{"product_id":"pololu-302-elenco-21-881-sound-reversing-car","title":"Pololu 302 Elenco 21-881 Sound Reversing Car","description":"\u003cmeta name=\"description\" content=\"Buy Pololu 302 Elenco 21-881 Sound Reversing Car online in India at best price from The Tech Depot, Bengaluru. Authentic product, 7-day warranty on manufacturing defects, fast delivery across India.\"\u003e\n\n\u003ch1\u003ePololu 302 Elenco 21-881 Sound Reversing Car\u003c\/h1\u003e\n\n\u003cp\u003eThe Pololu 302 Elenco 21-881 Sound Reversing Car is an educational robotics kit that combines mechanical assembly with sound-activated reverse functionality, designed to teach fundamental principles of motor control, sensor integration, and autonomous behavior. Electronics educators, STEM instructors, and hobbyists use this kit to demonstrate practical applications of sound detection circuits and directional motor control in a hands-on learning environment. This product solves the challenge of creating engaging, interactive demonstrations that help students understand how robots can respond to environmental stimuli through simple yet effective electronic circuits.\u003c\/p\u003e\n\n\u003ch2\u003eProduct Overview\u003c\/h2\u003e\n\u003cp\u003eThe Elenco 21-881 Sound Reversing Car operates on a sophisticated yet accessible principle: a sound-detection circuit continuously monitors ambient noise levels, and when a threshold is exceeded, it triggers a relay mechanism that reverses the polarity of the DC motor driving the vehicle. This creates the illusion of an autonomous response to sound, making it an excellent platform for understanding analog signal processing, threshold detection, and electromagnetic relay operation. The car features a pre-assembled chassis with a gearbox system that provides adequate torque for smooth forward and reverse motion on standard surfaces, while the sound-sensing electronics are housed in a compact circuit board that can be studied and modified for advanced learning applications.\u003c\/p\u003e\n\n\u003cp\u003eWhat distinguishes the Pololu 302 variant is its integration with Pololu's quality standards for motor efficiency and gear ratios, ensuring consistent performance across multiple units. The sound sensor employs a microphone element coupled with an amplification stage and comparator circuit, allowing students to observe real-time signal conditioning in action. The reversing mechanism utilizes a bistable relay configuration, meaning the car maintains its direction until the next sound trigger occurs, rather than continuously switching. This design choice makes the behavior more predictable and easier to troubleshoot, while also demonstrating the importance of state management in control systems.\u003c\/p\u003e\n\n\u003ch2\u003eKey Specifications\u003c\/h2\u003e\n\u003ctable\u003e\n\u003ctr\u003e\n\u003ctd\u003eSpecification\u003c\/td\u003e\n\u003ctd\u003eDetails\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eProduct Type\u003c\/td\u003e\n\u003ctd\u003eEducational Sound-Activated Reversing Robot Car Kit\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eBrand\u003c\/td\u003e\n\u003ctd\u003eElenco Electronics \/ Pololu\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eOrigin\u003c\/td\u003e\n\u003ctd\u003eOriginal\/Authentic\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eWarranty\u003c\/td\u003e\n\u003ctd\u003e7 days on manufacturing defects\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eShipping\u003c\/td\u003e\n\u003ctd\u003e1-5 days from Bengaluru\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eDelivery\u003c\/td\u003e\n\u003ctd\u003e7-8 days across India\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eSupport\u003c\/td\u003e\n\u003ctd\u003e24\/7 via Email and WhatsApp\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eMotor Type\u003c\/td\u003e\n\u003ctd\u003eDC Motors with Gearbox Assembly\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003ePower Supply\u003c\/td\u003e\n\u003ctd\u003e4 x AA Batteries (6V nominal)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eSound Sensitivity Range\u003c\/td\u003e\n\u003ctd\u003eAdjustable threshold, typically 60-80 dB\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eRelay Configuration\u003c\/td\u003e\n\u003ctd\u003eBistable electromagnetic relay for direction control\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eAssembly Time\u003c\/td\u003e\n\u003ctd\u003e45-60 minutes for complete build\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eDimensions\u003c\/td\u003e\n\u003ctd\u003eApproximately 150mm x 100mm x 80mm (assembled)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003c\/table\u003e\n\n\u003ch2\u003eKey Features\u003c\/h2\u003e\n\u003cul\u003e\n\u003cli\u003eSound