| 0,0 → 1,156 |
|---|
| EQ6 Mount controller analysis (v1 - 10 Jan 2004) |
| |
| Darren Hutchinson |
| dbh@gbdt.com.au |
| |
| $Id: eq6-mnt.txt,v 1.3 2004/03/07 07:44:59 dbh Exp $ |
| |
| Overview: |
| |
| CPU: AT87F51 |
| Clock speed: 3.52 MHz (measured at pin 18 of CPU) |
| Firmware: MotorDrive DW3505010 |
| |
| RA connector |
| 1 RA coil A Driven RA=2,8,16x |
| 2 RA coil C Driven RA=2,8,16x |
| 3 RA coil A Driven RA=1x, 22R to 1, 178R to 4 |
| 4 RA coli B Driven RA=Any, 157R to 1, 178R to 3 |
| 5 RA coil C Driven RA=1x 173R to 6, 155R to 2 |
| 6 RA coil D Driven RA=Any 173R to 5, 22R to 2 |
| |
| DEC connector |
| 1 DEC coil A A/B are coil with 16R3 resistance |
| 2 DEC coil B |
| 3 DEC coil C C/D are coil with 16R3 resistance |
| 4 DEC coil D |
| |
| Drive waveforms: |
| |
| RA 0X: Coils not driven |
| RA 1X: Driven +12V for 114 ms, 0V for 114 ms, not driven for 38ms b/w |
| driven states, overall time is 302ms [OSC only accurate to 2ms] |
| |
| Each coil driven at 90deg to other coil. |
| |
| Timing correct for half step mode |
| |
| RA 2X: Driven +12V for 75ms, 0V for 76ms, overall time is 151 ms, each coil |
| at 90deg to other coil |
| RA 8X: Overall period is 38ms, no undriven time, |
| coils at 90deg |
| RA 16X: Overall period is 12.8 ms, no undriven time, coils at 90deg |
| |
| - Timing indicates full step mode |
| - No evidence of velocity ramp in x2, x8, x16 mode |
| - RA 1X timinig is correct assuming 180 tooth worm and 1:132 transfer gear |
| & gearbox reduction ratio |
| |
| DEC 0X: Outputs not driven |
| DEC 2X: Overall period 151 ms, no undriven time |
| DEC 8X: Overall period 37.8ms, no undriven time, coils at 90 deg |
| DEC 16X: Overall period 12.6ms, no undriven time, coils at 90 deg |
| |
| - Timing indicates full step mode |
| - No evidence of velocity ramp in x16, x8, or x2 mode |
| |
| Drive circuit: |
| |
| The drive circuit is a fairly plain "H" driver with one quirk that may, or |
| may not, be intentional design from Synta. |
| |
| The half-"H" is built from a pair on PNP/NPN transistors operating in |
| common-emitter mode. This is somewhat unusual as circuits intended to |
| drive high currents typically operate in common collector mode. |
| |
| Anyway, the PNP transistor that pulls the output high has a base current of |
| about 11 mA (depending on the supply voltage). With a transistor hfe of |
| 40 this should give an output current of at least 500 mA. |
| |
| The other part of the bridge is another issue. The identical circuit is used to |
| drive the base of this NPN transistor, but in this case it will only give |
| the transistor 1.2 mA, leading to a lower current. |
| |
| The rated hfe of the transistor only guarantees a current of about 50 mA, but |
| the hfe is typically much higher. In the unit measured the coil current seemed |
| to be limited to about 250 mA. |
| |
| This may be an attempt to limit the current in fault conditions where |
| both the NPN and PNP transistors are active, or it may just be bad circuit |
| design. |
| |
| In any case there are two practical effects: |
| |
| First the transistor may not be saturated, so it will run hot. |
| Second the coil current is limited, giving less torque. |
| |
| Both of these effect mean that the existing electronics would be |
| a poor choice as the basis of a GOTO design (but I guess you knew |
| that ....) |
| |
| MCU Pin Label Use |
| 1 P1.0 1 = RA at 1x, 0 = RA != 1x |
| 2 P1.1 Same as P1.0 |
| 3 P1.2 Same as P1.0 |
| 4 P1.3 Same as P1.0 |
| 5 P1.4 Same as P1.0 but connected to relay (1 = relay off, 0 = on) |
| 6 P1.5 Same as P1.0 |
| 7 P1.6 Same as P1.0 |
| 8 P1.7 Same as P1.0 |
| 9 RST R/C reset circuit, C = 22uF, R = 5K1, active high |
| 10 RXD Data from controller via 1K resistor |
| 11 TXD No data |
| 12 INT0 0V |
| 13 INT1 +5V |
| 14 T0 +5V |
| 15 T1 +5V |
| 16 *WR +5V |
| 17 *RD +5V |
| 18 XTAL xtal out (freq meas point) |
| 19 XTAL Xtal in |
| 20 GND 0V |
| 21 P2.0 1 = RA coil A to +12v, 0 = No effect |
| 22 P2.1 1 = RA coil B to +12v , 0 = No effect |
| 23 P2.2 1 = RA coil C to +12v , 0 = No effect |
| 24 P2.3 1 = RA coil D to +12v, 0 = No effect |
| 25 P2.4 1 = DEC coil A to +12v, 0 = No effect |
| 26 P2.5 1 = DEC coil B to +12v, 0 = No effect |
| 27 P2.6 1 = DEC coil C to +12v, 0 = No effect |
| 28 P2.7 1 = DEC coil D to +12v, 0 = No effect |
| 29 *PSEN +5V |
| 30 ALE Toggle at 602 KHz (high 540 ns, low 1.1 us) [~6 clk / ALE ] |
| 31 *EA +5V |
| 32 P0.7 1 = No effect, 0 = RA coil A to 0V |
| 33 P0.6 1 = No effect, 0 = RA coil B to 0V |
| 34 P0.5 1 = No effect, 0 = RA coil C to 0V |
| 35 P0.4 1 = No effect, 0 = RA coil D to 0V |
| 36 P0.3 1 = No effect, 0 = DEC coil A to 0V |
| 37 P0.2 1 = No effect, 0 = DEC coil B to 0V |
| 38 P0.1 1 = No effect, 0 = DEC coil C to 0V |
| 39 P0.0 1 = No effect, 0 = DEC coil D to 0V |
| 40 Vcc +5V |
| |
| Controller connector port: |
| |
| Pin numbers from RIGHT looking into socket with tab up (as numbered on |
| controller board) |
| |
| 1: Switched +12V from hand controller |
| 2: Ground |
| 3: Data from hand controller via 1K resistor |
| 4: Short to pin 1 |
| 5: +12V from source via diode |
| 6: Short to pin 5 |
| |
| Notes: |
| |
| - Northern hemisphere selected during measurements |
| - Relay is 5V, but appears to be driven via a resistor from the 12V supply |
| - Finder LED has buffering (Q2) |
| - Controller is series diode protected from reverse power connection |
| |
| Mechanical details: |
| |
| 14mm from PCB to inside of cover plate |
| 5mm from PCB to top of MCU socket |
| 9mm from PCB to top of MCU |