µMD0 is intended for use in hobbyist, experimental, research, and other
applications where a bug in the hardware, firmware, or software, will not
have a significant impact on the future of the Universe or anything else.
While every effort has been made to avoid this possibility, µMD2 is an
on-going development effort. We will not be responsible for any consequences
of such bugs including but not limited to damage to the construction crane you
picked up on eBay for $1.98 + shipping, financial loss from ending up in
the Antarctic when the compass orientation provided by
your home-built ring laser gyro was off
by 1,536 degrees, or bruising to your pet's ego from any number
of causes directly or indirectly related to µMD0. ;-)
Thanks to Jan Beck for providing support for enhancements
and bug fixes and tolerating my silly C coding questions.
He was also instrumental in developing the initial
µMD1 firmware and GUI. And for getting me interested
in actually getting involved in that project. If anyone had told me
six months ago that I'd be writing code in C, MIPS assembly language,
and Visual Basic - and enjoying it (sort of) - I would have suggested
they were certifiably nuts. ;-) Jan maintains the master GUI source code
as well as slightly different versions of both the µMD1 and
µMD2 firmware and a development blog on these and other projects.
Introduction
The µMD0 kit of parts includes everything necessary for
a 1 axis readout. The extension to 2 or 3 axes is left as an
exercise for the user. But unlike µMD1 and µMD2,
this is quite straightforward without adding too many gray hairs. ;-)
The Atmega 328P Nano 3.0 microcomputer is fully assembled including
all pins. So µMD0 can be constructed on a solderless breadboard
for testing at least. Later, it can be transferred to a prototyping
board with soldered connections. All components are through-hole. The
only parts not included in the kit are jumper wires for the solderless
breadboard.
IMPORTANT: All the resistors are labeled using the standard color
as shown below. Normal color vision
is required to be able to identify these reliably. Even then, it is sometimes
difficult to confirm the values that differ in one band or in poor lighting.
And a magnifier may be required to read
some markings on these and other components. If in doubt, have someone
else assemble the kit or assist you.
For those not familiar with the common resistor color code
(Black/0, Blown/1, Red/2, Orange/3, Yellow/4, Green/5, Blue/6, Violet/7,
Gray/8, White/9), two of the resistors near the 8 pin UA9637 ICs in
the layout diagram are are 680 (blue-gray-brown
or 68 with 1 zero) ohms and 330 (33 with 1 zero) ohms. The gold stripe
indicates 5 percent tolerance on the value but for the use here, tolerance
doesn't matter. (It's possible the resistors you use will have 4 stripes
where 3 of them are the value and the 4th is the multiplier, along with one
for tolerance. If in doubt confirm the value with a multimeter.) The chart below is from Digikey. (If the link decays, a Web search will readily
locate another one.)
Resistor Color Code Chart (from the Digikey Web site)
The parts list below assumes populating the SG-µMD2 for 3 channels
with the OLED display. So for a single channel system, some parts in this
list may not be present and/or there is no need to install those associated
with channels 2 and 3 and/or for the OLED.
The OLED display color may be yellow/blue (yellow for first two lines of text
with blue for the remaining 6 lines), all blue, or all white. In addition,
they may differ slightly in their pinout and mounting hole type/location
as follows (viewed with the pins at the top):
Type 1: GND on the left and VCC (V3.3) on the right.
The mounting holes are round. Their locations match the
SG-µMD2 PCB holes.
Type 2: VCC (V3.3) on the left and GND on the right.
The mounting holes are elongated. Their locations do not match
the SG-µMD2 PCB holes.
There may be other variations. The kits will generally have the Type
1 yellow/blue OLEDs. If you bought a Type 2 OLED, DO NOT drill
holes in the SG-µMD2 PCB to make the screws line up as this risks
shorting the internal VCC and GND planes, use some insulated wires in place
of the screws and Epoxy - or duct tape. ;-) Elongating the holes in the
OLED PCB may be accepatable though.
( ) Confirm that all parts are present and undamaged:
( ) 1x blank SG-µMD2 V1.0 PCB. Confirm the version on the
silkscreen near the location of the USB connector. Inspect for plating
or other defects.
( ) 1x 10 ohm 1/8 W resistor (brown-black-black-gold).
( ) 1x 10K ohm 1/8 W resistor (brown-black-orange-gold).
( ) 3x 5 pin screw terminal block.
( ) 3x UA9637 or UA9639 line receiver (8 pin DIP in foam or tube).
( ) 3x 8 pin DIP socket.
( ) 3x 0.1 µF ceramic capacitor (marked with 104 or 0.1).
( ) 4x 3 mm red LED (3 required, a spare).
