Embedded Calculators & Part Finder
Size a value with 64 free calculators, then find the real component that fits — in stock, at the best price. For MCU, power, RF & firmware. No account.
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💡LED Resistor
⚡Ohm's Law
🚌CAN Bit Timing
🔻Voltage Divider
🔠Glyph Mapper
📦Struct Padding
PWM / Timer
Frequency, period, duty cycle
UART Baud Rate
Error rate, PASS/FAIL check
ADC Resolution
LSB voltage, SNR, dynamic range
Watchdog Timer
STM32 IWDG & WWDG timeouts
I2C Timing
Bus timing & pull-up values
CAN Bus Bit Timing
STM32 bxCAN/FDCAN & MCP2515
SPI Timing
Bit period, frame, throughput
RS-485 Bus
Cable length, termination, bias
LIN Bus Timing
Bit, break, frame time
Modbus RTU Timing
Char & inter-frame gaps
Ring Buffer / DMA
Buffer sizing
Register Map → C
Bitfield struct & macros
CRC → C Code
Lookup table & function
Stepper Motor
Steps/rev, microstep, pulse rate
BLDC / PMSM Speed
Motor electrical freq, pole pairs
Rotary Encoder
Motor encoder counts/rev
Motor Torque ↔ Power
N·m, RPM, Watts, hp
MOSFET Power Loss
Conduction & switching loss
Transformer Turns
Ratio, Ns, current ratio
LDO Dropout / Power
Heat dissipation & efficiency
I2S Audio Clock
BCLK, LRCLK, bit period
USB Data Lines
Bit time, 90Ω, termination
Ethernet Cable
Bit time, delay, 100m limit
Bit Field Visualizer
32-bit register breakdown
Q-Format Converter
Float ↔ fixed-point
Number Base Converter
Dec, Hex, Bin, Oct converter
IEEE 754 Visualizer
32-bit Float & 64-bit Double
Endian Swap
Big/Little/Mid-Endian byte swap
Struct Alignment
C struct padding & visualizer
Memory & Transmission
Bytes, baud rate & sample times
Glyph Mapper
7-Segment & Character LCD custom font generator
Crystal Load Cap
Oscillator load capacitor sizing
Ohm's Law
V, I, R, P — any 2 → all 4
Voltage Divider
Vout, loaded divider, Thevenin
LED Resistor
Series/parallel configs & E24
Resistor Code
Color bands & SMD decoder
Op-Amp Gain
Amp configurations & Schmitt
Instrumentation Amp
3-op-amp in-amp gain & Vout
Op-Amp Resistor
Inverting/Non-inv → R2,R3,R4
BJT Bias CE
Q-point & stability factor
NE555 Timer
Astable / monostable
Capacitor Charge
RC time constant, τ milestones
Buck / Boost
Switching regulator design
AWG Wire Gauge
Wire gauge & voltage drop
Series / Parallel
R · C · L equivalent value
LM317 Regulator
Adjustable Vout & R2 solver
Current Divider
Branch currents in parallel R
LC Resonance
LCR resonant freq, Q-factor
RC Filter
Cutoff frequency, gain & phase
dB Converter
dB, dBm & mW bidirectional
CRC Calculator
CRC-8/16/32, 7 polynomials
Checksum / CRC
XOR, Sum8/16, LRC, CRC
PCB Trace Calc
IPC impedance & trace width
Active Filter
Sallen-Key 2nd-order LPF/HPF
RF Trans. Line
Microstrip impedance (IPC-2141)
VSWR / Return Loss
Γ, return & mismatch loss
RF Link Budget
FSPL, Rx power, margin
Wavelength / Antenna
λ, λ/2 dipole, λ/4 whip
Attenuator Pad
T / Pi resistor values (dB)
Coil Inductance
Air-core solenoid (Wheeler)
Battery Life
Estimated system run-time
Temperature
Units & RTD sensor temps
Wheatstone Bridge
Bridge Vout & balance
Junction Temp
Thermal Tj & max power
Sallen-Key 2nd Order Active Filter Designer
Design active 2nd-order low-pass or high-pass Sallen-Key filters and evaluate Q-factor and frequency response approximation.
Component parameters
Filter Characteristics
Cutoff Frequency (f_c)—
Quality Factor (Q)—
Filter Response Shape:
—
💡 Usage & Formula
Sallen-Key 2nd-Order Cutoff Frequency:
f_c = 1 / (2 × π × sqrt(R₁ × R₂ × C₁ × C₂))
Quality Factor (Q)LP: Q = sqrt(R₁R₂C₁C₂) / (C₂(R₁ + R₂)). This Q-factor determines the shape of the transition band:
- Bessel (Q = 0.577): Best linear phase, minimal pulse overshoot but slow attenuation.
- Butterworth (Q = 0.707): Maximally flat passband response (no ripple) and sharp roll-off.
- Chebyshev (Q > 0.707): Sharpest attenuation slope but introduces amplitude ripples in the passband.
When you need it: Designing a second-order Sallen-Key low- or high-pass stage — ADC anti-aliasing, audio tone shaping, or sensor smoothing — by choosing R and C for a cutoff and Q.
Worked example: A Butterworth (Q = 0.707) low-pass at fc = 1 kHz with equal R = 10 kΩ needs C = 1/(2π × fc × R) ≈ 15.9 nF; the two capacitor values then set the Q.
Tips & gotchas:
- Q sets the peaking: 0.707 is maximally flat (Butterworth); higher Q peaks near fc and rings on transients.
- Cascade identical stages for steeper roll-off (4th order = two 2nd-order sections with the right Qs).
- The op-amp's GBW must comfortably exceed
fc × gain × Q, or the response droops early. - Use 1% resistors and C0G/NP0 capacitors — loose parts move both fc and Q noticeably.