[{"data":1,"prerenderedAt":672},["ShallowReactive",2],{"schematic:bjt-astable-multivibrator-led-flasher:en":3},{"schematic":4,"title":635,"shortDescription":22,"proseSource":636,"localizationFallbackIssues":252,"related":637,"confirmations":252},{"schemaVersion":5,"governance":6,"slug":18,"title":19,"cluster":20,"tier":21,"shortDescription":22,"deepTechnicalOverview":23,"theoryOfOperation":24,"keySpecifications":25,"applications":41,"gotchas":45,"formulas":61,"bom":122,"interactiveElements":175,"circuitJson":234,"svg":630,"relatedSchematicSlugs":631,"relatedComponentSlugs":633,"relatedBoardSlugs":634},"1.0",{"publication":7,"verification":10,"provenance":15},{"status":8,"publishedDate":9},"published","2026-10-14",{"status":11,"verifiedDate":9,"verifiedBy":12,"checklist":13},"verified","Codex (CC0 vector recapture, exact primary component datasheets, independent CAD\u002Fnet graph and LLM localization review; owner publication GO; no bench\u002Fnative-human signoff)",{"schema":14,"technicalFacts":14,"relationships":14,"sources":14},true,{"sourceUrls":16},[17],"https:\u002F\u002Fcommons.wikimedia.org\u002Fw\u002Findex.php?title=File:T-multivibrator.svg&oldid=1220800836","bjt-astable-multivibrator-led-flasher","BJT Astable Multivibrator LED Flasher","timing_oscillators","Tier 1","Discrete two-transistor cross-coupled relaxation oscillator driving alternating LEDs without an integrated circuit.","The BJT Astable Multivibrator is a classical discrete relaxation oscillator circuit. Two NPN bipolar junction transistors (Q1 and Q2) are configured in a cross-coupled feedback topology, where the collector of each transistor is AC-coupled to the base of the opposite transistor via timing capacitors C1 and C2. Under idealized symmetrical DC conditions, both transistors would theoretically be biased into simultaneous conduction; in practical hardware, minute component tolerances, device parameter variations, and ambient thermal noise can break this symmetry upon power application and initiate regenerative oscillation; startup is not guaranteed over component variation, supply ramps or temperature. Once oscillation is established, the circuit alternates between two quasi-stable states, generating complementary switching transitions that alternate the illumination of LED1 (D1) and LED2 (D2). Series collector resistors (R1 and R4) limit forward LED current, while base pull-up resistors (R2 and R3) supply sustained base bias from VCC and govern timing capacitor recharge rates.\n\nReference: T-multivibrator.svg by Д.Ильин (CC0 1.0). This fresh CircuitBase CAD adaptation adds series red\u002Fblue LEDs, selected nominal values and nonpolar MLCC timing capacitors to the basic two-transistor reference, which contains no LEDs or component values. The reference does not validate these added hardware choices or the calculated timing.","### 1. Circuit Startup and Initial Cycle Inception\nUpon DC power connection ($V_{CC} = 5.0\\text{ V}$ nominal), timing capacitors $C_1$ and $C_2$ are initially uncharged. Base pull-up resistors $R_2$ and $R_3$ supply charging current from $V_{CC}$ to the bases of $Q_1$ and $Q_2$. In an ideal mathematical circuit with perfectly identical components and zero noise, both transistors would turn on equally toward a symmetrical equilibrium. In practical physical circuits, microscopic variations in base-emitter threshold voltage ($V_{BE}$), current gain ($h_{FE}$), and resistor tolerances, along with power supply rise times and ambient thermal noise, can break symmetry so that one transistor (e.g., $Q_1$) conducts slightly more rapidly than the other. Regenerative feedback immediately accelerates this unbalance: as $Q_1$ conducts, its collector voltage falls, coupling a negative potential through $C_1$ to the base of $Q_2$, which can drive $Q_2$ off and initiate oscillation. This narrative does not guarantee startup for every component selection, supply ramp or temperature.