TAPR T-238+ User manual
T-238+ Assembly Manual Rev. 3 March 2006 Page 1 of 11
Tucson Amateur Packet Radio
Internet: [email protected] www.tapr.org
Non-Profit Research and Development
Corporation T-238+
Main Board (Rev B)
T-238+ Assembly Manual
This document was originally written April 2005. © 2005 Tucson Amateur Packet Radio Corp.
Reproduction or translation of any part of this work beyond that
permitted by sections 107 or 108 of the 1976 United States
Copyright Act (or its legal successor) without the express written
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Amateur Packet Radio Corporation. Except as noted above,
permission is hereby granted to any non-profit group or
individual to reproduce any portion of this document provided
that: the reproduction is not sold for profit, the intent of the
reproduction is to further disseminate information on Amateur
Packet Radio, the reproduction is not used for advertising or
otherwise promoting any specific commercial product, full credit
is given to Tucson Amateur Packet Radio Corporation (including
address) as the original source of information, and Tucson
Amateur Packet Radio Corporation is notified in writing of the
reproduction.
The information contained in this document has been carefully checked and is believed to be entirely reliable. However, no
responsibility is assumed for inaccuracies. Tucson Amateur Packet Radio Corporation (TAPR) reserves the right to make
changes in any products to improve reliability, function or design without obligation to purchasers of previous equipment.
TAPR does not assume any liability arising out of the application or use of any product or circuit described herein; neither
does it convey license under its patent rights or the rights of others.
Introduction......................................................................1
Acknowledgments............................................................2
Parts list...........................................................................2
Construction notes ...........................................................3
Construction.....................................................................3
Button Board Construction ...............................................7
Power-up and initial testing ..............................................6
Assembly drawings ........................................................11
Board layout...................................................................12
Schematic diagram........................................................13
Introduction
The TAPR T-238+ is a general-purpose Motorola
MC68HC908GP32 microcontroller-based board intended
for use with the Dallas Semiconductor 1-Wire™ bus and
any device that needs a serial connection. Four push-
button switches and a Liquid Crystal Display (LCD)
module provide the user interface. The initial application
for the T-238+ is a controller that accepts data from a
Dallas Semiconductor weather sensor unit, processes it,
and formats it for sending either directly to a Terminal
Node Controller (TNC) for broadcasting in APRS™
format, to a computer for processing and/or logging, or
directly to a radio using the MX-614-based modem. There
is nothing about this board that makes it solely a weather
station. This just happens to be what the software for it
does.
The T238+ is a successor to the TAPR T238. Software
releases will work with both projects. The software will
determine at startup which project it is running on and
configure itself as needed.
For the most current information on weather sensors,
software downloads, development tools, and related
information, visit http://www.tapr.org and follow the links
to the T238+ project, or visit http://www.beals5.com/wx.
The TAPR T-238+ is a ready-made kit with the weather
application pre-programmed into the microcontroller. It is
possible to develop your own applications on the T238+ as
well. A debug header is provided that with a small adapter
circuit can enable a fully functional development system.
The T238+ kit does not come with an enclosure or power
supply. It is left up to the builder to find an enclosure that
is suitable. For power, the user can use an ordinary wall
transformer (“wall wart”) that provides 8-12 Volts DC at
300 milliamps. The T238+ is fitted with a 2.1mm power
coaxial connector arranged so that the center conductor is
positive. Unlike the original T238, the T238+ contains
analog circuitry that is much more susceptible to RFI,
making the need for a metal case much greater.
As T-238 programs are developed they will be displayed
or linked from the TAPR Weather web site. Go to
http://www.tapr.org and follow the T238 links. If you’ve
created a project and would like to display or link to it,
The T238+ is discussed on the Weather Special Interest
Group (WXSIG). You can join WXSIG via the web at
http://www.tapr.org/cgi-bin/lyris.pl?join=wxsig.
