Logos Electromechanical ARD-SRG-IPS4X4 User manual

9/29/2010
High Current 16 Switch
Shield Manual
High current, high side switching for Arduino
Logos Electromechanical

Logos Electromechanical
1 
© 2010 Logos Electromechanical CC-BY-NC-ND 3.0
High Current 16 Switch Shield
Manual
High current, high side switching for Arduino
Introduction
The Logos Electromechanical ARD-SRG-IPS4X4 16 channel high current shield is
designed to enable users to switch DC loads up to 5A at up to 30V with no heat-sinking.
It uses four International Rectifier IPS6044 four channel fully-protected high side
MOSFET switch ICs. Each includes over-temp, over-current, and under-voltage
protection on each
switch. The high-
side topology is
safer in many
applications than
the more common
low-side topology
because a short to
ground cannot
energize the circuit
while the switch is
turned off, as it can with a low-side switch. Each four-channel chip has an independent
power supply to allow the user maximum flexibility in configuring this board for their
application.
Figure
1
: Kit Contents

Logos Electromechanical
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© 2010 Logos Electromechanical CC-BY-NC-ND 3.0
The PCB is made with generous traces to handle the current with minimal voltage loss
and heating on the board. A pair of 74AHCT595 8-bit shift registers allow the control of
sixteen high current channels from only four Arduino pins using the shiftOut() function.
The use of shift registers makes it possible to daisy-chain as many as 25 boards off a
single Arduino, for a total of up to 400 high current channels.iIn addition, it can be
daisy-chained with all other Logos output boards with a shift register input, i.e. those
with a part number of the form *-SRG-*.
This board is shipped as a kit, with none of the connectors soldered to the board. This
gives the user the flexibility to install the desired connectors for the application.
Board Overview
Board Layout
The switches are laid out around a vertical DB-25 to carry all of the high current signals .
The DB-25 was chosen due to its relatively high current capacity (5A/pin), long history,
and the enormous range of
types and grades the mating
connectors are available in.
Each of the four IPS6044 chips
houses four channels. Each
IPS6044 draws its power supply
from a pair of pins on the main
connector and switches it to
Figure
2
: Board Layout

Logos Electromechanical
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© 2010 Logos Electromechanical CC-BY-NC-ND 3.0
four output pins on the same connector. This arrangement allows the switching loads
with different power requirements on a single shield. However, each group must be
arrange so that it draws no more than 10A continuous in order to avoid overloading the
connector. A substantial anti-parallel diode protects each switch, allowing fast switching
of large inductive loads without damage to the switches.
The expansion connector, shift registers, and associated resistors are located on the left
side of the shield as seen in Figure 2. The shift registers are powered from the +5V logic
supply of the host Arduino. The board is shipped with the Arduino and expansion
connectors provided but not installed in order to permit the user to to install the
connectors most appropriate to their application.
Pin Descriptions
Table 1: Arduino Pins
Arduino
Pin Name Function
4
DAT Data Return
7
LAT
Register Clock (positive edge)
8
MR
Master Reset (active low)
12
SCK
Serial Clock (positive edge)
13
SIN
Serial Input
+5V
5V
Logic Supply
GND
GND
Logic Ground
(Shorted to power ground)
DAT: Data return. This allows boards on a daisy chain to return data to the
controlling Arduino. Each shift register compatible shield has a jumper that

Logos Electromechanical
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© 2010 Logos Electromechanical CC-BY-NC-ND 3.0
allows this pin to be connected to the SOUT pin (J-FB1) or digital pin 4 (J-FB2).
The last board in a chain must have this pin jumpered to SOUT in order to enable
data return and the board mounted to the host Arduino must have this pin
jumpered to digital 4 in order to allow the host to read the data.
LAT: A positive edge on this pin latches the current contents of all of the the shift
register to the outputs.
MR: Pulling the Master Reset low clears all of the shift registers.
SCK: A positive edge on this pin move the current value of the SIN pin to the
least significant bit of the first shift register (IC1), and shifts every current bit in
each shift register one bit up.
SIN: The value of this pin is shifted in to the least significant bit of the first shift
register on each rising clock edge.
Table 2: Expansion Connector Pinout
Input Pin
Name
Function
1
+5V
+5V power for shift registers
2
SCK
Serial Clock (positive edge)
3
GND
Ground
4
MR
Master Reset (active low)
5
DAT
Data Return
6
LAT
Register Clock (positive edge)
7
SOUT
Serial Data Out (to next board)
8
SIN
Serial Data In (from last
board/host)

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© 2010 Logos Electromechanical CC-BY-NC-ND 3.0
SCK, SIN, LAT, MR, DAT: These pins work as described above.
SOUT: When a bit is shifted past the end of the second shift register (IC2) it
appears on this pin. This is what allows multiple shields to be daisy chained.
Table 3: Power Connector Pinout
Power Pin
Name
Function
1
GND
Common Ground Reference
2
VCC2
Power supple for switches
0
-
3
3
OUT3
Switch 3
4
OUT2
Switch 2
5
OUT1
Switch 1
6
OUT
0
Switch 0
7
VCC2
Power supple for switches
0
-
3
8
VCC1
Power supple for switches
4
-
7
9
OUT7
Switch 7
10
OUT6
Switch 6
11
OUT5
Switch 5
12
OUT
4
Switch 4
13
VCC1
Power supple for switches
4
-
7
14
VCC3
Power supple for switches
8
-
1
1
15
OUT
8
Switch 8
16
OUT9
Switch 9
17
OUT10
Switch 10
18
OUT11
Switch 11
19
VCC3
Power supple for switches
8
-
11
20
VCC4
Power supple for switches
12
-
15

