Download Assembly and Checkout - StoutWare Engineering

Assembly and Checkout
of the
LoCoMoCo v1.0
Motor Controller Board
© 2006, 2007 StoutWare Engineering
This document is available online at:
http://www.StoutWare.com/downloads/LoCoMoCo/v1.0/assembly.doc
Note:
This kit is sold as-is, without warranty. No claims are made as to merchantability or fitness for a particular purpose.
The buyer assumes all risks associated with the assembly and operation of this kit. In no way may buyer or end user
hold Lawrence Technological University or StoutWare Engineering liable for damages associated with the construction
or use of the materials contained in this kit. If you do not agree with these conditions, return the kit in original
condition for a refund (minus restocking fees and handling charges).
Note:
Additional information that may be useful to less-experienced hobbyists is included in
shaded boxes such as this one. Experienced hobbyists may choose to ignore these.
Before getting started:
To save on manufacturing costs, four identical circuits were placed on the same printed
circuit board (PCB). These circuits, while identical in function, use different identifiers
to refer to the corresponding components. For example, diode D1 in the first circuit is
referenced as D8 in the second circuit, D13 in the third circuit, and D18 in the fourth
circuit. To minimize the confusion caused by this, references to components will use the
following notation: [ D1 / D8 / D13 / D18 ]. Use the reference that corresponds to that of
the printed circuit board included in your kit. (There is no duplication of identifiers
across the four circuits.)
Printed Circuit Board as received from manufacturer
You should have the following parts in your parts bag:
Notes on component leads:
Most components have metallic ‘leads’ that carry the electrical current to and from the
device. Often, these leads will need to be bent to accommodate insertion into the
printed circuit board prior to soldering. Use care when bending leads, as repeated
bending will weaken them and possibly change their electrical characteristics. After
soldering, excess lead material should be trimmed close to the circuit board, so as to
avoid unintended electrical connections.
Notes on soldering:
Soldering involves high temperatures and molten metals, with associated risks of fire
and serious injury. Be sure that you have the necessary soldering skills before
attempting assembly of this kit. You can acquire soldering skills in a number of ways:
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Have an experienced colleague demonstrate proper soldering techniques
Refer to any of a number of books on the subject
Attend classes at a local college that offers training
Attend a training session sponsored by a local hobby or electronics shop
Also keep in mind that many electronics components have a limited tolerance to the
temperatures involved in soldering, and should not be subjected to these temperatures
over an extended period of time. Counter intuitively; a hotter soldering iron is
generally better, as the required time for contact between the soldering iron and the
component is shorter, with less energy actually transferred to the component.
Notes on electrostatic discharge:
If you have ever felt the small electric shocks that are common when removing
clothing from the dryer, touching a doorknob after shuffling across the floor, or whilst
petting a cat, you have felt the effects of electrostatic discharge (ESD). (Commonly
but incompletely referred to as static electricity.)
Integrated circuits (ICs) often have very small conducting paths (wires) internally.
These paths can be damaged by relatively small ESD events. Care must be taken
when constructing electronic circuits to prevent such damage.
ESD-sensitive devices in your kit have been protected through the use of conductive
foam that distributes charges present to all pins on the devices equally. Use care when
handling these devices once they are removed from the conductive foam.
ESD damage is prevented by following practices that minimize the accumulation and
encourage the dissipation of electric charges. For more information on electrostatic
discharge see http://en.wikipedia.org/wiki/Electrostatic_discharge.
Assembly Instructions
Diodes allow current to flow in one direction only, so the orientation of a diode within
a circuit is significant. For this reason, both the diode and the circuit board are
marked with a band on one end of the component. When placing the diode in the
circuit board, make sure that these bands coincide.

Solder diode [ D1 / D8 / D13 / D18 ] to the circuit board.
Resistors are typically marked with colored bands to indicate their characteristics.
The last band is typically gold or silver and indicates the maximum variation in
resistance value of the resistor from the design value. Gold indicates 5% tolerance,
while silver indicates 10% tolerance.
The other bands indicate a resistance value. Each color corresponds to a digit, as
follows:
0 Black
5 Green
1 Brown
6 Blue
2 Red
7 Violet
3 Orange
8 Grey
4 Yellow
9 White
The band immediately preceding the tolerance band represents a power of 10
multiplier (this can be thought of as a number of trailing zeroes). The other preceding
bands represent a decimal number.
For example, the following resistor has bands of red (2), black (0), green (5), and gold
(5%), and so would be interpreted as 20 x 105 ohms (2.0M) with 5% tolerance.
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Solder 1/6W 2.0M resistor [ R1 / R6 / R11 / R16 ] to the circuit board.
o This resistor is smaller with colored bands red, black, green, gold.
Solder 1/6W 330K resistor [ R4 / R9 / R14 / R19 ] to the circuit board.
o This resistor is smaller with colored bands orange, orange, yellow, gold.
