A PCB design for Mel Bartels Alt/Az drive system - ATM pages of Berthold Hamburger

A Printed Circuit Board (PCB) design for Mel Bartels' Alt/Az drive system

NOTE 1:: This PCB Layout does NOT include the feature of field rotation! For a description of my fieldrotation daughterboard go to the Fieldrotation section of this page.
NOTE 2:: Many people asked me to sell them one of my circuit boards. I do NOT manufacture or sell those boards! It is actually quite easy to make them. I however will be happy to answer any question about the process of building one.
NOTE 3:: Neither PCB's manufactured using my design nor the design itself may be sold. The use of the content of this page for any kind of publication needs the agreement of Mel Bartels and myself.

Also see my pages about the mechanical aspects of the drive system.

Preface

I assume that the reader is familiar with the basic process of etching printed circuit boards. If not, I recommend to look through the reference section at the end of this page.

The reader has to take all necessary safety precautions while handling the chemicals for PCB etching!

Those include: Rubber Gloves, glasses to protect the eyes, apron, suitable and well-ventilated working area.

Materials needed

One single sided copper clad board 180x130 mm
Iron-on toner transfer foil/paper or laser printer transparencies
Postscript capable Laser printer or Xerox copy machine
Etchant (Ferric chloride)
Scotch brit cleaning sponge for cleaning the board
Etch resistant pen (Decon) for touching up badly transferred traces
Electric Iron

You can also expose the artwork on the board. In that case you will need a photosensitized copper board and all the chemicals to develop the board.

PCB Layout

Download the 120k ZIP file including the Postscript/Acrobat files and unpack it to a directory on your hard disk.

The archive contains the following files:

ARTWORK.PS / ARTWORK.PDF: is the unmirrored Artwork files in postscript/Acrobat format
MIR-ART.PS / MIR-ART.PDF: is the mirrored Artwork files in postscript/Acrobat format
SILK.PS / SILK.PDF: is the unmirrored Silkscreen files in postscript/Acrobat format
MIR-SILK.PS / MIR-SILK.PDF: is the mirrored Silkscreen files in postscript/Acrobat format
ALTAZ.JOB: is the JOB file for the PADS-PCB program. If you have PADS-PCB you can edit the Artwork.

Important:

If you are using Toner transfer paper then you must use:: ARTWORK.PS or ARTWORK.PDF and MIR-SILK.PS or MIR-SILK.PDF
If you want to expose the artwork on photosensitized board then you must use:: MIR-ART.PS or MIR-ART.PDF and SILK.PS or SILK.PDF
To view or print these files, you will need:: Acrobate reader or Ghostscript , which view and print postscript files on any computer or printer.

Images

The artwork unmirrored
(for the PCB, only use the supplied high resolution .PS Postscript file. This one is a low resolution .GIF file)
- The artwork includes a large surface-area groundplane for better circuit stability. The ground traces across the board are broader for the same reason.
- Above the transistor pads are the big 3mm mounting holes for the heatsinks. There is enough space on the board to mount the transistors/voltage-regulator + TO220 heatsinks horizontally.
- For offboard connections I used single row straight PCB plugs.

The silkscreen unmirrored
(for the PCB, only use the supplied high resolution .PS Postscript file. This one is a low resolution .GIF file)
- The black lines are jumper wires.
- PP2,PP3 etc. stands for connections to the referring pin of the parallel Port
- M1 is the output to the Altitude Motor. M2 is the output to the Azimuth Motor.
- The long 8-pin connector is the out/input to/from the handpad.
- +12V and GND are the pins for offboard voltage and ground connections, like the 12V connection to the stepper motors and the ground connection to the parallel port.
- On some diode symbols, the line to mark the cathode is missing. However the square pad marks the cathode.

The schematic
- Pin 7 and 14 of the Hex inverter are of course connected to Ground (pin7) and +5V (pin14). They don't appear on the circuit because the PCB software handles all Ground/Power connections by itself.
- The color coding for the handpad cable is my invention. You can of corse use whatever colors you want for the handpad wires.

Assembled PCB board

The bottom side gives a little impression about the quality of etching that can be achieved by using Iron-on-Foil. The top side shows the spacing of the assembled components.

Handpad and casing

I used a momentary On-Off-On switch for the Init-button . My electronic-box design:
Using the single row PCB-plugs for the offboard connections you can provide for clean wiring and avoid mistakes.