Wednesday, April 20, 2011

SLA7078 Step Motor Driver

A step motor driver using the SLA7078MPR has several advantages over one using the SLA7062M: one, a newer design, two,seems to be more available with a price of $12ea or $8 per ten, three, SLA7078 series has built in sense resistors and,four, the PR version has built in protection circuits.

The design shown below has two version: with and without opto isolation. An idle delay feature has been incorporated which places the motor in half power mode when idle for 10 seconds. This driver does not set motor current by a selection of sense resistors as with the SLA7062 driver. With that driver the reference voltage was fixed, such that a .5 ohm resistor gave 1 amp motor current, so three .5 ohm resistors in parallel gave 3 amps. In the SLA7078 the sense resistors are located in the chip and current settings are adjusted using the trimmer pot. To set the current, a multimeter is attached to the reference signal, JC1 in schematic above, and the trimmer adjusted to a voltage given in the SLA7078 datasheet.

The delay feature uses a 74HCT4538 retriggerable oneshot. A circuit using a LMC555 was investigated which would probably work, but the board space required is about the same as with the 4538 even though only half the 4538 package is used. The circuit works as follows: as long as step signals are arriving, the oneshot stays triggered and the motor stays at full power, but when the step pulses stop, 10 seconds later the motor switches to half power. The first step after a delay should immediately switch the motor to full power. Whether this switching is fast enough will be determined during testing of the prototype driver.

Stepit 4A: Driver using SLA7078MPR with delay

Schematic:


BOM:


Bill of Material for C:\PCB PIC\SLAgm_04C.PCB


On 4/28/11 at 12:18:18 AM








Count
Label-Value
Pattern
Designation(s)
Mouser










1
330uf 50V
C+400D200
C1
647-UHE1H331MPD
1
47uf
C+200D80H31
C2
647-UHE1E470MDD
4
.1uf
cap100
C3 C4 C5 C7
80-C320C104K1R
1
47uf 50V
C+200D100H31
C6
647-UPW1E470MDD
1
15uf tant
cap100
C8

581-TAP156K016SCS
1

DIP6
DS1

774-2063ST
1

XIDC10
J1
517-D2510-6002-AR
2

SIP2
JC1 JP1
517-647-01-02
1

SIP3
JP2
517-647-01-03
4
10K
AXIAL0.25
R1 R5 R6 R8
299-10K-RC
1
4k7
AXIAL0.25
R2
299-4.7k-RC
1
1M
AXIAL0.25
R3
299-1M-RC
3
1K
AXIAL0.25
R4 R7 R9
299-1K-RC
1
10K
SIP8
RN1
265-10K-RC
2
BC327
TO-92A
T1 T2
512-BC32740BU
1
BC547
TO-92A
T3
512-BC547CBU
1

TB508A_2
TB1
538-39880-0402
2

TB508-3
TB2 TB3
538-39880-0403
1
1K
TRIM2
TR1

858-67WR1KLF
1
SLA7078MPR
SLA7078
U1

1
74HCT4538
DIP16
U2

595-CD74HCT4538E
1

DIP16 Socket


517-4816-3004-CP


Next will be the schematic and BOM for the opto-isolated version, Stepit 4

Stepit 4: Driver using SLA7078MPR with opto-isolation, regulator and delay

Schematic:

BOM:
Bill of Material for C:\PCB PIC\SLAgm_05A.PCB


On 4/30/11 at 2:23:09 PM








Count
Label-Value
Pattern
Designation(s)
Mouser










1
330uf 50V
C+400D200
C1
647-UHE1H331MPD
6
.1uf
cap100
C10 C4 C5 C6 C8 C9
80-C320C104K1R
1
47uf
C+200D80H31
C2
647-UHE1E470MDD
1
47uf 50V
C+200D100H31
C3
647-UPW1E470MDD
1
15uf
cap100
C7

581-TAP156K016SCS
1
FR202
DIODE0.35
D1
583-FR202-B
1

DIP6
DS1

774-2063ST
2
Fuse Holder
Fuse3517
F1
534-3517
1
Socket IDC 10p
XIDC10
J1
517-D2510-6002-AR
2

SIP2
JC1 JP1
517-647-01-02
1

SIP3
JP2
517-647-01-03
1
HLMP1790
LED
LD1
638-HLMP1790
1
240R 1%
AXIAL0.25
R1
270-240-RC
1
1M
AXIAL0.25
R10
299-1M-RC
5
1K
AXIAL0.25
R11 R12 R6 R7 R9
299-1K-RC
4
10K
AXIAL0.25
R13 R14 R15 R16
299-10K-RC
1
720R 1%
AXIAL0.25
R2
270-720-RC
3
330R
AXIAL0.25
R3 R4 R5
299-330-RC
1
4K7
AXIAL0.25
R8
299-4.7K-RC
1
10K
SIP8
RN1
265-10K-RC
2
BC327
TO-92A
T1 T2
512-BC32740BU
1
BC547
TO-92A
T3
512-BC547CBU
1

TB508A_2
TB1
538-39880-0402
2

TB508-3
TB2 TB3
538-39880-0403
1
1K
TRIM2
TR1

858-67WR1KLF
1
SLA7078MPR
SLA7078
U1

1
74HCT4538
DIP16
U2

595-CD74HCT4538E
1
6N137
DIP8
U3
512-6N137
1
HCPL2631
DIP8
U4
512-HCPL-2630/31
1
LM317HV
TO-220V
U5
LM317HVT Digikey
2
IC Socket 8p

U3S U4S
517-4808-3004-CP
1
IC Socket 16p

U2S
517-4816-3004-CP


2 comments:

  1. Schematics and BOM will be added by 4/25/11???????????

    ReplyDelete
  2. Sorry. Have gotten behind. Will try to have both of these up by May 1 or earlier.

    ReplyDelete