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What's next?

mosquito56mosquito56 Posts: 387
edited 2008-01-05 13:47 in Propeller 1
·· I have finished all the info from the prop learning kit. I want to incorporate a large number of analog signals into the prop. Where do I go for info on ADC'S and some recomendations for parts? Analog.com has hundreds of chips for everything. Any ideas where to begin?

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Mosquito: An animal which buzzes in your ear and never stops. He may byte you, he may nibble you, but you will know you were bit.

·A good engineer borrows from others, a great engineer steals everything outright!!

Comments

  • bambinobambino Posts: 789
    edited 2007-12-24 23:51
    Maxium Maxim Max 1270!
    It is used by the Basic Stamp in the Stamp PLC. There is some downloadable code examples on how to use it written in PBasic. Converting them over for use by the Propeller is just a matter of replacing the PBasic code with an app written useing the Bs2_Functions object from the object exchange.

    Post Edited (bambino) : 12/25/2007 4:24:00 PM GMT
  • mosquito56mosquito56 Posts: 387
    edited 2007-12-25 00:15
    Thanx a· million, that looks perfect. Maximum Max

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    Mosquito: An animal which buzzes in your ear and never stops. He may byte you, he may nibble you, but you will know you were bit.

    ·A good engineer borrows from others, a great engineer steals everything outright!!
  • deSilvadeSilva Posts: 2,967
    edited 2007-12-25 11:51
    There are two aspects:
    - learning about ADC as such (deep thinking, lots of theory, Wikipedia is a good start)
    - just using a simple low cost device: I should definitely recommend the PCF 8591, a no-nonsense 8 bit 4-Channel ADC (and a 1 Channel DAC) with an extremely simple I2C interface (around $3) It is possible to understand what is does smile.gif
    www.selectronic.fr/includes_selectronic/pdf/Philips/PCF8591.pdf

    ---
    Edit: As it took me some time to find a datasheet for the MAX 1270, here to save YOU that time:
    micro.et-inf.fho-emden.de/datenblaetter/converters/max1270_1271.pdf

    ---
    Edit2: MAX 1270:The 24 pin narrow DIP is quite nice, 12 bits are nice, 8 channels are nice... The price tag is $30

    Post Edited (deSilva) : 12/25/2007 12:04:32 PM GMT
  • Nick MuellerNick Mueller Posts: 815
    edited 2007-12-25 11:55
    Or a MAX1036/MAX1038

    If you can accept the package. smile.gif


    Nick

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    Never use force, just go for a bigger hammer!

    The DIY Digital-Readout for mills, lathes etc.:
    YADRO
  • parts-man73parts-man73 Posts: 830
    edited 2007-12-25 16:05
    How about the MCP3208. "12-bit / 8-channel ADC. Also provides up to two 12-bit sigma-delta DACs."

    There's 2 objects in the OBEX, one written by Chip Gracey!

    I have future plans to create a SpinStudio plug-in module for this chip.

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    Brian

    uController.com - home of SpinStudio

    PropNIC - Add ethernet ability to your Propeller!

    SD card Adapter
  • mosquito56mosquito56 Posts: 387
    edited 2007-12-26 13:01
    Thanx for the numbers. Unfortunatly I am nowhere near ready for these chips. I was hoping to find a beginners tutorial. I was going to use the stamp tutorial for the maximum max but I will definetly be looking at your recomendations.
    · I have the temp sensor working nicely and would like some basic info. I will be checking the obex as soon as I hit the submit button. Thanx

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    Mosquito: An animal which buzzes in your ear and never stops. He may byte you, he may nibble you, but you will know you were bit.

    ·A good engineer borrows from others, a great engineer steals everything outright!!
  • deSilvadeSilva Posts: 2,967
    edited 2007-12-26 13:40
    Mosquito,
    I understand your reservations - all is new to you. Of course I could tell you two hours about ADCs but I could tell other persons as well about many things for two hours.....

    Can you work with I2C? This is most important, the I2C chips have advantages only, except they are not superfast.
    Start with a port expander PCF 8574 ($2).

    Then go to the PCF8591 ($3). The datasheet I linked above is very clear. As I said this is a no-nonsense converter and it will be useful to you. Use a $30.High-End converter around Easter (I just see Easter is quite early this year... so Pentecost maybe... smile.gif )

    Post Edited (deSilva) : 12/26/2007 9:05:37 PM GMT
  • mosquito56mosquito56 Posts: 387
    edited 2007-12-26 20:47
    sounds like a plan, I have been reading I2c and it looks perfect for my apps. When I get a chance I· will lookup the parts you recomend.

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    Mosquito: An animal which buzzes in your ear and never stops. He may byte you, he may nibble you, but you will know you were bit.

    ·A good engineer borrows from others, a great engineer steals everything outright!!
  • mosquito56mosquito56 Posts: 387
    edited 2008-01-01 04:02
    Everything is closed for the holidays. I plan on gettting the i2c and the 8574 tommorow. Best place to order from?

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    Mosquito: An animal which buzzes in your ear and never stops. He may byte you, he may nibble you, but you will know you were bit.


    Technologically challenged individual, Please have pity.
  • deSilvadeSilva Posts: 2,967
    edited 2008-01-01 09:50
    Mosquito,
    You need catalogs... I have no idea about the situation in the United States, but it should not be very different from Germany. There are large mail order houses having and sending willingly comprehensive and colourful catalogs. (Reichelt, Conrad, Pollin... never mind.)
    They have all the standard parts you are loooking for from time to time, from tin-solder to dremels, not to mention transisistors, caps, LEDs, ICs,....
    They have different price levels... This is mainly due to stock-keeping policy and even chance. You can buy the same part from $2 to $4 depending on that... They also differ in shipping and handling..

