Archive for category: Goliath Generation #1

By: Kevin Moran (Electronics and Control Engineer)

Since the analog output of the receiver is very noisy, my division manager suggested I use a Schmitt trigger which has 2 jobs:

1. It reduces noise from the circuit through hysteresis, the time-based dependence of a system’s output on present and past inputs.
2. It inverts the signal from the detector circuit and creates two thresholds-high and low. By changing resistor values we are able to control the high and low thresholds.

Below is the graph of a generic output using the Schmitt Trigger, as can be seen the signal is inverted, and the noise is relatively gone.

Now the challenge was selecting the correct Schmitt trigger that would work best with our receiver, after testing various resistor values, I made my choice between two sets of resistors.

I decided to go with the resistor values from Trigger 1, because It has a larger gap between the high and the low thresholds. When tested with the Phototransistor it provides a low threshold closer to 0 voltage

All values were taken with multi meter while changing the input voltage

Note: The high and low threshold change when the Resistor value connecting the receiver is changed from 100k ohms to 2M ohms (I did this in order to increase the sensitivity of the receiver)

Testing with Arduino Monitor:

• When light is applied to the photo-transistor and the input is placed through the Schmitt trigger
  • High Voltage= 3.76 V
  • Low Voltage= 0.02 V

In order to make the phototransistor sensitive enough to be able to detect the IR light, I am using a 2 mega ohm resistor from the detector to the 5v supply

Both the high and low voltage thresholds are shown using the Serial Monitor

This is the result.

I also conducted a test on the Schmitt Trigger using a potentiometer

Components for this test:

10k potentiometer

LM358 Op-Amp

Resistors: 100k, 51k, 51k

Capacitors:  10 microF

Arduino Uno

The threshold between a high or low input from this test is 2.6V

As I varied the resistance in the potentiometer I obtained the graph provided in this slide

Based on this experiment I concluded that my Schmitt trigger was ready to be used alongside the photo-transistor.

Below is the result from this test using both the Arduino plotter and monitor

As can be seen again, a very clean signal that has only two outputs a low 0.02v and a high at 3.78v

Sources:

Jeffrey Cool: Division Manager

http://www.ti.com/lit/an/scea046/scea046.pdf

http://pcbheaven.com/wikipages/The_Schmitt_Trigger/

By: Kevin Moran (Electronics and Control Engineer)

In this post we will explore the progression in the components explored throughout this project to make the Laser Tag game possible.

• My first idea was to use a laser diode as the emitter and a Photo-resistor as the receiver.
  1. Pros:
     1. 15 meter range
     2. No Assembly required

• Power dissipation of 75mW

1. Cons:
   1. Dangerous to the human eye
   2. No circuit to build and learn from

Simplistic Laser Receiver build with Fritzing diagrams (Photo-resistor)

• Since we are designing a 3DoT Rover that will be manufactured for children, the laser was discarded. My next idea was to use a simple LED alongside a collimator to simulate a safer laser beam.
  1. Pros:
     1. Safe to use
     2. 3 feet range

• Power dissipation of 60mW

1. Cons:
   1. Beam had a 3 inch diameter from 3 feet distance
   2. Did not meet the “cool” requirement

Red LED with collimator powered by a 4.5V power supply and       220ohm resistor

• The third option to be able to satisfy our requirements for the laser tag game was to use a Photo-transistor as a receiver alongside an IR LED as the emitter
  1. Pros:
     1. Safe to use
     2. Will require PCB board to cancel our noise and filter signal

• Analog voltage output can be manipulated

1. Cons:
   1. Output contains noise.
   2. Range has to be worked on

• Not visible to naked eye

Although the range is not as impressive as the laser, this is a safe device to use, as Infrared Light is not absorbed by the human eye. By using this device I will be able to satisfy the rubric for the PCB schematic design, as I will be adding on a Schmitt Trigger, which will be discussed in the following blog post.

Emmiter/ Receiver

Voltage output using Arduino Analog Pins

This circuit still needs to be filtered out and passed through an Inverting Schmitt Trigger. The Schmitt trigger will filtered out the noise and using voltage resistors there will be two voltage thresholds. Which will then be digitized and sent to the microcontroller for processing.

By: Rickeisha Brown (Manufacturing Engineer)

As a level one requirement, the customer requests to refrain from exceeding a total of 6 hours 3D printing time and not to exceed two hours per printed component. The customer has a project total budget of which ultimately limits the amount of spending power per division. Printing Cost estimates which is of total budget.

Maker’s Society is the organization handling our 3D prints. Their printers can print multiple parts at a time, they’re conveniently located on the campus of CSULB, and are reasonably priced to $5 per hour. Visit their website for more details regarding Maker’s Society and the services they offer: http://lbmakersociety.org/about-us/.

I submitted my design to Carlos Vergara¹, the AESB representative, and informed him of my 6 hour printing requirement. He uploaded the parts to a program which examines each component and estimates total printing time down, to the minute.

Figure 1: The table above shows the trade-offs between strength, quality, low cost, speed vs. layer height. ²

Figure 2: Maker’s Society printing time estimates for the original body with 0.3 mm layer height: 8 hours and 24 minutes.

Figure 2 shows the results for total printing time of Goliath components with 0.3 mm layer height, with 0.2 mm being an ideal layer height based on Figure 1.

This does not meet level one requirement, so we must revert to Plan B: reducing the amount of components which make up our body from 6 to 3 components, sides (2), and cellphone and periscope compartment (1).

Here are the results:

To my surprise, the printing time did not decrease!

I requested that Carlos increase the layer height to 0.4 mm which will decrease printing time and help our team meet the 6 hour printing time requirement. Here are the results:

For 3 components, the total time still exceeds 6 hours. Therefore, I will go back to the drawing board readjust components thickness.

References:

^1-Carlos Vergara, AESB Representative for Maker’s Society, E-mail: carloslbvergara@gmail.com

^2- “What Is the Influence of Infill %, Layer Height and Infill Pattern on My 3D Prints?” 3D Matter. N.p., 10 Mar. 2015. Web. 23 Mar. 2016.

By:  Tae Min Lee (Mission, Systems, and Testing Engineer)

As we get closer to the final product we started implementing the Arxterra Control Panel that will be used for the demo.  The Arxterra Control Panel will be used to control the Goliath and provide a live video feed from an android phone with a periscope.

Setup for Arxterra Application on Android/apple Device:

Going on your android/apple device go to the Arxterra application and click on community (see figure 1).

Now tap the connect button (see figure 2) and wait for the next screen to show up (see figure 3).

Now assign the robot’s name using an Arxterra application on the android/apple device.  For this example, I used TaeML7 as my pilot’s name and robot name as TaeML.

Arxterra Control Panel Setup:

Logging onto Arxterra using your computer type in your pilot’s name you assigned on your Arxterra application on your android/apple device.  For the password you can type in any password you wish for the login on Arxterra Control Panel (figure 4).

Once your login onto to the Arxterra control panel you should be able to see the robot name on the map (ex. TaeML).  Now click on the green man to enter the cockpit of the robot (Figure 5).

Now were in the cockpit of the Goliath where it displays the controls, speed, and battery levels of the Goliath (Figure 6).

Arxterra Control Panel Test:

After testing the Arxterra Control Panel we were able to control the Goliath by pressing a key on the keyboard (W = forward, A = left, S = backward, D = right).  In addition, the android device was able to provide a live video feed with the periscope as seen on figure 6.

Sources:

1. https://www.arxterra.com/bluetooth-interface-to-arxterra-application-in-progress/
2. https://www.youtube.com/channel/UCJXZGMpv8GqxkOi6W02GzoQ