\n\n### 2. Established Cycle State Transition ($Q_1$ Turn-On, $Q_2$ Cutoff)\nThe following is a pedagogical step model of established oscillation, not a measured waveform: assume fixed conducting-collector voltage, constant illustrative VBE and VCE(sat), negligible base loading, and the stated off-collector voltage. Actual off-collector voltage depends on LED current and capacitor recovery. The general instantaneous coupling relation is VB(after) = VB(before) + VC(after) − VC(before). Immediately before $Q_1$ turns on, $Q_2$ is conducting in saturation with $V_{B2}(0^-) \\approx V_{BE(on)} \\approx 0.7\\text{ V}$, and $Q_1$ is cut off with its collector resting near $(V_{CC} - V_{F(D1)})$. When $Q_1$ snaps into saturation, its collector voltage plunges rapidly to $V_{CE(sat)} \\approx 0.15\\text{ V} - 0.2\\text{ V}$. Because the charge on timing capacitor $C_1$ cannot change instantaneously, charge continuity dictates the resulting base voltage of $Q_2$:\n\n$$V_{B2}(0^+) \\approx V_{BE(on)} - \\left((V_{CC} - V_{F(D1)}) - V_{CE(sat)}\\right)$$\n\nIn an illustrative simplified step calculation with assumed parameters (the LED datasheet VF at its stated test current is not a measured drop in this circuit) ($V_{CC} = 5.0\\text{ V}$, Red LED $V_{F(D1)} \\approx 1.9\\text{ V}$, $V_{CE(sat)} \\approx 0.2\\text{ V}$, $V_{BE(on)} \\approx 0.7\\text{ V}$), the collector voltage step is $\\Delta V_C \\approx 2.9\\text{ V}$, which couples across $C_1$ to drive $V_{B2}(0^+)$ negative to approximately $-2.2\\text{ V}$. This reverse-biases the base-emitter junction of $Q_2$, driving it firmly into cutoff and extinguishing Blue LED $D_2$, while $Q_1$ conducts and illuminates Red LED $D_1$.\n\n### 3. Quasi-Stable Timing Interval 1 ($Q_1$ ON, $Q_2$ OFF)\nWhile $Q_2$ remains cut off, its collector node is pulled toward $V_{CC}$ through $R_4$ and $D_2$, restoring charge onto the collector plate of $C_2$. Sustained DC base current to keep $Q_1$ saturated is supplied directly from $V_{CC}$ through pull-up resistor $R_2$ ($I_{B1} \\approx (V_{CC} - V_{BE(on)}) \u002F R_2$). Simultaneously, timing capacitor $C_1$ (whose negative side is connected to $Q_2$'s base) discharges its negative potential and recharges toward $+V_{CC}$ through base pull-up resistor $R_3$ ($47\\text{ k}\\Omega$). In this simplified model with a fixed opposite capacitor terminal and negligible transistor input current, the base voltage follows:\n\n$$V_{B2}(t) = V_{CC} - \\left(V_{CC} - V_{B2}(0^+)\\right) e^{-t \u002F (R_3 C_1)}$$\n\nTransistor $Q_2$ remains in cutoff throughout the interval until $V_{B2}(t)$ reaches the forward conduction threshold $V_{BE(on)} \\approx 0.65\\text{ V} - 0.70\\text{ V}$. Solving for $V_{B2}(T_1) = V_{BE(on)}$ yields the cutoff duration:\n\n$$T_1 = R_3 \\cdot C_1 \\cdot \\ln\\left(\\frac{V_{CC} - V_{B2}(0^+)}{V_{CC} - V_{BE(on)}}\\right)$$\n\n### 4. State Transition ($Q_2$ Turn-On, $Q_1$ Cutoff)\nWhen $V_{B2}(t)$ reaches $V_{BE(on)}$, transistor $Q_2$ begins conducting base current. Regenerative cross-coupling rapidly pulls $Q_2$ into saturation. As $Q_2$'s collector drops from $(V_{CC} - V_{F(D2)})$ down to $V_{CE(sat)} \\approx 0.2\\text{ V}$, this negative voltage step is coupled through timing capacitor $C_2$ to the base of $Q_1$:\n\n$$V_{B1}(0^+) \\approx V_{BE(on)} - \\left((V_{CC} - V_{F(D2)}) - V_{CE(sat)}\\right)$$\n\nFor Blue LED $D_2$ (illustrative $V_{F(D2)} \\approx 3.3\\text{ V}$), the collector voltage step $\\Delta V_C \\approx (5.0 - 3.3) - 0.2 = 1.5\\text{ V}$ drives $V_{B1}(0^+)$ down to approximately $0.7\\text{ V} - 1.5\\text{ V} = -0.8\\text{ V}$, cutting off $Q_1$ and extinguishing Red LED $D_1$, while $Q_2$ conducts and illuminates Blue LED $D_2$.