T-238+ Assembly Manual Rev. 3 March 2006 Page 2 of 11
Acknowledgments
The Tucson Amateur Packet Radio T238+ Kit was made
possible by the efforts of (in alphabetical order):
William Beals, N0XGA -Conceptual Designer
John Bennett, N4XI –Sensors
Joe Borovetz,WA5VMS -Parts Management
Russ Chadwick, KB0TVJ -Conceptual Designer
John Koster, W9DDD –Project Manager
The T238+ consists of three boards. These are the main
board, the modem board, and the button board. The main
board and button board are kitted together and the modem
board is separately. The LCD module is a board too, but
is listed as a component for the main board. You will
assemble the main board and button board first, and
check them out. Finally, you will assemble and check out
the modem board.
T238+ MAIN BOARD
PARTS LIST
The parts list is organized by quantity and part type.
Verify that all parts are present by checking in the [ ] as
you locate the part in the list. You may wish to take this
opportunity to sort the parts into a compartmented
container such as an egg carton or muffin tin as you
inventory them. This will aid you in kit building.
Resistors 1/4 w, 5% Carbon Film:
[ ] (1) 10 ?(brown-black-black) R4
[ ] (1) 470 ?(yellow-violet-brown-gold) R9
[ ] (1) 1.5K ?(brown-green-red-gold) R16
[ ] (1) 2.2K ?(red-red-red-gold) R1
[ ] (4) 10K ?(brown-black-orange-gold) R2,3,8,18
[ ] (1) 20K ?(red-black-orange-gold) R20
Resistor 1/2 w, 5% Carbon Film:
[ ] (1) 4.7 ?(yellow-violet-gold) R5
Resistor Pack, 5% Carbon Film:
[ ] (1) 10K ?R19
Resistor, Trimpot
[ ] (1) 10K ?Trimpot (103) V1
Capacitors
Capacitors may be marked in various ways. The typical
markings are listed but may vary. Find all that match and
the remaining ones, if any, should become apparent by
elimination.
Mylar or Monolithic
[ ] (5) 0.1uf (104) C1,4,5,9,12
Electrolytic or Tantalum
[] (5) 1uF (1uf 50v) C3,6,7,8,13
[ ] (2) 10uF C2,14
Diodes
[ ] (2) 1N4148 Silicon Diode D2, D3
[ ] (1) 1N5817 Schottky Diode D1
Light Emitting Diodes
[ ] (1) Red LED DS1
Inductors
[ ] (5) Ferrite Beads L1,2,3,4,5
Integrated Circuits
NOTE: Do not handle the ICs at this time! Carefully
remove the black foam carrier with ICs from the bag and
verify the ICs against this list. Do not touch the ICs!
Leave them in the protective foam.
[ ] (1) MC68HC908GP32CP U2
[ ] (1) MAX232 or HIN232 U1
Voltage Regulators
[ ] (1) 7805 TO-220 case U3
Crystal Oscillator
[ ] (1) 32.000MHz U4
IC Sockets
[ ] (1) 16-pin DIP Socket U1
[ ] (1) 40-pin DIP Socket U2
Switches
[ ] (1) DPDT Momentary push button (6-pin) SW1
[ ] (4) Round momentary switches SW1-4 (button)
LCD Module
[ ] (1) 4 line by 20 character LCD module
Connectors
[ ] (2) 2x5-pin male header J2, P1(button)
[ ] (1) 2x8-pin male header J3
[ ] (1) 1x16-pin male header J1
[ ] (1) 1x16-pin female header J1(LCD)
[ ] (1) DE9 Female PCB right angle mount J4
[ ] (1) 2.1 mm Coaxial Jack J6
[ ] (1) 2.1 mm Coaxial Plug J6
[ ] (1) RJ-11 6-6 connector PCB mount J5
T-238+ Assembly Manual Rev. 3 March 2006 Page 3 of 11
Miscellaneous
[ ] (1) Printed Circuit Board (Rev B)
[ ] (1) Main Board Assembly Manual (this document)
[ ] (1) Operations Manual
[ ] (1) TO-220 heat sink
[ ] (1) 6-inch 10-conductor IDC cable with connectors
[ ] (1) 4-40 x ¼” screw
[ ] (1) 4x40 nuts
[ ] (4) 6-60 3/8” spacers
[ ] (4) 6-60 1/2” spacers
[ ] (2) 6-60 5/8” spacers
[ ] (4) 6-60 screws
Construction Notes
You are now ready to begin construction of the T238+.
