Project

# Title Team Members TA Documents Sponsor
24 Coat Hanger Light Switch Controller
 Birgit Alitz
Katherine Eaton
 Kexin Hui design_document0.pdf
final_paper0.pdf
photo0.jpg
presentation0.pdf
proposal0.pdf
Kate Eaton (kkeaton2) and El Alitz (alitz2)

PROBLEM: When leaving the house, I often forget to turn off lights, which uses extraneous electricity and drives up living costs.
SOLUTION: When grabbing my coat/purse off of the coat hanger on the way out the door, a sensor in the coat hanger notices that the jacket/purse is no longer there, and communicates with a remote fixture placed over light switches that will physically manipulate the light switches to be "off" in the house.
UNIQUE: There are coat hangers on the market that will already perform tasks to the clothing hung on the coat hanger (such as hangers that will dry clothing), but no hangers that interact remotely with other household implements. In the future, this could be included in smart home upgrades.

TECHNICAL:
HANGER
-pressure sensor for sensing whether there is a coat/purse
-PCB for sensing/control
-Bluetooth or RF communication point
-LEDs as a battery indicators for hanger and fixture
-Watch battery (CR2032) as power source
-printed/plastic housing to protect electrical components on hanger from a wet or soiled coat/purse

The circuit will be low-voltage and DC in order to allow the hanger to be mobile. The pressure sensor, which is probably going to be a form of variable resistance, will control a diode that powers the remote signal. (We don't have a lot of experience with remote signalling outside of with shields -- suggestions here are welcome). This circuit will also power an LED that will turn on when the voltage from the local battery gets low.

LIGHT SWITCH FIXTURE
-SCR for current control
-Bluetooth/RF communication point
-Watch battery as power source
-Insulating housing for the above to isolate from 120V AC system (possibly in the shape of a light switch cover)

This component will physically manipulate the light switch. Upon receiving a signal, this component reads the position of the servo, moves it into the "down" configuration if it isn't already there, then returns to idle. This circuit is also powered by a small DC source.

Previous Commentary:
At the power switch, an SCR may be more appropriate than a servo. There are power conversion concepts to be reconciled.... AC / DC, 120V (at light switch) / DC V??

Honestly, our intention was to make it manipulate the physical switch for two reasons: 1) as a consumer grade product, it seems safer to not go "inside" the house electrical system, and 2) it then is really easy to manually reset if it goes wrong. However, using an SCL and building the functionality into a new light switch cover seems doable. In this case, I'm inclined to still want to build the SCL circuit with a small DC battery just because I have more practice with DC circuitry, and include a "RESET" capability that will allow the light to turn on even if there has not been a signal from the hanger allowing otherwise.
I've updated the proposal above to include this change.

Covert Communication Device

Ahmad Abuisneineh, Srivardhan Sajja, Braeden Smith

Covert Communication Device

Featured Project

**Partners (seeking one additional partner)**: Braeden Smith (braeden2), Srivardhan Sajja (sajja3)

**Problem**: We imagine this product would have a primary use in military/law enforcement application -- especially in dangerous, high risk missions. During a house raid or other sensitive mission, maintaining a quiet profile and also having good situational awareness is essential. That mean's that normal two way radios can't work. And alternatives, like in-ear radios act as outside->in communication only and also reduce the ability to hear your surroundings.

**Solution**: We would provide a series of small pocketable devices with long battery that would use LoRa radios to provide a range of 1-5 miles. They would be rechargeable and have a single recessed soft-touch button that would allow someone to find it inside of pockets and tap it easily. The taps would be sent in real-time to all other devices, where they would be translated into silent but noticeable vibrations. (Every device can obviously TX/RX).

Essentially a team could use a set of predetermined signals or even morse code, to quickly and without loss of situational awareness communicate movements/instructions to others who are not within line-of-sight.

The following we would not consider part of the basic requirements for success, but additional goals if we are ahead of schedule:

We could also imagine a base-station which would allow someone using a computer to type simple text that would be sent out as morse code or other predetermined patterns. Additionally this base station would be able to record and monitor the traffic over the LoRa channels (including sender).

**Solutions Components**:

- **Charging and power systems**: the device would have a single USB-C/Microusb port that would connect to charging circuitry for the small Lithium-ion battery (150-500mAh). This USB port would also connect to the MCU. The subsystem would also be responsible to dropping the lion (3.7-4.2V to a stable 3.3V logic level). and providing power to the vibration motor.

- **RF Communications**: we would rely on externally produced RF transceivers that we would integrate into our PCB -- DLP-RFS1280, https://www.sparkfun.com/products/16871, https://www.adafruit.com/product/3073, .

-**Vibration**: We would have to research and source durable quiet, vibration motors that might even be adjustable in intensity

- **MCU**: We are likely to use the STM32 series of MCU's. We need it to communicate with the transceiver (probably SPI) and also control the vibration motor (by driving some transistor). The packets that we send would need to be encrypted (probably with AES). We would also need it to communicate to a host computer for programming via the same port.

- **Structural**: For this prototype, we'd imagine that a simple 3d printed case would be appropriate. We'd have to design something small and relatively ergonomic. We would have a single recessed location for the soft-touch button, that'd be easy to find by feel.

**Basic criterion for success:** We have at least two wireless devices that can reliably and quickly transfer button-presses to vibrations on the other device. It should operate at at *least* 1km LOS. It should be programmable + chargeable via USB. It should also be relatively compact in size and quiet to use.

**Additional Success Criterion:** we would have a separate, 3rd device that can stay permanently connected to a computer. It would provide some software that would be able to send and receive from the LoRa radio, especially ASCII -> morse code.