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3Lab Switch
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7<H1>Lab Switch</H1>
8
9The Lab Switch is a USB-attached device that has a few galvanically
10isolated inputs and output for switching loads and signals in a lab
11environment.
12<P>
13<A href="labsw-0-off.jpg"><IMG src="labsw-0-off-small.jpg"></A>
14<A href="labsw-0-inside.jpg"><IMG src="labsw-0-inside-small.jpg"></A>
15
16<H2>What it can do</H2>
17
18It has two relays to switch loads of several ampere connected to the
19banana jacks on the front panel.<BR>
20There are four independent opto-coupler inputs and outputs at the rear.<BR>
21In parallel to the relays, there are opto-couplers that can be used
22instead if only a low current needs to be switched.
23<P>
24<IMG src="ovr-front.png" align="middle">&nbsp;
25<IMG src="ovr-rear.png" align="middle">
26
27
28<H2>Example usage</H2>
29
30The images below show the Lab Switch being used to test how power cycling
31affects a
32<A href="http://milkymist.org/">Milkymist&trade; One<A>.
33<BR>
34The Lab Switch is inserted into the 5 V DC power supply such that
35it can switch the 5 V supply and ground.
36<BR>
37For further control, the M1 is connected to a PC via the JTAG board.
38<P>
39
40<IMG src="loop-left.png" align="middle">
41<A href="labsw-m1-off.jpg"><IMG src="labsw-m1-off-small.jpg" align="middle"></A>&nbsp;
42<A href="labsw-m1-boot.jpg"><IMG src="labsw-m1-boot-small.jpg" align="middle"></A>&nbsp;
43<A href="labsw-m1-render.jpg"><IMG src="labsw-m1-render-small.jpg" align="middle"></A>
44<IMG src="loop-right.png" align="middle">
45<P>
46In the left image, power is turned off. This is indicated by green LEDs
47on both channels. The red main LED indicates that the switch is under
48remote control.
49<BR>
50In the middle image, power has been turned on and the M1 is booting
51into RTEMS and Flickernoise. One can see two small LEDs (appearing
52yellow) in the M1 that indicate this it is powered and booting.
53<BR>
54In the right image, the M1 has booted into Flickernoise and is rendering
55a visual effect. This is also indicated by all three LEDs of the M1
56being lit.
57<BR>
58A few seconds later, the Lab Switch cuts power and the cycle repeats.
59
60
61<H2>The software</H2>
62
63The firmware is currently extremely simple and just handles toggling
64via the front buttons and direct remote control via USB.
65
66
67<H2>Future work</H2>
68
69The hardware is currently only designed for low "safe to touch" voltages.
70<BR>
71It would be desirable to be able to also switch AC mains and to connect
72inputs or outputs to places that may be at a high potential with respect
73to other inputs and outputs. For this, it will be necessary to make a
74number of modifications to the circuit. Some of them are detailed in
75the
76<A href="http://projects.qi-hardware.com/index.php/p/wernermisc/source/tree/master/labsw/README">README</A>.
77<P>
78In the future, the firmware will be extended to allow the uploading
79of "scripts" that will allow for more complex patterns of interaction.
80<BR>
81For example, instead of using a channel button as a toggle, it could
82switch a device on for a defined interval and then switch it off again.
83
84
85<H2>Sources, mailing list, IRC</H2>
86
87The electrical design, the mechanical design, and the firmware can
88all be found in
89<A href="http://projects.qi-hardware.com/index.php/p/wernermisc/source/tree/master/labsw">the Qi-Hardware git</A>.
90<P>
91Development discussions and such happen on the
92<A href="http://lists.en.qi-hardware.com/mailman/listinfo/discussion">
93qi-hardware mailing list</A> and on the
94<A href="http://webchat.freenode.net/?randomnick=1&channels=qi-hardware">#qi-hardware
95channel</A> on
96<A href="http://freenode.net/">freenode</A>.
97
98<P>
99<HR>
100Last update: 2011-09-12&nbsp;&nbsp;<I>Werner Almesberger</I>
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