-
Notifications
You must be signed in to change notification settings - Fork 1
/
mfg.tex
185 lines (168 loc) · 11.4 KB
/
mfg.tex
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
\subsection{PCB House}
After carefully designing our schematics, we first need to decide on a PCB
manufacturer to use for our printed circuit boards. There are a few popular and
affordable options available for hobbyists and small run jobs. We weigh the
options available in the following sections.
\subsubsection{Seeed Studio}
This PCB house offers many services including a low cost PCB service. The
pricing model is based off of the number of layers, thickness, and size class.
The size class of 10cm x 10cm would have a base cost of around \$21.00. This is
quite fair and would meet our needs for manufacturing. Seeed Studio is based
in China, which is something to take in to considering if we are ordering
boards and need them quickly. Also, even ordering initial boards would have a
long enough turn around time that we wouldn't be able to test and construct our
design iteratively. Seeed's cost is very competitive, but we would be losing
time to save cost.
%\subsubsection{4PCB}
\subsubsection{OSH Park}
OSH park is quite a popular option due to their low price point for small
boards. They are known by their distinctive purple boards. WHCS has decided to
choose OSH Park due to the fair price for a 2 layer board run. A single
run would yield 3 copies for \$5 a square inch. Unfortunately, this pricing
model will make any significantly large boards too expensive. For the control
modules, it is possible to create a very small design that still meets the WHCS
requirements. WHCS has no special PCB requirements beyond being able to create
surface mount pads for the control module and base station boards. The base
station PCB will be limited by the size of the LCD, but this is only around 2
by 3 inches.
Overall, OSH park is the best choice for WHCS' budget and technical
requirements. Its fast shipping time will ensure that we have plenty of time to test our board and make any additional runs if the worst happens.
\subsection{Parts}
This section will discuss how parts come into the play of the manufacturing of
our PCB. With parts there is much to consider. In addition to whether or not
the part performs as we need them to, and whether or not it{}'s these parts are
in stock we also have to take a look at how this part will need to be
implemented into our design.
\subsubsection{Footprint (SMD vs Through-Hole)}
The footprints of our board will rely mostly on the parts that were chosen to
be part of our design. The parts needed for a surface mounted board and the
parts needed for a through hole boards are unique. Therefore in order to
continue in our design we had to make a design choice. In WHCS we considered
both through hole boards, and surface mounted boards. Through hole board
technology is the older of the two technologies and is currently much less
popular than surface mounting. One of the of the advantages of surface mounting
is that it takes up less space allowing more real estate for parts for a given
board. Because surface mounting does not involve drilling it is simpler and
faster to construct. Although there are some advantages in through hole boards
for most applications surface mounted technology wins. Therefore in our design
we will be using surface mounted technology. With the exception of the power
board which will indeed use through hole. The footprints in our control module
and base station will therefore use parts that are SMT.
\subsection{Construction}
In this section we will be discussing the assembly of our project. This
involves decisions that were made for the board construction of our boards
along with the construction of the displays that will be used to show how WHCS
operates.
\subsubsection{Soldering}
Once we receive our etched boards it will be time for us to solder on the
components. There are various methods that can be used to accomplish soldering.
Note that any of the methodologies described can be used to accomplish the
task. The method that we choose, will be the one that is most
convenient/easiest to implement and seems to do the most professional job. The
first of the methods to be described is the use of hand soldering. This is by
far the simplest and the easiest conceptually for our group to implement. Every
member of our group has some experience soldering by hand. This method is cheap
as it only really requires a soldering iron, which most if not all members in
our group own. The main takeback with this method is that while it is easy by
methodology it is difficult in the fact that it is extremely time consuming.
Also since everything is done by hand this method tends to be a little messy
and may tend to look less professional, because in reality it is. This is even
more so the case if we make use of flux, which can tend to make the board look
dirty. To be honest this method is the the last resort method. In the case that
there is a problem in the soldering job of some kind of a different method,
this method will be used to repair any mishaps.
\subsubsection{Reflow Oven}
Reflow methods are different from hand soldering in that it separates the
placement of the components from the soldering. It tends to be less time
consuming and does a more consistent professional looking job. There are
various method that our group could use to reflow the solder for our PCBs. The
UCF amateur radio club has access to a professional reflow oven if we were to
head in this direction. Additionally, there are online methods describing how
to use a toaster oven to achieve the same affect.
