Hardware Design, Faster
Reusable KiCad design blocks, free electronics calculators, and expert hardware design services.
What Circuit Issues is
Circuit Issues is run by hardware engineers who design, build and ship embedded boards, and publish what they learn along the way, failures included. The site has three parts: free calculators for the questions that come up on every board, KiCad 10 design blocks taken from our own hardware, and the Hardware Clinic, where an engineer reviews your design for a fixed price before you order boards.
The tools and blocks come out of our own projects, such as an ESPHome air-conditioner controller, a solar greenhouse controller and an EV charger build, and the build logs show how each one went.
Free engineering calculators
They run in your browser, need no account, and keep your data on your machine.
Battery life & current calculator
Build the power budget of a multi-state device from its rails, regulators and loads, and see the average current and battery life, with optional solar charging.
Voltage divider calculator
Pick E-series resistors for a target output, then check divider current, resistor dissipation and the worst-case tolerance window.
PCB panel utilization estimator
See how many boards fit on a JLCPCB, PCBWay or Eurocircuits panel and how a few millimetres off the outline changes the count.
All tools, including the web serial monitor and the ATSAMD21 pin configurator →
KiCad 10 design blocks from real boards
Schematic and layout you drop into your own project, with the design notes and BOM that go with it.
ESP32-S3 Core (WROOM-2)
Free KiCad 10 design block: ESP32-S3-WROOM-2 (16 MB flash, 8 MB PSRAM) with native USB-C, ESD protection, BOOT/RESET buttons and 22 GPIOs on labels.
TPS562203 Buck 2 A
KiCad 10 design block: TI TPS562203 synchronous buck, 4.5–17 V in, 3.3 V / 2 A out (4.93 V option), with optional reverse-polarity diode.
BQ24650 MPPT Solar Charger
KiCad 10 design block: TI BQ24650 MPPT charger for a 12 V lead-acid battery (14.1 V) from a solar panel up to 28 V; status and PV-voltage outputs.
Hardware Clinic: a second pair of eyes before you order
Many respins come from small things: a connector with the wrong pitch, swapped TX and RX, a strap pin left floating. The Clinic catches them before the boards are made. The pre-fab check costs €690 with a 72 hours turnaround and returns an annotated PDF and an issue list. The full design review (€1,890) adds the layout, manufacturability and an EMC risk register. Prices are fixed and shown up front.
See the Clinic servicesEverything You Need
From reusable circuit blocks to free calculation tools and expert consulting.
Reusable Blocks
KiCad 10 design blocks from our own hardware: ESP32-S3, power, sensing and switching. Stop reinventing the wheel.
Free Tools
Battery life calculators, current estimation tools, and more. All free, no signup required.
Real Projects
Learn from documented builds, debugging sessions, and production designs, such as the ESPHome AUX AC controller build log.
Don't Want to Route It Yourself?
PCB Composer will assemble our template blocks into a single routed board. Select your tiles, configure connections, and receive Gerbers, BOM and assembly files.
Select Your Tiles
Choose from power supplies, MCUs, sensors, and connectivity modules
Configure Signals
Map power rails and communication buses between modules
Get Production Files
Receive Gerbers, BOM, and assembly files ready for manufacturing