Follow these standard construction practices when
building the unit.
Use a temperature-controlled, fine-tipped soldering iron of
relatively low wattage (25 watts maximum, 15 watts is
ideal) and a good quality 60/40 or 63/37 rosin-core solder
for construction. Keep the tip of your soldering iron bright
and clean, wiping it frequently on a wet rag or sponge.
Make solder joints carefully, but swiftly. Prolonged heat
on a PC board pad can be as disastrous as it can ruin the
PC board. Two to three seconds should be enough time
to apply heat to any joint. Due to the proximity of some of
the traces on the PC board, solder bridges are a very
distinct possibility. Following the important points above
could eliminate several hours of troubleshooting (or
worse). This is good practice when working on any kit.
You will need small flush or semi-flush cutting pliers and
small-tipped long nosed pliers. A magnifying glass may
prove helpful to identify the values of the small
components.
Pay careful attention to the directions that follow:
1) Read this entire document prior to starting construction
of your kit.
2) Identifying the pins on headers and ICs -Pin 1 is
identified by the square pad on silk-screen.
Electrostatic Protection
The Integrated Circuits and crystal oscillators are
susceptible to static discharge. Observe anti-static
precautions when assembling the T-238+. Never handle
the ICs without grounding yourself, the protective foam,
and the PCB first. Always touch and hold the foam first
before touching the IC. Always touch and hold the printed
circuit board before inserting the IC into its socket. Never
leave the ICs on anything but the foam or the PCB.
Construction
Refer to the layout diagram for clarification of parts
placement. All references to up, down, left, and right
assume that you are looking at the PCB side with the
TAPR logo with the text right side up. Sample pictures of
the overall construction are available on the T238 website.
Resistors
Resistors have a lead spacing of 0.4" and should lie flat on
the PC board. You may wish to use a lead former to pre-
form the resistor leads for neatest appearance.
NOTE: –Save the clipped leads as you will use them to
solder the ferrite beads in place in a later step.
Install the following 5 resistors:
[ ] R1 2.2K ?(red-red-red-gold)
[ ] R2 10K ?(brown-black-orange-gold)
[ ] R3 10K ?(brown-black-orange-gold)
[ ] R4 10 ?(brown-black-black-gold)
[ ] R5 4.7 ?1/2 Watt (yellow-violet-gold)
NOTE: R5 is a ½ watt resistor. It is slightly larger than all
the other resistors. The lead spacing is 0.5”.
WARNING! –Be careful when clipping leads, as they
have a tendency to fly towards your eyes! Take
appropriate precautions (grasp leads and wear eye
protection).
[ ] Solder and clip the leads (10 leads total)
[ ] R8 10K ?(brown-black-orange-gold)
[ ] R9 470 ?(yellow-violet-brown-gold)
[ ] R16 1.5K ?(brown-green-red-gold)
[ ] R18 10K ?(brown-black-orange-gold)
[ ] R19 10K ?RPACK (pin 1 closest to J2)
[ ] Solder and clip the leads (10 leads total)
[ ] R20 20K ?(red-black-orange-gold)
[ ] Solder and clip the leads (2 leads total)
Now check your work. All leads should be soldered. There
should be no solder bridges or cold solder connections.
[ ] OK so far.
This completes the resistor installation. You should have
no remaining resistors.
[ ] No resistors remaining.
Diodes
Diodes are polarity sensitive devices. Diodes are mounted
flat near the surface of the board like the resistors
previously installed. The cathode end of the diode is
banded and corresponds to the banded silk-screen legend
on the PCB.
T-238+ Assembly Manual Rev. 3 March 2006 Page 4 of 11
Install the following diodes:
[ ] D1 1N5817 Schottky
[ ] D2 1N4148
[ ] D3 1N4148
[ ] Solder and clip the leads (6 leads total)
Now check your work. All leads should be soldered. There
should be no solder bridges or cold solder connections.
[ ] OK so far.
This completes the diode installation. You should have no
remaining diodes.
[ ] One LED remaining.