\subsubsection{Proto-Panel}
\label{sec:proto-panel}
In this section we will focus on some of the details of the construction of our
design, the general overview of how the display board is to be put together is
given in \autoref{sec:proto-panel-proto} This section will not explain how the
proto{}-panel will come together, rather it will explain the non obvious
construction details.We will discuss the design considerations that have to be
accounted for. This section will take into consideration the norms that go into
home construction. This will go into the specifics of safety precautions as
well as regular sizes and spacing used in a home.
First let{}'s talk about the wiring. The amount of current that can be drawn
from an outlet is 15 amps if not 20 amps, therefore we will have no problem in
drawing enough current from the outlet to power our board. 15 amps is more than
enough to satisfy our needs even if the current is divided into five different
applications. Other things to consider is the gauge of the wire used. The gauge
of the wire is dependent on the amount of current it can safely handle. As
discussed previously 1 amp is larger than anything we expect to see from our
circuit. Therefore if we design our wire gauge for 1 amp we should be fine.
However as stated before most homes are designed to be able to draw 15 if not
20 amps. This level of amperable is equivalent with wire of gauge 14 and 12. A
common brand of wiring used for these tyes of applications is Romex. Just for
the sake of being consistent with what is used in the home we{}'ll use 12 or 14
gauge wire. To splice the wire we could either solder it or we could use a wire
nut. Both are an acceptable method for joining the wires, and both are used in
homes. Wire nuts are considered to be an easier/ faster method for doing the
job. While soldering and using a heat sink is seen as the higher performing
link. We will make our link by soldering because it is slightly more
professional than using a wire nut but really this is simply a matter of
preference.
When wiring something it is often a good idea to attach your wire at more
locations than simply the location where the connection is made. This way if
for whatever reason the wire is pulled the stress will not go completely to the
connection. Before splicing the wire and connecting the wires to the different
control modules and base station, it would be a smart safety precaution to run
the unspliced wire through the wood framing and attach it. After splitting the
wire it would also be a smart idea to continue the practice of attaching the
wire at more places than the connections. Although not completely necessary it
would be nice if the color of our wires followed the understood meanings of
wire colors in home wiring. In our design we have a single phase hot and
neutral and ground. In the US the ground wire matches with green, the black
wire matches with the hot wire, and the white wire matches with neutral.
\cite{link14}
Using these color codes will make it easier to keep the project neat and
organized. It will make it easier to avoid mistakes made in wiring a circuit
Now let{}'s discuss the boards themselves and how they will be placed into the
framework of our wall. The boards will require some sort of casing that can
hopefully easily be attached to the framework of the home. The less the number
of things needed for installation the better. The easiest way to do this will
be to attach them to or place them inside of the electrical boxes that we are
using for our applications. Having only one thing to install per control module
or base station will make real installation of our device more realistic for
actual use in the future. In our design we will make use of electrical boxes
since they are used in home electrical wiring. The boxes can be either metal or
plastic, yet plastic boxes are a little easier to work with as they the holes
are easier to punch out.
\cite{link15}
There are some specific considerations that must be made with the different
control modules. First off for the light it is important that we use an actual
wall mounted light, as this is the type of light fixture that we are hoping to
be controlling in an actual home. It is important that it is not simply a plug,
because this would defeat the purpose of having light fixture control module.
The wall mounted light should come with three wires; a hot, a neutral, and a
ground wire. From these three wires we will be able to install the fixture in
the same way as what would be expected in a real home. The hot wire is the wire
that we will be interrupting with the relay in order to switch the light on and
off.
The outlet we will be using is a GFIC. GFIC stands for ground fault
interrupter. Using this outlet will provide extra safety precaution. What a
GFIC outlet does is constantly compare the output current from the neutral wire
to the input current from the hot wire. If there{}'s a difference in current,
within the range of a few milliamps, the outlet will shut off in 20-30
milliseconds. In the case that someone were to be electrocuted by this outlet,
the current that goes into their body would cause a current leakage that would
cause the GFIC to have a current difference and thus shut off. GFIC outlet are
normally required for kitchen and bathrooms. Since none of the members in our
group have extensive experience in working with AC power it is best that we
take every safety precaution available. We do not expect that homes that
actually implement our design to use GFIC outlets, it is simply an extra safety
precaution that our group decided to take. \cite{link16}
For the door control module we decided to make our own door of the size 18'{}'
by 18.'{}' Since we are not buying the door but are custom making it ourselves
we need to cut the holes ourselves. The first order of business is cutting the
door to length and leaving a frame of the right size. To cut the hole of the
latch we will need to use a $\frac78$'' spade bit. The hole for the door knob
will have to be made with 2-$\frac18$'' diameter hole saw. A 1'' wide chisel is
used to cut out the recess of the latch. We are now able to install the door
knob.