\n\n### 5. Quasi-Stable Timing Interval 2 and Timing Approximations\nTransistor $Q_1$ is held in cutoff while $C_2$ recharges toward $+V_{CC}$ through base resistor $R_2$ ($47\\text{ k}\\Omega$). Sustained base current for $Q_2$ is supplied from $V_{CC}$ through $R_3$. The base voltage $V_{B1}(t)$ rises exponentially until reaching $V_{BE(on)}$, snapping $Q_1$ back on and restarting the cycle.\n\nIn standard idealized textbook analysis, diode forward drops and transistor saturation offsets are neglected ($V_B(0^+) \\approx -V_{CC}$, $V_{BE(on)} \\approx 0$). Under these ideal reference assumptions, the half-period equations simplify to:\n\n$$T_1 \\approx \\ln(2) \\cdot R_3 \\cdot C_1 \\approx 0.693 \\cdot R_3 \\cdot C_1, \\quad T_2 \\approx \\ln(2) \\cdot R_2 \\cdot C_2 \\approx 0.693 \\cdot R_2 \\cdot C_2$$\n\nFor symmetrical components ($R_2 = R_3 = 47\\text{ k}\\Omega$, $C_1 = C_2 = 10\\mu\\text{F}$), this ideal textbook reference yields $T \\approx 1.386 \\cdot R \\cdot C \\approx 0.651\\text{ s}$ ($f \\approx 1.535\\text{ Hz}$) with 50% duty cycle. In physical circuits, unequal forward LED drops ($V_{F(D1)} \\ne V_{F(D2)}$), finite collector pull-up recovery via $R_C$, and component tolerances alter the switching thresholds and restore intervals. Accurate prediction of physical waveform timing requires full transient simulation or laboratory oscilloscope measurement.",[26,29,32,35,38],{"label":27,"value":28},"Nominal Operating Supply Voltage","5.0 V DC nominal design assumption for educational demonstration. Requires sufficient headroom above the blue LED forward voltage (~3.3 V typ) to bias collector and base resistors; reverse base-emitter transients must remain within the transistor's absolute maximum rating (VEBO = 6.0 V for 2N3904BU).",{"label":30,"value":31},"Oscillation Frequency (Ideal Reference Model)","≈1.54 Hz calculated ideal textbook estimate (f ≈ 1 \u002F (1.386 · R · C) for R=47 kΩ, C=10 µF under simplified zero-offset assumptions). Physical frequency depends on LED forward drops, collector recharge time, and component tolerances, requiring transient simulation or bench measurement for exact figures.",{"label":33,"value":34},"Nominal Duty Cycle (Symmetrical Ideal Reference)","50% under ideal identical half-periods (T1 = T2 = ln(2) · R · C). Practical builds exhibit duty cycle divergence due to unequal LED forward voltages (Red ~1.9 V vs Blue ~3.3 V) and resistor\u002Fcapacitor tolerances.",{"label":36,"value":37},"Transistor Type and Ratings","NPN Silicon Epitaxial Planar BJT (onsemi 2N3904BU, Case 135AN TO-92; absolute maximum ratings at TA=25°C: VCEO=40 V, IC=200 mA, VEBO=6.0 V; breakdown test V(BR)EBO ≥ 6.0 V at IE=10 µA, IC=0)",{"label":39,"value":40},"Timing Capacitors","C1 and C2: Murata GRM31CR71E106KA12L, nominal 10 µF ±10%, DC 25 V, X7R, EIA 1206. Effective capacitance in this timing circuit must be evaluated under actual voltage, AC amplitude, temperature and aging; 1.535 Hz remains a nominal ideal reference, not guaranteed physical timing.",[42,43,44],"Visual warning beacons and dual-LED alternating signal blinkers","Educational electronics laboratory demonstrations of regenerative switching and BJT relaxation oscillation","Basic cross-coupled discrete timing oscillator study",[46,51,56],{"title":47,"trap":48,"solution":49,"severity":50},"Reverse Base-Emitter Voltage Stress (Vebo = 6.0V Rating Limit)","When either switching transistor turns on, the negative voltage step at its collector couples across the timing capacitor to the opposite base node. The onsemi 2N3904BU datasheet specifies an absolute maximum emitter-base voltage rating of VEBO = 6.0 V (with breakdown test V(BR)EBO ≥ 6.0 V at IE = 10 