LAB 8

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Instructions on how to solder correctly and accurately will be given at the beginning of this lab. Additionally, we will discuss how to use Scotchflex and wire up your vector board computer.

1. After you have installed the GAL, check that the VIA Test Program still works.


2. If it does, wire the HORNBY SIGNAL CIRCUIT to the CB1 and CB2 lines of the VIA at $A000. Use "pigtails" to wire the HORNBY Controller into the opto-isolator (through two 220-ohm resistors). BE VERY CAREFUL -- THE HORNBY SHOULD CONNECT ONLY TO THE OPTO-ISOLATOR (THROUGH RESISTORS). NO ELECTRICAL CONNECTION SHOULD BE MADE TO THE COMPUTER POWER OR GROUND. (THE HORNBY 'TRACK GROUND' IS NOT (REPEAT NOT) TO BE CONNECTED TO THE COMPUTER GROUND.


3. Now test your computer using the ECHO Test Program V2.0.
• This program interprets the signals that are sent along the track by the Hornby controller. The Horby can send signals both to the trains on the track and to peripheral devices. In this case, your computer acts as one of those devices. Each computer is assigned a number within the Echo Program. Find this number within the Echo Code. The Echo program listens to the signals being sent over the train tracks by the Horby. If it finds that one of these signals is for its computer number, it interprets the command and outputs the number to the display.
• If all is well you should be able to send a message to your TIL displays by pressing (computer number) (data number) (left or right arrow) on the HORNBY Remote Control Panel. The Panel is located in the MAE412 Folder.


4. Check the quality of the HORNBY SIGNAL Circuit by observing the waveform at the output of the 4N33 and at the output of the LM339. Look at the data burst -- you should see the beginning of the burst as a clean symmetric square wave. Show this to your lab instructor.

CONGRATULATIONS YOU NOW HAVE A WORKING 'ECHO' ON THE TRAINER

5. It is now time to start building the vector board computer. Some prep work is needed before the full board wiring can be accomplished. Begin by reading up on how to use Scotchfex. We will be going over how to solder properly in class. Get comfortable with soldering now because your computer will be better as a result.
• Using Schotchflex


6. Read rules 1-27 in Volume II of the on-line manual. A number of rules apply to the Vector Board Computer (5-9,16,25-27 and others). BE CAREFUL TO FOLLOW ALL OF THE RULES. THEY WERE DEVELOPED TO MINIMIZE THE PROBLEMS ENCOUNTERED IN BUILDING THESE COMPUTERS. ADHERENCE TO THE RULES ALSO IS A FACTOR IN YOUR FINAL GRADE


7. Get the parts for transfering your computer to a Vector Board. Parts you need:
• Vector Board Components (STAFF), if you will be using an Arduino, get an ATMEGA328 chip from the staff
• Chip ID Sheet (STAFF)
• Vector Board (STAFF)
• Scotchflex (Cabinet)
• Heat Sink (Staff)
• ZIF (STAFF)
• Bus Bar Strips (STAFF, return extra)
• Header
• 2 x Standoffs (0.75", 4-40 screw)
• Assorted screws (found in cabinet)


8. Layout (but do not insert) components on the Vector Board. This includes finding space for all of the chips on the proto board but also finding a place for the power bus and regulator. Remember to leave some additional space to add a few more chips near the the connector edge. (You need to buffer all I/O lines entering or leaving your board using 74LS244 buffers. Most Vector Board Computers need at least three 74LS244's.)
• Don't forget to leave room for the ZIF socket that is used with your EPROM or EEPROM. The ZIF socket is bigger that then 28-pin chip that it holds. Note that the Scotchflex sockets have pin one marked with a notch. Make sure that you match pin one of the chip to pin one on the socket.
• The opto-isolator should be placed near pins A&B on the Vector Board so that Track Power (pin B) and Track Ground (pin A) are localized in one corner of the Vector Board. This is done so that the noise associated with the +/-20V track signal does not create any noise on the rest of the board.
• The power regulator will be receiving unregulated power on pins X&Z on the Vector Board. Connect the ground to pin Z and the unregulated power (~9V) to pin X.
• Almost all passive components get added to the computer through a header (in the drawers behind bench 8). This allows you to create a secure connection. Find a place for the header near the other chips that require resistors. Note: the resistors used in the Hornby opto-isolator circuit are not placed in the header but soldered directly to the chip. When soldering resistors to the header, insert the header into your aluminum block (or a socket & vice) to make sure the header pins don't move around while soldering.


9. If you get this far, go on to next week's labs and start assembling the computer.