Hexapod Foot Sensor Assembly Guide

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4	<td valign="top" align="left"><font size="2" face="Verdana, Helvetica, sans-serif"><b>Hexapod Foot Sensor Assembly Guide.<br>
5	</b>By James Frye</font>
6	<p><b><font size="2" face="Verdana, Helvetica, sans-serif">Updated <!--webbot bot="Timestamp" startspan s-type="EDITED" s-format="%m/%d/%Y" -->02/14/2008<!--webbot
7	bot="Timestamp" i-checksum="12568" endspan -->.</font></b></p>
8	<p><font size="2" face="Verdana, Helvetica, sans-serif">This tutorial will guide you through the process of building and setting up your Hexapod
9	Foot Sensor. The sensor used is a Force Sensing Resistor, FSR for short.</font></p>
10	<p><font size="2" face="Verdana, Helvetica, sans-serif">The kit includes two FSRs, hexapod foot caps, rubber bumpers, and hubs. You will need to
11	provide the following:</font></p>
12	<p><font size="2" face="Verdana, Helvetica, sans-serif"> o Electrical tape.<br>
13	o 24 - 28 awg hook up wire.<br>
14	o Heat shrink.<br>
15	o Solder.<br>
16	o Nylon wire tie.</font></p>
17	<p><font size="2" face="Verdana, Helvetica, sans-serif"><b>Note</b>, this kit is compatible with the AH3-R
18	and 3DOFA legs (BRU/BLK).</font></p></td>
19	<td align="center" valign="top" width="320"><font face="Verdana, Helvetica, sans-serif"><img src="https://wiki.lynxmotion.com/info/wiki/lynxmotion/download/servo-erector-set-robots-kits/ses-v1-robots/ses-v1-3-4-dof-hexapods/hexapod-foot-sensor/WebHome/fsrft00.jpg" border="2" hspace="10" ><br>
20	<font size="2"><b>Image of included components.</b></font></font></td>
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22	<tr>
23	<td valign="top" align="left" colspan="2"><font face="Verdana" size="2"> </font></td>
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25	<tr>
26	<td valign="top" align="left"><font face="Verdana" size="2"><strong>Step 1.</strong><br>
27	Solder some 24 gauge or lighter wires onto the force sensors as shown. Cover the connections with heat shrink.</font>
28	<p><font face="Verdana" size="2">Note, the wires will need to have enough slack to not bind the legs while the robot is walking. It's best to be
29	generous with the wire at first - you can always trim the wires after everything's in place.</font></p>
30	</td>
31	<td align="center" valign="top" ><font face="Verdana" size="2"><img src="https://wiki.lynxmotion.com/info/wiki/lynxmotion/download/servo-erector-set-robots-kits/ses-v1-robots/ses-v1-3-4-dof-hexapods/hexapod-foot-sensor/WebHome/fsrft01.jpg" border="2" hspace="10" ><br>
32	Figure 1.</font></td>
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34	<tr>
35	<td valign="top" align="left" colspan="2"><font face="Verdana" size="2"> </font></td>
36	</tr>
37	<tr>
38	<td valign="top" align="left"><font face="Verdana" size="2"><strong>Step 2.</strong><br>
39	Attach the tubing hub to the tubing using a button head screw as shown.</font>
40	<p><font face="Verdana" size="2">Note, if your hubs include additional 4-40 socket head cap screws, they are not needed in this assembly.</font></p>
41	</td>
42	<td align="center" valign="top" ><font face="Verdana" size="2"><img src="https://wiki.lynxmotion.com/info/wiki/lynxmotion/download/servo-erector-set-robots-kits/ses-v1-robots/ses-v1-3-4-dof-hexapods/hexapod-foot-sensor/WebHome/fsrft02.jpg" border="2" hspace="10" ><br>
43	Figure 2.</font></td>
44	</tr>
45	<tr>
46	<td valign="top" align="left" colspan="2"><br class="pb">
47	</td>
48	</tr>
49	<tr>
50	<td valign="top" align="left"><font face="Verdana" size="2"><strong>Step 3.</strong><br>
51	Cover the side of the tube opposite the screw head with electrical tape. This will prevent the sensor terminals from shorting to the tube.</font></td>
52	<td align="center" valign="top" ><font face="Verdana" size="2"><img src="https://wiki.lynxmotion.com/info/wiki/lynxmotion/download/servo-erector-set-robots-kits/ses-v1-robots/ses-v1-3-4-dof-hexapods/hexapod-foot-sensor/WebHome/fsrft03.jpg" border="2" hspace="10" ><br>
53	Figure 3.</font></td>
54	</tr>
55	<tr>
56	<td valign="top" align="left" colspan="2"><font face="Verdana" size="2"> </font></td>
57	</tr>
58	<tr>
59	<td valign="top" align="left"><font face="Verdana" size="2"><strong>Step 4.</strong><br>
60	Use an exacto knife to carefully peel away the CLEAR plastic piece covering the black adhesive. <b>Be very careful doing this!</b> If not done
61	carefully the sensor can be damaged!</font></td>
62	<td align="center" valign="top" ><font face="Verdana" size="2"><img src="https://wiki.lynxmotion.com/info/wiki/lynxmotion/download/servo-erector-set-robots-kits/ses-v1-robots/ses-v1-3-4-dof-hexapods/hexapod-foot-sensor/WebHome/fsrft04.jpg" border="2" hspace="10" ><br>
63	Figure 4.</font></td>
64	</tr>
65	<tr>
66	<td valign="top" align="left" colspan="2"><font face="Verdana" size="2"> </font></td>
67	</tr>
68	<tr>
69	<td valign="top" align="left"><font face="Verdana" size="2"><strong>Step 5.</strong><br>
