Basic build

The basic Fochica build supports a maximum of one parent connected at the same time, one child seat with two specific sensors; a capacitive sensor and an on/off sensor at the chest buckle. This is the recommended build to start with, especially for beginners.

This build requires no or minimal changes to the default Fochica Arduino code that is available on GitHub.

Requirements

Skills

• Basic Arduino experience. Specifically with the Uno. It is assumed you know how to build basic circuits and upload sketches/code. If this is your first Arduino project look at the getting started guide.
• Basic Soldering skills are recommended. Preferably you will solder connections where relevant but you can also twist wires, use connectors, secure stuff with electrical/sticky tape and use a breadboard. Just understand that your connections might be less reliable if you are unable to solder.

If you feel that you lack the skills, perhaps one of your friends loves to build electronics and could help you. You can also seek assistance in your local maker or DIY space.

Equipment

• PC with the Arduino suite - for programming the Arduino
• Android smartphone with Bluetooth Low Energy (BLE) - for interfacing with the device
  • iOS support is in the roadmap, please sign up for a notification when it is available

Tools

• Digital Multi Meter - highly recommended - to troubleshoot the circuit and to measure values of parts
• Soldering tools - recommended - for making good electrical connections
• Crimper and crimp plugs or connectors of various size - optional - might be useful for connecting parts

Parts

See link on each part for a part selection and shopping guide.

• Arduino Uno - can be any working Arduino Uno or a clone
• HM-10 BLE module (or compatible clone) - must have a STATE pin
• Passive buzzer - one that can be driven by an Arduino
• 7-25+V to 5V step-down buck converter module - preferably one that is efficient at low currents
• Breadboard / perfboard / protoboard
• Resistors
  • 1kΩ
  • 10kΩ, a few
  • 20kΩ, a few

Materials

• Wires
• Aluminum foil - for the capacitive sensor

Optional parts

• Logic level converter - if your BLE modules needs one and you choose this method
• NPN transistor - if your passive buzzer needs one
• Chest buckle sensor - if you want a second sensor on the seat for improved reliability
  • Chest buckle - if you don't have one or if you don't want to mess with your existing one
  • Magnetic reed switch - set of reed and magnet, such as ones used for doors or windows
• Power source
  • Cigarette/Cigar lighter plug - if you want to power from the cigar socket/receptacle
  • Fuse tap - if you need to rewire your cigar socket for constant power
  • OBD‐II plug - if you want to power from the OBD-II socket
• Misc connectors, plugs - whatever you want for your layout
• Capacitors
  • between 10µF and 47µF - for improving stability of power supply and wireless modules

Planning

You can consider installation requirements from the start or you can build a device in the "lab" first and then adapt it for car installation. If you are planning to assemble and test the device outside of the car first, skip the power related steps and just power your device via the Arduino USB port. Once satisfied with the operation in the "lab" you can come back to plan the installation in the car.

Before starting to assemble the parts, think where each part will go in the car.

Read the power source guide to understand how you will be powering the device.

Understand and decide on placement of the power cable, the device, sensors, etc.

Measure lengths of the different cables, such as the power cable and sensor cables.

Building the device and sensors

Work in progress

Electronics

Software

Installing the App and testing

Installing in the car