Circuit Design


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Child Pages

Microcontroller ADCs, measurement techniques, accuracy and resolution, 4-20mA current loops and more info on analogue-to-digital converters (ADCs).
Antenna Design
Dipoles, PCB antennas, problems with shorting out antennas and more info about RF antennas.
BLDC Motor Control
Information about BLDC motor control. Explains the different types, communtation cycles, control method, and also has a review on some BLDC controller chips and useful external links.
Capacitive Sensing
Linear sensors, rotational sensors, applications and more info about capacitive sensing.
Capacitive Touch Sensing
Types of interfaces, buttons, detection limits, ESD protection, manufacturers and more info on capacitive touch sensing.
Component Designators
A list of the common designator names (incl. various official standards) used to label electrical components on schematics.
Current Sensing
Low-side current sensing information and circuit schematics. Useful for measuring the current through a wire/circuit track (e.g. motor wire) with a microcontroller ADC.
Hardware and firmware debouncing tricks for debouncing switches in embedded circuitry.
Digital Logic
Karnaugh maps, binary counters, grey-encoded counters, quadrature detection circuits, delay circuits and more info about digital logic.
Electrical Signal Types
Information on electrical signal types such as TTL, CMOS, LVTTL, DCS, DTLL and PECL.
Information about extruded aluminium enclosures.
ESD Protection
Ceramic capacitors, zener diodes, TVS diodes, internal ESD protection on CMOS I/O, backpowering, disabling ESD diodes, series resistance, pull-up/pull-down issues and more information about ESD protection.
Example schematics, gain equations, passive vs. active, design tools and more information on electrical filters such as low-pass filters and high-pass filters.
Four Terminal (4T) Sensing
Information on the four-terminal (4T) sensing method to measure resistance (electrical impedance).
GPRS modules, popular AT commands, example GPRS devices and more info about general packet radio service (GPRS) technology.
H-Bridges (and Half-Bridges)
Example schematics, H-bridges using mechanical switches, driver ICs, bi-colour/tri-colour LEDs, filtering and more info about half-bridges and H-bridges (full-bridges).
Inrush Current
How to limit inrush current using either standard resistors or NTC thermistors. Example schematics and graphs included.
Light Dimmers
ContentsOverviewResistive DimmingPhase CuttingZero-Cross DetectionLED Light DimmingOverview Light dimmers are circuits which vary the amount of power going to a light source. The common one associated with the word “light dimmer” is a circuit which dims incandescent bulbs running of a mains (110, 230VAC) supply. Resistive Dimming The most basic way to dim a light is to put … Continue reading Light Dimmers
Logic Familes
ContentsHSTLCMOSOverviewAUCLVCMOS HSTL HSTL compares the input voltage with a reference voltage. CMOS Overview Complementary metal-oxide semiconductor. AUC Advanced ultra-low CMOS (AUC) is a CMOS logic family. It is optimised for 1.8V operation and voltage tolerant up to 3.6V. LVCMOS Voltage specifications: Parameter Minimum Typical Maximum \( V_{CCO} \) 2.3V 2.5V 2.7V \( V_{REF} \) – … Continue reading Logic Familes
Made For iPod/iPhone/iPad (MFi)
ContentsOverviewiPod Accessory Protocol (iAP)3rd Party LibrariesOverview Official information about this protocol is restricted by Apple to people who have joined the MFi program. Therefore, I can’t mention anything of this page which isn’t public knowledge. You can get to Apple’s MFi landing page here. iPod Accessory Protocol (iAP)  This is the protocol you can use … Continue reading Made For iPod/iPhone/iPad (MFi)
ContentsCurrent SharingAll microcontroller-related programming stuff is found under Programming->Microcontrollers. Current Sharing When driving large loads, you can normally tie many microcontroller GPIO together for increased output current capability. This is because microcontroller GPIO have a comparatively large and consistant (from one pin to another) output impedance. This output impedance (well, resistance at DC levels) servers … Continue reading Microcontrollers
Miller Effect
The Miller effect causes disruptions in the rising and falling of a MOSFET’s gate signal. Like this:Like Loading...