70	Stick the adhesive side of the sensor to the end of the leg as shown, then carefully bend the wires to lay along the leg. Make sure you don't
71	try to bend the sensor tail too sharply! Secure the sensor tail and wires to the leg as shown using electrical tape.</font>
72	<p><font face="Verdana" size="2">Note, the sensor should be centered on the flat of the aluminum hub.</font></p>
73	</td>
74	<td align="center" valign="top" ><font face="Verdana" size="2"><img src="https://wiki.lynxmotion.com/info/wiki/lynxmotion/download/servo-erector-set-robots-kits/ses-v1-robots/ses-v1-3-4-dof-hexapods/hexapod-foot-sensor/WebHome/fsrft05.jpg" border="2" hspace="10" ><br>
75	Figure 5.</font></td>
76	</tr>
77	<tr>
78	<td valign="top" align="left" colspan="2"><br class="pb">
79	</td>
80	</tr>
81	<tr>
82	<td valign="top" align="left"><font face="Verdana" size="2"><strong>Step 6.</strong><br>
83	Peel an adhesive-coated bumper off of the paper, and stick it firmly on the end of the leg as shown.</font>
84	<p><font face="Verdana" size="2">Note, this should be centered precisely on top of the FSR. We chose clear rubber bumpers to make this easier.</font></p>
85	</td>
86	<td align="center" valign="top" ><font face="Verdana" size="2"><img src="https://wiki.lynxmotion.com/info/wiki/lynxmotion/download/servo-erector-set-robots-kits/ses-v1-robots/ses-v1-3-4-dof-hexapods/hexapod-foot-sensor/WebHome/fsrft06.jpg" border="2" hspace="10" ><br>
87	Figure 6.</font></td>
88	</tr>
89	<tr>
90	<td valign="top" align="left" colspan="2"><font face="Verdana" size="2"> </font></td>
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93	<td valign="top" align="left"><font face="Verdana" size="2"><strong>Step 7.</strong><br>
94	Attach a nylon wire tie to the wires. Attach an ohm meter to the FSR wires. Gently slide the rubber foot over the sensor and tip of the foot.
95	Push it on till the meter reads some resistance, then carefully and slowly work the rubber end cap in the opposite direction just till the meter
96	reads open. If you are unable to get the meter to read open (infinite resistance) then you may need to adjust the wire tie, or the bend on the
97	sensor in Step 5. After proper set up the sensor should read open until it makes contact with the ground.</font>
98	<p><font face="Verdana" size="2">On a moving robot, the rubber end cap holds the sensor in place even with significant lateral loading. Also the
99	sensor will return to an open even after being under load for a long time. This simple robust design will easily handle the weight of our AH3-R
100	robot.</font></p>
101	</td>
102	<td align="center" valign="top" ><font face="Verdana" size="2"><img src="https://wiki.lynxmotion.com/info/wiki/lynxmotion/download/servo-erector-set-robots-kits/ses-v1-robots/ses-v1-3-4-dof-hexapods/hexapod-foot-sensor/WebHome/fsrft07.jpg" border="2" hspace="10" ><br>
103	Figure 7.</font></td>
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106	<td valign="top" align="left" colspan="2"><font face="Verdana" size="2"> </font></td>
107	</tr>
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109	<td valign="top" align="left"><font size="2" face="Verdana, Helvetica, sans-serif"><b>Step 8.</b><br>
110	There are many ways to use the FSR, but the simplest is to just use a 10k pull-up resistor.</font>
111	<p><font size="2" face="Verdana, Helvetica, sans-serif">Using setup "A" shown in Figure 8, we were able to get the following response,
112	illustrated by the red line in the Sensor Output Chart.</font></p>
113	<p><font size="2" face="Verdana, Helvetica, sans-serif">Using setup "B" shown in Figure 8, we were able to get the following response,
114	illustrated by the blue line in the Sensor Output Chart.</font></p>
115	</td>
116	<td align="center" valign="top" ><font face="Verdana, Helvetica, sans-serif"><img src="https://wiki.lynxmotion.com/info/wiki/lynxmotion/download/servo-erector-set-robots-kits/ses-v1-robots/ses-v1-3-4-dof-hexapods/hexapod-foot-sensor/WebHome/fsrft08.jpg" border="2" hspace="10" ><br>
117	<font size="2">Figure 8.</font></font></td>
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120	<td valign="top" align="left" colspan="2"><br class="pb">
121	</td>
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124	<td valign="top" align="left" colspan="2"><font size="2" face="Verdana, Helvetica, sans-serif"><b>Sensor Output Chart</b></font><font face="Verdana, Helvetica, sans-serif"><b><font size="2">.</font></b><font size="2"><br>
125	Refer to the following chart for expected pressure vs voltage values.</font></font>
126	<p align="center"><font face="Verdana, Helvetica, sans-serif"><img src="https://wiki.lynxmotion.com/info/wiki/lynxmotion/download/servo-erector-set-robots-kits/ses-v1-robots/ses-v1-3-4-dof-hexapods/hexapod-foot-sensor/WebHome/hfschart.gif" border="2" hspace="10" ></font></p>
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