( ) 4x 3 mm green LED (3 required, a spare).
( ) 12x 150 ohm 1/8 W resistor (brown-green-brown-gold).
( ) 6x 330 ohm 1/8 W resistor (orange-orange-brown-gold).
( ) 6x 680 ohm 1/8 W resistor (blue-gray-brown-gold).
( ) 3x 1K ohm 1/8 W resistor (brown-black-red-gold).
( ) 1x 10K ohm 1/8 W resistor (brown-black-orange-gold).
( ) 3x 36K ohm 1/8 W resistor (orange-blue-orange-gold).
( ) 1x 40 pin female-male socket strip.
( ) 1x 1 pin male-male socket strip to be cut in pieces for
jumper headers (JBx) if desired.
( ) 1x 0.96" 128x64 OLED IIC display in antistatic wrap or bag.
( ) 1x 4 pin SIP male-male socket strip for OLED.
( ) 2x M2*16 screw for OLED mounting.
( ) 2x M2 nut for OLED mounting.
For a single axis system, approximately 2/3rds of the components in the
last block will not be present. And the OLED will not be present, uh, for
the system with OLED. :)
The "Optional" parts identified below
can be omitted if that feature is not being
implemented. The LEDs especially are not really
that useful and with the 10K ohm current limiting resistors, annoying bright.
So you may want to at least experiment with higher values of resistors (like
22K or even 47K) to tame them.
( ) Install R0 (10K ohms) under where the Teensy socket will go.
( ) Install R31 (10 ohms) under where the Teensy socket will go.
( ) Trim the large socket if necessary so it has two rows of 14 pins.
This is for MPB1, the Teensy 4.0 PCB.
( ) Carefully insert it in the PCB confirming no bent pins. Rather
than flipping a coin :), orient it so the large cutout faces the USB to
the left. Then solder
two corners and confirm it seats flat, then solder the other pins. Inspect
for solder bridges and unsoldered pins.
( ) Install the 8 pin sockets for U1 (single axis) and U2,U3 (three axes).
Note orientation - the cutout goes to the right as viewed in the layout
diagram. Solder and inspect for solder bridges and unsoldered pins.
( ) Install C1 (0.1 µF, single axis) and C2,C3 (three axes).
C1,C2,C3 are the oval outlines to right of U1,U2,U3 respectively.
( ) Install R4,R9 (330 ohms, single axis) and R14,R19,R24,R29 (three axes).
( ) Install R5,R10 (680 ohms, single axis) and R15,R20,R25,R30
(three axes).
( ) Install D0 (3 mm blue LED). The anode is the longer lead
and goes to the right as viewed in the layout diagram. The flat is the
cathode and goes to the left. Cut the leads about 1/10" from the body
if the LED can't be inserted to sit flush on the PCB. Take care not
to overheat or stress the leads on the LED when soldering. Be as quick
as possible.
( ) Optional signal LEDs:
( ) Install R3 (36K ohms, single axis) and R13,R23 (three axes).
( ) Install R8 (1K ohms, single axis) and R18,R28 (three axes).
( ) Install D1 (3 mm green LED, single axis) and D3,D5 (three axes).
( ) Install D2 (3 mm red LED, single axis) and D4,D6 (three axes).
The anode is the longer lead
and goes to the right as viewed in the layout diagram. The flat is the
cathode and goes to the left. Cut the leads about 1/10" from the body
if the LED can't be inserted to sit flush on the PCB. Take care not
to overheat or stress the leads on the LED when soldering. Be as quick
as possible.
( ) Install J1 (screw terminal block, single axis) and J2,J3 (three
axes). Make sure the entrance holes for the wires face away from the
PCB! Solder the center pin and confirm they are flat on the PCB, the
solder the others. Check for solder bridges and unsoldered pins.
( ) Install jumper wires (cut resistor leads) at JB1 and JB2 as shown
in blue on the layout diagram. This selects the Homodyne signals.
( ) Carefully inspect for unsoldered pins, solder bridges and
other blemishes. Correct as needed. THIS IS ESSENTIAL!
It would be bad form to blow the brain due to an errant blob of solder. :(
( ) Test the Teensy before doing anything to it. If it fails this test,
contact me before proceeding.
Connect it to a USB port using the USB A to USB Micro B cable.
Assuming the µMD2 firmware has been installed, after a
second or so, D13, the on-board LED, acts as a heartbeat monitor and
should start flashing in some pattern not yet fully determined, but
it will be unlike the "Blink" sketch. ;-) Currently it's a short flash
ever 0.5 to 1 seconds.
