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\F4\←L\-R\/'7;\+R\→.\→S   Telephone:
\F1\CAugust 4, 1975

Professor John Luh
Department of Electrical Engineering
Purdue University
West Lafayette, Ind. 47907

Dear Professor Luh:
	Enclosed are the drawings for the Stanford Arm-PDP11/45 interface.  As I have
mentioned before.  At Stanford we bring the Unibus right out to the arm power
supply.  Gafford used one a/d and a multiplexer, as is standard, but he also
used one DAC and lots of sample and holds.  This just makes for complicated software,
as you have to keep refreshing the sample and holds,etc.  It is much better to
use one DAC for each joint (pot. joints only). I am still working on a good
encoder interface card.  University of Ill. says they have designed a good
up-down counter encoder interface card already.  

	Of Gafford's complete system, I suggest you just copy his amplifiers. 
These are the drawings on pages 5.6.7.and 8. Also 14.
You will also need brake drivers (page 24).  The entire system is build on
DEC size cards- single and double high- execpt for the heat sinked components.

	For power supplies we use two Wanlass  "Big Brute" supplies at about
+-28vdc- 20 amps.  These are expensive and much more than necessary.  I 
suggest a 500va transformer at 45vac center tapped and a bridge rectifier with
two 30,000 mfd caps. This should be sufficient for the high power.  Low power-
op amps and logic can use smaller lab.type supplies.

	I have included a cable clamp for joint #6, and have also included a
sketch of the installation of the joint #1 connector.  You will have two cables
going into the arm.  One goes into the base through a 20 pin Winchester MRAC type
connector.  This goes only to joint 1 (motor, brake, tach, encoder, spares). The
other connector is mounted on the boom.  It is a 50 pin Winchester MRAC type
connector.  It is prewired for joints 4,5,6,hand and spares.  The empty holes are
for the wires for joints 2 and 3. The pins push in.  They can be removed with a
Winchester pin removal tool...or you can make one out of a piece of 1/8 inch dia.
thin wall tube, which will compress the tines, and a small rod to push the pin out.
	I have included a sketch of how the delrin cable guide works.  If there
are no screw holes in the cable assembly base- drill and tap two to mount the

	I hope this helps you out for the time being.\.

Yours sincerely,

Vic Scheinman