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<DIV class=OutlookMessageHeader dir=ltr align=left><SPAN
style="FONT-SIZE: 10pt; FONT-FAMILY: Arial"><SPAN class=496162020-29072007>Hello
DPRG...</SPAN></SPAN></DIV>
<DIV class=OutlookMessageHeader dir=ltr align=left><SPAN
style="FONT-SIZE: 10pt; FONT-FAMILY: Arial"><SPAN
class=496162020-29072007></SPAN></SPAN> </DIV>
<DIV class=OutlookMessageHeader dir=ltr align=left><SPAN
style="FONT-SIZE: 10pt; FONT-FAMILY: Arial"><SPAN class=496162020-29072007>I
thought to take a minute and share some progress on my outdoor robot, Protobot,
in the hopes that in some small way it may inspire at least one other
amateur roboticist to get out to their garage / attic / basement and work on
their robot as well.</SPAN></SPAN></DIV>
<DIV class=OutlookMessageHeader dir=ltr align=left><FONT face=Arial size=2><SPAN
style="FONT-SIZE: 10pt; FONT-FAMILY: Arial"></SPAN></FONT><FONT face=Arial
size=2><SPAN style="FONT-SIZE: 10pt; FONT-FAMILY: Arial"></SPAN></FONT><FONT
face=Arial size=2><SPAN
style="FONT-SIZE: 10pt; FONT-FAMILY: Arial"></SPAN></FONT> </DIV>
<DIV class=OutlookMessageHeader dir=ltr align=left><SPAN
style="FONT-SIZE: 10pt; FONT-FAMILY: Arial"><SPAN class=496162020-29072007>The
first piece is pretty basic but fun as it is up and running. (sorry for
the blurry picture I'll re-take later...) The board in the photo is a
radio interface board. It uses a pre-made, pre-certified module from Linx
technologies that has a digital decoder on the back end. The decoder
listens for modulated pulse trains of coming from the radio section and
when the appropriate number of bits have been received, look at the first 10 for
an encoding pattern (much like a garage door opener.) On the sending side
I am using a nice little keychain side pre-made keyfob. On the board if
one looks closely they can see a set of red hexadecimal displays showing the
currently captured codes. The large white monstrosity in the middle is a
break out adapter and all of the wires off the top of it are routed back to a
digital logic analyzer.</SPAN></SPAN></DIV>
<DIV class=OutlookMessageHeader dir=ltr align=left><FONT face=Arial size=2><SPAN
style="FONT-SIZE: 10pt; FONT-FAMILY: Arial"></SPAN></FONT> </DIV>
<DIV class=OutlookMessageHeader dir=ltr align=left><FONT face=Arial size=2><SPAN
style="FONT-SIZE: 10pt; FONT-FAMILY: Arial"><A
href="http://nikita.argia.net/kmaxon/proto_bot_129.jpg">http://nikita.argia.net/kmaxon/proto_bot_129.jpg</A></SPAN></FONT></DIV>
<DIV class=OutlookMessageHeader dir=ltr align=left><FONT face=Arial size=2><SPAN
style="FONT-SIZE: 10pt; FONT-FAMILY: Arial"></SPAN></FONT> </DIV>
<DIV class=OutlookMessageHeader dir=ltr align=left><SPAN
style="FONT-SIZE: 10pt; FONT-FAMILY: Arial"><SPAN class=496162020-29072007>The
next one to share is the new motor driver I have just finished working on.
In this photo (sorry this one is blurry also) the heat sinks have
been removed to give a better image. The analog section includes a
pair of back to back inverting op-amps on the sense resistor. The first
op-amp is configured in differential mode. The second op-amp references
the signal to board ground and I have split the gain between the two of them so
as not to surpass the GBWP of the op-amps used. (something missed in the
original design consideration that I'll update the schematics on my web site
with this afternoon.) The amplified analog signal is driven off
board to an AtoD converter for monitoring by the robots embedded processor
system. Both stages of the amplifier now contain low pass filtering such
as not to exceed the slew rate of the AtoD converters used.
</SPAN></SPAN></DIV>
<DIV class=OutlookMessageHeader dir=ltr align=left><SPAN
style="FONT-SIZE: 10pt; FONT-FAMILY: Arial"><SPAN
class=496162020-29072007></SPAN></SPAN> </DIV>
<DIV class=OutlookMessageHeader dir=ltr align=left><SPAN
style="FONT-SIZE: 10pt; FONT-FAMILY: Arial"><SPAN class=496162020-29072007>In
the near right section of the board are a pair of op-amps. These op-amps
locally monitor for maximum current levels and control local shutdown functions
on board for short circuit protection. The two stage low pass
filtering (mentioned above) not only helps with the slew rate limiting of the
signals into the off-board AtoD, but they additionally keep transients from
reaching the sensitive inputs of the comparators thus helping with false trigger
problems.</SPAN></SPAN></DIV>
<DIV class=OutlookMessageHeader dir=ltr align=left><SPAN
style="FONT-SIZE: 10pt; FONT-FAMILY: Arial"><SPAN
class=496162020-29072007></SPAN></SPAN> </DIV>
<DIV class=OutlookMessageHeader dir=ltr align=left><SPAN
style="FONT-SIZE: 10pt; FONT-FAMILY: Arial"><SPAN class=496162020-29072007>The
last piece that just doesn't show well in this photo are all of the components
involved with gate driving and signal shaping for moving the significant charge
needed to punch these MOSFETs on an off in a proper manner. Again a change
or two from the original design, I've lowered the Zener clamps to 15v which when
combined with the forward diode drop of the back to back diode sets the trip
point only slightly above the operating range clamping below the damage level of
the MOSFETs. If I had it to do again I'd go with 16V Zeners for slightly
more operational range.</SPAN></SPAN></DIV><SPAN
style="FONT-SIZE: 10pt; FONT-FAMILY: Arial">
<DIV class=OutlookMessageHeader dir=ltr align=left><SPAN
style="FONT-SIZE: 10pt; FONT-FAMILY: Arial"></SPAN> </DIV>
<DIV class=OutlookMessageHeader dir=ltr align=left><SPAN
style="FONT-SIZE: 10pt; FONT-FAMILY: Arial"><SPAN class=496162020-29072007>There
are more components on the bottom of the board including (barely visible black
edges, front, left) isolated switching supplies and pi-filtering to provide
clean split rails for the op-amps and large 5-Watt surface mount current sense
resistors as well as some other miscellaneous parts...</SPAN></SPAN></DIV>
<DIV class=OutlookMessageHeader dir=ltr align=left><SPAN
style="FONT-SIZE: 10pt; FONT-FAMILY: Arial"></SPAN> </DIV>
<DIV class=OutlookMessageHeader dir=ltr align=left><SPAN
style="FONT-SIZE: 10pt; FONT-FAMILY: Arial"><A
href="http://nikita.argia.net/kmaxon/proto_bot_146.jpg">http://nikita.argia.net/kmaxon/proto_bot_146.jpg</A></SPAN></DIV>
<DIV class=OutlookMessageHeader dir=ltr align=left><SPAN
style="FONT-SIZE: 10pt; FONT-FAMILY: Arial"></SPAN> </DIV>
<DIV><SPAN class=496162020-29072007>Anywho, Hopefully this work will inspire
someone to pick up a soldering iron, write a line of code or grab a hack saw
and start fabrication on their own robot project...</SPAN></DIV>
<DIV><SPAN class=496162020-29072007></SPAN> </DIV>
<DIV><SPAN class=496162020-29072007>-Kenneth</SPAN></SPAN></DIV></BODY></HTML>