You have likely come across images from ‘RoboCup,’ where robot skillfully kick footballs across the pitch. Constructing an electromechanical robot capable of such actions is entirely feasible for hobbyists, especially with the assistance of affordable everyday items.
High-Speed Foot Actuation with Linear Solenoids
To propel the ball effectively, the robot’s feet are powered by linear solenoids. Emphasizing acceleration over force, we avoid commonly available solenoids operating at 12 V or 24 V. Although potent, they prove far too sluggish for our requirements.
Impulse Generation and Voltage Requirements
The impulse generated by a coil with an iron armature, considering factors like turns count, coil geometry, and permeability, relies on the change in coil current. The swifter the current change desired, the higher the voltage required. Thus, a high-voltage supply becomes necessary. To achieve this, we utilize the flash component from a disposable camera, often available for free at photography shops.
Repurposing Camera Components for Robotics
The inner workings of a camera contain valuable components, notably a high-voltage cascade circuit and a storage capacitor for the flash. These elements are perfect for repurposing in a robotic soccer player. Carefully open the camera, ensuring the battery is removed to prevent accidental shocks. To ensure safety, discharge the capacitor with a resistor before removing the circuit board. Since continuous charging of the capacitor is needed later, bridge the power supply switch connections. The camera circuit tested by the author, a Kodak model, charges a 120 pF high-voltage capacitor to 330 V in 16 seconds from a 1.5 V battery.
Innovative Inductor Crafting from Sewing Supplies
Inventive solutions can be found in unexpected places, like a sewing box. To create inductors, two cotton reels serve as a foundation, wound with enameled copper wire. The wire’s thinness allows for more turns, increasing inductance, but its high ohmic resistance limits the maximum current achievable. A balance must be struck. Making winding easier, the coil former is wrapped in thin double-sided adhesive tape for each layer of wire. Once wound, insulating tape wraps the coil, leaving only the connection wires exposed, now reinforced. Iron cores, possibly found in electronics stores or made to order, fit into the cotton reels, each drilled with a hole at one end, equipped with a washer to prevent the compression spring from slipping. The spring ensures the foot’s swift return to its initial position after a kick.
Efficient Drive Circuit for Robotic Kicks
Simplicity characterizes the drive circuit illustrated in Figure 2. It utilizes a TIC126D thyristor, strategically placed between the high-voltage generator and the coil, to trigger kicks. An optical link, employing an LDR, ensures isolation between the high-voltage electronics and the control circuit, ensuring seamless coordination between the components.