1. Re-read
the Safety Guide and Warning
2. attach the circuit
board to the
computer's parallel port using a straight through 25 pin serial cable
3. attach the hand
paddle to the circuit board
4. using a small 12
volt battery, or two
6 volt dry cell batteries connected in series, attach the battery's (-)
post to the circuit board ground, which will be the black lead
5. turn on the
computer
6. enter the
appropriate parallel port in
the config.dat file: look near the end of the file for a line that
starts PportAddr, and enter the desired lpt #, usually a 1
7. run scope.exe,
selecting either altazimuth or equatorial alignment
8. attach the
battery's positive (+) post to the circuit board's red lead
9. check the hand
paddle operation by
pressing the hand paddle buttons in turn, verifying that scope.exe is
reading the buttons properly
10. using the optional LED tester unit, plug it
into the
altitude or the azimuth motor port (do not plug it into the field
de-rotator port), then turn on tracking in scope.exe, and verify that
a. the lights turn on and off in sequence from one side to the other,
and b. no more than 2 lights are on at any one time
11. verify motor movement by attaching a motor to
the
azimuth/right ascension port of the circuit board (the middle db-9
connector), then turn on tracking in scope.exe
12. attach the other unipolar stepper motor to the
altitude/declination port of the circuit board and verify movement by
using the up button of the hand paddle
13. if using a bipolar field rotator motor, attach
it to
the field rotator port (the bottom db-9 connector, next to the raised
IC), then set the altitude to 80 degrees in scope.exe
config.dat settings:
set InvertOutput to 0 in config.dat.
Original designed called for 7404 inverters to drive the transistors,
hence InvertOutput 1 in the original config.dat (parallel port output
goes high, hex inverters go low, and drive transistors turn off, hence
the need to invert the output).
In the original design, if opto-isolators were used, then InvertOutput
0 (parallel port output goes high, hex inverters go low, opto-isolators
turn on pulling output low, hex inverters go high, and drive
transistors turn on, hence no need to invert output).
This pcb design uses 7408 and gates (parallel port output goes high,
7408 and gates go high, opto-isolators turn off allowing output to
return to high, 7408 and gates go high, and drive transistors turn on,
hence no need to invert the output).
heatsinks:
no heatsinks are required on the power transistors as the software
ensures that only the needed current is sent to the motors, for
instance, 1 amp motors typically draw 0.1 amps while tracking and
slewing; a heatsink on the 7805 voltage regulator might be required if
you jumper it so as to power the computer side of the board and then
use the board in poor ventilation or warm temperature (current draw
with motors off at 12 VDC is 0.22 amps), or with higher drive voltages
up to 24 VDC;
*** note by Pat Sweeney: I found that if the motors draw less than 1
amp each the transistors do not get hot while slewing or
tracking. Currents of 4 or 5 amps while ramping up or down also are OK.
If currents of around 2 amps per motor are expected. insure cooling via
a small fan blowing on the TIP120s If
currents much
above 2 amps are expected I would suggest heat sinks But they must be
electrically isolated. the collectors are tied to the tab on the
TIP120s ***
motor sizes and current
limit:
Use unipolar steppers in the range of 6 to 12 volts with amperage of
0.5 to 1 amps and winding or coil resistances of very roughly 5
ohms. Smaller and lighter motors will work also, even for
rather
large scopes. You can find these in old floppy drives, for
instance. If the motor winding or coil resistance is 1 ohm or
less, then the output power transistors will likely burn out in
seconds. If you need to use more powerful motors of 1 to 3
volts
with amperage up to 4 amps, then add either series power resistors, or
better yet, install the current limiting add-on circuit designed by
Jean-Charles Vachon. Here are the details: Current Limiting Addition by
Jean-Charles Vachon
power/ground connections:
the 6 holes for power and ground go as follows (board face up with the
6 holes to the lower left, starting from the hole closest to the DB25
connector and finishing with the hole closest to the board's edge):
computer side of the PCB::
1. gnd (optionally jumper to
the motor side gnd #5)
2. +5 vdc (optionally jumper to 7805
+5vdc output pin ([turning board upside down, the outside most pin of
the 7805])
3.
gnd
motor side of the PCB:
4. +12 vdc
5.
gnd
6. +12 vdc
for complete isolation, use separate computer and motor grounds, and
supply an external +5.0 VDC source for the computer side or use the
+5VDC output from pin 1 of the joystick port DB15; the vast majority of
us will not require this total isolation, instead, tie computer and
motor grounds together, and supply the computer +5 VDC from the 7805
power regulator (U6 - it will get hot supplying both sides of the board
so consider a heat sink if not well ventilated or used in hot clime):
do this best by jumping 1. gnd and 5. gnd together, then jump the
bottom lead of the 7805 to 2. +5 vdc, and finally bring out two wires
from 5. gnd and 6. +12-24 vdc for the ground and positive power
connection respectively;
Be very careful when
testing so as to not risk your computer's parallel port.