µA, IC = 0). If an astable multivibrator is operated at higher supply voltages or with resistive collectors lacking series LED drops, the negative base excursion can exceed this VEBO rating. Repetitive reverse breakdown of the base-emitter junction can cause junction stress, potentially leading to cumulative degradation of transistor current gain (hFE) and elevated base leakage.","The illustrative step assumptions at nominal 5.0 V give reverse base excursions below the 6.0 V absolute limit; they are not a validated worst-case operating envelope. Check actual transients. A reverse clamp, if added, has anode at GND and cathode at the NPN base; such diodes are absent from this CAD and change timing, so reevaluate the circuit before using them.","critical",{"title":52,"trap":53,"solution":54,"severity":55},"Nonpolar Timing Capacitor Application Limits","Use a nonpolar timing capacitor because its terminal voltage reverses during the cycle. The selected Murata X7R MLCC has a 25 V DC rating, but capacitance tolerance and voltage\u002Ftemperature\u002Faging dependence can change timing. Nonpolarity does not by itself establish repetitive-waveform suitability or lifetime. The nominal 5.0 V educational step model gives capacitor voltages of a few volts; this is not a validated worst-case waveform envelope.","For the exact 01CA specification, keep the greater of peak-to-peak and zero-to-peak applied voltage within 25 V when AC is superimposed on DC. For AC\u002Fpulse use, check actual current and body self-heating: below 20°C rise at 25°C ambient for this \u003C100 V DC-rated part, and total surface temperature at or below 125°C. Assess actual capacitance in the timing circuit and verify waveform and heating before claiming application readiness. No ripple-current, frequency, startup or lifetime guarantee is asserted.","warning",{"title":57,"trap":58,"solution":59,"severity":60},"Metastable Equilibrium at Power-Up","Theoretical analysis indicates a possible symmetric equilibrium where both transistors conduct in forward active mode or saturation simultaneously with identical collector potentials. If the DC supply voltage rises very slowly or ramps monotonically in a heavily decoupled environment, both transistors may draw base current simultaneously through R2 and R3 without triggering regenerative oscillation.","In typical physical breadboard builds, inherent component variations (such as differences in hFE and VBE) and ambient thermal noise are usually sufficient to initiate oscillation upon rapid power connection. To avoid startup stall in production or slow-ramp environments, a dedicated timer IC (e.g. NE555) or an asymmetrical startup network should be utilized rather than relying on unassisted discrete BJT cross-coupling.","info",[62,77,100],{"name":63,"latexOrText":64,"description":65,"variables":66},"Ideal Reference Half-Period (Q2 Cutoff)","T_1 = \\ln(2) \\cdot R_3 \\cdot C_1 \\approx 0.693 \\cdot R_3 \\cdot C_1","Calculates the ideal textbook cutoff duration in seconds for Transistor Q2 (while Q1 conducts and LED1 illuminates) as capacitor C1 recharges through base pull-up resistor R3 toward VCC, assuming zero forward diode drops and negligible transistor saturation voltages.",[67,72],{"symbol":68,"name":69,"typicalValue":70,"unit":71},"R_3","Base Pull-Up Resistor for Q2","47","kΩ",{"symbol":73,"name":74,"typicalValue":75,"unit":76},"C_1","Timing Capacitor 1","10","µF",{"name":78,"latexOrText":79,"description":80,"variables":81},"Total Oscillation Period and Frequency (Ideal Reference)","f = \\frac{1}{T_1 + T_2} = \\frac{1}{\\ln(2) \\cdot (R_3 C_1 + R_2 C_2)} \\approx \\frac{1}{0.693 \\cdot (R_3 C_1 + R_2 C_2)}","Total ideal relaxation oscillation frequency in Hertz under simplified textbook assumptions. For symmetrical