IC Sockets
NOTE: If any socket pins are bent, carefully straighten
them with a pair of long-nose pliers before assembly.
Some types of IC sockets have crimps in the pins to hold
them in place when automatic wave soldering is
performed. These sockets may be tricky to install if you
are not familiar with them. If your kit contains these
sockets, you may want to straighten the pins before
attempting to insert them into the PC board.
When installing IC sockets double check to ensure that the
socket is seated properly against the board with the notch
matching the silk-screen. Pin 1 (nearest the socket notch)
has a square solder pad. Be sure that all IC socket pins
are showing on the solder side of the board. Next, tack-
solder two diagonally opposite corners first (such as pins 1
and 8 on a 14-pin socket).
Then solder the remaining pins of that socket before
proceeding to the next one. If you find a socket is difficult
to install, remove it and double-check for a bent pin.
CAUTION! –Take care to avoid solder bridges!
Install the following IC sockets. Align the notch in the
socket to the notch in the silkscreen outline:
[ ] U1 16-pin
[ ] U2 40-pin
Now check your work. All leads should be soldered. There
should be no solder bridges (a blob of solder that shorts
two adjacent soldered connections) or cold (gray and/or
grainy looking) solder connections.
[ ] OK so far.
This completes the IC socket installation.
Ceramic Capacitors
All capacitors should be mounted as nearly flush to the
board surface as practical without stressing the leads.
Install the following capacitors:
[ ] C1 0.1 uF (104)
[ ] C4 0.1 uF (104)
[ ] C5 0.1 uF (104)
[ ] C9 0.1 uF (104)
[ ] C12 0.1 uF (104)
[ ] Solder and clip the leads (10 leads total)
Electrolytic and Tantalum capacitors
Electrolytic and Tantalum capacitors are polarized. The
positive lead goes in the hole on the board marked with a
"+". Be careful! Typically the negative lead is marked but
sometimes the positive lead is marked.
NOTE: The orientation of the positive “+” leads are not all
the same.
[ ] C3 1 uF (105 or 1+35)
[ ] C6 1 uF (105 or 1+35)(text obscured, next to C7)
[ ] C7 1 uF (105 or 1+35)
[ ] C8 1 uF (105 or 1+35)
[ ] C13 1 uF (105 or 1+35)
[ ] Solder and clip the leads (10 leads total)
[ ] C2 10 uF (106 or 10uF)
[ ] C14 10 uF (106 or 10uF)
[ ] Solder and clip the leads (4 leads total)
Now check your work. All leads should be soldered. There
should be no solder bridges or cold solder connections.
[ ] OK so far.
This completes the capacitor installation. You should have
no remaining capacitors.
[ ] No capacitors remaining.
T-238+ Assembly Manual Rev. 3 March 2006 Page 5 of 11
Ferrite Beads
Ferrite beads are cylinder shaped. String a clipped lead
from a resistor or capacitor though the ferrite bead.
Position the ferrite bead over the silkscreen outline and
insert the leads into the solder holes. Solder the leads and
clip them flush on the bottom of the PCB.
Install the following ferrite beads:
[ ] L1
[ ] L2
[ ] L3
[ ] L4
[ ] L5
[ ] Solder and clip the leads (10 leads total)
Trimpot
Align the trimpot according to the three solder leads.
Note: the silkscreen is incorrect! It shows the small
plastic tabs on the wrong side.
Install the trimpot:
[ ] V1 10K ohm
[ ] Solder and clip the leads (3 total)
Light Emitting Diode (LED)
LEDs are polarized components. The flat side on the
base and the shorter lead identifies the cathode lead.
Insert the LED according to the silk-screen outline, the flat
side or short lead to the flat side of the silkscreen
NOTE –Mounting the LED on this board assumes you do
not want to see the heartbeat LED once the project is put
in a chassis. If you want to see the heartbeat after the
project is in a chassis, save the LED and mount it on the
button board instead.
[ ] DS1 Red LED (if you want it here)
[ ] Solder and clip the leads (2 total)
Male Headers
The male headers will be installed next. Except for J1,
the plastic body of the part should rest flush with the top
surface of the PC board. Note that the short end of the
pins go into the PC board, the long end sticks up. J1 is a
special case that will be handled later.
