LCS-1M - A Low-Cost Hobby Oscilloscope
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I did schematic capture as well as the layout with the free design tools from ExpressPCB. I find
their software easy to use and quite capable (but of course no match for really professional tools in
terms of performance); also you get one-stop shopping, no complicated layout file set generation
etc. The only hitch is that you can't send the files to any other fab house because they get encoded.
Still, for moderate quantities their pricing is reasonable.
To obtain the design files, go to the download section.
I made the board a two-layer board. A four-layer board would have been much easier to route but
would also be much more expensive. I would not recommend etching and drilling this board
yourself, it really isn't worth the effort and would require quite advanced PCB skills - the lines are
quite narrow (most are 10mils/0.25mm), there are hundreds of holes and vias, and the two sides
would need to be aligned very precisely. I offer the board for sales (see the "Buy It" tab in the menu
bar), in volume pricing this is a much better solution.
The bottom has a flood-filled ground plane for optimum grounding. Still, because there are so
many lines closely together, one must take care to avoid "islands", i.e. patches of supposed
ground fill that do not have any connection to the surrounding ground.
The routing is done in classical fashion, with the top layer carrying all the vertical traces, the bottom
layer all the horizontal traces, with very few exceptions. The power rails are routed using wider
traces to minimize inductance and ohmic drop.
Without exception all the components are through-hole, and all the chips are DIP packaged
(mounted in sockets for easy replacement). This makes the design very easy to assemble even
with moderate soldering skills. It also allows for inexpensive assembly and wave soldering for
vendors willing to offer it as a completely assembled unit.
The components placement follows largely the logical structure of the design. On the left is the
interface (power and serial) and the power supply regulators. Left in the middle is the sample logic
(four chips), below are the microcontroller and the RS-232 level converter (note that the latest
revision of the scope replaces the MAX232 with a simpler - and lower noise - resistor interface.
More to that in the "Upgrade" section).
The very right side is taken up by the analog frontend (probe connectors, amplifiers, bias DACs,
discrete elements), one channel on the top and one at the bottom.
Left to the frontend is the conversion (ADC) and storage (SRAM) section, with the I/O expander
needed for data readback from the memory chips in the center.
their software easy to use and quite capable (but of course no match for really professional tools in
terms of performance); also you get one-stop shopping, no complicated layout file set generation
etc. The only hitch is that you can't send the files to any other fab house because they get encoded.
Still, for moderate quantities their pricing is reasonable.
To obtain the design files, go to the download section.
I made the board a two-layer board. A four-layer board would have been much easier to route but
would also be much more expensive. I would not recommend etching and drilling this board
yourself, it really isn't worth the effort and would require quite advanced PCB skills - the lines are
quite narrow (most are 10mils/0.25mm), there are hundreds of holes and vias, and the two sides
would need to be aligned very precisely. I offer the board for sales (see the "Buy It" tab in the menu
bar), in volume pricing this is a much better solution.
The bottom has a flood-filled ground plane for optimum grounding. Still, because there are so
many lines closely together, one must take care to avoid "islands", i.e. patches of supposed
ground fill that do not have any connection to the surrounding ground.
The routing is done in classical fashion, with the top layer carrying all the vertical traces, the bottom
layer all the horizontal traces, with very few exceptions. The power rails are routed using wider
traces to minimize inductance and ohmic drop.
Without exception all the components are through-hole, and all the chips are DIP packaged
(mounted in sockets for easy replacement). This makes the design very easy to assemble even
with moderate soldering skills. It also allows for inexpensive assembly and wave soldering for
vendors willing to offer it as a completely assembled unit.
The components placement follows largely the logical structure of the design. On the left is the
interface (power and serial) and the power supply regulators. Left in the middle is the sample logic
(four chips), below are the microcontroller and the RS-232 level converter (note that the latest
revision of the scope replaces the MAX232 with a simpler - and lower noise - resistor interface.
More to that in the "Upgrade" section).
The very right side is taken up by the analog frontend (probe connectors, amplifiers, bias DACs,
discrete elements), one channel on the top and one at the bottom.
Left to the frontend is the conversion (ADC) and storage (SRAM) section, with the I/O expander
needed for data readback from the memory chips in the center.