networks (R2=R3=R, C1=C2=C), simplifies to f ≈ 1 \u002F (1.386 · R · C) ≈ 1.535 Hz. In physical hardware, forward LED drops, finite collector pull-up recovery, and component tolerances alter the effective charging bounds, requiring transient simulation or laboratory measurement for exact timing.",[82,87,90,93,95,97],{"symbol":83,"name":84,"typicalValue":85,"unit":86},"T_1","Half-Period 1 (Ideal Calculation Benchmark)","0.326","s",{"symbol":88,"name":89,"typicalValue":85,"unit":86},"T_2","Half-Period 2 (Ideal Calculation Benchmark)",{"symbol":91,"name":92,"typicalValue":70,"unit":71},"R_2","Q1 Base Resistor (Ideal Calculation Benchmark)",{"symbol":68,"name":94,"typicalValue":70,"unit":71},"Q2 Base Resistor (Ideal Calculation Benchmark)",{"symbol":73,"name":96,"typicalValue":75,"unit":76},"Timing Capacitor 1 (Ideal Calculation Benchmark)",{"symbol":98,"name":99,"typicalValue":75,"unit":76},"C_2","Timing Capacitor 2 (Ideal Calculation Benchmark)",{"name":101,"latexOrText":102,"description":103,"variables":104},"LED Branch Current Estimate","I_{LED} \\approx \\frac{V_{CC} - V_F - V_{CE(sat)}}{R_C}","Quasi-steady Ohmic approximation for the LED\u002Fresistor branch using actual LED forward voltage and an assumed conducting-collector voltage. It excludes coupling-capacitor transients and is not the total transistor collector current during switching.",[105,110,114,118],{"symbol":106,"name":107,"typicalValue":108,"unit":109},"V_{CC}","Supply Voltage","5.0","V",{"symbol":111,"name":112,"typicalValue":113,"unit":109},"V_F","LED Forward Voltage Drop (Illustrative Calculation Value)","2.0",{"symbol":115,"name":116,"typicalValue":117,"unit":109},"V_{CE(sat)}","Transistor Saturation Voltage (Illustrative Assumption)","0.2",{"symbol":119,"name":120,"typicalValue":121,"unit":71},"R_C","Collector Limiting Resistor (R1 or R4)","1",[123,131,134,141,146,149,152,159,162,169],{"refDes":124,"componentName":125,"value":126,"package":127,"quantity":128,"role":129,"notes":130},"Q1","NPN Bipolar Junction Transistor","2N3904BU","TO-92 (Case 135AN)",1,"Primary cross-coupled switching transistor","onsemi 2N3904BU through-hole BJT (Rev. 3, Oct 2024, order code BU, Case 135AN); absolute maximum ratings at TA=25°C: VCEO=40V, IC=200mA, VEBO=6.0V; breakdown V(BR)EBO ≥ 6.0V (tested at IE=10µA, IC=0)",{"refDes":132,"componentName":125,"value":126,"package":127,"quantity":128,"role":133,"notes":130},"Q2","Complementary cross-coupled switching transistor",{"refDes":135,"componentName":136,"value":137,"package":138,"quantity":128,"role":139,"notes":140},"R1","Carbon Film Resistor 1\u002F4W","1kΩ","Axial Leaded","LED1 collector current limiting resistor","Yageo CFR-25JB-52-1K, 1.0 kΩ ±5%, 0.25 W at TA=70°C, carbon film; derate above 70°C",{"refDes":142,"componentName":136,"value":143,"package":138,"quantity":128,"role":144,"notes":145},"R2","47kΩ","Base pull-up timing resistor for Q1 (governs T2 with C2)","Yageo CFR-25JB-52-47K, 47 kΩ ±5%, 0.25 W at TA=70°C, carbon film; derate above 70°C",{"refDes":147,"componentName":136,"value":143,"package":138,"quantity":128,"role":148,"notes":145},"R3","Base pull-up timing resistor for Q2 (governs T1 with C1)",{"refDes":150,"componentName":136,"value":137,"package":138,"quantity":128,"role":151,"notes":140},"R4","LED2 collector current limiting resistor",{"refDes":153,"componentName":154,"value":155,"package":156,"quantity":128,"role":157,"notes":158},"C1","Nonpolar X7R Multilayer Ceramic Capacitor","10µF","EIA 1206 (3216M)","Timing capacitor coupling Q1 collector to Q2 base","Murata GRM31CR71E106KA12L, nominal 10 µF ±10%, rated DC 25 V, X7R, EIA 1206 (3216M); 01CA specification Jun. 25, 2026. Nominal capacitance is measured at room temperature, 1.0 ±0.1 kHz and 1.0 ±0.2 Vrms; effective capacitance depends on actual