Nervous Machine

The design and assembly of Nervous Machine for ECE 577j, Technolory: art and sound design at Wichita State University, College of Engineering.

My hope through this page is to give enough detail that you could build a similar the project from this, but hopefully with less difficulty than we have had! Note, some of the pictures are of poor quality, but should convey the idea. If there are any questions that are left unanswered, please leave a comment, I will try to respond in a timely manner. Many thanks to my team members: Steve Atwood, Paul Chen, and Tim Force. Here are their sites which will offer additional information:

for Steve:  http://atwood.wordpress.com/  

for Paul: http://paulchen.wordpress.com/

for Tim: http://dagentooboy.wordpress.com/  

1) Design: Overall design comes from Steve. The idea being that people become uncomfortable around large machines, but that the machines also bemome uncomfortable (ie. Nervous) around us! So his idea is to create a machine that shows some obvious sign of nervousness when people come near. Several questions and difficulties arise from this, like: What kind of actions should the machine have? How do we give it an imposing size? What should it look like? What automation should we have? What sensors and electronics do we need? 

After a few debate sessions we came up with solutions to all of the afore mentioned questions. For actions, we decided on a shivering motion only, with the option of adding more if time allowed. We considered rotation and lighting, but felt it might delay the completion of the project past the due date. To give it an imposing size, Steve came up with having multiple tentacles on its back that projected up, like a porcupine. A far as the body shape, something like an angular teardrop was decided. For automation, we would use Ultrasconic sensors to detect the proximity of people around it. These would give us a relatively wide detection pattern when compared to an Infrared sensor while giving us precise distances. This selection would add some complexity and cost to it but would deliver a better result. Lastly for the electronics we will use a logo chip to control transistors that will read from the ultrasonic sensors and supply power to pager motors in the ends of the tentacles.  

   conceptual body design

   Here is a possible idea of the concept

2) Manufacturing:

Tentacles: Aluminum rods of 1/8" ID were selected and cut to 6' lengths. These rods were painted red, then aged by scuffing with medium grit sandpaper. Ends were made of a 1/4" ID tubing cut to 3" that was polished and slip fit on both ends. The bottom was lathe turned down to a diameter that would accept a brass threaded fitting. Then that fitting was pressed onto the assembly. On the upper end, an additional tubing of 3/8" ID and 3" lenght was slip fit to the end, this would give a large enough ID to accept the motor. All slip fits were crimped using an industrial crimper, to create a one piece solid tentacle. Later, the brass fittings would be aged by using a chemical that would give a oxidized finish.

  Tentacle layout

        Assembly of tentacle, this was to originally be repeated 100 times, later it was reduced to 80, to fit the project needs.

Body: The body was fabricated by Steve and made of 1/16" mild steel. Due to his access to a CNC plasma cutter, all parts were produced using that method. So, the shape was defined in the computer and then flattened into a pattern that the computer could cut. Then he folded the cut shape at the predefined perferations into the final 3-D shape. Then using a MIG welder he stich welded all the sides together, making a hollow shell that was very durable. He left access panels on the front, bottom, and back while also having locations for the ultrasconic sensors. Later he designed cover plates for all access panels and mounts specifically for the sensors. At the end of the project it was decided to locate power switches and the serial cable on the access panel at the rear. The body was then painted yellow and aged, again using medium grit sandpaper. Threaded bungs were MIG welded into the top that would later accept the tentacles. In each bung, a brass threaded coupler was inserted. and finally four handels were placed around the sides to ease movement of the assembeled machine. To provide an aged look to the couplers, handels, and misc. bolts / screws, a chemical process was employed, called "patena." This process involves stripping coated parts using an acid. Then oxidation of the metals were accellerated using a product called tri-brown. Finally, all parts were rinsed, dried and some were wax coated to prevent further oxidation.

 cad layout.pdf   layout and assembly of the main body

     Body prepared for electronics and assembly.  

3) Electrical:

Sensors and brains: electrical and automation is a cornerstone in this project. so we wanted to have a well functioning yet simple device that required little intervention when on display. The overall controll will be from a pic micro controller, that will be programmable on the fly by computer, through a serial cable. this controller will be loaded with an open source software called LOGO that is readily available through the internet, see link on the main page. as mentioned before, ultrasconic sensors will be used to detect when people are nearby. Because of the cone of detection associated with these sensors, which appears to be about 20-30 degrees off center, we will need to use three. locating these sensors about 45 degrees apart will give a complete coverage of the entire front of the project. Also the nature of the sensors will allow us to have about a 9' range and quite good resolution between about 1'-9'.To connect these sensors, four leads are required; power, ground, trigger, and signal.Trigger will be activated by the LOGO chip, then it will measure the time it takes to receive a return signal from the sygnal wire. We will have all three sensors sharing the same signal input to minimize connections. To give movement to the project, each tentacle will have a motor in its end. all of these motors will be tied off into banks, or zones of 10 each. The logo chip will have control over two zones at a time.