It should also be spitting out data via the USB COM port. In the
Arduino IDE, go to Tools->Port and select the port that it is plugged
into. It should show something like: COM5 "Serial (Teensy)".
Go to Tools-Serial Monitor. A window should appear showing data
being sent to the COM port. It will be mostly boring but the 6th value
should be incrementing by 1, probably at around 1 kHz:
(Should you care, the 6th and 7th values are the "Low Speed Code" and
"Low Speed Data", respectively. 10,124 is the firmware version 1.24;
8,100000 is the sample rate of 1,000 x 100, and 20,4099 specifies 3 homodyne
axes + a homodyne multiplier of 4 x 256.)
Unplug the USB cable.
( ) Assemble the Teensy 4.0 PCB to the pin or socket strips. There will
either be a pair of 14 pin female-male socket strips precut or the male to
male pin strip that needs cutting:
Female to male socket strips: The male pins slip through the
Teensy PCB holes from the top so the female sockets are accessible when
Teensy is plugged into the large socket on the SG-µMD2 PCB.
Male to male pin strip: The short pins slip through the Teensy PCB
from the bottom. (This is what's shown in the photo of the completed
SG-µMD2 PCB, above.)
Solder a single pin near the center and
confirm it seats flush, then solder the rest.
To assist in alignment, the strips can be inserted in the 28 pin socket
taking care not to push any of the individual pins out of position.
( ) Test the Teensy as above before plugging it into the SG-µMD2 PCB
to confirm the soldering hasn't done anything bad. Then unplug the USB
cable.
( ) Carefully plug the Teensy into the 28 pin socket. The USB socket
faces off the left side of the PCB as shown in the layout diagram.
Make sure all pins are seated and none are hanging off the socket.
CAUTION: Make sure all the pins line up with their entry points in the
socket to avoid squashing the leaf sprint contacts.
( ) Reattach the USB cable. The power LED should come on immediately
and after a second or so, the Teensy LED should start flashing as before.
Unplug the USB cable.
( ) Plug a UA9637 or UA9639 IC into the U1 position. The dot or cutout
should face to the right - these ICs are upside-down compared to the
Teensy part labeling as shown in the layout diagram.
( ) Reattach the USB cable. The power LED and possibly one or both
LEDs near U1 (if installed) should come on immediately
and after a few seconds, the Teensy LED should start flashing as before.
( ) (Optional) Here is the nifty bit. ;-) Moisten a finger (doesn't matter
which one) and touch the pins on J1. With some practice, it will be possible
to make the LEDs near U1 to go on and off as the input to the line receivers
cause them to toggle. While the behavior is not really predictable, just
the fact that they change indicates the the line receiver is working.
Since the UA9637 has some hysteresis, it latches but the slight charge
from your electric personality is enough to toggle it. CAUTION: Don't
get carried away, these parts can be damaged by static discharges.
So, no cat's fur and plastic rods, please. :( ;-)
(This will not be possible if the terminating resistors are installed, thus
holding off on them for now.)
If you're wondering how the OLED in the photo, above, can be displaying
such large numbers with nothing attached to the inputs, it was done this
way except the board was plugged in a USB charger, not a USB port. That must
have a lot of ripple relative to my moistened finger, enough to easily
trigger the UA9637 even with its hysteresis.
( ) Start the µMD GUI and select the COM port used to upload
the firmware. The graph should start scrolling. But now, if you do the
moistened finger thing, it should be possible to get the displacement
to change for Axis 1. Once confirmed, unplug the USB cable.
( ) Repeat the previous 3 steps for axes 2 and 3 (U2/J2 and U3/J3)
if desired.
( ) Heterodyne systems ONLY. Add the following wire jumpers on the
bottom of the SG-µMD2 PCB on the Teensy socket as required depending
on the number of axes. Use thin insulated wire and take care to avoid
solder bridges. The second attachment point for each jumper can be to
the appropriate labeled header pad:
Single axis:
( ) Install jumper for REF: D1 to D9. (MPB1 socket pins 3 to 11.)
( ) Install jumper for MEAS1: D2 to D10. (MPB1 socket pins 4 to 12.)
Three axis:
( ) Install jumper for MEAS2: D3 to D0. (MPB1 socket pins 5 to 2.)
( ) Install jumper for MEAS3: D4 to D14. (MPB1 socket pins 6 to 16.)
Note: The original design had the heterodyne signals assigned to pins that
were the same as homodyne signals. But so far it has not been possible to
decipher the control of the ARM Cortex M7 crossbar to put them there and
the pins above need to be used for now at least. Thus the duplicate
set of signals on the PCB V1.2 layout diagram. If that gets resolved,
the additional jumpers will not be necessary.
