Monday, September 11, 2017

Disk emulator interface card fully tested, ready for Alto test; work on pirate ship bar


The ship consists of three sections, to allow us to transport it from my house to the end location. The main section is eight foot wide and four foot high, with a lowered notch to allow attendees to interact with the bartenders behind the ship. The stern is four foot wide and a bit over six foot high, while the prow is five foot high at the bowsprite and four foot wide. 

I finished building all the framing with 2x4s and nailed the thin sheet plywood to the three sections. Using a jigsaw I cut the curves for the stern and bow next. My wife will paint these black before I attach the cannons to the front, the bowsprite and decorate the stern with some balustrades and wood strips.

The mast will be twelve feet high, standing behind the bartenders table with a 4x8 black sail about 2/3 way up  and a pirate flag above it. We are currently debating adding two more masts, with sails which would mean we downside the sail on the center mast to perhaps 4x4 since three have to fit across in less than 16' total length. It will all come down to proportions and ease of building.

I cut the thick tubes that will represent the cannons on the side of the ship. There will be a line of eight cannons across the side, four across the bar area and two each on the prow and stern. The end cannons stick out about 8" from the side of the ship but I had to cut the four in the middle down to less than 4" since attendees will stand in front of them while picking up drinks at the bar.


I put back the pullup resistors - 120 ohm since that was what I had, sufficient to pull 42 ma when the gates are conducting on, well below their 300ma recommended max and generating about 208mw per gate. The entire package is rated for 750mw dissipation and contains two gates so running at 416mw when both gates driven 'on'.

The relatively high current when the gate conducts ensures that swing is sufficient to be read as a 0 or 1 by the Alto. That is, we want relatively low resistance on the pullup since it forms a voltage divider with the Alto input gate resistance and thus the 1 level will be somewhat less than 5V by the ratio of the input gate resistance to the sum of input gate plus 120 ohms.

I set up my testbed to measure the on and off voltages of the driver gates with +3.3V and ground applied to them. Functionally the driver is an inverter, thus grounded input pins lets it float the output up near 5V while an open or 3.3V input will pull the output down toward ground.

Every output signal to the Alto was tested and passed - inverting the 0/3.3 signals to 5/0 outputs. Previously I had tested every input line from the Alto, where the 0/5 input was converted to the fpga input as 0/3.3V which means the board is ready to test on the real system.

1 comment:

  1. I REALLY want to see pix, maybe a video, of this pirate bar in action.