P19363: Player Piano
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Integrated System Build & Test

Table of Contents

Team Vision for Integrated System Build & Test Phase

This iteration, we were focusing on the full-scale build and testing of our complete system. Goals included mounting all the solenoids on the rack, extend the testing of the solenoid system to a larger number of keys, and integrating the feedback system and showing feedback on the screen. Work was begun on the web interface, and songs can now be selected for playback. The plunger extensions were made and prototypes were made with two different brands of epoxy to stress test under high heats to check for melting glue. The design of the solenoid control circuit was finalized, and a 12 key model of the final circuit was constructed and tested. A song, ‘Hot Cross Buns’, was successfully played on the 12 key piano.

Test Results Summary

Subsystem Fabrication: Manufactured first solenoid control final circuit for 12 solenoids and was able to vary the volume level while playing “Hot Cross Buns”.

Contoll Circuit

Contoll Circuit

Widened gap for solenoid extenders in the flat brackets for upper solenoid rack using a vertical mill. Brackets still able to hold solenoids without deforming even with much smaller support area.

Solenoid Bank

Solenoid Bank

Finalized dimensions for solenoid extender. Cut white abs rod and black abs tube to length using band saw, box cutters/knives and pipe cutters. Increased bore of black abs tube to an eighth of an inch using lathe. Glued pieces together and added orange pla end caps.

Solenoid Extender

Solenoid Extender

Created guides for sensor rack as suggested in previous design review. Will permanently attach to sensor rack holders once testing is completed.

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Angle Bracket

Angle Bracket

Test Results: Solenoid Stress Testing
Solenoid Extender 2

Solenoid Extender 2

We performed a heat stress test to test two brands of epoxy for plunger to plunger extension bonding. Loctite and Devcon were chosen and rated for up to 180F and 200F respectively. The reason for the test was because Loctite is a surefire plastic to metal bonder. While Devcon was not necessarily for all types of plastic and metal bonding. Loctite ultimately softened and a little bit of excess was caught in the solenoid channel and set after the solenoid cooled down and sealed the channel. Devcon performed much better and did not soften.

Teensie transmission

Teensie Setup

Teensie Setup

The timing issue for the transmitting of the data between teensies has been addressed. The teensies were looked at a 9600 with an added delay to assure that we could see it. The total time was roughly a second from teensie to teensie.Since the teensie has a top baud rate 2000000 with a 0% error rate the timing is within scope.

Risk and Problem Tracking

Did not have a workspace. Borrowing tables and blocking the hallway was frowned upon. Office repurposed workspace for a team that meets in another section and have given us one of the spare workbenches. Raspberry pi would not boot. Works now, but was a significant setback. Defective mosfets. When integrated into the solenoid control circuit, a defective MOSFET caused malfunctions that took several days to find. We tested all of the other MOSFETs and found one other defective unit. High temperature hot glue softening within minutes of stress testing. Solenoid extender dropping out of position, glue rolling into barrel of solenoid and prevent plunger from reaching full stroke as a result. Stopper (i.e. neoprene washers to dampen clicking) adhesive (super glue [loctite super glue extra liquid control] and extra boost from activator [bsi insta-set accelerator]) recommended by machine shop not bonding well to stoppers. Stoppers fell off of solenoid plungers within minutes of stress testing. Currently searching for another steel to neoprene adhesive. Having issues finding another adhesive that is suitable for flexible material and doesn’t drip if bond breaks from high temperature. Sensors deformed when soldering, the deformation caused erratic responses from the key presses. Being so annoying that another team comes in the dead of night and cuts our wires

Future Risks/Risk Management: Applying epoxy onto plunger and plunger extension must be done carefully as once the epoxy cures it will not come off without acetone. Also excess epoxy must be wiped off as prolonged contact with the heated parts of the solenoid may soften the epoxy and cause the plunger to be glued to the solenoid after cooling down.

Frame moving while solenoids are being actuated, this could be because weight on frame is off centered and above center of gravity. Should check whether this issue will be solved when lower rack of solenoids is installed. If issue persists, must brainstorm new methods to stop frame shaking while songs are being played. Previous solution, with longer/weighted stands, made placing frame in piano difficult.

Burning through supply of extra solenoids. A couple of the solenoids may have been defective. They deformed internally and or shorted early during heat stress testing whereas other solenoids have withstood heat stress testing for a couple hours. These problems have stopped the plunger from reaching full stroke. These problems may be resolved by lessening play time or volume level.

Plans for next phase

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