Engineering Calculators

Motor Shunt Resistor

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)

BLDC frequencies

Notes

Ideal PWM frequency for BLDC motors

CAN-Bus Termination

Notes

Source: Designing CAN-Bus Circuitry: CAN-Bus PCB Layout Guidelines
Rated power based on square (half-on, half-off) wave

Gate Drive 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

f_{eff} = \frac{f_{s}}{2\pi(D-D^2)}

Based on: Selecting IHLP Composite Inductors for Non-Isolated Converters Utilizing Vishay’s Application Sheet

TODO:

Skin Depth for PWM signals

Notes

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

Based on: Selecting IHLP Composite Inductors for Non-Isolated Converters Utilizing Vishay’s Application Sheet

TODO:

Adopt better effective area calculation from here

Exponential Moving Average (EMA) Low-pass Filter

Notes

Source for equation

Passive Low-pass Filter

Notes

TODO:

Passive 2nd order Low-pass Filter

Notes

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=\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:

STM32 RC + EMA filter interaction

Notes

Source for equation
The aim is to use the STM32 (G4) ADC at as much sample time as possible (640.5 cycles) to maximize the duty cycle.

Power Supply

Buck converter resistor divider

Notes

TODO:

Boost converter

Input voltage min. (

V_{in_{min}}

)

Input voltage nom. (

V_{in}

)

Input voltage max. (

V_{in_{max}}

)

Output voltage (

V_{out}

)

Switch current (

I_{sw}

)

Interleaved phases

Efficiency @

V_{in_{min}}

Efficiency @

V_{in}

Efficiency @

V_{in_{max}}

Duty cycle @

V_{in_{min}}

Duty cycle @

V_{in}

Duty cycle @

V_{in_{max}}

PWM frequency

Inductance

Inductor ripple current @

V_{in_{min}}

Inductor ripple current @

V_{in}

Inductor ripple current @

V_{in_{max}}

Output current @

V_{in_{min}}

Output current @

V_{in}

Output current @

V_{in_{max}}

Output power @

V_{in_{min}}

Output power @

V_{in}

Output power @

V_{in_{max}}

Input capacitance

Output capacitance

Input voltage ripple @

V_{in_{min}}

Input voltage ripple @

V_{in}

Input voltage ripple @

V_{in_{max}}

Output voltage ripple @

V_{in_{min}}

Output voltage ripple @

V_{in}

Output voltage ripple @

V_{in_{max}}

Notes

TI Basic Calculation of a Boost Converter's Power Stage Application Note
StackExchange Filtering capacitors
Capacitance should be derated value

TODO:

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

Texas Instruments TPS65261

Output 1

Current (

I_{out}

)

Top resistor (

R_1

)

Bottom resistor (

R_2

)

Output voltage (

V_{out}

)

Feedback current (

I_{fb}

)

Output 2

Current (

I_{out}

)

Top resistor (

R_1

)

Bottom resistor (

R_2

)

Output voltage (

V_{out}

)

Feedback current (

I_{fb}

)

Output 3

Current (

I_{out}

)

Top resistor (

R_1

)

Bottom resistor (

R_2

)

Output voltage (

V_{out}

)

Feedback current (

I_{fb}

)

Power Failure Detector on VDIV

Top resistor (

R_1

)

Bottom resistor (

R_2

)

Reset (ok) voltage

Fail voltage

Switching Frequency

Resistor (

R

)

Frequency

Inductors

Maximum input voltage (

V_{in_{max}}

)

Output 1

Inductance 1

Ripple current 1

RMS current 1

Peak current 1

LIR (should be 10-30%)

Output 2

Inductance

Ripple current

RMS current

Peak current

LIR (should be 10-30%)

Output 3

Inductance

Ripple current

RMS current

Peak current

LIR (should be 10-30%)

Notes

Calculations based on the datasheet values

Datasheet
Product Page
The lower feedback resistor should be 10k in most cases

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

STM32G4 sampling times: 2.5, 6.5, 12.5, 24.5, 47.5, 92.5, 247.5, 640.5 cycles
STM32G4 conversion times: 15 cycles
The STM32G4 datasheets have a table of maximum impedances @ 60MHz ADC clock. Source for the equation here.