Use a 6 volt drycell battery for motor voltage during initial testing.
*** note by Pat Sweeney: I left the computer 5volt supply separate from
the 12 volt supply to isolate the parallel port from the drive circuit.
If a catastrophic failure on the drive circuitry occurs there is the
possibility of wrecking the parallel port on the computer. If + 5 volts
is not available from the computer for this then I suggest using a
small isolated DC to DC converter off the 12 volt side. I found that a
12 to 9 volt 250 mA DC to DC converter from JAMECO Part #
153736
for $1.95, and, a 5 volt regulator will provide the isolation for my
laptop. ***
9/25 pin connectors:
circuit board 9 pin and 25 pin connectors are straight (not angled)
connectors; use thin flat cable to connect these to a set of connectors
that you have mounted in the electronics box's face plate;
*** note by Pat Sweeney: you can mount all but the 25 pin parallel port
connector from underneath on the solder side ***
The optional field derotator/focuser chip can be added
later.
The circuit board was designed with the SAA1042 in mind.
However,
the now discontinued SAA1042 has been replaced by the MC3479 (or
ECG1859). Here's a graphic of the MC3479 installed with the
modifications on the pcb:
*** following note on how to hook up the MC3479 and ECG1859 by Bob
Norgard ***
Three pairs of wires need to be reversed to make it function properly
with the circuit board, plus a resistor needs to be
added.
Get a little daughter board designed to handle a single IC chip of 16
pins to float above the field derotator socket. Pins
1&2,
16&16, and 8&9 need to be reversed. Cut 15
pieces of
insulated 22 ga solid hookup wire 3/4 inch long. Take a 2k
ohm
1/4w resistor and trim its leads to the same overall length.
Solder one end of the resistor to pin #11 of the 16 pin
socket.
Additionally, the existing 56k bias resistor may not be optimum for
different motors. The MC3479 handles up to 350 ma motors
while
the ECG1859 handles up to 500 ma motors. The stepper can
handle
larger amperage motors with Chuck Shaw's modifications mentioned below
(be sure to still swap the 3 pairs of leads for the new chips).
Main_Board ECG-1857
Board
SAA1042 site
1*
2*
2*
1*
3
3
4
4
5
5
6
6
7
7
8*
9*
9*
8*
10
10
11 2K* 11
12
12
13
13
14
14
15*
16*
16*
15*
* Note lead reversals and
added 2K resistor!!!
I mounted the little board using 4 stand-offs inside the aluminum box
that houses the rest of the drive circuitry. For testing purposes, I
used a Mitsumi Electric M68SP-4 12V/33ohm stepper salvaged from an old
floppy drive. It has 1.8 degree steps. The chip ran
barely
warm to the touch.
*** note by Pat Sweeney on the field derotator/focuser portion of the
pcb ***
The schematic and silk screen does show
the 3.9 volt
zener in backwards. (sorry ) The rest of the circuit is OK. The chip is
configured to drive a 2 phase bipolar stepper motor. (4 wire motor) I
tested the circuit on a stepper that draws 200MA per winding and it
seems to work properly. Only the pins 6,7,8,and 9 are used. Pins
1,2,3,4, and 5 can supply + 12 volts for external transistors to power
a stepper that will draw more than 500MA. Ground for external
transistors will have to be supplied from another location on the
board.
I wrote a program fldrot.exe (download here)
that will run from DOS or WINDOWS 3.1 & 95 . It will step a
bipolar
motor 1 step per second for 200 steps forward and then 200 steps in
reverse and continue in this mode until "Q" is pressed. It should help
in debugging the circuit. Note don't have the ALT or AZ motors attached
while using FLDROT.EXE.
