SawSafe

1. SawSafe Prof. Omid Oliaei Chad Baldi Julian Salai Linwood Williams Allan Maina

2. Background Chainsaws have long been one of the most dangerous hand-held tools in the landscaping industry. Currently, there are mechanical safety systems on some chainsaws such as the kick-back breaking mechanism. When using a chainsaw with this device, the operator’s hand must be located on a specific area of the chainsaw in order for the kick-back brake to function properly. This device relies on the operator’s competence in using the chainsaw and also doesn’t prevent all chainsaw related injuries. Our goal is to design and implement an electrical sensing system to supplement the existing mechanical braking device. This system, known as SawSafe, will detect the operator’s proximity to the saw’s blade and quickly stop the chain.

3. The Deliverables • One working SawSafe prototype that cuts dry wood and not human flesh • System status and warning indicator • Operation manual • Wiring/Circuit diagram • Complete timing profile including: • Time delay for saw to stop moving • Trigger delay from sensor chip • Parts list and assembly drawings • Cost vs. Benefit Analysis

4. Principle of Operation The design will incorporate sensors in the saw’s bar that will monitor changes in the electric field around the chain. These changes induced by human capacitance will be processed digitally to determine whether or not to stop the chain. This will also update the system status indicator keeping up to date with what’s happening around the blade.

5. User Interface/Inputs/Outputs The user interface is the operation of the chainsaw accompanied by the following inputs and outputs. Inputs: • Feed from the sensors on the chain bar • A reset mechanism to re-engage the chain and reset the electrical system Outputs: • System status display • The stopping of the chainsaw when the operator comes in close proximity to the blade

6. Acceptance Tests/Cost • The saw will be able to cut wood under normal operating conditions. When the blade is dangerously close to the operator, the blade will stop moving. • For demonstration purposes, a foot-long wiener will supplement human tissue • The status indicator will provide the correct state of the saw during operation • As for cost, the current goal of out team is to remain within the provided six hundred dollars

7. System Block Diagram PCB Sensor Circuitry Saw Bar Sensors User Readable System Indicator A/D User Reset Lever Mechanical Braking System Programmable Microcontroller Solenoid

8. Design Alternatives • Sensor chip options and how the handle the following issues: • Interference from engine’s magneto • Response of chain stopping • Implementation of the different ideas (mostly on the sensing mechanisms) • Chainsaw (electric vs. gasoline) • They both have the mechanical kickback system • Different in their power sources • Sparkplug vs. an AC motor affects the implementation of either chip. Particularly in the noise factor • Power source for electronics • Possibility of using a battery • Exploring the idea of power from magneto

9. Proposed MDR Specifications • Analog aspect of design • Test circuits of prospected IC’s (Bread boards) • Determine sensors to be used (new IC has little test information available) • Test chainsaw for noise (primarily for sensor interference) • Use collected information to formulate mounting design of sensors onto chainsaw bar

10. Points of Consideration • Effects from different conditions such as: • Gloves and how they change readings from the sensor • Boots and the different surfaces the operator walks on. (Does the body’s capacitance change from surface to surface or boot to boot?) • Wet vs. dry wood. How do these readings relate to those from human flesh?

11. TheEnd