bias, AC amplitude, temperature and aging. No component-catalog lifecycle or application validation is implied.",{"refDes":160,"componentName":154,"value":155,"package":156,"quantity":128,"role":161,"notes":158},"C2","Timing capacitor coupling Q2 collector to Q1 base",{"refDes":163,"componentName":164,"value":165,"package":166,"quantity":128,"role":167,"notes":168},"D1","Standard 5mm Red Indicator LED","Red","T-1 3\u002F4 (5mm)","Visual state indicator for channel 1 (active when Q1 conducts)","Kingbright WP7113ID, standard 5mm red LED (dominant 617nm, peak 627nm), VF = 1.9V typ (2.3V max) at IF = 10mA, TA = 25°C; absolute maximum continuous IF = 30mA at TA=25°C; datasheet VF footnote: ±0.1 V. These are specified test-point values, not guaranteed voltage or current in this circuit.",{"refDes":170,"componentName":171,"value":172,"package":166,"quantity":128,"role":173,"notes":174},"D2","Standard 5mm Blue Indicator LED","Blue","Visual state indicator for channel 2 (active when Q2 conducts)","Kingbright WP7113QBC\u002FD, standard 5mm blue LED (dominant 465nm, peak 460nm), VF = 3.3V typ (4.0V max) at IF = 20mA, TA = 25°C; absolute maximum continuous IF = 30mA at TA=25°C; datasheet VF footnote: ±0.1 V. These are specified test-point values, not guaranteed voltage or current in this circuit.",{"Q1":176,"Q2":185,"R1":188,"R2":196,"R3":202,"R4":206,"C1":209,"C2":217,"D1":220,"D2":228},{"refDes":124,"name":177,"value":126,"role":178,"description":179,"footprint":127,"specs":180},"NPN Transistor 2N3904","Switching Transistor","Cross-coupled NPN switch. When conducting, it pulls the cathode of D1 low through R1 in the collector branch, allowing LED current. The D1 cathode and Q1 collector are separate nodes. Its falling collector voltage couples a negative transient to the Q2 base through C1.",{"Polarity":181,"Vceo":182,"Ic Max":183,"Vebo":184},"NPN","40 V abs max at TA=25°C","200 mA abs max at TA=25°C","6.0 V abs max at TA=25°C",{"refDes":132,"name":177,"value":126,"role":178,"description":186,"footprint":127,"specs":187},"Cross-coupled NPN switch. When conducting, it pulls the cathode of D2 low through R4 in the collector branch, allowing LED current. The D2 cathode and Q2 collector are separate nodes. Its falling collector voltage couples a negative transient to the Q1 base through C2.",{"Polarity":181,"Vceo":182,"Ic Max":183,"Vebo":184},{"refDes":135,"name":189,"value":137,"role":190,"description":191,"footprint":138,"specs":192},"Collector Resistor","LED Current Limiter","Limits forward current through D1 when Q1 is in saturation.",{"Resistance":193,"Tolerance":194,"Power":195},"1.0 kΩ","±5%","0.25 W at TA=70°C; derate above 70°C",{"refDes":142,"name":197,"value":143,"role":198,"description":199,"footprint":138,"specs":200},"Base Timing Resistor","RC Timing Network (Q1 Base \u002F C2 Recharge)","Provides sustained base pull-up current to Q1 from VCC. Governs the recharge of capacitor C2 toward VCC and defines cutoff half-period T2.",{"Resistance":201,"Tolerance":194,"Power":195},"47.0 kΩ",{"refDes":147,"name":197,"value":143,"role":203,"description":204,"footprint":138,"specs":205},"RC Timing Network (Q2 Base \u002F C1 Recharge)","Provides sustained base pull-up current to Q2 from VCC. Governs the recharge of capacitor C1 toward VCC and defines cutoff half-period T1.",{"Resistance":201,"Tolerance":194,"Power":195},{"refDes":150,"name":189,"value":137,"role":190,"description":207,"footprint":138,"specs":208},"Limits forward current through D2 when Q2 is in saturation.",{"Resistance":193,"Tolerance":194,"Power":195},{"refDes":153,"name":210,"value":155,"role":211,"description":212,"footprint":156,"specs":213},"Timing Capacitor","Cross-Coupled AC Feedback","Couples negative collector voltage step from Q1 to Q2 base, holding Q2 in