I have printed circuit boards both populated and unpopulated. The opto-isolator circuit, the field derotator circuit, and the main driver circuit, are on the 5.7" x 6.1" sized board. A parts list and layout graphic are included.
Pat Sweeney is populating and testing some of the printed circuit boards (the field derotator portion of the printed circuit board is left unpopulated).
I am charging $25 per unpopulated board plus either $5 for US shipping or $10 for overseas shipping.
I am charging $65 per populated and tested board (the field derotator portion is not populated) plus either $5 for US shipping or $15 for overseas shipping.
Mel Bartels
1294 B Street
Springfield, OR 97477 USA
*** 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 ***
+12-24 vdc
gnd
+12-24 vdc
for complete isolation, use separate computer and motor grounds, and
supply an external +5.0 VDC source for the computer side;
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 bottom lead of U6;
*** note by Pat Sweeney: I left the computer 5volt supply separate from
the 12-24 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 12-24 volt side. I found a 12 to 9 volt 250
MA ,DC to DC converter from JAMECO Part # 153736
$1.95 and a 5 volt regulator will provide the isolation for my laptop.
***
*** note by Pat Sweeney: you can mount all but the 25 pin parallel port
connector from underneath on the solder side ***
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).
*** note by Pat Sweeney on the field derotator 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
fldrot.zip 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 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
1 small plastic box about 4 inches (1.5cm)
x 2.5 inches (1cm) x 1 inch (.5cm) in size
4 momentary push buttons - normally off,
temporarily on
1 3-way center-off switch (can
be spring loaded to return to center position)
1 2-way switch
6 small diodes
Here's how Ned Smith built his handpad:
I used the following from TechAmerica: 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.
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
1 C1
4.7/35V tantalum cap
1 C2
47/35V electrolytic cap
6 C3-C8
0.1 monolithic cap
1 D1
3.9V/1W zener
8 D2-5, D7-10
1N4004
small signal diode
4 D6, D11-13
30V/1W
zener
10 ISO1-10
4N26 optoisolator
1 P1
DB25F connector
3 P2-4
DB9F connector
2 Q1-2
2N2222 transistor
8 Q3-6, Q9-12
TIP120
transistor
4 Q7-8, Q13-14 MJE3055
transistor
14 R1-4, R6, R10, R12, R14, R17-18, R26-27, R29, R31
220 ohm resistor
1 R5
56k resistor
11 R7, R9, R13, R15-16, R19, R24-25, R28, R30, R38
4.7k resistor
4 R8, R11, R32, R37 2.2k resistor
8 R20-23, R33-36 470 ohm resistor
1 RJ11
RJ11 connector
1 U1
SAA1042 IC (needed only if you will be doing field derotation,
obtain from Newark Electronics http://www.newark.com)
4 U2-5
74LS08 IC
1 U6
7805 regulator
Current Limiting Addition by Jean-Charles Vachon
...by Mel Bartels