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00100	\\M1BDR25;\M2NGR40;\M3NGR25;\M4NGR20;\F2\CSTANFORD UNIVERSITY
00200	\F3\CSTANFORD, CALIFORNIA 94305
00300	\F4COMPUTER SCIENCE DEPARTMENT\←L\-R\/'7;\+R\→.\→S   Telephone:
00400	\←S\→.415-321-2300
00500	\F1\COctober 28,1973  
00600	
00700	
00800	
00900	
01000	Dear Russ:
01100	
01200	\J		Enclosed youIll find some details of my idesa on
01300	just what sort of electronics package is necessary for the small arm.
01400	I intend to use a low cost unregulated power supply of +30 and -30 vdc. This will merely be a transformer,diode bridge and two
01500	filter capacitors. Regulated + and - 15 volts for the ic op-amps
01600	will come from an ic dual regulator module in the controller- this runs off
01700	of the dc supply voltage .  The amplifiers initiall will be RCA HC2000H power
01800	operational amplifiers.  These have a 7 amp. capability and a
01900	maximum supply voltage rating of 37 vdc.  The motors use a maximum of 2 amperes at 30 vdc so these amplifiers are more than sufficient.
02000	To insure that the current limited motors never see a current greater than
02100	their max. allowable current, the amplifier is operated in a constant current configuration.
02200	This means that the output current to the motors is linearly proportional to
02300	the voltage in. This is just what you want for good arm control, as current is
02400	analogous to joint torque, and it appears that the controlled torque mode is the most desirable
02500	mode to operate in.  The RCA amplifiers have been chosen over a less expensive,
02600	741 driven power amplifier, because they do not latch up when one half of the
02700	power supply dissappears.  This is an important point, because the current limit
02800	in the motors is due to the demagnetization flux level of the magnet 
02900	fields.  Exceeding the max. current level in the armature for even 1 ms. is
03000	sufficient to demagnetize the motor and reduce its maximum torque output
03100	to a level much lower than the as delivered levels.
03200	\.\←L\→S\←R\-L\/'2;\+L\→L
03300	
03400	Yours sincerely,
03500	
03600	
03700	
03800	Victor Scheinman
03900	
04000	\←S\→L
04100	RP:pdp10