Solder ½W 1.3K resistor [ R2 / R8 / R13 / R18 ] to the circuit board.
o This resistor is larger with colored bands brown, orange, red, gold.
Solder ½W 2.0K resistor [ R3 / R10 / R15 / R20 ] to the circuit board.
o This resistor is larger with colored bands red, black, red, gold.
Your circuit board should now look like this:
Integrated circuits (ICs) can be packaged in many ways. Most of the ICs for this kit
are packaged in dual in-line package (DIP) form. The leads of ICs are often referred
to as ‘pins’, especially when they extend away from the package.
ICs have a specific orientation in a circuit. The standard way of expressing this
orientation is to identify one lead as ‘pin 1’ and to designate that pin with a special
marking, both on the IC and on the circuit board. This often takes the form of a dot,
indentation, or a chamfered corner. When soldering ICs to the circuit board, make
sure that the position of the marking on the IC corresponds that of the silk-screened
marking on the circuit board (note that the appearance of the markings may not be
similar – it is the location of the markings that is significant).
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Solder the 20-pin DIP [ U2 / U10 / U16 / U22 ] to the circuit board.
o These parts have SN74LV8153N or similar shown on top.
Solder the 14-pin DIP [ U3 / U9 / U15 / U21 ] to the circuit board.
o These parts have SN74HC04N or similar shown on top.
Solder the 4-pin DIPs [ U5 / U7 / U13 / U19 ] and [ U6 / U12 / U18 / U24 ] to the
circuit board.
o These parts have DF04M or similar shown on top.
Solder the 6-pin DIP [ U1 / U11 / U17 / U23 ] to the circuit board.
o These parts have CNY17-4 or similar shown on top.
Your circuit board should now look like this:
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
Solder 0.1uF capacitors [ C2 / C6 / C10 / C14 ], [ C4 / C8 / C12 / C16 ], and
[ C1 / C5 / C9 / C13 ] to the circuit board.
Solder the 8-pin SIP ladder resistor [ R5 / R7 / R12 / R17 ] to the circuit board.
o Note: The ladder resistor has an orientation. Pin 1 of the ladder resistor
must be placed adjacent to pin 1 of the 20-pin DIP.
LED stands for ‘light-emitting diode’. Since these devices are diodes, their
orientation is significant. Holes in the PCB intended for insertion of component leads
are surrounded by metallic ‘pads’ that help the solder to form robust physical and
electrical connections. When inserting a LED into the PCB, the orientation should be
such that the longer lead on the LED is inserted into the pad having the square shape.
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Solder red LEDs [ D2 / D10 / D15 / D20 ] and [ D4 / D7 / D12 / D17 ] to the
circuit board.
Solder green LEDs [ D3 / D9 / D14 / D19 ] and [ D5 / D6 / D11 / D16 ] to the
circuit board.
Your circuit board should now look like this:
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Solder the DB9 connector [ J2 / J7 / J12 / J17 ] to the circuit board.
o The pins of the DB9 connector are placed on either side of the circuit
board, aligned with the corresponding pads, and soldered into place. Two
of these pins (on the back of the PCB) are used in the circuit, and are
identified by the PCB ‘trace’ that leads away from them. For a robust
physical connection, solder every pin of the connector to the
corresponding pad on the PCB.
Note: The PCB is designed for use with terminal blocks having up to four leads. The kit
includes terminal blocks having two leads (more appropriate to the designed current
levels). It is recommended that the terminal blocks use the interior set of holes (those
farthest from the edge of the board). Make sure that the receiving holes (those in which
power and motor wires will be inserted) face outward!
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Solder terminal blocks [ J4 / J10 / J15 / J20 ] and [ J5 / J6 / J11 / J16 ] to the
circuit board.
o These terminal blocks are keyed so that they can be joined together in
series. Two terminal blocks should be joined and inserted into the PCB as
a single unit and then soldered.
Solder terminal block [ J3 / J9 / J14 / J19 ] to the circuit board.
Your circuit board should now look like this:
Electrolytic capacitors have a specific orientation – they fail (sometimes
catastrophically) when ‘reverse biased’. To indicate the orientation, an electrolytic
capacitor will always be marked with either a plus ‘+’, a minus ‘-‘, or both. The PCB
will have similar markings.
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Solder the electrolytic capacitor [ C3 / C7 / C11 / C15 ] to the circuit board.
o Make sure that the minus ‘-‘ side of the capacitor is oriented so that it is
closest to the interior of the PCB.
Solder the 3-pin voltage regulator IC [ V1 / V2 / V3 / V4 ] to the circuit board.
o Pin 1 is not marked on the PCB. The voltage regulator IC should be
oriented such that pin 1 is farthest from the edge of the board.
Solder the 15-pin driver IC [ U4 / U8 / U14 / U20 ] to the circuit board.
o This part will have L298N or similar shown on front.
o There is only one valid orientation for this part – pin 1 is not explicitly
shown.