Detection Circuit with adjustable sensitivity potentiometer, allowing students to calibrate the microphone threshold and understand frequency response characteristics of analog sensors\u003c\/li\u003e\n\u003cli\u003eBistable Relay Reversal Mechanism that maintains directional state between sound triggers, demonstrating latching logic without microcontrollers\u003c\/li\u003e\n\u003cli\u003eDual DC Motor Drive System with mechanical gearbox providing balanced torque distribution for stable forward and reverse locomotion\u003c\/li\u003e\n\u003cli\u003eTransparent Chassis Design enabling visual inspection of internal mechanisms, motor operation, and gear engagement during demonstration\u003c\/li\u003e\n\u003cli\u003ePre-soldered Circuit Board reducing assembly complexity while leaving key learning points intact for educational value\u003c\/li\u003e\n\u003cli\u003eBattery-Powered Operation with standard AA batteries, making the kit portable and suitable for classroom demonstrations without external power requirements\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch2\u003eApplications and Use Cases\u003c\/h2\u003e\n\u003cul\u003e\n\u003cli\u003eSTEM Classroom Instruction where students learn fundamental robotics, sensor integration, and motor control through hands-on assembly and observation of real-time behavior\u003c\/li\u003e\n\u003cli\u003eElectronics Lab Demonstrations for teaching analog signal conditioning, threshold detection circuits, and relay operation in undergraduate engineering programs\u003c\/li\u003e\n\u003cli\u003eRobotics Club Projects where hobbyists modify the sound detection circuit to respond to specific frequencies or integrate additional sensors for enhanced autonomous behavior\u003c\/li\u003e\n\u003cli\u003eScience Fair Exhibits showcasing the practical application of sound sensors and control systems, with students explaining the physics of microphone operation and electromagnetic relays\u003c\/li\u003e\n\u003cli\u003eMaker Space Prototyping where the kit serves as a foundation for custom robotics projects, with modifications including light sensors, obstacle detection, or wireless control integration\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch2\u003eHow to Use\u003c\/h2\u003e\n\u003cp\u003eBegin assembly by carefully following the included instruction manual, which provides step-by-step guidance for chassis assembly, motor installation, and circuit board mounting. Ensure all solder joints are properly formed and connections are secure before inserting the four AA batteries into the battery holder. Once assembled, place the car on a flat surface and verify that both motors rotate smoothly when power is applied. Adjust the sound sensitivity potentiometer using a small screwdriver while clapping or speaking near the microphone until the car reliably reverses direction in response to sound stimuli at normal conversational levels.\u003c\/p\u003e\n\n\u003cp\u003eFor optimal performance, test the car in a quiet environment first to establish baseline behavior, then gradually introduce sound stimuli to understand the sensitivity range. If the car does not respond consistently, check that the microphone is unobstructed and that the battery voltage is adequate by testing with fresh batteries. The sound detection threshold can be fine-tuned by rotating the sensitivity adjustment potentiometer counterclockwise to increase sensitivity or clockwise to decrease it. For educational demonstrations, explain to observers that the relay mechanism creates a bistable state, meaning the car remembers its last direction until the next sound trigger occurs, which is fundamentally different from continuous proportional control systems.\u003c\/p\u003e\n\n\u003ch2\u003eFrequently Asked Questions\u003c\/h2\u003e\n\u003cdetails\u003e\n\u003csummary\u003eWhat is the sound sensitivity range and how do I adjust it?\u003c\/summary\u003e\n\u003cp\u003eThe Elenco 21-881 typically responds to sound levels between 60-80 dB, which covers normal conversation and classroom noise. The sensitivity is controlled by a potentiometer on the circuit board that you can adjust with a small screwdriver. Turning it counterclockwise increases sensitivity, making the car respond to quieter sounds, while turning it clockwise decreases sensitivity, requiring louder sounds to trigger reversal. Start at the middle position and adjust incrementally based on your environment and desired responsiveness.\u003c\/p\u003e\n\u003c\/details\u003e\n\u003cdetails\u003e\n\u003csummary\u003eHow long do the batteries last during typical operation?