I am looking for a new technology to support disabled individuals who use switches to interact with their environment - in particular, computers. Most assistive technology (AT) switches are wired and plug into a switch adapter that converts the circuit closure to a keyboard event. Wireless AT switches typically use Bluetooth as their communication protocol - that’s
serious overkill for carrying an open/close signal and power-hungry to boot. My idea is to put an RFID tag in the switch and shield/unshield it when the switch is activated. No power. No wire. The switch can be 3D printed for about $3 and the tag can be had for pennies.
It is great to see you put focus on this area to help disabled individuals and I had quick read and looked at your website. There are 2 assumptions that I would challenge:
The read distance of RFID. With a good power supply and external antenna + normal tags one can get up to 7 meters in free air. Indeed there are RFID systems that can work on larger distance, but the cost is high ( I expect exceeding the budget). It is not only the TAG, but also the special antenna + strong power supply needed. As this is a the strong signal one need to check that it is not exceeding any safety levels AND not interfering with other sensors/devices that might be around.
The cost of an Bluetooth switch. While I expect it is true to many “off the shelf” that they are expensive ad power hungry, but one can build a Bluetooth switch easily.
a. Take an Edge-board and build a switch around that. The software to load on the board is easily build around BLE/Bluetooth and it runs on a battery with low power usage
b. look at a LORA device. Lora is aimed at small packets, low bandwidth, low power usage. Build a switch around that and software is not difficult to build. Another Lora board can act as receiver OR you will need a separate receiver (around 60 euro). Lora is aimed to work up to 300m free air.
C. An (upcoming) alternative is NB-IOT, which works on LTE-M (say part of GSM). It is similar to Lora, but you do not need a separate receiver and use a bit more power. That said, it is not available everywhere yet and requires a subscription with a phone company
I’m only looking for 1 to 2 meters. I think I’m seeing that I will need to have an off-board antenna for that. What is the minimal antenna (and cable to connect it to the board) that will provide that read distance?
I need to be able to get the tag ID to a PC to prove the concept. What minimal set of hardware would that take?
I agree that I could look at other technologies to accomplish this task but I’m “excited” about proving it’s possible to create a no-power, sub-five-dollar switch. “No-power” is important because it’s a level of maintenance that therapists just don’t have time for. Also, I’ve personally experienced difficulty “pairing” Bluetooth components. This approach would eliminate all that troubleshooting.
Strangely, the point may be moot for now with the board on back order and the corona virus shutting down China.