( ) Optional OLED:
( ) Install the 4 pin female-male socket strip for the OLED
between JB3 and JB4 and HDR3. If longer, it will need to be trimmed.
( ) Install wire jumpers to select V3.3 and GND for the
OLED at JB3 and JB4 depending on which version you have. The outer positions
select V3.3/VCC on the left while the inner positions select V3.3/VCC
on the right. DO NOT plug in the OLED until correct power connections are
confirmed with a DMM:
OLED OLED
VCC GND SCL SDK GND VCC SCL SDK
o o
|
JB4 o JB4 o
|
o o
o o
|
JB3 o JB3 o
|
o o
CAUTION: DO NOT jumper the middle pins together by accident, that will
short V3.3 to GND. :(
( ) If the OLED does not already have a 4 pin header attached,
cut off a 4 pin section of male-to-male pin strip and insert it under
the OLED with the short side through the OLED PCB just as with the
Teensy. Solder one pin, confirm it seats flush,
and solder the rest. Inspect for solder bridges and unsoldered pins.
( ) Insert an M2*16 mm screw through each of the bottom holes of the OLED
and loosely thread an M2 nut onto each.
( ) Plug the OLED into the 4 pin socket strip.
The holes in the PCB are a snug fit for
these screws so it should be possible to thread them in without nuts. Set
them so the OLED is level and tighten the nuts just snug.
( ) Power up the PCB via the USB cable. After a second or so, the OLED
should display something like "µMD2 V1.xx" on the top line and
the sequence number on the 3rd line incrementing at the sample rate
(probably 1 kHz). These OLEDs can display 8 lines of text; for the version
provided in these kits, the top two are yellow while the other 6 are blue.
It is NOT a color display.
( ) Using the moistened finger trick :), it should be possible to fool the
system into thinking there is activity on each of the installed axes
at which point lines will appear on the OLED with the relevant axis ID
and count. This can be more fiddly than might be assumed as the Quadrature
counting hardware of the Teesny will ignore sequences of A and B that don't
make sense.
( ) (Optional) Install R1,R2.R6,R7 (single axis) and
R11,R12,R16,R17,R21,R22,R26,R27
(three axes). The terminating resistors included in the kit are 150 ohms,
which is generally satisfactory. However, your specific situation may
differ. If in doubt, cut the 40 pin female-male socket strip
into pieces and solder them in so other value terminating resistors
can be swapped in without desoldering.
Congratulations, you're all set to go. Order that construction crane
in need of a controller with free shipping on eBay. ;-)
Where the input signals are differential with approximately equal average
levels and an amplitude more than about 0.5 V, the UA9637 RS422 receivers
are all that's needed. This includes Quad-Sin-Cos which will automaigically
convert to digital.
But where the input signals are single-ended such as normal TTL or only
one polarity of a Quad-Sin-Cos, there are locations on the SG-µMD2
PCB for a reference voltage divider.
The threhsold voltage should be selected to be approximately mid-way between
the nominal high and low levels. For standard TTL, this would be 1.4 V. The
resistor values can be in the 10K range with C4 of 0.5 µF.
These are for both the RS422 and analog versions.
The LEDs (along with their
associated current limiting resistors) can be omitted if desired.
But every digital system requires some lights! ;-)
Refer to the schematic for more details.
RS422 Version Parts List
Reference Type Part/Value Function
-------------------------------------------------------------------------------
C1 Capacitor 0.1 µF U1 5 V bypass
LD1 LED 3 mm HB LED Red LED
LD2 LED 3 mm HB LED Green LED
MPB1 CPU Atmega 328P Nano 3.0 Nano soldered to header
SBB1 Solderless Breadboard
R1 Resistor 1K ohm, 1/4 W Red Power LED current limiting
R2 Resistor 100 ohms, 1/4 W Termination
R3 Resistor 36K ohm, 1/4 W Green Power LED current limiting
R4 Resistor 100 ohms, 1/4 W Termination
U1 IC UA9637 or UA9639 RS422 line receiver
More to come.
Quad-Sin-Cos Analog Version Parts List
Reference Type Part/Value Function
-------------------------------------------------------------------------------
C1 Capacitor 0.1 µF U1 5 V bypass
LD1 LED 3 mm HB LED Red LED
LD2 LED 3 mm HB LED Green LED
MPB1 CPU Atmega 328P Nano 3.0 Nano soldered to header
SBB1 Solderless Breadboard
R1 Resistor 1K ohm, 1/4 W Red Power LED current limiting
R2 Resistor 36K ohm, 1/4 W Green Power LED current limiting
U1 IC LM393 Sin/Cos thresholding
More to come.