Motors: To power these motors we will use an array of 8 MOSFET transistors, each will allow us to power on the motors with the LOGO chip seeing almost no current draw. each transistor will have one connection to the positive power from the battery and the other connection to the positive terminal of the motor bank. For the motors, we will need to wire them specifically for this application since our battery powering the machine is making 6.0 volts, but the motors are rated for 3.0 volts. To do this we will will need to connect our motors in series pairs, then inside each pair we will place 5 motors in parallel. This configuration will apply the proper voltage while giving us only two terminals per zone of motors, see schematic. To make the motors active, much work was needed on them. each motor had 2" stranded leads soldered on an then heat shrink tubing applied. Then each stranded wire was extended with about 8' of solid 22 ga wire that was also soldered and heat shrink tubing wrapped, Paul an I enjoied most of this work. Finally each motor's weight was increased by soldering on a small piece of lead. See picture in part 1, tentacles. 

Placement: To maintain a neat home for the electronics, Steve made a plate that is accessible from the front of the machine. On this plate, centrally located we have the LOGO chip with lts connections, then on each side we have a bank of four transistors. All electronics are surface mount soldered to boards, this should give an orderly appearance and be durable. This configuration will provide a tidy location for everything and allow for ease of part changing. The 4 lead-acid batteries that we are using will fit inside the main body, and power switches were later added to the rear of the body. Having averything internal should give a clean look to the machine once it is finished!

 Schematic.pdf

    electronics  installation and assembly

 MOSFET assemblies with Steve's Heatsinks

4) Powering up:

Initial reactions: When first powering on everything, we tested each individual zone of motors for current draw and functionality. Most worked well but some seemed to require a relatively large current of 2 amps. Continuing on we loaded Tim's software into the controller to see if we could get good readings off of the sensors. After some time the sensors were working well, as were the motors, so we allowed the LOGO chip control over the motors. To our surprise, there were difficulties with the unit functioning correctly when all parts were connected. After trying two sets of transistors, a handful of diffeent configurations, a full day of work, and four tired guy's ideas, we were able to get about half of the motors to run when controlled by the logo chip.

Refining: Now that we had a functional model it was time to clean up our act! First on the list was verifing motor connection on the zones that didn't work. During this step we also cleaned up and routed many of the internal wires to give a cleaner, more professional look. We also dipped a few of the motors in laquer thinner to remove any flux that could have creeped inside them. Now things looked better but, we again had a non-functioning project!

Trouble shooting: Now we had developed a much more serious problem, Transistors burning up! After some searching, it was found that the current flow through each motor set was skyrocketing, and in-turn damaging FETs. It was eventually attributed to heat shrink on the motors wearing through. Which was painstakingly replaced motor by motor. Before each motor was re wrapped, each one had to be cut down with a dremel tool to keep the same problem from happening again. This is where the project fell together. Now that all of the shorts were worked out, we could actually configure it to function properly without worring about parts catching fire. Also, with the fully functional unit, we were seeing a total current draw of about 2.1 Amps. Finally we were blessed with a project that was functional and reliable, all openings were buttoned up, and it was ready to go for viewing.

 A late night trouble shooting.

 Final Friday debugging

 Motors getting dremeled and re-wrapped

5) My opinions: Over all, I am quite satisfied with the Nervous Machine. Physically, it is a heavy, large, and overbaring machine that suits the roll it was designed for. The fit and finish of it is remarkable and it looks professionally built. The aging processes applied to it, give it the appearance that it has been sitting in some industrial shop collecting dust for years.

As for functionality, it works well and has few issues that can't be solved by turning it off and on. Nervous Machine reacts to anything coming within 8 feet of it. It starts off with a little rattle and shake and progresses to a full-bore visual and auditory expierence when you get close. A somewhat unexpected result of the vibrating tentacles is that they are equite noisy, which just adds to the expierence. As you back away it calms down, making it obvious that the person's presence is what is causing Nervous Machine to act this way. Another important part of this project is how the unit reacts so quickly to someone's presence, there is no delay! This also adds to the person understanding that they are causing the reaction.  

  Switch plate with serisl connection.  

6) Afterthoughts: looking back there are a few changes I would have made that would have simplified the project or make it more reliable. 

i) To power the unit, I would have employed a stable power source, like used for a computer. this would have allowed for a permanent mounting inside the unit and have eliminated the need for charging.

ii) I would have looked into using a negative ground for the chassis (like in automobiles), this would have reduced the the wiring signifigantly and allowed for a clean ground. 

iii) Using a single motor to vibrate a plate that all of the tentacles were attached to could have greatly simplified the entire project, and could of delivered the same results.

iv) I would have created a dedicated wiring harness that ran the entire length of the machine, allowing for a tidy internal appearance and eliminate possibilities of wire chaffing and shorting. 

7) final thoughts: The project went quite well thanks to my team members. They were all instermental in bringing their own specialties to the table and seeing that Nervous Maching was all that it could be. Despite some difficulties in the end wrapping all of it up, the finished, working project was spectacular. This project has proven to be avalueable learning expierence for the views of art, sound, and technology.