiver of this information?