*** note by Chuck Shaw on how to modify the field derotator/focuser
portion of the pcb for a unipolar stepper ***
select
here for Chuck's note
select
here for Chuck's circuit mod
select
here for Chuck's pcb mod graphic #1
select
here for Chuck's pcb mod graphic #2
·
orient the
board so that the parallel port 25 pin connector is to the left
·
the tip 120
transistors will face to the bottom, and the mje 3055 and 7805 voltage
regulator will face to the left
·
the diodes
must be soldered so that their banded marking matches the diode marking
on the pcb
·
some capacitors have a long leg - these solder into the '+' marking
·
all the
opto-isolators solder in with the alignment marker to the top of the
pcb, (alignment marker is to the upper left of the indented side)
·
make sure you
mount the 7408 AND gates so that the alignment marker is either to the
top or to the right
·
do not
overheat components while soldering: solder one lead, then move onto
the next part, returning later to solder the next lead
·
double check all solder joints before applying power
·
before
mounting the 7408 AND gates, apply power and verify the ground and +5
VDC lines through the pcb, and particularly at each 7408 AND gate
·
use a straight
through 25 pin to 25 pin connector with male ends on each side to
connect the parallel port to the pcb
·
be careful to
not cause a short if using metal screws to attach the DB9 connectors to
the circuit board
·
after mounting
the 7408 chips and before attaching the stepper motors, use the
parallel port test option of scope.exe to exercise the output lines and
verify with a voltmeter that the 8 output lines to the 2 steppers are
functioning properly
here's the handpad circuit diagram
here's how I solder the handpaddle circuitry
1 handpaddle plastic box Jameco 18922 (3.1"x2"x.9"ABS) $3.15
or Mouser 546-1591BS-BK (4.4"x2.4"x1.2"ABS) $3.34
6 push button momentary on switches Jameco 26622 $.49
1 2-way switch Jameco toggle 21936 $1.09
6 small diodes Jameco 35991 $.40/10
1 RJ11 connector Jameco 124039 $.95
Here's how Ned Smith built his handpad:
I used the following from TechAmerica (RadioShack):
910-1075 $15.48 It is a 1 x 2.4 x 3.8 inch
enclosure with a
membrane
switch pad. It has a 3 x 4 switch array. I cut off one row to
make a 3 x 3. This gives me Up, Down, Right, and
Left. I
used the upper R and L corners for the for the self-centering toggle
switch. I only had to add SPDT to handle the two stepping rates. The
membrane switches add about 50 ohms to the circuit which reduced the
voltage at the connector. I used RJ12 connectors for the hand
paddle to PCB enclosure and stepper motor to enclosure.
handpad cable:
cable: 10 foot length of flat 6 wire Jameco 103448 ($.07/foot)
connectors: (2) RJ11 6p Jameco 79273 $.15
Using RJ11 connector with straight through cable
(comparing cable ends side by side with clips up, wiring is the same
color sequence from left to right), hookup is:
pin number looking face-on to connector with clip on top:
******
*******************
* rd wh
ye *
* bk
gr bl *
*******************
parallel port pin 13 is the yellow wire
parallel port pin 12 is the red wire
parallel port pin 11 is the white wire
parallel port pin 10 is the black wire
+5 VDC is the blue and green wires
Using RJ11 connector with crossover cable, hookup is:
pin number looking face-on to connector with clip on top:
******
*******************
* rd wh
ye *
* bk
gr bl *
*******************
parallel port pin 13 is the black wire
parallel port pin 12 is the green wire
parallel port pin 11 is the blue wire
parallel port pin 10 is the yellow wire
+5 VDC is the white and red wires
here's the printed circuit
board circuit diagram
Use the part numbers here and on the printed circuit board -
any
part numbers on other circuit diagrams do not necessarily correspond to
the pcb
click here for parts layout
Here are the circuit board graphics: pcb_graphics.zip
All capacitors are in microfarads and all resistors are 1/4 watt: there
is a fair degree of latitude in selecting parts.