cutoff until recharged toward VCC via R3.",{"Capacitance":214,"Voltage":215,"Type":216},"10 µF nominal ±10%","25 V DC rated","Nonpolar X7R MLCC (Murata GRM31CR71E106KA12L)",{"refDes":160,"name":210,"value":155,"role":211,"description":218,"footprint":156,"specs":219},"Couples negative collector voltage step from Q2 to Q1 base, holding Q1 in cutoff until recharged toward VCC via R2.",{"Capacitance":214,"Voltage":215,"Type":216},{"refDes":163,"name":221,"value":165,"role":222,"description":223,"footprint":166,"specs":224},"Red Indicator LED","Visual State Indicator","Illuminates when Q1 is saturated and collector current flows from VCC through R1.",{"Color":225,"Forward Drop":226,"Max Current":227},"Red (dominant 617nm, peak 627nm)","1.9 V typ, 2.3 V max at IF=10 mA, TA=25°C; VF footnote ±0.1 V; not an actual circuit drop guarantee","30 mA absolute maximum continuous DC at TA=25°C",{"refDes":170,"name":229,"value":172,"role":222,"description":230,"footprint":166,"specs":231},"Blue Indicator LED","Illuminates when Q2 is saturated and collector current flows from VCC through R4.",{"Color":232,"Forward Drop":233,"Max Current":227},"Blue (dominant 465nm, peak 460nm)","3.3 V typ, 4.0 V max at IF=20 mA, TA=25°C; VF footnote ±0.1 V; not an actual circuit drop guarantee",{"schemaVersion":235,"id":236,"meta":237,"components":244,"nets":322,"junctions":383,"netLabels":416,"wires":417},"1.5","bjt-led-flasher-cc0-recapture",{"title":238,"locale":239,"grid":240,"source":241},"Two-Transistor LED Flasher — CC0 Reference Adaptation","en",20,{"type":242,"ref":243,"url":17},"public-domain","Fresh CAD replacement capture from Д.Ильин, T-multivibrator.svg, CC0, Commons page revision oldid1220800836; retained reference SVG SHA256 59a7c48d55dc48ccba517ed2fe5e9e5c85986f87228ec7efe5cded374005b836. Original vector basic two-NPN cross-coupled oscillator: source VT1\u002FVT2 map Q1\u002FQ2; collector resistors R1\u002FR4 retained; source inner R2 feeds VT2 and maps to our R3(Q2 base); source inner R3 feeds VT1 and maps to our R2(Q1 base); source C1\u002FC2 mapped by connected collector\u002Fbase, not graphical position alone. Adaptations: add D1 red and D2 blue in series above collector resistors, select exact parts and nonpolar MLCCs, use supported normal NPN orientation for both devices, orthogonal20px routing and staggered T junctions, omit Vout port. This replaces the old unknown-source traced layout; it does not recover its original source. No measured operation, guaranteed timing\u002Flifetime\u002Fstartup, or independent original topology 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font-family=\"'Space Mono', 'SFMono-Regular', Consolas, 'Liberation Mono', monospace\" font-size=\"11\">GND\u003C\u002Ftext>\u003C\u002Fsvg>",[632],"ne555-astable-square-wave-generator",[],[],"BJT Astable Multivibrator & Dual LED Flasher","canonical",[638,651,661],{"slug":632,"cluster":20,"tier":21,"supplyVoltage":639,"voltageSpecification":642,"signalDomain":645,"breadboardFriendly":14,"title":646,"shortDescription":647,"bomCount":648,"formulaCount":649,"search":650},[640,641],"5v","12v",{"kind":246,"value":643,"label":644},"4.5 V – 16 V DC (Texas Instruments NE555; shown circuit uses +5 V)","Operating Supply Voltage","mixed","NE555 Astable Square Wave Generator","Standard astable relaxation oscillator topology outputting continuous square wave clock pulses with adjustable duty cycle.",7,4,"ne555 astable square wave generator\nindustry-standard relaxation oscillator generating precision clock pulses, audio tones, and variable-frequency square waves.\nne555 astable square wave generator\nstandard astable relaxation oscillator topology outputting continuous square wave clock pulses with adjustable duty cycle.