Question about multiplexers

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I am going to be building an array of 8 IR range sensors which output a variable voltage level based upon how an object is away from it.

Instead of using all 8 A2D ports on the mega128, I want to use a multiplexer and make a scanned type interface where I'll have the mega128 set the selection bits on a MUX and poll the 8 devices one at a time.

The problem I am having is that all of the MUX's I have seen online that I have searched for will only output 5v or 0v depending on whatever the input that's selected is.

I need the output to be variable from 0v to 5v so it can be hooked into the A2D.

The problem with the mux is that each of the 8 inputs go directly into an AND gate (which also has the three selection lines going into them). I think what I want instead is for the output of those AND gates to be hooked into a tri-state gate (and the input to the tri-state gate would be one of the 8 outputs from the IR sensors) and for each of the tri-state gates to be controlled by each of the outputs from the AND gates. Then all of those would be tied together and only one of them would be active at a time.

Does anyone know of an IC that already does this, I haven't been able to find one.

Thanks,
Dan

"I only speak one language .... 101001 ..." - Mr. Rat from The Core (r)

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This is the MUX I was originally looking at which I now know won't work for what I need. It also has a logic diagram that I am referring to on page 2 (if you look at the datasheet).

edit: oops, here's the link: http://focus.ti.com/docs/prod/fo...

"I only speak one language .... 101001 ..." - Mr. Rat from The Core (r)

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You're looking in the wrong series: those are digital multiplexers

Checkout: CD4051 from the CD4000-series: that will probably be your best choice. Low cost too :)

Nard

A GIF is worth a thousend words   They are called Rosa, Sylvia, Tricia, and Ulyana. You can find them https://www.linuxmint.com/

Dragon broken ? http://aplomb.nl/TechStuff/Dragon/Dragon.html for how-to-fix tips

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Wow, I'm an idiot!

That will work great, thanks!

"I only speak one language .... 101001 ..." - Mr. Rat from The Core (r)

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Quote:
Wow, I'm an idiot!
No, you're not. All you needed was a hint. And that's OK

Nard

Edit: language-thingie

A GIF is worth a thousend words   They are called Rosa, Sylvia, Tricia, and Ulyana. You can find them https://www.linuxmint.com/

Dragon broken ? http://aplomb.nl/TechStuff/Dragon/Dragon.html for how-to-fix tips

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I would suggest the 74HC4051 for better performance on a 5 volt supply.

Tom Pappano
Tulsa, Oklahoma

Tom Pappano
Tulsa, Oklahoma

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Agreed. Much better indeed.

Nard

A GIF is worth a thousend words   They are called Rosa, Sylvia, Tricia, and Ulyana. You can find them https://www.linuxmint.com/

Dragon broken ? http://aplomb.nl/TechStuff/Dragon/Dragon.html for how-to-fix tips

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If you really want to get nutz use the cd4067. it has 16 inputs and can go as high as 12vdc as long as the supply is 12v. you will need a 5v/12v translator for the logic, but that is easy

If you just want 16 inputs and 5v then it is an all in one solution.

By the way I have dozens of both the 4051 and the 4067 if you need any I can send them

Jim

I would rather attempt something great and fail, than attempt nothing and succeed - Fortune Cookie

 

"The critical shortage here is not stuff, but time." - Johan Ekdahl

 

"Step N is required before you can do step N+1!" - ka7ehk

 

"If you want a career with a known path - become an undertaker. Dead people don't sue!" - Kartman

"Why is there a "Highway to Hell" and only a "Stairway to Heaven"? A prediction of the expected traffic load?"  - Lee "theusch"

 

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Please Read: Code-of-Conduct

Atmel Studio6.2/AS7, DipTrace, Quartus, MPLAB, RSLogix user

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Maxim also has a wide portfolio of analog muxes. And theyr samples policy is also helpful.

Guillem.

Guillem.
"Common sense is the least common of the senses" Anonymous.

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Quote:
Maxim also has a wide portfolio
The client also needs a "wide portfolio" with Maxim stuff :) (portfolio should be close in Spanish for wallet :) )

John Samperi

Ampertronics Pty. Ltd.

https://www.ampertronics.com.au

* Electronic Design * Custom Products * Contract Assembly

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js is correct that Maxim is a tad pricey, but their samples policy rules!!

I sampled 5 pieces each of two plcc based chips that cost $30.00 each from digikey.

That's $300.00 worth of silicon for free, and they paid the freight from the Phillipines to boot

I would rather attempt something great and fail, than attempt nothing and succeed - Fortune Cookie

 

"The critical shortage here is not stuff, but time." - Johan Ekdahl

 

"Step N is required before you can do step N+1!" - ka7ehk

 

"If you want a career with a known path - become an undertaker. Dead people don't sue!" - Kartman

"Why is there a "Highway to Hell" and only a "Stairway to Heaven"? A prediction of the expected traffic load?"  - Lee "theusch"

 

Speak sweetly. It makes your words easier to digest when at a later date you have to eat them ;-)  - Source Unknown

Please Read: Code-of-Conduct

Atmel Studio6.2/AS7, DipTrace, Quartus, MPLAB, RSLogix user

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Thanks for your guys' input, I'll look into all of the different ones you've suggested and figure out which one will be the best fit.

"I only speak one language .... 101001 ..." - Mr. Rat from The Core (r)

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Tom's suggestion, the 74HC4051, will probably be your best choice: € 0.25 (here in the Netherlands), widely used and available, and good spec's. This tip may save you some time. :)

Nard

A GIF is worth a thousend words   They are called Rosa, Sylvia, Tricia, and Ulyana. You can find them https://www.linuxmint.com/

Dragon broken ? http://aplomb.nl/TechStuff/Dragon/Dragon.html for how-to-fix tips

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John, wallet in spanish is 'cartera'. Portfolio is close to portafolios, that means some kind of paper holder.

Of course, italian should be different ;)

Back to topic: Maxim sells pretty good IC's, but at also pretty good money, and pretty good delivery time. Thus I use them for one-off products, or production tools or so on.

Also about theyr pretty nice samples policy: watch the specs. I suspect that they send as samples the IC's that are just a little below specs to sell, but not so much to trhow away. If you buy the 'good ones', then probably Maxim is the manufacturer that you can trust more, but I don't have enough experience to reassure that.

Guillem.

Guillem.
"Common sense is the least common of the senses" Anonymous.

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Quote:
and pretty good delivery time
I have designed 2 modules with RTC and used the DS32KHz DIP package which Maxim supplied as samples...then I got an enquiry for 20 units and guess what? 20 weeks delivery lead time!! Needless to say the inquirer lost interest. After screaming at Maxim (I would have been swearing at them if I learned how to do that when I was young :) ) and a worldwide search, it happens that Avnet (or was it Arrow?) in Australia keep them in stock, it took me about 2 weeks just to find that out.

John Samperi

Ampertronics Pty. Ltd.

https://www.ampertronics.com.au

* Electronic Design * Custom Products * Contract Assembly

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Re: Maxim being expensive / Samples.

Worked on me. They played ball and provided samples VERY quickly. Good solution albeit expensive. That IC (which isnt cheap) is now used in a product that will be churned out in large numbers for the next 3-5 years. Lead times can be a bitch (I always tell clients to order 4 months supply and buffer it*), also they have just dropped IC's in the past which isnt nice but there we go :)

Edited to add: ...yes I do check the shelf life ;)