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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:

Component

Description Supplier
U1 UCN5804B Cricklewood ElectronicsUCN5804
U2 PIC16F870 Rapid 73-3312
U3 MAX232 Rapid 82-0148
U1 HOLDER 16W Rapid 22-0160
U2 HOLDER 28W Rapid 22-0175
U3 HOLDER 16W Rapid 22-0160
TP1, 2, 3 Test point Rapid 22-0545
PL1 2W HEADER - Rate Rapid 22-0545
PL2 5W HEADER - Step Control Rapid 22-0545
PL3 3W HEADER - Display Type Rapid 22-0545
PL4 2W HEADER - Reset Rapid 22-0545
LED1 Poll LED Rapid 56-0740
LED2 Rx LED Rapid 56-0740
LED3 Tx LED Rapid 56-0745
LED4 Power LED Rapid 56-0740
C1, 2, 11 100nF Rapid 08-0275
C3, 4 10uF Rapid 11-1436
C5 100nF Rapid 10-3260
C6 330nF Rapid 10-3266
C7, 8, 9, 10 1uF Rapid 11-0205
C12 10uF Rapid 11-1436
XTAL1 4MHz Rapid 90-3106
CONN1 Encoders Rapid 24-0465
CONN2 Endstops Rapid 20-0144
CONN3 Focusser Rapid 24-0460
CONN4 Sensor Rapid 20-0144
CONN5 Programmer Rapid 77-2047 or 19-0500
CONN6 RS232 Rapid 24-0450
CONN7 Hand Control Rapid 20-0144
CONN8 Power In Rapid 20-0975
CONN9 Port B Rapid 22-1703
R1 1K 7W SIL Rapid 63-0110
R2, 4 1K 4W SIL Rapid 63-0250
R3 1K 8W SIL Rapid 63-0215
R5 220R Rapid 62-0354
R6 1K Rapid 62-0370
R1,2,3,4 Holder Holder for R1, 2, 3, 4 Rapid 22-1703
DISP1 CCD Temperature Display Maplin FE33L
BEZEL For DISP1 Maplin
SENSOR For DISP1 Maplin
DISP1 HOLDER For DISP1 Rapid 22-1703 & 22-0545
DISP2 Position Display

Active Robots LCD0831-R

DISP2 HOLDER For DISP2 Rapid 22-1703
D1, 2, 3, 4, 5, 8, 9 1N4001 Rapid 47-3420
D6,7 1N4148 Rapid 47-3308
REG1 LM7805 Rapid 47-3313
HS1 For REG1 Rapid 36-0115
BOX1 For DSC Maplin LH22Y
BOX2 For Hand Control Maplin KC91Y
SW1, 2 Focuser Switches Rapid 78-1550
  LED Spacers Rapid 38-0760
  LCD Spacers Rapid 33-2065

 

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 donít 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 ICís 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.

 

Return to main telescope page

 

Copyright © 2007 Phil Davis

email: phil@philchris.co.uk

Last updated 29th July 2014