Matt Switzer (ME)

Tyler Josselyn (ME)

Evan Hall (EE)

Phil Floroff (EE)

Faculty Guide: Sarah Brownell Customer: Fermin Reyegadas, Fundacion Cantaro Azul

Overview • Project background

• Planning

• System design

• Testing

• Conclusions

• Recommendations

• Questions

Project Background

• Existing UV water treatment system

• Gravity fed

• Weak local power grid

• Objective:

– Detect failure & protect clean water

Customer Needs • Prevent contamination of clean

tank during given failure modes: -Power outage -Brownout -Blown UV bulb • Warn kiosk operator of failure • Allow for independent UV

chamber operation • Made from materials available

in Mexico • Require few consumable parts • Maintain 5 L/min flow rate per

chamber • Low cost solution

Engineering Specs

System Architecture

Control Board (PCB)

Irrigation Valve 1

Irrigation Valve 2

Water Flow Control

UV photodiode 1

UV photodiode 2

Failure Detection

Warning Speakers

LED System Indicators

Operator Interface

Valve Assembly

• Irrigation valves

• Solenoid/diaphragm

• Low flow, low pressure operation

• Fail Closed

• Easy integration

Dual irrigation valve assembly

Electronics

• The printed circuit board shown here controls the valves and warns the operator that there is a failure

• Requires some trained assembly (to be assembled by PCB assembly service)

Electronics Enclosure

• The PCB was designed to fit into a small conduit box that can be mounted in the kiosk, near the valves

• Speakers and LEDs are mounted externally on box

Photodiodes

• Capable of detecting all failure modes

• Design allows system prevents flow restart until safe level of UV output is reached

• No UV Chamber draining will be necessary

• Automatic restart after power loss

• Simple installation in chamber

Photodiode

UV Bulb

Warning the operator

• Failure – Speaker sounds and red LED lights, both powered by 9V battery

• To turn off the speaker and red LED, the operator can flip a switch

• Once the problem is fixed, a green LED will light, the switch is flipped back

• The system also includes an amber LED that turns on when the battery voltage is low

Speaker

System Ready Switch

Test Rig

• We built a test rig to simulate the gravity fed system in the actual kiosks

• The two irrigation valves run in parallel to two UV chambers

• We are able to simulate a power failure by pressing the red button seen to the left

Test Results

• Gravity fed system achieved a flow rate of 4.5 L/min

• Inlet/outlet height differential must be >4 ft.

• Circuit board closes valve when UV light is not present

• Speaker/LED gets attention of operator at > 8 meters

• Backup alarm/LED will run for 17 consecutive hours on one 9V battery

• Valves seep 15.5mL/hr average

Budget

MSD Costs Budgeted Actual

Test Stand (tanks, pump,

structure) $400 $184.39

Electrical (wire, circuits,

PCB) $100 $202.63

Plumbing (Pipe, flow stop

mechanism) $100 $63.10

Total $600 $450.12

Costs to Customer Quantity Total Price

Valves 2 $34.10

PCB 2 $66.00

Photodiodes 2 $44.88

LEDs 6 $1.96

Speakers 2 $4.58

Wiring As

Necessary ~$10.00

Assembly - Need Quote

Other Parts - $40.71

TOTAL per Kiosk $202.93

Conclusion: Successes • Independent chamber operation

– Using two independent circuits

• Under budget

• LEDs and speakers will get operator attention

• Valves stop water flow

• Auto-restart when safe UV output level sensed in chamber

Conclusion: Challenges • Valve leakage due to dirty diaphragm

• Mousetrap valve concept

• Getting system to work on one circuit

• Speakers not as loud as expected

• Couldn’t incorporate rapid power on-off delay • Deemed unnecessary

• Customer will not be able to fix electrical issues in field

• PCB assembly for customer

Recommendations

• 2 independent circuits

• Periodic diaphragm cleaning

• Test correlation between UV output and photodiode voltage

• Valves located close to UV chambers

• Upon install, ensure valve seals water flow

Questions?