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TelescopE Digital Setting
Circles Mark III PCB

Introduction

I have designed a new Printed Circuit Board (PCB) to add more functionality to the DSC board for my telescope.

If you have visited my other pages then you will know that I have also modified a TouCam Pro webcam for long exposure astronomical use. This was then further enhanced by adding a Peltier cooler to the CCD chip with an on-board LCD temperature display.

I decided that the temperature display need not be in the camera itself, and would therefore save valuable weight from the camera housing, and instead made it an integral part of the DSC PCB and simply plug in the temperature sensor to the DSC interface box instead.

A second LCD display was added to allow the telescope position to be displayed on the interface box.

The focusser interface, which was added in the MKII board, now has a hand controller fitted and the option of focusser end-stop detection to stop the motor from running when the focus travel reaches either end (fully in or fully out).

PCB Layout

The new design was done so from scratch. The 16F84A PIC microcontroller used in the previous versions of the DSC was no longer good enough for the job, as I had run out of I/O ports with the features I had added.

The new microcontroller I chose was the 16F870 which has a total of 22 I/O ports, more then enough for what I needed. As well as that it has an integral RS232 interface, which I used to connect it to the PC and the software RS232 port from the original code was used to talk to the serial LCD telescope position display.

Design Tools

To design the PCB I used Easy-PC for Windows V6 from Number One Systems.

To check the outputted Gerber design files I used GC-Prevue from GraphiCode.

The printed circuit board was manufactured by PCBTrain.

PCB Layouts

Here are the pictures of the top and bottom sides of the new PCB.

Click on the links below to see the full size PCB track layouts. The top side layout has a ground plane that is not shown for clarity  of the silk screen printing.

Bottom side tracks                    Top side tracks

Parts Required

The parts required for the new DSC project are listed below:

Circuit DiagramS

Click on the circuit diagrams below to open full size .PDF versions of the schematics.

Circuit Board Construction

The order in which I install the parts on a PCB is always the same. Simply start with the component that has the lowest profile on the board and work upwards. This usually means starting with any wire links, diodes or resistors. Here is the order that I used on the project.

1. Resistors. They have no polarity and can be inserted either way round.

2. Diodes. Make certain you install them with the proper polarity according to the circuit diagram. One end of the diode has a band around it. Align the component so the band on the component matches the band part of the diode on the circuit diagram.

3. SIL resistor and IC Sockets. You don’t have to use sockets for the IC's, (although I would recommend it), since the PIC can be programmed without the need for it to be removed. Ensure that the sockets are the correct way around. Do not install the IC’s in their sockets yet.

4. Oscillator. Make sure that the device is installed the correct way around according to the PCB layout.

5. 0.1 uF capacitors. They do not have a polarity so either lead can go in either hole.

6. 100nF and 330nF capacitors. They do not have a polarity so either lead can go in either hole.

7. Electrolytic capacitors. These devices do have polarity so ensure correct installation. Normally the negative side of an electrolytic device is marked on the body.

8. Voltage Regulator. This device can only be fitted one way around. Secure with the heatsink to the board with an M3 screw and then solder into place.

9. Install the two, three and five way link headers. Fit a link to PL2 1-2 and 3-4.

10. Install the Endstops, temperature sensor and hand control sockets.

11. Install the 10W IDC programmer connector.

12. Install the encoder, focusser, RS232 connectors.

13. Install the power connector.

14. On the underside of the board install the LED's not forgetting to use the LED spacers.

15. Install the PORT B connector.

16. Install the LCD connectors

17. Install the LCD position display using the M2.5 spacers.

18. Install the LCD temperature display using the M2.5 spacers.

Final Assembly

Here is a picture of the final assembly of both sides of the new PCB.

Here is an end shot showing the LED mounting detail.

And a shot of the LCD display mounting detail.

Enclosure

Once the project is complete I will show the PCB enclosure details here.

Click HERE to see the mechanical drawing of the enclosure details.

Hand Controller

The following pictures show the hand controller. First a top down view:

and an end shot showing the different size buttons. The lower profile button is the focus in button and the other the focus out button. No need to strain in the dark to see which is which!!!

PIC Software

There are four different versions of PIC software depending on which version of DSC you are building.

Basic DSC

Basic DSC + Focusser

Basic DSC + LCD

Full DSC (Focusser and LCD)

SkyMap Pro Drivers

There are four different versions of driver for SkyMap Pro depending on which version of DSC you have.

Basic DSC

Basic DSC + Focusser

Basic DSC + LCD

Full DSC (Focusser and LCD)

Cable Connections

The cable connections diagrams are available for download HERE.

DSC PCB Kits

I have had several enquiries in the past about selling the DSC PCB, either in kit form or as a ready made item, and it may now be purchased as a blank PCB for assembly by yourself, a kit of parts, again assembled by yourself, or a ready made and tested unit with any combination of the DSC PCB features installed.

It must be stressed that these kits are for the DSC interface only, and do not include the rotary encoders required, since there are too many different scopes out there and all may use different encoders.

The encoders I used on my Orion Europa were purchased from Jim's Mobile Inc. See their model list to check out if your mount is listed. Don't worry too much if it isn't, neither was mine, but after e-mailing some pictures of the EQ5 mount I have they told me it was a Celestron CG5 mount. They must have been right as the parts fitted perfectly.

The prices for the DSC interface are as follows:

Not everybody has an electronic focusser, a cooled camera or wants a position readout, so you may simply pick and choose the features you require.

Example 1:
If you wanted a ready made DSC + Position readout it would cost £99 + £54.00 = £153.00

Example 2:
If you wanted a kit for DSC + Focusser it would cost £69 + £16.00 = £85.00

All kits will include a ready programmed PIC 16F870 device, and the PCB only option may have a pre-programmed PIC 16F870 device added for only £5.00 extra.

UK power supplies are available at an extra £6.99.  Users in other countries, or those wishing to source their own supply, will need a 12V DC power supply, with a 2.1mm plug on the end, with the positive terminal in the centre of the plug.

If I get enough interest then I will be in a position to pass on reduced prices as I will be able to buy in bulk.

P + P in the UK will be £5.00, which also includes insurance up to the cost of the items ordered. For overseas orders, e-mail me and I will give you a quote for P+P.

All enquiries to dsc.sales@dsl.pipex.com where I will normally reply within 24 hours.

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