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From: gcarlisl@cln.etc.bc.ca (Gale Carlisle)
Subject: Re: Quadrature decoder/Counter IC HCTL 2000
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Reply-To: gcarlisl@cln.etc.bc.ca (Gale Carlisle)
Organization: The Education Technology Centre of British Columbia. (Canada)
References: <3r8f6g$eve@harbinger.cc.monash.edu.au>  
Date: Sun, 11 Jun 1995 23:17:39 GMT
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In a previous article, Tom.Harris@sci.monash.edu.au () says:

>sun@np.ac.sg (Sunarto) writes:
>
>>I am using 2-phase incremental encoders as feedback sensors for 
>>my robotic project. From the HP data book, the above counter IC 
>>(HCTL 2000) seems to be the perfect choice to interface the encoders to
>>the microprocessor. 
>>
>>However, I can only get this counter IC from the HP representative company and
>>the lead time takes about 20 weeks. This means I could not start testing my
>>project until 20 weeks later.
>>
>>Would anyone kindly let me know where I can get this IC in Singapore,
>>Malaysia,  Hong Kong or U.K.
>>
>>Thanks
>>
>>
>
>This IC is sold by Farnell Electronic Components P/L, ph. +612 645 8888,
>fax +612 644 7898. They are also in the UK and I suspect 
>also in Singapore or Malaysia. The part no. is (would you believe) 
>'HCTL2000',price AUS$40.87.
>
>This is a lot of money for basically a counter. Looking in my HP data book
>I see that the IC consists of a digital noise filter for the 2 phases, a 
> state machine to drive an up/down counter, and a mux to allow the outputs
>of the counter to be read. Why not build your own counter/decoder? You'll
> learn a lot more and save a lot of money.
>
>Use a RC filter for the encoder outputs, sometimes they can be noisy.
>The only really tricky bit is the state machine to decide whether to 
>count up or down. The HP chip will clock the count on _all_ transitions of
>both phases from the encoder. This gives a fourfold increase in resolution
>over a decoder that clocks the count on only _one_ transition of _one_
>phase. A good exercise in synchronous design. If you do not need this 
>higher resolution then one encoder phase can clock
>the up/down counter and the other can suppliy the up/down control to the 
>counter. The 74LS569 is an 8 bit up/down counter. Your computer can then
>read this periodically and maintain a position count to any no. of
>bits by counting over/underflows.
>
>Or, put the whole thing in a PAL and learn about them as well!
>
>Probably someone else in netland has done all this already and has other
>ideas. Post again if you need more help.
>
>Regards
>

	Suggestion; do not re-invent the wheel, shaft encoders and 
interface chips are also available from US Digital, 8409 N.W. 15th Court
, Vancouver, Washington.  206-576-0514  fax 206-576-0515. They list a 
encoder interface chip to micro, LS7166 for $11.65 US in 1994. They offer
encoder to counter chips , optical encoders, softpots. They list single
unit price's on there products.

					Good Luck  Steve Carlisle