WARNING! –Do not hold these parts with your fingers
while soldering. The pins get very hot.
Place a 2-pin jumper on the header to insulate your finger
from the pins, hold the header in place and tack solder
one pin. Check for proper alignment. If alignment is off,
you can reheat the one pin to adjust. Once the alignment
is correct, solder the rest of the pins and then reflow
(reheat) the first pin you soldered.
NOTE: It is important to ensure these headers are
installed flush so they come out of the board vertically.
This is especially important for J3, the modem header.
[ ] J2 2x5 male header DO NOT INSTALL J1 YET!
[ ] J3 2x8 male header
Note that P2 and P3 are not stuffed for normal use, they
are for debugging or special applications.
Connectors
Gently rock the RJ-11 connector until it snaps into place
and solder the leads.
[ ] J5 RJ-11 connector
CAUTION! –Soldering the coaxial power connector is a
bit tricky because of the large mounting holes.
[ ] J6 Coaxial power connector
Install the DE-9 connector. Solder in the tabs that hold the
connector in place first, then solder the pins.
[ ] J4 DE-9 female
[ ] Solder the leads
Switches
Install the square DPDT momentary switch. The
orientation matters! Look at the plunger to see which side
has a depression in it. Install the switch with that
depression “up” (toward the potentiometer).
[ ] SW1 DPDT Momentary Push Button
[ ] Solder the leads
Voltage Regulator
Refer to the assembly diagram at the end of this
document for how to assemble the voltage regulator and
heatsink. The regulator will be mounted with its metal tab
against the heatsink and that in turn compressed to the
component side of the board. This needs to be a secure
mechanical connection for decent heat flow to both the
heatsink as well as the main board as the ground plane is
being used as a heatsink too. While heat sink grease
would be nice, it is not necessary.
Temporarily mount the assembly to the board and note
(with a pen or scribe) where to bend the regulator leads to
line up with their solder pads. Remove the regulator, bend
the leads 90 degrees, and then re-assemble the
heatsink/regulator assembly.
T-238+ Assembly Manual Rev. 3 March 2006 Page 6 of 11
Double-check the orientation per the paragraph above and
the assembly diagram at the end of this manual.
[ ] Solder U3, 7805 assembly
[ ] Solder and clip the leads (3 total)
Crystal Oscillator
The crystal oscillator for this project looks like an IC
except it has only four pins. Note the pin 1 marking on the
IC (round dot) and make sure the oscillator is oriented
correctly.
NOTE: If you feel you may want to develop software for
the T238+, It may be a good idea to socket the oscillator.
As we don’t expect many people to become software
developers, a socket is not being included in the kit.
[ ] Solder U4, Oscillator
LCD Module
Now you will prepare the LCD module for connection to
the T-238+ PCB. The LCD module connects to the PCB
via a male/female set of connectors. Refer to the
assembly drawing at the end of this manual.
[ ] Carefully remove the LCD module from its protective
packaging. If it has a protective plastic cover over the
glass, leave it on.
You will be soldering a 1x16-pin male header to the back
of the LCD module. During this time you need to protect
the LCD screen from splatter while soldering.
[ ] Ensure the LCD screen is protected.
[ ] Loosely insert the 16-pin male header into the female
header just to the point where there is some resistance to
the insertion.
[ ] Install the four 1/2" spacers on the back of the LCD
module. Install them by screwing in the 3/8” spacers into
them. The 3/8” spacers should be on the front of the
display with their threads going through the LCD module
into the 1/2" spacer.
[ ] Install the male side of the 16-pin header pair into the
back of the LCD module. Line up the two boards so the
threads from the 1/2" spacers go into the holes of the main
board. Squeeze the two boards together, compressing the
headers until the spacers are firmly seated. This will
ensure accurate alignment of the connector while
soldering. Temporarily install two more 5/8” spacers on
the threads of the 1/2" spacers to hold the two boards
together for soldering. Verify your assembly looks like the
assembly drawing at the end of this document.
[ ] Solder both 1x16-pin headers.
[ ] Unscrew the two temporary 5/8” spacers, separate the
two boards, and put the LCD module back in it’s protective
packaging.