1 C1
4.7/35V tantalum
cap Jameco 33806 $.35
1 C2
47/35V
electrolytic cap Jameco 31114 $.15
6 C3-C8
0.1 monolithic
cap Jameco 25523 $.15
1 D1
3.9V/1W zener Jameco
178765 $.12, Allied 568-0135 $.08
8 D2-5,
D7-10 1N4004 diode Jameco
35991 $.40/10
4 D6, D11-13
30V/1W zener Jameco
178925 $.08, Allied 568-0045 $.06
10 ISO1-10
4N35 optoisolator
Jameco 41056 $.35 (optional socket Jameco 112192 $.08)
1 P1
DB25F connector Jameco
15165 $.65
3 P2-4
DB9F connector Jameco
15780 $.49
2 Q1-2
2N2222
transistor Jameco 28628 $1.10/10
8 Q3-6,
Q9-12 TIP120 transistor Jameco
32993 $.65
4 Q7-8,
Q13-14 MJE3055 transistor Jameco
25857 $.65
14 R1-4,
R6, R10, R12, R14, R17-18, R26-27, R29, R31
220 ohm resistor
Jameco 30470 $.89/100
1 R5
56k resistor Allied
526-1666 $2.94/200
11 R7,
R9, R13, R15-16, R19, R24-25, R28, R30, R38
4.7k resistor Jameco
31026 $.89/100
4 R8,
R11, R32, R372.2k resistor Jameco
30314 $.89/100
8 R20-23,
R33-36 470 ohm resistor Jameco
31165 $.89/100
1 RJ11
RJ11 connector Jameco
115836 $.65
1 U1
MC3479 IC
(replaces SAA1042) Jameco
25216 $5 (needed only if you will be doing field derotation or
motorized focus control)
1
socket
16 pin Jameco
37372 $.07 (needed only if you will be doing field derotation and using
the SAA1042 chip; for the MC3479 chip use wire wrap socket Jameco 37411 $2.25
with 2.2k resistor Jameco 30314 $.89/100 as 3 pairs of wires need to be
reversed and one lead replaced with the resistor)
4 U2-5
74LS08 IC Jameco
46375 $.25
4
14
socket pin Jameco
37161 $.06
1 U6
7805 regulator Jameco
51262 $.29
optional
TO-220 heatsink
for the 7805 Jameco 107297 $.39 (heatsink
compound Jameco 167249 $7.95)
(solder Jameco 141778 $13.95)
|
||||||
So, you've decided to check out motorizing your telescope.
Perhaps you saw
another tracking telescope and wish the same ability for your scope,
perhaps
you want the goto
ability in your light polluted
skies with few signposts, or perhaps you want to try your hand at CCD
imaging.
As you surf through the wepages,
you may feel
overwhelmed by the material and the many options. What to do?
- Get the circuit board, hand paddle, and cabling (you can purchase
stepper and
servo systems from me)
- Get two surplus motors, either steppers (5 leads or more), or, servos
with
optical encoders, and two small gear reducers of about 50:1
- Get a cheap pc or laptop (suitable used laptops average $100)
- Hook up the components and get the motors to track and slew while
holding
them in your hand
- Switch teflon pads to
small bearings:
- Replace formica
bearing surfaces with sheet metal
- Make one of the bearing points in each axis a small drive shaft that
is
attached to the small gear reducer
- Get optional encoders and encoder interface box
- Configure for your particular combination of parts
- Total cost ~$100 - $500 for the stepper version and $300 - $700 for
the servo
version
Inexpensive
bearing ideas |
altitude
axis with 60:1 gear reducer feeding a 30:1 roller drive |
My first fully computer
operated telescope, the 20 inch [0.5m] (1992)
early CCD imaging with the 20
inch (1995)
ultralight
computerized 20 inch (2002)
Chuck Shaw's computer operated telescope ATM pages http://www.ghg.net/cshaw/stars.htm
Berthold Hamburger's computer operated telescope pages http://www.astro.artinso.com/
Ben Davies has extensive documentation culled from the scope-drive@yahoogroups.com discussion group of 2500 enthusiasts http://ben.davies.net/scopemanual.htm
Chris Rowland has developed GPS software to connect scope.exe to GPS units via a serial port. See http://groups.yahoo.com/group/scope-drive/files/Other_Software/gpsscope_v2.zip
French translation of these webpages http://ftissera.free.fr/Webmel/altaz.html
German version of scope.exe http://www.gotodobson.de/software.htm
German translation of the webpages by Yvonne and Alexander Urban http://www.geocities.com/alexanderurban/melspage/altaz.html
Italian translation of the webpages by Marco Bagaglia now available at http://www.astrofili.org/~atmitalia/altaz_mel.html
Loboyko Steve [sloboyko@yahoo.com] touchscreen modification: http://8080geek.freeservers.com/touch.html
Martin Niemi's quickcam autoguider now outputs guiding commands via a serial port using LX200 compatible commands, which scope.exe understands, see http://www.ameritech.net/users/mniemi000/auto.html
Larry Strange's innovative mouse encoders LarryStrangeInvention.html
article appearing in May, 2000, Circuit Cellar magazine
article appearing in April, 2000, Sky and Telescope magazine
join the scope-drive mailinglist
(servo software may be ordered here)
stepper software
licensed under GPL, see http://www.fsf.org/copyleft/gpl.html
if you have trouble, e-mail me and I will e-mail you back the files
download
the executable program (2009-March-26 310kb)
download
the source code (2007-Sept-1 240kb)
download
the associated data files, epoch 2005 (2005-Sept-11 675kb)
NGC and IC1-IC5 data contributed by
http://www.geocities.com/kindellism/
here you will find solar system and comet calculator programs by Rex Kindell
![My first fully computer operated telescope, the 20 inch [0.5m] (1992](20inch-1994.jpg){kind=link}