Vishay SiC471 Calculator

Input voltage min. (

V_{\text{in}_{\text{min}}}

)

Input voltage nom. (

V_{\text{in}}

)

Input voltage max. (

V_{\text{in}_{\text{max}}}

)

Output voltage (

V_{\text{out}}

)

Switching frequency

f_{\text{SW}}

R_f_{\text{SW}}

R_{FOD}

R_{I_{\text{LIM}}}

K_{I_{\text{MAX}}}

Expected max output current

I_{MAX}

Hardware current limit

I_{LIM}

R1

R2

R3

β_{NTC}

R_{NTC}

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

Figure 9-2. Dual Resonant Circuit With the Receiver Coil

Coil specified inductance

L_{S}

Coil measured inductance

L_{S}'

Coil

R_\text{DC}

Switching frequency

F_S

Switching frequency

F_D

Matching capacitor

C1

Matching capacitor

C2

Quality factor

Q

Quality factor margin

Q_\text{margin}

Matching capacitor

C1_A

Matching capacitor

C1_B

Matching capacitor

C1_C

Matching capacitor C1A,B,C total

Matching capacitor deviation

Matching capacitor

C2_A

Matching capacitor

C2_B

Matching capacitor

C2_C

Matching capacitor C2A,B,C total

Matching capacitor deviation

Notes

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

Source for most equations: datasheet

TI BQ51013B Design Calculator

Figure 9-1. BQ51013B Used as a Wireless Power Receiver and Power Supply for System Loads

R1

R_{FOD}

R_{I_{\text{LIM}}}

K_{I_{\text{MAX}}}

Expected max output current

I_{MAX}

Hardware current limit

I_{LIM}

Figure 8-12. NTC Circuit Options For Safe Operation of the Wireless Receiver Power Supply

R1

R2

R3

β_{NTC}

R_{NTC}

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

Coil specified inductance

L_{S}

Coil measured inductance

L_{S}'

Coil

R_\text{DC}

Switching frequency

F_S

Switching frequency

F_D

Matching capacitor

C1

Matching capacitor

C2

Quality factor

Q

Quality factor margin

Q_\text{margin}

Matching capacitor

C1_A

Matching capacitor

C1_B

Matching capacitor

C1_C

Matching capacitor C1A,B,C total

Matching capacitor deviation

Matching capacitor

C2_A

Matching capacitor

C2_B

Matching capacitor

C2_C

Matching capacitor C2A,B,C total

Matching capacitor deviation

Notes

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

Source for most equations: datasheet

LED resistor calculator

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

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

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

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

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

Notes

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

Packing of Two Sphere sizes

Notes

Implementation of Multi-Sized Sphere Packing.
Imperfect spheres pack slightly better

Assumptions

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

Engineering Calculators

Motor Shunt Resistor

Notes

I2C Pull-up

Notes

TODO

BLDC frequencies

Notes

CAN-Bus Termination

Notes

Gate Drive Resistor

Notes

TODO:

Effective Sinusoidal Frequency for PWM signals

Notes

TODO:

Skin Depth for PWM signals

Notes

TODO:

Exponential Moving Average (EMA) Low-pass Filter

Notes

Passive Low-pass Filter

Notes

TODO:

Passive 2nd order Low-pass Filter

Notes

TODO:

Switched Passive Low-pass Filter

Notes

TODO:

Filtered Resistor Divider

Notes

TODO:

STM32 RC + EMA filter interaction

Notes

Power Supply

Buck converter resistor divider

Notes

TODO:

Boost converter

Notes

TODO:

Texas Instruments TPS65261

Notes

TODO

STM32 Clock Config

Notes

TODO:

STM32 ADC

Notes

Vishay SiC471 Calculator

Notes

TI BQ51013B Design Calculator

Notes

LED resistor calculator

Notes

TODO

Battery Pack

Planetary Gearset calculator

Notes

BLDC calculator

Notes

Ball Screw Drive calculator

Notes

Timing belt calculator

Notes

Encoder calculator

Notes

Flight-time and added drag

Notes

Packing of Two Sphere sizes

Notes

Assumptions

YOLO calculator