\u003c\/summary\u003e\n\u003cp\u003eBattery life depends on motor usage frequency and sound trigger rate. In continuous operation with frequent reversals, four AA alkaline batteries typically provide 4-6 hours of runtime. If the car is used intermittently with occasional sound triggers, battery life can extend to 12-24 hours. We recommend using high-capacity alkaline or NiMH rechargeable batteries for extended use. Always remove batteries when the kit is not in use to prevent drain from the always-active microphone circuit.\u003c\/p\u003e\n\u003c\/details\u003e\n\u003cdetails\u003e\n\u003csummary\u003eCan I modify the circuit to add additional sensors or features?\u003c\/summary\u003e\n\u003cp\u003eYes, the Elenco 21-881 is designed with educational modification in mind. The circuit board includes accessible connection points where you can integrate additional components such as light sensors, obstacle detection modules, or even wireless control circuits. However, modifications should be attempted only by individuals with basic soldering skills and understanding of circuit design. Any modifications may void the warranty, so proceed at your own risk and document your changes for troubleshooting purposes.\u003c\/p\u003e\n\u003c\/details\u003e\n\u003cdetails\u003e\n\u003csummary\u003eWhat happens if the car doesn't respond to sound triggers?\u003c\/summary\u003e\n\u003cp\u003eFirst, verify that the batteries are fresh and properly installed with correct polarity. Check that the microphone element is clean and unobstructed. Test the motors independently by temporarily disconnecting the relay circuit to confirm they function. If motors work but reversal doesn't occur, the relay may be stuck or the sound detection circuit may need adjustment. Rotate the sensitivity potentiometer fully counterclockwise and clap loudly near the microphone to test responsiveness. If the relay clicks audibly but the motors don't reverse, there may be a wiring issue at the motor connections.\u003c\/p\u003e\n\u003c\/details\u003e\n\u003cdetails\u003e\n\u003csummary\u003eWhen will I receive my order?\u003c\/summary\u003e\n\u003cp\u003eOrders are dispatched within 1-5 business days from our Bengaluru warehouse. Delivery takes 7-8 days to most locations across India.\u003c\/p\u003e\n\u003c\/details\u003e\n\u003cdetails\u003e\n\u003csummary\u003eWhat is your return and warranty policy?\u003c\/summary\u003e\n\u003cp\u003eWe offer a 7-day return policy on manufacturing defects only. Contact support within 7 days of receipt for free replacement or full refund. Not applicable for user damage or misuse.\u003c\/p\u003e\n\u003c\/details\u003e\n\u003cdetails\u003e\n\u003csummary\u003eAre bulk discounts available?\u003c\/summary\u003e\n\u003cp\u003eYes, wholesale pricing for orders of 10 or more units. Contact our sales team via WhatsApp or email for a customized bulk quote.\u003c\/p\u003e\n\u003c\/details\u003e\n\n\u003ch2\u003eWhy Buy from The Tech Depot\u003c\/h2\u003e\n\u003cul\u003e\n\u003cli\u003eGenuine Products: Sourced directly from authorized distributors with authentication\u003c\/li\u003e\n\u003cli\u003eExpert Team: Our technical team validates every product before listing\u003c\/li\u003e\n\u003cli\u003eFast Shipping: Dispatched within 1-5 days from our Bengaluru warehouse\u003c\/li\u003e\n\u003cli\u003ePan-India Delivery: 7-8 days to Mumbai, Delhi, Chennai, Hyderabad, Pune, Kolkata\u003c\/li\u003e\n\u003cli\u003ePayment Options: COD, UPI, credit\/debit cards, net banking, EMI available\u003c\/li\u003e\n\u003cli\u003eTechnical Support: 24\/7 expert guidance via email and WhatsApp\u003c\/li\u003e\n\u003cli\u003eReturns: 7-day return policy on manufacturing defects only\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch2\u003eBuy Pololu 302 Elenco 21-881 Sound Reversing Car Online in India\u003c\/h2\u003e\n\u003cp\u003ePurchase the \u003cstrong\u003ePololu 302 Elenco 21-881 Sound Reversing Car\u003c\/strong\u003e online at \u003ca href=\"https:\/\/thetechdepot.in\"\u003eThe Tech Depot\u003c\/a\u003e, India's trusted source for genuine electronics. We deliver across Bengaluru, Mumbai, Delhi, Chennai, Hyderabad, Pune, Kolkata, Ahmedabad, Jaipur, and Surat. Get the best price on \u003cstrong\u003ePololu 302 Elenco 21-881 Sound Reversing Car\u003c\/strong\u003e with fast shipping and expert support.\u003c\/p\u003e\n\u003cp\u003eOur team in Bengaluru is available 24\/7 to support your journey from product selection to project completion.\u003c\/p\u003e","brand":"The Tech Depot","offers":[{"title":"Default Title","offer_id":48743829766401,"sku":"TES-EV02640","price":2255.68,"currency_code":"INR","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0819\/1577\/3185\/files\/robot_Spund-228x228.jpg?v=1778063527","url":"https:\/\/techdepot.in\/products\/pololu-302-elenco-21-881-sound-reversing-car","provider":"Tech Depot India","version":"1.0","type":"link"}