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Old October 27th, 2005, 07:45 PM   #1
sis
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Make shift register with ladder solution

Dear specialists,
For several years I read in this forum about solution to make a shift register vith a simple ladder. I can not find it again because there are so many threads about real shift registers. What I am planning to do is making simple solution for a conveyor belt taking out failed product using plc without shift register on board. I whould be greatful if some one knew where the old article is where the ladder was made to act as shift register. I am using a small control relay from Moeller that ladder programming is easy. I have used this control 412 AC RC relay for teaching ladder programming for beginners and if I find the solution for the problem I mention earlier I will gladly post it here if some of you think it is possible to find a solution.
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Old October 27th, 2005, 08:04 PM   #2
Eric Nelson
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You CAN do a shift register in the Moeller Easy, but it can't have too many positions, due to the limited number of internal relays. The user manual gives an example, starting on page 115, of how to program a 4-position shift register.



-Eric

Last edited by Eric Nelson; October 27th, 2005 at 08:11 PM.
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Old October 28th, 2005, 06:38 PM   #3
sis
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Dear Eric,
Thanks a lot for the user manual. I am so glad that this methode is possible. This will save my course. I never thought it could be so easy like that. I have been reading this great forum from time to time but never had a question until now. And I have to say I am so greatful that Your answer was the perfect solution for me. Many, many, thanks!
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Old October 28th, 2005, 06:57 PM   #4
TConnolly
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You can shift the bits left in any binary number by multiplying the number by 2. Then you set the least significant bit or leave it cleared depending on if you want to shift a bit into the register or not.

To shift the bits right, you clear the least significant bit and divide by 2.

0101010101010101 multiplied by 2 becomes
1010101010101010

Now if for example you are tracking parts on a conveyor, and a part is present, then set the least signficant bit so that the register becomes

1010101010101011

Last edited by TConnolly; October 28th, 2005 at 07:07 PM.
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Old October 28th, 2005, 07:17 PM   #5
sis
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Dear Alaric,
I have also Hitachi H 252 that I can use this methode. There I am sure that I have on board a real shift register. But there are also some other larger versions of EASY from Moeller that I know that can make some calculation and I am planning to find whether your methode is possible there. Many thanks!

Last edited by sis; October 28th, 2005 at 07:39 PM.
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Old October 28th, 2005, 07:19 PM   #6
rsdoran
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Have they added Math functions to the Smart Relays?
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Old October 28th, 2005, 07:32 PM   #7
TConnolly
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Ron,

I didn't think that the smart relays had the "smarts" to do math but I re-checked. It looks like the Easy 800 can do Add, Sub, Mul, Div on 32 bit words no less. The FB looks like a pain in the butt to use however.
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Old October 28th, 2005, 08:36 PM   #8
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Now it works...


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