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104 lines
3.6 KiB
HTML
104 lines
3.6 KiB
HTML
<HTML>
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<TITLE>
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Lab Switch
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</TITLE>
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<BODY>
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<H1>Lab Switch</H1>
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The Lab Switch is a USB-attached device that has a few galvanically
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isolated inputs and output for switching loads and signals in a lab
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environment.
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<P>
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<A href="labsw-0-off.jpg"><IMG src="labsw-0-off-small.jpg"></A>
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<A href="labsw-0-inside.jpg"><IMG src="labsw-0-inside-small.jpg"></A>
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<H2>What it can do</H2>
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It has two relays to switch loads of several ampere connected to the
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banana jacks on the front panel.<BR>
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There are four independent opto-coupler inputs and outputs at the rear.<BR>
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In parallel to the relays, there are opto-couplers that can be used
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instead if only a low current needs to be switched.
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<P>
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<IMG src="ovr-front.png" align="middle">
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<IMG src="ovr-rear.png" align="middle">
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<H2>Example usage</H2>
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The images below show the Lab Switch being used to test how power cycling
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affects a
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<A href="http://milkymist.org/">Milkymist™ One<A>.
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<BR>
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The Lab Switch is inserted into the 5 V DC power supply such that
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it can switch the 5 V supply and ground.
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<BR>
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For further control, the M1 is connected to a PC via the JTAG board.
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<P>
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<IMG src="loop-left.png" align="middle">
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<A href="labsw-m1-off.jpg"><IMG src="labsw-m1-off-small.jpg" align="middle"></A>
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<A href="labsw-m1-boot.jpg"><IMG src="labsw-m1-boot-small.jpg" align="middle"></A>
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<A href="labsw-m1-render.jpg"><IMG src="labsw-m1-render-small.jpg" align="middle"></A>
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<IMG src="loop-right.png" align="middle">
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<P>
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In the left image, power is turned off. This is indicated by green LEDs
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on both channels. The red main LED indicates that the switch is under
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remote control.
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<BR>
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In the middle image, power has been turned on and the M1 is booting
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into RTEMS and Flickernoise. One can see two small LEDs (appearing
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yellow) in the M1 that indicate this it is powered and booting.
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<BR>
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In the right image, the M1 has booted into Flickernoise and is rendering
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a visual effect. This is also indicated by all three LEDs of the M1
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being lit.
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<BR>
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A few seconds later, the Lab Switch cuts power and the cycle repeats.
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<H2>The software</H2>
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The firmware is currently extremely simple and just handles toggling
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via the front buttons and direct remote control via USB.
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<H2>Future work</H2>
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The hardware is currently only designed for low "safe to touch" voltages.
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<BR>
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It would be desirable to be able to also switch AC mains and to connect
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inputs or outputs to places that may be at a high potential with respect
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to other inputs and outputs. For this, it will be necessary to make a
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number of modifications to the circuit. Some of them are detailed in
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the
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<A href="http://projects.qi-hardware.com/index.php/p/wernermisc/source/tree/master/labsw/README">README</A>.
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<P>
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In the future, the firmware will be extended to allow the uploading
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of "scripts" that will allow for more complex patterns of interaction.
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<BR>
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For example, instead of using a channel button as a toggle, it could
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switch a device on for a defined interval and then switch it off again.
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<H2>Sources, mailing list, IRC</H2>
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The electrical design, the mechanical design, and the firmware can
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all be found in
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<A href="http://projects.qi-hardware.com/index.php/p/wernermisc/source/tree/master/labsw">the Qi-Hardware git</A>.
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<P>
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Development discussions and such happen on the
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<A href="http://lists.en.qi-hardware.com/mailman/listinfo/discussion">
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qi-hardware mailing list</A> and on the
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<A href="http://webchat.freenode.net/?randomnick=1&channels=qi-hardware">#qi-hardware
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channel</A> on
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<A href="http://freenode.net/">freenode</A>.
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<P>
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<HR>
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Last update: 2011-09-12 <I>Werner Almesberger</I>
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<HR>
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</BODY>
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</HTML>
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