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© 2010 Logos Electromechanical CC-BY-NC-ND 3.0
Power Pin
Name
Function
21
OUT1
2
Switch 12
22
OUT13
Switch 13
23
OUT14
Switch 14
24
OUT1
5
Switch 15
25
VCC4
Power supple for switches
12
-
15
Electrical Characteristics
Table 4: Switch Electrical Characteristics
Symbol
Parameter
Max
Typ
Min
Units
R
ds
(on)
Resistance, on state 0.13 0.12 0.11 Ω
V
clamp Clamping Voltage 39 39 37 V
I
lim Current Limit 10 7 4 A
VccOp
Recommended Operating Voltage
Range 28 - 6 V
Td
on Turn-on Delay Time - 5 15
µs
Tr(90%) Rise Time to 90% of Vcc - 4 20

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© 2010 Logos Electromechanical CC-BY-NC-ND 3.0
Board Usage
Electrical Connection
The ideal connector to use is a high-grade DB-25 with high-quality crimp-style socket
terminals. Solder-style are also acceptable, but less durable and more labor-intensive to
assemble correctly. In both cases,
appropriate strain-relief is crucial
to reliability and durability. A
good quality backshell for the
connector will come with
appropriate strain relief
components. Figure 3 shows a
schematic of a typical connection.
Software Interface
This board is designed to work
with the shiftOut() library function from the Arduino library. Since this board
includes two shift registers, two calls are required in order to operate all of the switches.
The following code will write the contents of lowByte and highByte to S0-S7 and S8-
S15, respectively.
digitalWrite(7, LOW); // Prepares latch
digitalWrite(8, HIGH); // Deactivates master reset
shiftOut(13, 12, MSBFIRST, highByte); // shift data for OUT8-OUT15
shiftOut(13, 12, MSBFIRST, lowByte); // shift data for OUT0-OUT7
digitalWrite(7, HIGH); // latch data
Figure
3
: Typical
power c
onnection

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© 2010 Logos Electromechanical CC-BY-NC-ND 3.0
On the last line, all of the switches will switch at once. The most significant bit of
highByte will control OUT15 and the least significant bit will control OUT8 and
likewise for lowByte, OUT7 and OUT0.
Daisy Chaining
This shield is designed to be
daisy-chained in order to get
greatly expanded numbers of high
current outputs. This requires a
cable of the type shown in Figure
4. All of the pins are carried over,
with the exception of SIN & SOUT
(pins 8 & 7, respectively). SOUT of
the source shield must be
connected to SIN of the next
shield, and so on down the chain.
If you're using IDC connectors with ribbon cable to make your daisy chain cable, this is
straightforward. Assemble the first connector normally. At the second connector,
separate and swap conductors seven and eight. After assembling the connector, cut
conductor seven (now plugged into pin eight of the second connector) downstream of
the second connector and conductor eight (now plugged into pin seven of the second
connector) upstream of the connector. Assemble the third connector normally, but after
you have assembled it, trim conductor eight downstream and conductor seven
upstream. Assemble the fourth connector as you did the second and the fifth as you did
Figure
4
: Daisy
chain cable s
chematic

Logos Electromechanical
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© 2010 Logos Electromechanical CC-BY-NC-ND 3.0
the third, alternating for any additional connectors. See Figure 5 for how it should look.
Connector 1 is on the left end of the cable.
Figure 5: Daisy chain cable
Certain other Logos Electromechanical parts also use shift registers compatible with this
shield – see the product page for which ones. They will have expansion connectors
compatible with the eight pin connector on this shield.
The daisy chain also contains the option to pass information from the daisy chain back
to the controlling host. This does nothing on this board except wrap the transmitted
value back to the host, but is included for compatibility with future planned boards.
There are two jumpers on the board that control this function – one between the SOUT
and DAT lines on the expansion connector and one between the DAT line and digital pin
4 on the Arduino. In a project where no wrap-around or feedback is desired, both
jumpers should be left open. If feedback is desired, the SOUT-DAT jumper should be
made on the last board in a chain, in order to wrap the serial stream back to the return
line. The DAT-D4 jumper should be made on the board connected to the host Arduino,
in order to allow the host to receive the returned serial stream.

Logos Electromechanical
10 
© 2010 Logos Electromechanical CC-BY-NC-ND 3.0
Stepper Motor Control
This shield can be used, with
some caution, to control up to
four unipolar stepper motors.
However, the connection is a little
different than the usual for
conventional unipolar stepper
motors. Typically, one connects
the common lead(s) of the
stepper motor to a power source
and then switches the four coil
terminals to ground in a pattern
that moves the stepper motor as
desired.
However, the switches on this board are all high-side switches. That means that you
have to flip the polarity of all of the coils, and wire the common terminal to ground.
While this works with most unipolar stepper motors, it cannot be guaranteed to work
with any particular motor.
Figure
6
: Unipolar steppper wiring schematic

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© 2010 Logos Electromechanical CC-BY-NC-ND 3.0
References
Datasheet for 74HC595 shift registers http://datasheet.octopart.com/MM74HC595MTC-
Fairchild-datasheet-12735.pdf
Datasheet for IPS6044GPBF http://www.irf.com/product-
info/datasheets/data/ips6044g.pdf
Arduino Language Reference http://arduino.cc/en/Reference/HomePage
iThe limiting factor on the number of boards that can be daisy-chained off a single Arduino is the fan-out
of the pins that drive the three inputs common to all devices in the chain (SCK, MR, and LAT). This can be
expanded by adding a non-inverting buffer to drive these pins out farther along the chain.