Attach standoffs to the board at the corner holes.
o Use the shorter screws for this – the longer screws can be used to attach
the board to thicker materials.
Assembly is finished. Your circuit board should now look like this:
Warning:
During operation, and depending on the application and the environment, the driver IC
and / or voltage regulator IC may become VERY HOT. Use extreme caution when
handling the LoCoMoCo board during and after operation. To prevent damage to the
circuitry and /or for safe operation, your application may require additional heat sinks
attached to the driver and / or voltage regulator ICs. These ICs are quickly identified
by their characteristic metal tabs with through-holes (used for securing the heat sink).
Heat sinks are not included with this kit.
Testing the Communications Circuitry
As when initially connecting any circuit, check immediately to see whether any parts
quickly become abnormally warm. Be extremely careful to avoid burns if using your
fingers to perform this check. When correctly constructed, this circuit will not get
abnormally warm from just applying power. If you observe a large spark when
connecting power, you most likely did something wrong during construction, and
probably did damage to the circuit when the spark jumped.
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Connect a 12V battery to the power connector (on the opposite side of the board
from the DB9 connector). Observe the polarity markings on the PCB. You are
responsible for damage to the circuitry that will occur if you connect the battery
incorrectly.
Connect the DB9 connector to a computer’s serial port.
Configure your communications program for 2400 bps, 8 data bits, no parity, and
one (two preferred) stop bits.
Two characters are required for each command sent to the LoCoMoCo. The first
character corresponds to the left channel, the second character corresponds to the
right channel. The following characters are valid (there are others, but these will
exercise all features):
Hex
Value
0x0F
0x1F
0x2F
0x3F
0x4F
0x5F
0x6F
0x7F

Keyboard
Character
ctrl-O
ctrl-_ (underscore)
/
?
O (oh)
_ (underscore)
o (lowercase oh)
DEL
Effect
drive disabled (coast)
drive disabled + reverse (coast)
drive disabled + forward (coast)
drive disabled + reverse + forward (coast)
drive enabled (braking)
drive enabled + reverse (reverse)
drive enabled + forward (forward)
drive enabled + reverse + forward (braking)
Check that the corresponding LEDs light when forward (green) and reverse (red)
options are enabled. (Typing DEL DEL should light all lights, for example).
If everything works as intended both consistently and reliably, proceed to the next
section. Otherwise, check the following:
 Is the RS-232 cable connected properly?
 Is the correct port being referenced (COM1 vs. COM2, for example)?
 Communications parameters – are they 2400 bps, 8 data bits, no parity?
 Supply voltage – is it 12VDC with correct polarity?
 Resistors – were the correct values used for each? Was the ladder resistor
installed with the correct orientation?
 Diodes – were all diodes (including LEDs) installed in the correct orientation?
Testing the Driver Circuitry
Once the communications circuitry has been successfully tested, the driver circuitry may
be tested.
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Attach a voltmeter to the outputs of either the left (L) or right (R) terminal block.
Exercise the communications interface as before, verifying that when drive is
enabled, the voltage differential between the terminals is as expected.
Attach the voltmeter ground to the 12VDC ground and check the output at each
terminal is as expected while exercising the communications interface.
Repeat the procedure for the other terminal block.
Attach a small DC load (such as a small motor) to each terminal block and verify
expected operation.
Does everything work? If so, congratulations! You’re ready to integrate LoCoMoCo
into your project. Otherwise, check the following:
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
Verify that the 4-pin DIP components have the proper orientation.
Verify that the solder joints on the driver chip and terminal blocks are well
formed.
Operation
LoCoMoCo is designed to drive loads of up to 0.5 amps per channel steady state, with
transient loads of up to 1.0 amp per channel. When integrating LoCoMoCo into your
project, operation should be closely monitored to determine whether additional heat sinks
are required.
While 2.4kbps is the only supported data rate it may be possible to send commands to
LoCoMoCo at speeds of up to the theoretical maximum standard rate of 19.2kbps. This
will be dependent upon the characteristics of your RS-232 transmitter and the cable used
for communications. No changes to the circuitry are necessary to support the higher data
rates. (There will be no response to questions regarding unsupported data rates! If you
really feel the need to tweak, you’re on your own - the resistor values of interest are:
[ R1, R6, R11, R16 ], [ R2, R8, R13, R18 ], and [ R3, R10, R15, R20 ].)
Sample java code used for driving small motors via RS-232 can be found at:
http://www.StoutWare.com/downloads/LoCoMoCo/v1.0/java.zip
Note that this sample code uses the javax.comm package, which is no longer available for
Win32 platforms from the java.sun.com site (at least the time of this writing). You can
obtain a previous release (rather old) of this package at:
http://www.StoutWare.com/downloads/LoCoMoCo/misc/javacomm20-win32.zip