Path: utzoo!utgpu!jarvis.csri.toronto.edu!rutgers!cmcl2!ccnysci!sukenick
From: sukenick@ccnysci.UUCP (SYG)
Newsgroups: sci.electronics
Subject: Re: Stepper Motor
Summary: method using one less part (no EPROM required)
Message-ID: <2293@ccnysci.UUCP>
Date: 18 Jun 89 13:42:03 GMT
References: <7137@cbnews.ATT.COM> <21000026@m.cs.uiuc.edu> <8462@pyr.gatech.EDU>
Reply-To: sukenick@ccnysci.UUCP (SYG)
Organization: City College Of New York
Lines: 47

In article <8462@pyr.gatech.EDU> byron@pyr.UUCP (Byron A Jeff) writes:
>-a stepper motor with the following data sheet:
>-	Four-Step Input Sequence  [1 = on, 0= off
		step#	c1  c2  c3  c4
>-step		1	1   0   1   0
>-		2	1   0   0   1
>-		3	0   1   0   1
>-		4	0   1   1   0
>-		1	1   0   1   0   ]
>If you have access to an eprom programmer a really quick solution

>Step Pulse---| Counter |--------| EPROM   |-------| Drivers |------| Motor |

My solution:
Step Pulse---| data flip flop |-------| Drivers |------| Motor |
 
(-: Ah, kids nowadays. `just grab an EPROM and program'. Back in my day,
if we needed sdfgsatubesrewf we purified the silcon dgdgdwalked 10miles in snow

Ok serious: The above looks like  a problem in logic: how do you connect
a bunch of flip flops to get the above output? 

Answer: use 4 data flip flops (74xx174 is a quad in one package with common
clock) call each c1,c2,c3,c4 to correspond to the above table. 
Use  Q outputs of   c2  and c4;  Q bar  of c1 and c3.  Now, at startup,
you have step#1, 1010.   Now, if you notice that the columns form  the same
pattern, but shifted from one another.
ie: c1 is c3 shifted down one; c2 is c4 shifted once; etc.

Final connection:
	data input connected to output of
	c1			Q    c3
	c2			Qbar c4
	c3			Q    c2
	c4			Qbar c1
This will give the required output, without resorting to eproms.
(Of course the advantage of EPROM is that if you get another motor
with different specs, all you do is pop out the old chip.  This
method saves a chip, though.)
To reverse direction, a  4pole DT switch may be used.  Instead of
feeding back Q  Qbar Q Qbar, you feed back the opposite:
Qbar C3 to c1 in;  Q c3 to c2 in, etc.   If it is desired to
control up/down via computer, etc. then a quad 2->1 data selector
is required and you lost the lower part count advantage.

							-george
							ccnysci!sukenick