- Battery Holder
- Printed Circuit Board
- Toggle & Micro Switches
- Red & Green LEDs
- 2 – 56 Ohm Resistors
- Hook-Up Wire
- Heat Shrink
Tip: Helping Hands In the above photo you’ll see various ways of holding parts steady in order to solder them. A PanaVise on the left is a great tool to own if you do any soldering.
But don’t go out and buy one just for this project. Less expensive alligator-clip contraptions are available as well as just macgyvering with what you have on hand.
We don’t recommend using a real hand as shown above…
Soldering is so easy there’s a comic book instruction guide called Soldering is Easy that we recommend. It was created by DIY guru Mitch Altman, Andie Nordgren & Jeff Keyzer.
Here’s the basics:
1) Soldering is easiest with “lead” solder (40% lead, 60% tin) that has a rosin (also called flux) core.
2) Heat your soldering iron. Air will oxidize the hot tip quickly. Oxides insulate the tip and interfere with heat transfer, so …
3) Clean the tip before making each solder by gently rubbing the hot tip on a wet sponge. A clean tip will appear bright and shiny.
4) Hold the soldering iron in your preferred hand and the solder wire in your other hand.
5) Touch the hot tip to the lead (the component wire that you want to solder) and the pad (the hole on the circuit board) to preheat the parts for a few seconds.
6) Then touch the solder wire under the hot tip and let the solder melt into the joint.
7) Remove the solder, but hold the hot soldering tip to the joint a moment longer to allow the solder to finish flowing into the joint.
Warning: Lead is poisonous. Work in a well-ventilated area. Avoid breathing solder fumes. Wash your hands when done.
Cut the red and black wire into two pairs: one pair about 16 cm (6.5 inch) long and one pair 10 cm (4 inch) long.
Strip about 3 mm (1/8 inch) of insulation off the ends of each wire.
Melt some solder on to the ends of each wire; this is called “tinning.”
Tin the outside pins on the micro-switch.
Note: The middle pin is not used.
Solder the shorter, 10cm (4 inch) wires to the outside pins of the micro-switch.
Polarity doesn’t matter so red or black can go on either pin on the switch.
TIP: With solder already on the both parts (the pin and the wire) you won’t need to add any more solder. Just hold the parts together and touch them for a moment with the hot tip.
Cut the heat-shrink tubing into two pieces.
Slip one piece of heat-shrink over each of the solder connections on the micro-switch.
Then shrink the heat-shrink using a heat gun or a lighter.
Caution: Take care not to melt the switch.
Step 5. Solder the longer pair of wires to the electric motor exactly as shown in the photo.
Note: Make sure the red and black wires are soldered to the correct pins; otherwise the motor will run backwards.
Slip the wires underneath the plastic strap for added strain relief as shown in the photo.
Twist the wire leads and strip back the insulation on the ends 6mm (1/4 inch).
Now it’s time to “populate” (insert electronic components into) the printed circuit board.
Note: The positions of all components are labeled on the top of the circuit board. Most of the components and wires are mounted on the top side of the circuit board. Only the LEDs are mounted on the bottom.
Insert the toggle switch and resistors into their respective locations as shown.
Note: You can insert the toggle and the resistors in either direction.
Bend the leads of the resistors outwards to hold them in position.
Flip the circuit board and solder them in place.
Snip the excess leads off of the resistors.
Insert the leads from the battery case and the leads for the motor as shown on the right.
Note: The battery case comes with its wire leads stripped and tinned.
Polarity matters for the battery case and motor:
▪ The red wire of the battery case pack goes into Bat +
▪ The black wire for the battery case goes into Bat -
▪ The red wire for the motor goes into Mot +
▪ The black wire for the motor goes into Mot –
Tip: Strip a little more insulation from the wires than normal, then insert and bend the wires to hold them in place while soldering.
Solder the wire leads for the motor and
Insert the wire leads for the micro switch into the circuit board and solder the wires in place.
Note: Polarity doesn’t matter on the micro switch, so the red and black wires can go either way.
Insert the light emitting diodes (LEDs) into the back of the circuit board.
Note: Which LED is red and which is green? When not illuminated, the LEDs look identical. We’ve marked the leads of the red LED with a red marker so you can tell.
You’ll notice that one pin on each LED is shorter. This is the negative (cathode) lead and it faces to the left as shown.
The green LED goes in the location marked LED1 on the circuit board. The red LED goes in LED2.
Before soldering the LEDs, check that the red and green LEDs are correctly positioned. The above photos show how the circuit operates. NOTE: DO NOT SOLDER LEDs flush to the board, see below.
▪ When the toggle switch is flipped ON, the red LED is on and the motor turns counter-clockwise.
▪ When the toggle switch is flipped OFF, the green LED is on and the motor turns clockwise.
▪ Depressing the micro switch shuts power off to the whole circuit only when the toggle switch is in the OFF position.
Install batteries and check how the operation of the circuit to ensure that you have placed your LEDs correctly.
Place the LEDs so that they hang down about 6mm (1/4 inch) below the board.
Slightly bending the leads of the LEDSs to keep the LEDs in place while you solder.
Solder the LEDs.
After soldering the LEDs and trimming the excess leads, carefully bend the LEDs 90 degrees forward as shown.
You are now finished soldering the electronics!
Next step is to install the electronics assembly in the acrylic case.
The final assembly instructions are here.