Thursday, October 16, 2014
A lot of Arduino coding, some hardware prototyping
1131 DISK DRIVE RESTORATION
I received all my parts and began assembling the disk drive delay system that waits 90+ seconds after the platter motor spins before loading the heads. I gave up on trying to shoehorn it all inside the power box in the place that the relay itself had taken, instead placing the circuit into a plastic project box that I can put nearby to the power box but still within the 1131.
I wasn't happy with the performance of my first circuit after some testing. I will try a different approach. I certainly don't want anything that might dump the heads onto the disk surface too early.
NEW KEYPUNCH INTERFACE DEVELOPMENT
I coded the remainder of the Arduino code for the keypunch interface today. While I still believe it would be better to add a signal from the keypunch when it is actually punching, both for validating proper execution and to time the release of the punch relays,
I implemented this with the timing based logic used in the original keypunch interface. For example, the punch relays are held for 10 milliseconds then released, after which I wait another 100 milliseconds for the punch cycle to complete.
I believe that the read pins in the duplicate station are active just after I drop the punch relays, which is how I coded the controller, but I can slide this anywhere in the 110 ms total cycle to ensure I capture the state of the holes at the read station while in the midst of punching at the punch station.
I have a small bit to change in how I handle the binary mode lines, otherwise this is ready to begin testing.