In the world of DIY electronics, there’s a certain satisfaction in building systems that not only function but respond intuitively to user interaction. If you're someone who enjoys blending simplicity with clever function, then constructing a motor control system that manipulates the direction of two motors independently might be your next favorite project. At the heart of this build is the 40107 – a dual 4-input NAND buffer/driver that’s built to handle the task of interfacing logic signals with medium-power loads like motors.
Let’s take a journey through the creation of a dual-motor direction controller, perfect for use in small robotics or automated mechanisms where independent movement is key. This isn't a sprawling guidebook of all possible uses or configurations. Instead, it’s a focused walkthrough of how to bring a very specific, useful, and flexible system to life using the 40107.

The Project Concept
The idea is straightforward: create a simple control unit that allows two motors to spin independently in either direction. Think of it like a basic tank steering system, where one motor controls the left track and the other controls the right. If you want the machine to turn left, the right motor runs forward while the left one reverses. Straightforward movement is both motors running in the same direction.
Rather than using a microcontroller, which adds complexity, we’ll design the system to be logic-driven. That’s where the 40107 becomes essential. This IC is robust and fast enough to handle logic inputs and power-level outputs simultaneously, making it ideal for acting as a smart intermediary between simple controls (like switches or buttons) and motors.

The Role of the 40107
To understand what makes the 40107 so suitable, it helps to know that this component can function as a buffer or driver. Each of its two internal units accepts four logic inputs and produces one output. If all four inputs are high, the output will be low, and vice versa – a typical NAND gate behavior. However, this IC stands out because it’s designed to handle higher current loads than typical CMOS logic chips, making it suitable for directly controlling motor drivers or relays without needing additional transistors in many cases.
In our project, we’ll use two 40107 units to handle motor direction control logic. Instead of feeding the motors directly, the outputs from the IC will control relays or transistors that determine the current flow direction in each motor, thus enabling bidirectional motion.

Planning the Interface
Our control system needs to read simple user inputs and translate them into motor behavior. Let’s keep it simple: four push buttons for each motor – forward, reverse, stop, and brake. These buttons feed into the 40107’s logic inputs in carefully configured combinations.
Each group of four buttons connects to the 40107 such that pressing one button activates a unique combination of input states. The output then triggers a control action on the motor driver circuit. For example, pressing “forward” for Motor A sends a high signal to three inputs and a low to one input, creating the appropriate output to trigger the forward driver relay. Pressing “reverse” changes that pattern, and so on.
Why use the 40107 for this? Because it simplifies logic routing and offers a level of electrical protection between your controls and the power electronics driving the motors. It's a digital bouncer—only letting the right signals through under the right conditions.

Wiring Up the Motor Driver Logic
We’ll use standard DPDT relays or H-bridge motor drivers, depending on availability. For simplicity, imagine two relays per motor – one for forward and one for reverse. The 40107 output controls which relay energizes. When neither relay is active, the motor is stopped. When both are off and the power lines are shorted through the driver, that’s a braking mode.
Here’s the idea: the 40107 outputs respond to very specific logic input patterns and only allow one action at a time per motor. This prevents conflicting commands like activating forward and reverse at the same time, which could damage components.
In practice, this might look like setting three of the four inputs to logic HIGH and the fourth to LOW to produce the desired output. You determine the combinations based on your specific control setup. The good news is that thanks to the NAND nature of the chip, you can creatively combine signals without needing to daisy-chain other gates or components.

Powering the System
The 40107 runs happily on a typical 5V logic power rail, but its outputs can interface with higher voltage levels used for relay coils or logic-level MOSFET gates. Make sure your control buttons and any indicators (like LEDs) also run at this level for consistency.
The motors themselves require a separate, more robust power source—usually 12V or higher depending on size and application. Proper isolation between the logic and power sections is important, and that’s another area where the 40107 helps by acting as a buffer.

Building the Control Panel
Let’s make this functional and fun. You’ll need eight push buttons – four per motor. You can arrange them in two clusters, left and right, corresponding to Motor A and Motor B. Each button gets labeled: FWD, REV, STOP, and BRAKE.
Under the hood, these buttons connect to a simple pull-up resistor setup and then to the inputs of the 40107 IC. The buttons themselves pull the inputs low when pressed. When released, the resistors pull the lines high. This logic is perfect for the NAND-based operation of the chip.
Want to go fancy? Add LEDs that light up when a command is active, using the 40107 outputs to drive them via small transistors. That way, you get visual feedback of the system’s state – a valuable feature, especially in testing.

Enclosure and Finishing Touches
Once you’ve verified the circuit on a breadboard or prototype board, consider mounting everything into a project box. Use panel-mount buttons and a printed label for clarity. Route the outputs to a screw terminal block so that you can easily connect and disconnect motors or test different types.
A clear plastic lid on the box can let you see the IC and wiring without exposing everything to dust or damage. Drill ventilation holes if the relays or drivers run warm. And remember to mount the 40107 on a socket if you ever want to remove or replace it without desoldering.

Testing and Tuning
With your panel assembled and motors connected, begin testing each button combination. Pressing FWD on Motor A should make the motor spin in one direction. Pressing REV should spin it the other way. STOP should cut power, and BRAKE should lock the motor (depending on driver behavior). Do the same for Motor B.
Watch how the 40107’s logic gates work to prevent bad input combinations. Try pressing FWD and REV at the same time – nothing should happen. The IC protects you by not producing output under conflicting input states.

Project Expansion Ideas
Once you’re comfortable with the basics, there are ways to expand this project. You could:
●  Replace buttons with toggle switches for longer-term settings
●  Use joystick modules to control direction (translating movement into logic signals)
●  Add wireless control using simple RF modules to feed signals into the 40107
●  Integrate current sensing to protect motors from overloads
●  Include a microcontroller later for programmable patterns while keeping the 40107 as a hardware backup failsafe

Final Thoughts
This project is a satisfying blend of logic control and real-world mechanical action. The 40107 is the quiet hero here—it does its job without needing attention, turning your button presses into precise, reliable control signals. It makes an excellent choice for anyone looking to build a robust dual-motor control system without the need for microcontrollers, code, or complex analog circuitry.
By the end of this build, you’ll not only have a functional dual-motor controller but also a deeper appreciation for how logic components like the 40107 can empower creative control systems. Whether you install this into a robot base, a conveyor mechanism, or a custom rotating display, it offers both performance and simplicity in a compact, elegant form.
Now it’s your turn—grab those buttons, wire up the 40107, and bring your dual-motor ideas to life.