We'll use a potentiometer with a built-in on/off switch to control the speed of the motor and be able to turn on/off the circuit. We'll need four wired connections to achieve this. Going for modularity, again, we'll use jumper wires to make assembly easier. These female/male extension jumper wires are great, perfect wire length and good selection of colors to choose from.
Most pots have this little protruding nub near the top side of the metal bracket. It's probably meant for keying when panel mounting but for our project it actually gets in the way – remove it by snapping it off with pliers. If it's left on the knob cannot be flush with the enclosure thus making it difficult to secure. It's fairly easy to break off using needle nose pliers.
In order to plug the female connectors into the terminals on the pot switch, we'll need to remove the plastic housing. Using the same technique as before, I used an x-acto knife to lift the tabs and remove the headers. We won't need them for the rest of the build so you can discard them.
The jumper wires will plug into the terminals but they won't hold very well. I tinned each of the terminals by adding a bit of solder to them. This made them thick enough for the jumper wires to grab hold. These connections can optionally be soldered for a more secure connection. I left them unsoldered – keeps it modular and easy to disconnect.
Connect Jumper Wires
The terminals on the potentiometer are far apart enough to not warrant insulating the bare metal. However, it would've been nice to add some heat shrink. Connections on this potentiometers, going from left to right, are the ground, signal, and voltage.
We'll use the fourth extension jumper wire to hook up the on/off switch from the potentiometer. We'll cut it in half and connect the male and female ends to the two terminals separately. This allowed me to easily connect/disconnect the wiring when hooking it up to the DC jack.
Cut the single jumper extension wire in half and use wire strippers to remove a bit of insulation from the tips. Then add a bit of solder to tin the exposed stranded wire. This will make it easier to solder onto the on/off terminals on the potentiometer.
Now we can attach the two wires to the terminals – The two unused terminals are for the on/off mechanism built into the potentiometer. The terminals are mounted to a separate PCB. Securing the shaft to helping hands helps the potentiometer stay in place while soldering. I tinned the terminals with a bit of solder first and then attached the wires. Polarity doesn't matter much here.
And now we have a wired potentiometer! Yay, its ready for plug-n-play adventures. What I like about this wiring is the ability to switch around the connections. I tend to mix the voltage and ground wires in my projects that use potentiometers, so it's nice to be able to easily switch them around. The on/off switch feature on this particular potentiometer is nice and makes one less component to worry about!