T-238+ Assembly Manual Rev. 3 March 2006 Page 7 of 11
Almost done with the main board
At this point, these should be the only items left in the
main board kit:
NOTE: Keep U3 and U4 in the antistatic foam
[ ] U3 MC68HC908GP32
[ ] U4 MAX23
[ ] 2.1 mm Coaxial Plug
Board Check
You are now complete with the soldering of the main
board. Other than the two ICs mentioned, the only
component locations that should not have anything loaded
are P2 and P3. These are for debug and program
development use and should not normally be needed.
DS1 may or may not be loaded depending on where you
want your activity LED to be.
T-238+ Assembly Manual Rev. 3 March 2006 Page 8 of 11
T238+ BUTTON BOARD
Construction
Refer to the layout diagram for clarification of parts
placement. All references to up, down, left, and right
assume that you are looking at the PCB with the text right
side up. The front of the board is the side with button text
(UP, DOWN, SEL, MENU). Switches and the LED are
installed on this side; the header is installed on the
back side.
Switches
Install the four SPST momentary switches. Note the flat
end of the switch and line it up with the flat edge marked
on the silkscreen. All four switches are the same.
[ ] SW1 SPST Momentary Push Button
[ ] SW2 SPST Momentary Push Button
[ ] SW3 SPST Momentary Push Button
[ ] SW4 SPST Momentary Push Button
Light Emitting Diode (LED)
LEDs are polarized components. The flat side on the
base and the shorter lead identifies the cathode lead.
Insert the LED according to the silk-screen outline, the flat
side or short lead to the flat side of the silkscreen
NOTE –Mounting the LED on this board assumes you did
not mount it on the main board.
[ ] DS1 Red LED (if you want it here)
[ ] Solder and clip the leads (2 total)
Male Header
The male header will be installed next. The plastic body of
the part should rest flush with the top surface of the PC
board. Note that the short end of the pins go into the PC
board, the long end sticks up.
WARNING! –Do not hold these parts with your fingers
while soldering. The pins get very hot.
NOTE: This header must be installed on the back of the
board.
Place a 2-pin jumper on the header to insulate your finger
from the pins, hold the header in place and tack solder
one pin. Check for proper alignment. If alignment is off,
you can reheat the one pin to adjust. Once the alignment
is correct, solder the rest of the pins and then reflow
(reheat) the first pin you soldered.
[ ] P1 2x5 male header
T-238+ Assembly Manual Rev. 3 March 2006 Page 9 of 11
Power Up And Initial Testing:
In this section you will slowly power-up the board and
check for assembly errors. It is important that you follow
these steps carefully. You will systematically apply power
to sections of the board while checking voltages to find
and eliminate errors. Errors take two forms, the kind that
damage components and the kind that don’t. Neither is
desirable, but the kinds that damage components will
require you to find a replacement part.
Pre-Power Check
Before applying power for the first time, please check the
following:
[ ] ICs U1 and U2 are NOT installed.
[ ] Check the polarity of all the electrolytic or tantalum
capacitors. The capacitorsnegative side is usually
identified with a white stripe and a big minus sign on it.
The positive side is identified on the PCB. Not all the
capacitors have the same orientation; double-check them
with reference to PCB silkscreen.
[ ] Check the polarity of diodes D1, D2, and D3. The
band on the diode should match the extra stripe on the
PCB silkscreen.
[ ] Headers P1, J1, J2, j3, J4, J5 and J6 are not
connected.
[ ] The LCD module should not be plugged in.
First Power Check
The T238+ kit does not come with a power supply. An
ordinary wall transformer (“wall wart”) that provides 7 to 12
Volts DC at 300 milliamps will work fine. The closer you
can get to 7V the cooler the regulator will be. Be warned
that may “12V” wall transformers supply much higher
voltages even under load. The T238+ is fitted with a
2.1mm power coaxial connector such that the center
conductor is positive and the outer barrel is ground.
Measure this with a voltmeter to confirm both the voltage,
but more importantly, the polarity. The Radio Shack
Model 19-1120/19-1140, supplied with the HTX-202 and
the HTX-404 handheld radios, is suitable for this
application.
