| 508 |
kaklik |
1 |
EQ6 Mount controller analysis (v1 - 10 Jan 2004)
|
|
|
2 |
|
|
|
3 |
Darren Hutchinson
|
|
|
4 |
dbh@gbdt.com.au
|
|
|
5 |
|
|
|
6 |
$Id: eq6-mnt.txt,v 1.3 2004/03/07 07:44:59 dbh Exp $
|
|
|
7 |
|
|
|
8 |
Overview:
|
|
|
9 |
|
|
|
10 |
CPU: AT87F51
|
|
|
11 |
Clock speed: 3.52 MHz (measured at pin 18 of CPU)
|
|
|
12 |
Firmware: MotorDrive DW3505010
|
|
|
13 |
|
|
|
14 |
RA connector
|
|
|
15 |
1 RA coil A Driven RA=2,8,16x
|
|
|
16 |
2 RA coil C Driven RA=2,8,16x
|
|
|
17 |
3 RA coil A Driven RA=1x, 22R to 1, 178R to 4
|
|
|
18 |
4 RA coli B Driven RA=Any, 157R to 1, 178R to 3
|
|
|
19 |
5 RA coil C Driven RA=1x 173R to 6, 155R to 2
|
|
|
20 |
6 RA coil D Driven RA=Any 173R to 5, 22R to 2
|
|
|
21 |
|
|
|
22 |
DEC connector
|
|
|
23 |
1 DEC coil A A/B are coil with 16R3 resistance
|
|
|
24 |
2 DEC coil B
|
|
|
25 |
3 DEC coil C C/D are coil with 16R3 resistance
|
|
|
26 |
4 DEC coil D
|
|
|
27 |
|
|
|
28 |
Drive waveforms:
|
|
|
29 |
|
|
|
30 |
RA 0X: Coils not driven
|
|
|
31 |
RA 1X: Driven +12V for 114 ms, 0V for 114 ms, not driven for 38ms b/w
|
|
|
32 |
driven states, overall time is 302ms [OSC only accurate to 2ms]
|
|
|
33 |
|
|
|
34 |
Each coil driven at 90deg to other coil.
|
|
|
35 |
|
|
|
36 |
Timing correct for half step mode
|
|
|
37 |
|
|
|
38 |
RA 2X: Driven +12V for 75ms, 0V for 76ms, overall time is 151 ms, each coil
|
|
|
39 |
at 90deg to other coil
|
|
|
40 |
RA 8X: Overall period is 38ms, no undriven time,
|
|
|
41 |
coils at 90deg
|
|
|
42 |
RA 16X: Overall period is 12.8 ms, no undriven time, coils at 90deg
|
|
|
43 |
|
|
|
44 |
- Timing indicates full step mode
|
|
|
45 |
- No evidence of velocity ramp in x2, x8, x16 mode
|
|
|
46 |
- RA 1X timinig is correct assuming 180 tooth worm and 1:132 transfer gear
|
|
|
47 |
& gearbox reduction ratio
|
|
|
48 |
|
|
|
49 |
DEC 0X: Outputs not driven
|
|
|
50 |
DEC 2X: Overall period 151 ms, no undriven time
|
|
|
51 |
DEC 8X: Overall period 37.8ms, no undriven time, coils at 90 deg
|
|
|
52 |
DEC 16X: Overall period 12.6ms, no undriven time, coils at 90 deg
|
|
|
53 |
|
|
|
54 |
- Timing indicates full step mode
|
|
|
55 |
- No evidence of velocity ramp in x16, x8, or x2 mode
|
|
|
56 |
|
|
|
57 |
Drive circuit:
|
|
|
58 |
|
|
|
59 |
The drive circuit is a fairly plain "H" driver with one quirk that may, or
|
|
|
60 |
may not, be intentional design from Synta.
|
|
|
61 |
|
|
|
62 |
The half-"H" is built from a pair on PNP/NPN transistors operating in
|
|
|
63 |
common-emitter mode. This is somewhat unusual as circuits intended to
|
|
|
64 |
drive high currents typically operate in common collector mode.
|
|
|
65 |
|
|
|
66 |
Anyway, the PNP transistor that pulls the output high has a base current of
|
|
|
67 |
about 11 mA (depending on the supply voltage). With a transistor hfe of
|
|
|
68 |
40 this should give an output current of at least 500 mA.
|
|
|
69 |
|
|
|
70 |
The other part of the bridge is another issue. The identical circuit is used to
|
|
|
71 |
drive the base of this NPN transistor, but in this case it will only give
|
|
|
72 |
the transistor 1.2 mA, leading to a lower current.
|
|
|
73 |
|
|
|
74 |
The rated hfe of the transistor only guarantees a current of about 50 mA, but
|
|
|
75 |
the hfe is typically much higher. In the unit measured the coil current seemed
|
|
|
76 |
to be limited to about 250 mA.
|
|
|
77 |
|
|
|
78 |
This may be an attempt to limit the current in fault conditions where
|
|
|
79 |
both the NPN and PNP transistors are active, or it may just be bad circuit
|
|
|
80 |
design.
