If you’re someone who enjoys working with RC models, then this circuit is designed with you in mind! The compact RC Switch allows you to control the activation and deactivation of a device using a standard R/C channel. This device operates solely using power from the receiver and consumes minimal current. Additionally, the output load that it controls is completely isolated from the R/C circuit, enabling the simultaneous operation of two separate ground systems without any interference or noise coupling between them. You can adjust the device’s trip point using a potentiometer, and if desired, onboard LEDs can be integrated to display the system’s status.
The compact R/C switch easily connects to a standard hobby radio control receiver, just like a servo. You can link this module to the load you wish to control. Depending on the channel you choose, you can then control the switching action by manipulating your control stick in various ways, such as moving it up or down, left or right, or using another preferred method. In practical terms, an RC aircraft comprises a radio transmitter operated by the pilot, and the airborne unit includes a radio receiver, along with one or more servos, depending on the number of radio channels utilized, along with a battery pack.
The RC transmitter transmits data to the RC receiver by generating a modulated radio frequency carrier, while the receiver detects and decodes data from this modulated carrier, subsequently directing it to the corresponding servo. A typical R/C transmitter typically offers around 4 to 6 channels, with at least 4 of them being proportional. Any additional channels are typically used to activate features like retractable landing gear, airbrakes, lights, and so on (e.g., landing gear control on channel 5).
While this circuit was originally designed for the on/off control of lighting in radio-controlled (R/C) models, it can undoubtedly be applied to other radio control projects. The circuit follows the signal pattern from the receiver and, at a preset pulse width, triggers a switch to activate the load. This allows you to fine-tune the circuit to operate when another device controlled by the same receiver channel reaches a specific critical point (e.g., 60% travel). The slight hysteresis at the trip point helps prevent potential switch instability.
Following the assembly of the circuit, connect it to the relevant RC channel, such as channel 5, on the receiver. Then, power up the circuit. Turn on your transmitter and confirm that the relay’s activation reliably corresponds to the movement of the R/C stick (or the operation of an auxiliary toggle switch).
The possibilities of what you can control with your RC system using this device are entirely open to your creativity. For instance, you can employ it to remotely activate aircraft lights, release payloads, switch video signals, operate landing gear, and a wide range of other functions. The switch output can be configured to manage high currents, meaning there are virtually no constraints on what you can achieve!
The circuit, centered around the LM358 comparator (IC1), responds to a 50Hz PWM signal with a pulse width typically ranging between 1 to 2 milliseconds. When the reference voltage, set by the 10K potentiometer (P1) at pin 2 of IC1, is lower than the filtered signal voltage at pin 3 of IC1, the comparator’s output goes high. This, in turn, activates the relay driver BC547 (T1), causing the 5V relay (RL1) to engage. To prevent the comparator from reacting to minor voltage fluctuations on the non-inverting input (pin 2) of the comparator, the 100K resistor (R5) introduces a slight hysteresis effect.