Date: Fri Mar 02 2012 - 08:32:44 EST
Bro;
I cannot believe that I just received this from vectorlist! I was just going through some "to-do" and was going to follow up on the last e-mail you sent and before I did, I got this! I guess we are all "connected" in this hobby....
I am really psyched that you are making progress, you know that I am in for the least, one of these once you are ready to produce them.
Keep up the good work and may your iron be true!
Jeff
On 3/1/2012 1:48 AM, Zitt Zitterkopf wrote:
Bet most of you forgot about the XY Pattern Generator project... I’m sure some of you thought it was vaporware...Welp; It took longer than expected; but after several off/on months of debug – I finally got it working.During debug board#1; I managed to short +12 to +5 frying all the logic.So I restarted with my second board and built/debugged a section at a time.Here’s what I posted to KLOV’s forums where I started a picture Worklog:Several months ago I posted in my Star Trek Captains' Chair worklog that I intended to modernize a old XY Pattern Generator design on the interwebs. Many of the guys on VectorList provided valuable insight into the interworkings of the circuit... and provided many layers of helpful advice.
The result was the following schematics and a set of FabA prototype boards from BatchPCB.com as a dual sided board.
Surface Mount ( yes; I can hear the screams of horror ) as I wanted to minimize PCB size – thereby cost.
If your interested in the prototype schematics; they are here:
http://pinball-mods.com/blogs/wp-content/uploads/2011/11/XYPattern.pdf
I'm pleased to report that tonight I finally debugged the last problem (that I know about).
There is a small list of issues I had to work thru; but for the most part the design worked almost out of the box.
1) The clock generator circuit (3.578MHz xtal) and U1ABC was not "locking". This was due to the buffered logic of the newer 74HC* logic. Some research on the internet indicated I needed a 150pf cap from pin1 U1A to ground to allow the clock generator to excite enough to lock. Another recommendation was to use a Unbuffered HC inverter... which I'll incorporate into the next revision of the schematics.
2) The -12V buck converting power supply wasn't outputting the correct voltage. It'd start out at ~11V.... the drop to ~5V over several minutes. On my debugged board; shorting R26 (10meg ohm) allows the -12V to become rock steady at -11.8V. Unsure here; the Maxim EE sim was very specific on the 10meg ohm value... but the maxim datasheet indicated two modes for VL to operate in. So for now will error on the practical side.
3) The 5V regulator did not have enough copper to heatsink to. Next revision of the FAB will have a large 5V copper heatsink built into the board. For my prototype; I thermal epoxied a small heatsink from a old motherboard onto the top of the regulator to give it some thermal sink.
4) The Linear POT datasheet was missing details regarding the LED side of the POT. One hole was off and will need to be moved.
Things I still need to do:
1) Hook it up to my G08 and align me some guns.
2) check the +12V portion of the buck converter. Right now I'm using the backup +12V linear regulator (U9).
3) Modify schematics and board for FabB (learnings above).
4) Create an enclosure to house the unit.
Nice to haves:
A) Retrofit EPROM sockets to toggle A11 for a 27C32 eprom(s)... allowing for more user designed test patterns.
B) Rename topside adj pots to indicate X and Y.
C) make 3pin jumpers so the jumpers can be mecahnically sound output swing is not shorted
PCB pictures and Oscope captures are posted at the KLOV worklog for your reading enjoyment:
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Received on Thu Mar 1 08:33:46 2012