|
|
|
81 |
|
|
|
82 |
In any case there are two practical effects:
|
|
|
83 |
|
|
|
84 |
First the transistor may not be saturated, so it will run hot.
|
|
|
85 |
Second the coil current is limited, giving less torque.
|
|
|
86 |
|
|
|
87 |
Both of these effect mean that the existing electronics would be
|
|
|
88 |
a poor choice as the basis of a GOTO design (but I guess you knew
|
|
|
89 |
that ....)
|
|
|
90 |
|
|
|
91 |
MCU Pin Label Use
|
|
|
92 |
1 P1.0 1 = RA at 1x, 0 = RA != 1x
|
|
|
93 |
2 P1.1 Same as P1.0
|
|
|
94 |
3 P1.2 Same as P1.0
|
|
|
95 |
4 P1.3 Same as P1.0
|
|
|
96 |
5 P1.4 Same as P1.0 but connected to relay (1 = relay off, 0 = on)
|
|
|
97 |
6 P1.5 Same as P1.0
|
|
|
98 |
7 P1.6 Same as P1.0
|
|
|
99 |
8 P1.7 Same as P1.0
|
|
|
100 |
9 RST R/C reset circuit, C = 22uF, R = 5K1, active high
|
|
|
101 |
10 RXD Data from controller via 1K resistor
|
|
|
102 |
11 TXD No data
|
|
|
103 |
12 INT0 0V
|
|
|
104 |
13 INT1 +5V
|
|
|
105 |
14 T0 +5V
|
|
|
106 |
15 T1 +5V
|
|
|
107 |
16 *WR +5V
|
|
|
108 |
17 *RD +5V
|
|
|
109 |
18 XTAL xtal out (freq meas point)
|
|
|
110 |
19 XTAL Xtal in
|
|
|
111 |
20 GND 0V
|
|
|
112 |
21 P2.0 1 = RA coil A to +12v, 0 = No effect
|
|
|
113 |
22 P2.1 1 = RA coil B to +12v , 0 = No effect
|
|
|
114 |
23 P2.2 1 = RA coil C to +12v , 0 = No effect
|
|
|
115 |
24 P2.3 1 = RA coil D to +12v, 0 = No effect
|
|
|
116 |
25 P2.4 1 = DEC coil A to +12v, 0 = No effect
|
|
|
117 |
26 P2.5 1 = DEC coil B to +12v, 0 = No effect
|
|
|
118 |
27 P2.6 1 = DEC coil C to +12v, 0 = No effect
|
|
|
119 |
28 P2.7 1 = DEC coil D to +12v, 0 = No effect
|
|
|
120 |
29 *PSEN +5V
|
|
|
121 |
30 ALE Toggle at 602 KHz (high 540 ns, low 1.1 us) [~6 clk / ALE ]
|
|
|
122 |
31 *EA +5V
|
|
|
123 |
32 P0.7 1 = No effect, 0 = RA coil A to 0V
|
|
|
124 |
33 P0.6 1 = No effect, 0 = RA coil B to 0V
|
|
|
125 |
34 P0.5 1 = No effect, 0 = RA coil C to 0V
|
|
|
126 |
35 P0.4 1 = No effect, 0 = RA coil D to 0V
|
|
|
127 |
36 P0.3 1 = No effect, 0 = DEC coil A to 0V
|
|
|
128 |
37 P0.2 1 = No effect, 0 = DEC coil B to 0V
|
|
|
129 |
38 P0.1 1 = No effect, 0 = DEC coil C to 0V
|
|
|
130 |
39 P0.0 1 = No effect, 0 = DEC coil D to 0V
|
|
|
131 |
40 Vcc +5V
|
|
|
132 |
|
|
|
133 |
Controller connector port:
|
|
|
134 |
|
|
|
135 |
Pin numbers from RIGHT looking into socket with tab up (as numbered on
|
|
|
136 |
controller board)
|
|
|
137 |
|
|
|
138 |
1: Switched +12V from hand controller
|
|
|
139 |
2: Ground
|
|
|
140 |
3: Data from hand controller via 1K resistor
|
|
|
141 |
4: Short to pin 1
|
|
|
142 |
5: +12V from source via diode
|
|
|
143 |
6: Short to pin 5
|
|
|
144 |
|
|
|
145 |
Notes:
|
|
|
146 |
|
|
|
147 |
- Northern hemisphere selected during measurements
|
|
|
148 |
- Relay is 5V, but appears to be driven via a resistor from the 12V supply
|
|
|
149 |
- Finder LED has buffering (Q2)
|
|
|
150 |
- Controller is series diode protected from reverse power connection
|
|
|
151 |
|
|
|
152 |
Mechanical details:
|
|
|
153 |
|
|
|
154 |
14mm from PCB to inside of cover plate
|
|
|
155 |
5mm from PCB to top of MCU socket
|
|
|
156 |
9mm from PCB to top of MCU
|