Wondering if this is possible. Can I somehow use Arduino to trip a SPST 12V DC relay using a passive NFC tag? Or possibly a Bluetooth connection from a cell phone? Also - what would the power consumption be like on this setup while in "standby"?
For my gas-powered motorcycle. I'm already keyless - I have a mechanical switch that I use to trip an existing relay to turn the bike "ON" and activate the ignition circuit, but I'd like to replace the physical switch with an NFC tag and NFC reader controlling the relay (or a Bluetooth setup). Don't want it to drain the bike's battery while not in operation though. Thoughts?
Sure... have the Arduino interface with an RFID reader, and when it finds the correct tag switch on a relay. Very simple.
To not drain your bike's power supply you at least have to go barebones (i.e. get rid of the Arduino board overhead), use power saving techniques such as sleep (just wake up every 0.5 seconds to check the reader), and a low-power RFID reader to match. Maybe even add a physical switch to switch off the system when not in used for a long time (e.g. when parked at home for the night or even a few days).
wvmarle:
Sure... have the Arduino interface with an RFID reader, and when it finds the correct tag switch on a relay. Very simple.
To not drain your bike's power supply you at least have to go barebones (i.e. get rid of the Arduino board overhead), use power saving techniques such as sleep (just wake up every 0.5 seconds to check the reader), and a low-power RFID reader to match. Maybe even add a physical switch to switch off the system when not in used for a long time (e.g. when parked at home for the night or even a few days).
I would be totally fine keeping the physical switch to conserve power. What about Bluetooth? Possible to energize relay if within range of Bluetooth phone?
Of course. Bluetooth acts here as just an input. A relay is an output. The key strength of Arduinos is taking specific inputs and turning that into specific outputs. But it's not going to be exactly low power that way of course, with the power needed to run that bluetooth transmitter.
Just be aware that "within range" is a very ambiguous actual distance. Can be as little as 1 meter, can be as much as 100 meters.
Start researching what you want/can do; look at different hardware options (physical size will matter); and get a prototype working on your bench with an Arduino and breakout boards for the various components you may want to use.
When that's working reliably (just replace that relay with an LED while testing) it's time to look into using barebones processors (so without bootloader, without USB connectivity, without built-in regulator, and all the other goodies and protection an Arduino development board comes with). You may consider an ATtiny for less size. Build it on a solderless breadboard. When all works, try replacing the LED with the actual relay, make sure it still works (power supply issues may pop up).
We're a few months into the project by now.
Next step: power supply. Automotive power (so also motorcycles) are notoriously noisy and need very good filtering, decoupling, overvoltage and voltage reversal protections.
Then, time to look how to build everything onto your motorbike. Find a suitable container (water/weather proof etc).
Now you know how to program the chips, have your circuit working and tested, software (mostly) finished, and the actual relay working reliably, it's time to get out the soldering iron, and solder everything firmly onto a piece of perfboard, sized to fit in your container.
Then test again, and when confident it all works reliably build it onto your bike. Work regularly on it and you should be able to have it done by next summer's biking season.