\nne555 astable square wave generator\nindustry-standard relaxation oscillator generating precision clock pulses, audio tones, and variable-frequency square waves.\ntiming_oscillators\nprecision bipolar timer ic\nne555p\nu1\nmetal film resistor 1\u002F4w\n10kω\nr1\nmetal film resistor 1\u002F4w\n47kω\nr2\nmetalized film \u002F ceramic capacitor\n100nf\nc1\nmultilayer ceramic capacitor (mlcc)\n10nf\nc2\naluminum electrolytic capacitor\n100µf\nc3\nmultilayer ceramic capacitor (mlcc)\n100nf\nc4",{"slug":652,"cluster":20,"tier":21,"supplyVoltage":653,"voltageSpecification":654,"signalDomain":656,"breadboardFriendly":14,"title":657,"shortDescription":658,"bomCount":648,"formulaCount":659,"search":660},"ne555-monostable-delay-timer",[640,641],{"kind":246,"value":655,"label":644},"4.5 V – 16 V (TI §7.3)","digital","NE555 Monostable Delay Timer (One-Shot)","The one-shot circuit from the TI NE555 datasheet: press START and the output stays high for a fixed time set by one resistor and one capacitor, about 1.1 s with 100 kΩ and 10 µF.",2,"ne555 monostable delay timer (one-shot)\nthe one-shot circuit from the ti ne555 datasheet: press start and the output stays high for a fixed time set by one resistor and one capacitor, about 1.1 s with 100 kω and 10 µf.\nne555 monostable delay timer (one-shot)\nthe one-shot circuit from the ti ne555 datasheet: press start and the output stays high for a fixed time set by one resistor and one capacitor, about 1.1 s with 100 kω and 10 µf.\nne555 monostable delay timer (one-shot)\nthe one-shot circuit from the ti ne555 datasheet: press start and the output stays high for a fixed time set by one resistor and one capacitor, about 1.1 s with 100 kω and 10 µf.\ntiming_oscillators\nprecision timer\nne555p\nu1\nresistor\n100kω\nr1\naluminium electrolytic capacitor\n10µf\nc1\nceramic capacitor\n10nf\nc2\nceramic capacitor\n100nf\nc3\nresistor\n10kω\nr2\ntactile switch\nstart\nsw1",{"slug":662,"cluster":663,"tier":21,"supplyVoltage":664,"voltageSpecification":666,"signalDomain":656,"breadboardFriendly":14,"title":669,"shortDescription":670,"bomCount":648,"formulaCount":649,"search":671},"2n2222-relay-driver-flyback-protection","microcontroller_interfaces",[665,640,641],"3.3v",{"kind":246,"value":667,"label":668},"+12.0 V DC nominal (+10.8 V to +13.2 V operating range)","Relay Supply Voltage (VLOAD)","2N2222 \u002F 2N2222A NPN BJT Relay Driver with 1N4007 Flyback Clamping Diode","Discrete NPN bipolar junction transistor low-side relay driver circuit with 1N4007 flyback suppression diode, base saturation drive, and supply decoupling for 3.3V\u002F5V MCU control.","2n2222 \u002F 2n2222a npn bjt relay driver with 1n4007 flyback clamping diode\ndiscrete npn bipolar junction transistor low-side relay driver circuit with 1n4007 flyback suppression diode, base saturation drive, and supply decoupling for 3.3v\u002F5v mcu control.\n2n2222 \u002F 2n2222a npn bjt relay driver with 1n4007 flyback clamping diode\ndiscrete npn bipolar junction transistor low-side relay driver circuit with 1n4007 flyback suppression diode, base saturation drive, and supply decoupling for 3.3v\u002F5v mcu control.\n2n2222 \u002F 2n2222a npn bjt relay driver with 1n4007 flyback clamping diode\ndiscrete npn bipolar junction transistor low-side relay driver circuit with 1n4007 flyback suppression diode, base saturation drive, and supply decoupling for 3.3v\u002F5v mcu control.\nmicrocontroller_interfaces\nnpn general purpose bipolar transistor\n2n2222a\nq1\ngeneral purpose rectifier \u002F clamp diode\n1n4007\nd1\nsubminiature spdt signal \u002F power relay\ng5v-1-dc12\nk1\nbase current-limiting resistor 1 kω\n1kω\nr1\nbase pull-down bleeder resistor 10 kω\n10kω\nr2\nhigh-frequency ceramic decoupling mlcc\n100nf 50v\nc1\nbulk aluminum electrolytic decoupling\n47µf 25v\nc2",1793836428865]