PCB Fault Finding
ContentsSolder BridgesFlux ResidueSolder Bridges Solder bridges are unwanted flecks of solder that cause shorts between two or more tracks on a PCB. Flux Residue PCB soldering flux is designed to be as PCB-friendly as possible, but flux residue from soldering can still cause problems in the long run (e.g. accelerated corrosion, moisture absorbtion leading to … Continue reading PCB Fault Finding
Power Management
ContentsOverviewDisabling Sections Of A CircuitThe “Suicide Switch”UVLO (Under-voltage Lockout)Stabilising UVLOVoltage/Current/Power Monitoring Overview Power management is a big design consideration of battery powered and eco-friendly mains powered circuits. There are many ways of saving energy, some of the commonly used techniques are: Switching of sections of the circuit when they are not needed Slowing the clock … Continue reading Power Management
ContentsOperating ModesEdge-Aligned (aka Asymmetric)Centre-Aligned (aka Symmetric)A Warning About PWM And OscilloscopesOperating Modes PWM hardware peripherals may not support every one these modes. Edge-Aligned (aka Asymmetric) Edge-aligned, the most common (and usually the default) operating mode for a PWM peripheral, is when one edge of the switching from on/off is aligned with the edge of of … Continue reading PWM
ContentsOverviewAcronymsFrequenciesLow Frequency (LF)High Frequency (HF)Ultra-high Frequency (UHF)Microwave Frequency (MF)Power ConfigurationsPassiveSemi-ActiveActivePower LimitationsReadersModulesChipsTagsPassive IC’sInlays/LabelsCablesMetal CompatibleAntennasPropertiesLinear Polarization (Dipole)Circular PolarizationStandardsEPC Global Class 1 Generation 2 UHF Air Interface Protocol Standard “Gen 2”ISO/IEC 11784/11785ISO/IEC 14443ISO/IEC 15693ISO/IEC 18000-3ISO/IEC 18000-6CRecyclingRFID SoftwareRFdumpManufacturers/SuppliersExternal Links Overview RFID (radio-frequency identification) is a wireless method of transmitting data between a reader and tag, for the purposes of … Continue reading RFID
Smith Charts
ContentsOverviewTerminologySolving Impedance Matching ProblemsSeries InductorsSeries CapacitorsParallel InductorsParallel CapacitorsTransmission LinesWhat If My Point Is Outside The Chart?Online Calculators Overview Smith charts are used to display RF-relevant information about a particular circuit, device, or antenna trace. Smith charts show information such as the real and imaginary parts of both impedance and admittance and the reflection coefficicent (S11). … Continue reading Smith Charts
Snubber Circuits
Contents RC SnubberHow To Choose R And CExternal Resources RC Snubber Non-dissipative Passive How To Choose R And C Choose a capacitance that is larger than the circuit capacitance. Choose R to match the impedance of the LC components. External Resources Snubber Circuits: Theory, Design and Application by Philip C. Todd is a good read. … Continue reading Snubber Circuits
Temperature Sensing
ContentsTemperature Management of ComponentsDefined Temperature RangesTemperature Management of Components The behaviour of electrical components is highly dependent on the temperature. Almost always you will see performance measures of data sheets such as resolution, accuracy and speed decrease when specified over a larger temperature range. Temperature fluctuations can also damage components by repeated thermal expansion and … Continue reading Temperature Sensing
Thermal Management
ContentsThermal ResistanceInaccuracies In The Thermal Resistance ModelHeat Flow CalculatorList Of Component Package Thermal Resistances Thermal Resistance Thermal resistance is way of modelling the thermal behaviour of an object in a way analogous to calculating the current through a resistor by measuring it’s voltage. The equation is given by: $$P_D = \frac{\Delta T}{\sum R_\theta}$$ where: \( … Continue reading Thermal Management
Voltage-Level Translation
The uses of voltage-level translation on circuit boards, and example schematics using a discrete MOSFET-based design.
Voltage-To-Current Converters
ContentsOverviewHowland Current SourcePre-built ICsXTR111XTR117DigiKey Search Overview Voltage-to-current converters are circuits which convert an input voltage into an output current. The output current is usually proportional to the input voltage, over some suitable range. Many of these circuit designs use op-amps. Please see the Op-Amp page for more general information on operational amplifiers. Howland Current Source The Howland current … Continue reading Voltage-To-Current Converters