[ ] The voltage is between 9 and 12 Volts DC and the
center conductor is positive and the barrel is ground
[ ] Apply power to the T238+. Observe anything unusual
such as components heating up, smoke or smell.
Remove power immediately if anything unusual appears.
Place the ground lead of your voltmeter on the center pin
of U3. This will be the ground reference for the rest of the
measurements.
[ ] Measure the voltage on the voltage regulator U3 on the
pin closest to the edge of the board. It should be between
8 and 14V. If it is 0V, then L5 is likely missing or
damaged. If it is low, the transformer may not be rated for
the right voltage or something may be overloading it.
[ ] Measure the output voltage on the voltage regulator U5
on the pin furthest from the edge of the board. It should
be between 4.90V and 5.10V. If it is low, something could
be overloading the regulator and whatever is doing that
should be hot.
WARNING! –Don't proceed until the voltages in and out
of the voltage regulator U5 are within proper limits.
[ ] Voltages in and out of voltage regulator U5 are within
limits.
NOTE –In the sections below, there are frequent
references to +5V, which actually means the voltage
between 4.90V and 5.10V that you measured above.
With the ground lead of your voltmeter still on U3 pin 2
(center), confirm all the following test points also measure
+5V. Remedies are listed if you do not see +5V.
Check Pin Remedy if not +5V
[ ] U1 pin 16 Check socket.
[ ] J5 pin 5
(pin 1 closest to
board edge)
Check socket and L4
[ ] J5 pin 3 Check socket, L1, and R16
[ ] U2 pins 1, 20,
and 31 SW1 possibly installed
backwards. Check by
pressing SW1. If voltage
appears when the switch is
pressed, it is in backwards.
[ ] U4 Pin 14
(above square
pad)
Check socket
Next install the button board cable and the button board.
Convention has the brown wire as Pin 1, but as long as
you are consistent on both ends it does not matter. Check
the four switches following the table below. For each pin
on the microcontroller, verify that the voltage is normally
5V. Pressing the switch makes the voltage go to 0V. If
the voltage is always low (regardless of the switch), then
likely the RPACK is not installed correctly or the switch is
installed 90 degrees off.
Check U2 Pin number Switch
[ ] U2-26 SW1 (up)
[ ] U2-27 SW2 (down)
[ ] U2-28 SW3 (select)
[ ] U2-29 SW4 (menu)
T-238+ Assembly Manual Rev. 3 March 2006 Page 10 of 11
Using a small wire bent in a U-shape, short between U2
pins 20 and 21. Do this carefully so you don’t damage the
IC socket. The LED should light (wherever you installed it,
main board or button board). If it does not, there is a
problem with R12 or more likely, the LED is installed
backwards.
[ ] LED works
[ ] Remove power from the T238+.
Board Level Power Check
Next you will insert U1 and U2. Make sure you match the
pin-1 notch of the device to the notch on the silkscreen.
There are a lot of pins on U2 and it can be difficult to line
them up with the socket. Your best bet is to place the chip
sideways on a flat static-safe surface so that one row of
the pins all lie flat on the surface. Carefully rotate the
body of the IC while pushing down on the pins. Rotating
while pushing down should bend all the pins together and
bend them where they protrude from the body. Bend the
pins a little at a time, then check to see if they are
perpendicular to the body of the IC. Once perpendicular,
the pins of the IC will be much easier to insert as they line
up with the socket.
Insert U2 slowly. Observe that all the pins slide into the
socket. Watch for pins that bend under the IC or out of
the IC socket.
[ ] Insert U2, MC68HC908GP32
[ ] The notch on the chip is aligned with the silkscreen
notch on the PCB.
[ ] Apply power to the T238. The LED will flash three
times quickly, and after approximately 10 seconds it
should start flashing once per second. If it does not flash
immediately, remove power and perform all the above
checks again as a precaution. If they are all OK, the only
thing left is the clock. Check U4 for any errors or
soldering problems.
If the LED still does not start flashing, make sure that all
the pins in U2 were inserted cleanly into the socket and
check the following components carefully: R1, R2, R3, R8,
and R11. Do not proceed until the LED flashes as
described above.
