Engineering Calculators

Motor Shunt Resistor

Motor
Shunt
Amplifier
ADC

Notes

For BLDC motor controller shunt resistors, using a bi-directional current sense amplifier.

  • The amplifier reference is the 'mid' or 0-current voltage (the average of vref1 and vref2 in -for example- TI amps).
  • If no amplifier is used set the gain to 1 and reference to 0

I2C Pull-up

Notes

  • Source TI SLVA689: I2C Bus Pullup Resistor Calculation
  • According to TI SLOA013 traces on a PCB with a ground and power plane will be about 1-3 pF/in. and low capacitance cables about 20-30 pF/ft conductor to shield.
  • According to NXP UM10204 each device can add up to 10pF of bus capacitance. STM32 MCUs have a typical capacitance of 5pF per IO.
  • Low-level output current for Standard (100kb/s) and Fast (400kb/s) modes are min. 3mA, 20mA for Fast-mode Plus (1Mb/s) at 0.4V.
  • For a more detailed guide on trace capacitance see: I2C Design Mathematics: Capacitance and Resistance
  • Rise times: max. 1000, 300, 120ns for Standard, Fast, Fast+ modes respectively. Min 20ns only for Fast mode.

TODO

  • Add some power estimations, for example by providing a data size in bytes, determining the clock pulses required, then the energy to create those based on the bus capacitance and 'low' duration (resistive losses)

CAN-Bus Termination

Notes

Gate Drive Resistor

Driver
FET
Resistor

Notes

  • See TI's take on ringing.
  • Does not include any diodes for asymmetric control.
  • Takes the minimum of the sink / source currents.

TODO:

  • Use gate capacitance to determine average power rating
  • Suggest a resistor size based on current and power limits (0805 ~ 1A, 1206 ~2A, etc)
  • Separate out sink/source
  • Support diodes

Effective Sinusoidal Frequency for PWM signals

Notes

feff=fs2π(D−D2)f_{eff} = \frac{f_{s}}{2\pi(D-D^2)}

TODO:

Skin Depth for PWM signals

Notes

δ=2(D−D2)ρwμ0μRfs\delta = \sqrt\frac{2(D-D^2)\rho_{w}}{\mu_{0}\mu_{R}f_{s}}

TODO:

  • Adopt better effective area calculation from here

Passive Low-pass Filter

Notes

Low_pass_filter

TODO:

Passive 2nd order Low-pass Filter

Notes

Low_pass_filter

TODO:

Switched Passive Low-pass Filter

Notes

    This assumes the 'on' state capacitance is so much more that the filter resistance can be simplified to R+Ron. Same for the capacitances

TODO:

Filtered Resistor Divider

fc=(R1+R2)(103/10−1)2π∗R1∗R2∗C1≈(R1+R2)2π∗R1∗R2∗C1fc=\frac{(R_1+R_2)\sqrt{(10^{3/10}-1)}}{2\pi*R_1*R_2*C_1}\approx \frac{(R_1+R_2)}{2\pi*R_1*R_2*C_1}

Notes

TODO:

Power Supply

Buck converter resistor divider

Notes

TODO:

Boost converter

Notes

TODO:

  • List input currents and powers
  • Determine more of efficiency by ESR, etc

Texas Instruments TPS65261

Output 1
Output 2
Output 3
Power Failure Detector on VDIV
Switching Frequency
Inductors

Output 1

Output 2

Output 3

Notes

Calculations based on the datasheet values

TODO

  • Loop compensation, etc.

STM32 Clock Config

Notes

To quickly find the right clock configuration for an STM32(G4), without the tedious drop-downs in CubeMX.

TODO:

STM32 ADC

Notes

Vishay SiC471 Calculator

NOTE: TS pin 10k to ground if not used.

Notes

Calculator for design parameters for the TI BQ51013B Wireless Qi / WPC v1.2 Power Receiver.

TI BQ51013B Design Calculator

NOTE: TS pin 10k to ground if not used.

Notes

Calculator for design parameters for the TI BQ51013B Wireless Qi / WPC v1.2 Power Receiver.

LED resistor calculator

Power Supply
LEDs
Resistor

Notes

Calculate a LED current limit resistor

  • An STM32 can handle up to 20mA per GPIO
  • For most 3.3V MCUs a GPIO will output approx 3.2V

TODO

  • List / select standard resistor values

Battery Pack

Cell
Pack
System

Planetary Gearset calculator

Notes

Calculate a some base parameters of a planetary gearset.

  • The tip clearance is the space between between the individual planetary gears
  • The ring OD needs backing 'thickness'

BLDC calculator

Torque based:

Speed based:

Notes

Ball Screw Drive calculator

Notes

  • Pitch diameter is normally similar enough to the lead OD
  • Friction guestimated from Koyo data
  • Force to torque from here

Timing belt calculator

Pulley
Belt
System

Notes

  • Common issue with suppliers: GT2 and GT3 are Gates tooth shapes and come in several sizes, they don't indicate pitch, but Chinese suppliers sometimes do use the digit for pitch.
  • A typical belt breaking strength for common Chinese 2M GT2 is 85N per mm of width. Approx. 150N for 3M HTD & 300N for 5M HTD.
  • MIT list of belt strengths. These need dividing by 25.4 as they're using a 1" reference belt width. Warning: The ultimate strength figures here are much higher than regular Chinese OEMs.
  • Belt surface speeds: General / large pitch 28m/s, HTD 33m/s, GT2 38m/s, T[n] 20m/s. Source: SDP/SI
  • In general a gear or pulley with an odd tooth-count will have better vibration characteristics than even ones, especially for the smaller pulleys.

Encoder calculator

Angular
Linear
Performance

Notes

Calculator for hall encoders, with a focus on hand-over encoders

  • Angular encoder based on the AS5047D
  • Linear encoder based on the AS5311
  • High-speed accuracy meaning: If the motor spins at maximum speed and you'd be able to instantly freeze the motion, the read position would deviate at most this much from the actual position (at working radius).

Flight-time and added drag

Airframe

Notes

  • For reference: A Mini Talon (Pro) does approx 55-90 mAh/km with a 4S battery pack

Packing of Two Sphere sizes

Notes

Assumptions

  • Using RCP, 'Random Close Packing', not compressed, but shaken or vibrated to pack

YOLO calculator

Input Image
Input