Nuts & Volts - May 2004

Tech Forum

back service reports as an unreachable private line?

#5048 Ed Research

Indiana, PA

I have just finished building a small CNC router table. It works well for making relatively shallow cuts, like in PCBs. I would like to start working with plastics, like Lexan and PVC. These are more difficult to cut with a small CNC router, since they are normally 3 to 6 mm thick. I know of ARC welders that can be used to cut through sheet metal, but I am looking for "simple" lasers that can be used to cut through these plastics and not metal. Is there a solution out there?

#5049 Ronald Wijngaarde

The Netherlands

adapter cable, but none of them works. I'm guessing that there is some other incompatibility preventing this old keyboard from working on a more modern computer.

Can anyone point me toward the parts and instructions I would need to build a new keyboard from this old one's keys and a modern PS/2 bit of electronics or suggest another way to get it to talk to a PS/2 keyboard port?

#50410 Dick Steffens via Internet

battery, but doesn't run in sync with the sound, which I’ve recorded on a digital real time recorder.

I’m looking for kits or plans to build my own crystal sync for a 7.2 volt motor. I tried searching the Internet, but there is no information available! Thank you!

Can anyone suggest a source for negative-acting, photo-sensitized boards, such as those Kepro used to supply?

#50411

Don Wruck via Internet

I have an old keyboard (from a Wyse 2108 computer, vintage 1988 or so). It has a fantastic touch that I have been unable to find in modern keyboards. I've tried all 24 possible combinations of the four signals in an

ANSWERS

[1048 — January 2004]

I have a Super 8 motion picture camera that runs on a 7.2 volt

F o r

E l e c t r o n i c s

NUTS & VOLTS E v e r y t h i n g

#1 It may be impractical to add crystal sync to your Super 8 camera unless you want to heavily modify the camera — a job best left for professionals. You’d need a service manual first and you’d be attempting to control the motor speed while sampling its speed with some sort of tachometer device. That signal would be fed to a phase locked loop and compared to a crystal-based reference. It’s a very ambitious project and not at all for the casual tinkerer. However, there is another alternative that might work, depending on what type of film you are trying to produce and requires no equipment modification.

If your final film is to be edited and shown on a Super 8 sound projector with magnetic stripes on the film, here is a suggestion. Most cameras and projectors run at a fairly stable — but perhaps inaccurate — speed. Try loading your location sound into a computer with an audio editing program.

The program will allow you to make adjustments to the speed of the audio without changing pitch. With a bit of experimentation, you should be able to get your sound to sync with your film for at least a minute or so. You can then dub it — perhaps in short sections — to your magnetically striped film as it runs through your sound projector.

Sure, there are limits to this, but, if you are committed to shooting and showing Super 8 film, it may be your cheapest fix. Try downloading the open source program Audacity — it’s free and very cool ( audacity.sourceforge.net) and available for PCs and Macs. It has all the features you will need to not only correct your sync, but to actually build a soundtrack.