[ ] LED flashing approximately once per second
Remove power, then insert U1 slowly. Observe that all
the pins slide into the socket. Watch for pins that bend
under the IC or out of the IC socket.
[ ] Insert U1, MAX232
With the ground lead of your voltmeter on pin 15 of U1,
check the following voltages:
Check
Pin Voltage Remedy
[ ] U1 Pin 16 +5 Check IC socket
[ ] U1 Pin 2 Greater than
8V Check IC socket,
C3, C6, C7, C8
[ ] U1 Pin 6 Less than
-8V Check IC socket,
C3, C6, C7, C8
[ ] Remove power from the T238+.
Attaching the LCD Module
[ ] Re-install the LCD module as you did when you
soldered the connectors and per the assembly drawing at
the end of this document. Refer again to the assembly
drawing at the end of this manual.
[ ] Adjust VR1 to mid-position.
[ ] Apply power to the T238+.
[ ] After about 1 second you should see the opening
banners displayed on the LCD module. If the display is
blank, shows overly dim or dark text, or nothing but
blocks, adjust VR1, the LCD contrast adjustment. Adjust
VR1 for best viewing. If text cannot become visible,
check the soldering on U2 and J1 as well as the header on
the LCD module.
[ ] LCD showing legible text.
During the power up sequence, you will get a message
saying that there is a 1-wire bus error. If the error says no
devices are present, you are OK. If it says the bus is
shorted to ground, then check U2, J5, D2, D3, R16, and
L1 for assembly problems or bad solder joints.
Do not select any menu options at this time.
[ ] Received error message saying no devices on the bus.
If you haven’t already done so…
[ ] Assemble the 1-Wire™ Weather Sensor using the
instructions that came with the unit.
[ ] Confirm that the Weather Sensor is operational with
the PC software that came with the unit.
[ ] Weather station sensor unit works with PC software
[ ] Remove power from the T238+.
[ ] Plug in the telephone cable supplied with your sensors
into J5 and in the weather sensor unit. A good approach
here is to mount the 1-Wire weather station sensor unit to
a bench with a C-clamp, aligning the aluminum square
tube in the same orientation that it will have when the
weather sensor unit is permanently mounted outside.
T-238+ Assembly Manual Rev. 3 March 2006 Page 11 of 11
[ ] Apply power to the T238+. The LCD should display its
opening messages. If the LCD says that the 1-Wire bus is
shorted then most likely the 1-Wire bus has been
reversed. This will not cause any damage, but the unit will
not work. Some telephone cables reverse the wires and
some do not. In addition, some telephone cord couplers
reverse the wires. Find a telephone cable that does not
reverse the wiring.
Hold the connectors side-by-side and oriented the same
direction (for example, the clip tab down on both
connectors). Observing the red and green wires inside. If,
for example, red is on the left in both connectors, then this
cable does not reverse the signal wires.
When the weather sensor is connected properly, the LCD
will not give any bus error messages. It will complain that
it has no IDs and will ask that your run setup. This is
perfectly normal.
[ ] No bus error messages at all when powering up the
weather station.
Congratulations!
You have completed the power-up and initial testing
phase! If you do not intend to use the T238+ modem you
are done and can start to operate the T238+. Otherwise,
continue with the modem board assembly next.
To learn how to setup and operate your T238+ APRS™ 1-
Wire™ Weather Station, please refer to the T238
Operations Manual. It is available on the T-238 web site
at
http://www.beals5.com/wx
or
http://www.tapr.org/
and follow the links for the T238+.
T-238+ Assembly Manual Rev. 3 March 2006 Page 12 of 11
Assembly Drawings:
LCD Module
T238+ Main Board
Modem Board
3/8" Standoff (4)
1/2" Spacer (4)
1/2" Standoff (2)
Chassis Screws (4)
Board Screws (2)
Board Screws (2)
Spacers, Screws, and Inter-board Connectors (view from top)
16x1 Male
16x1 Female
2x8 Female
2x8 Male
Component side of T238+ Main board
Solder side of T238+ Main board
Regulator
Heatsink
Heatsink Assembly
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