If you're like me, you nearly always carry your phone or are frequently at a computer. I often find it more convenient when I can interact with the things around me like the garage doors, car starter, sprinklers, electric blankets, holiday decorations, etc. via my phone or computer.
It is relatively easy to Bluetooth enable many devices. These instructions will explain how I Bluetooth enabled my garage doors and car starter. The implementation is quite generic. Similar techniques could be used to Bluetooth enable many other things too.
The Bluetooth board that was used has at least six different connections that could each possibly control a different thing.
There is a corresponding free Android application that you can download; Daisy On/Off. It allows dynamically creating, labeling, and configuring multiple buttons so that you can easily control the various things that are Bluetooth enabled.
There are risks associated with wireless control and modifying any equipment. You assume full responsibility and associated risks related to your use of this information.
- Bluetooth board - newer plug & play version
- Perf board - approximately 1.1" x 1.5" (29mm x 38mm)
- BS170 N-Channel MOSFET, or similar transistor
- Resistor 1K - 1M
- Wire for hookup - old phone wire works well
- Soldering iron and solder
- Wire cutters/strippers
Step 1: Getting to know the circuit and parts
The Bluetooth board has at least six pins that can be used for general purpose input/output (GPIO). The Bluetooth module on the board operates at 3.3V, however the board has a voltage regulator so that it can be powered from USB power or via other power sources like wall-warts or batteries up to 18VDC. By connecting the Bluetooth module to a general purpose MOSFET switch it can switch higher voltages and currents.
The BS170 MOSFET is a general purpose N-Channel transistor. This means that the switch turns on when the voltage on the gate is positive ~2.1V with respect to the source. The MOSFET source and Bluetooth module ground are connected together so they are properly referenced to each other. The gate of the MOSFET is the control and gets connected to one of the Bluetooth board GPIO pins. The MOSFET is turned on by driving the corresponding GPIO pin high.
When the Bluetooth module is reset or not set as an output, the pin effectively floats - it actually has a weak pull-down. By connecting a resistor between the MOSFET gate and source, we ensure that it always turns off.
Alternatively, if we wanted to turn positive power on to a device instead of grounding it for control, we could connect a P-Channel MOSFET to the N-Channel MOSFET. The source would connect to power, the gate to the drain of the N-Channel MOSFET and the drain to the devices positive terminal. The device would be directly connected to ground. A resistor should be connected between the MOSFET gate and source to ensure proper turn-off.
The Bluetooth board GPIO 3, 6, 7, 10, and 11 default to low upon power-up and will be off. GPIO 8 and 9 default to high upon power-up and will be on. The power-up state of each pin is configurable, see the quick reference manual and/or user manual.