    Someone else will give you the addresses I am sure..
  • Paul BakerPaul Baker Posts: 6,351
    edited 2008-01-01 10:38
    Digikey is in my opinion the best hobbist's drool catalog, there are a couple otheer more esoteric ones that are real gems, but Digikey's the best all around. (Mouser is a very close second)·Just be sure to check availibility before ordering, information availible online but not in catalog.

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    Paul Baker
    Propeller Applications Engineer

    Parallax, Inc.

    Post Edited (Paul Baker (Parallax)) : 1/1/2008 10:45:12 AM GMT
  • deSilvadeSilva Posts: 2,967
    edited 2008-01-01 12:19
    Digi-Key delivers worldwide! Due to extensive advertising in Germany it is becoming popular here too. Shipping is high, but they send charge free above 150 Euro (ca.$200)
    Prices are not really low, but they have a VERY comprehensive stock, which can be VERY confusing for the casual shopper!
    They have quantity discount; sometimes from 5 or 10 pcs on. This is not quite obvious from the display, you have to click the price link to learn that.

    And they have no colored catalog smile.gif
    But they have this super Mouse/KB/VGA adapter for the proto board at a good price...
  • PatMPatM Posts: 72
    edited 2008-01-01 13:24
    bambino said...
    Maxium Maxim Max 1270!
    It is used by the Basic Stamp in the Stamp PLC. There is some downloadable code examples on how to use it written in PBasic. Converting them over for use by the Propeller is just a matter of replacing the PBasic code with an app written useing the Bs2_Functions object from the object exchange.
    Are my eyes deceiving me? Does this ADC accept negative input signals while needing only a single supply? In other words, if I have·a +5V to -5V volt signal to measure I can set this to bipolar and it will read it even though it has only a +5V and 0V supply/ground?
    ·
  • deSilvadeSilva Posts: 2,967
    edited 2008-01-01 14:00
    No that's correct - why do you think it is $30 rather than $3 smile.gif It's a "processor" of its own as it were, also generating the needed voltage (as the MAX232 does) MAXIM seems good at this..
  • bambinobambino Posts: 789
    edited 2008-01-01 14:28
    (Are my eyes deceiving me? Does this ADC accept negative input signals while needing only a single supply? In other words, if I have a +5V to -5V volt signal to measure I can set this to bipolar and it will read it even though it has only a +5V and 0V supply/ground?)
    Not only that, it can tolerate voltages somewhat higher without frying. I'll admit, It's a bit pricey just to add a perihperal to the propeller to learn on, but it's very forgiving if you not experienced with hooking up sensors to measure stuff.
  • mosquito56mosquito56 Posts: 387
    edited 2008-01-01 16:13
    Ordered the catalog from digikey and mouser. Mouser's catalog is a mess.· I can't make heads or tails out of it.

    I hope the catalog is a little clearer.

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    Mosquito: An animal which buzzes in your ear and never stops. He may byte you, he may nibble you, but you will know you were bit.


    Technologically challenged individual, Please have pity.
  • deSilvadeSilva Posts: 2,967
    edited 2008-01-01 17:14
    Mosquito, this is one of most likely many, many suppliers of electronic articles www.bgmicro.com/ However I cannot assess it in any way...
  • RDL2004RDL2004 Posts: 2,554
    edited 2008-01-01 17:33
    Once you get a paper catalog, finding things gets a bit easier. With the online search it can be difficult to drill down to what you need. Mouser's pages are not that bad just make sure to put a check mark in the "Stocked" box from the beginning.

    Also, shipping can be a killer on small orders, being in Texas you will probably get 1-2 day service from Mouser by UPS ground or 1st class mail which will be pretty cheap (I almost always get my orders in 2 days and I'm in Mississippi).

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    - Rick
  • mosquito56mosquito56 Posts: 387
    edited 2008-01-02 17:33
    ·I will order about $400 from parallax tommorow for as many toys as looked interesting. I found everything Desilva recommended but the order only came out to $22 at mouser. Need some more ideas thanx

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    Mosquito: An animal which buzzes in your ear and never stops. He may byte you, he may nibble you, but you will know you were bit.


    Technologically challenged individual, Please have pity.
  • deSilvadeSilva Posts: 2,967
    edited 2008-01-02 17:41
    Well, I have generally a low cost approach: "No waste, no want" smile.gif
    The dial plate was $1, the 2x16 display $5
    attachment.php?attachmentid=49875
  • mosquito56mosquito56 Posts: 387
    edited 2008-01-02 17:44
    you have a part number for that display, also do I need the hm4478? mouser shows this as obsolete. Also anything from parralax shows obsolete


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    Mosquito: An animal which buzzes in your ear and never stops. He may byte you, he may nibble you, but you will know you were bit.


    Technologically challenged individual, Please have pity.
  • deSilvadeSilva Posts: 2,967
    edited 2008-01-02 17:54
    You mean: HD44780 ? That's the type of controller on the back of that display, generally not available separately. All those displays have one (or even two) on the backside. Have a look here!

    search.ebay.com/search/search.dll?from=R40&_trksid=m37&satitle=hd44780&category0=
    A lot goes through ebay.. But mind the shipping! Many vendors have "shops" where you can augment your shopping cart with further unneedded things..
  • mosquito56mosquito56 Posts: 387
    edited 2008-01-02 18:06
    Actually I meant the lcd. I want a cheap easy to use lcd display. I don't have e-bay yet so mouser would be nice. Apreciated the help thanx

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    Mosquito: An animal which buzzes in your ear and never stops. He may byte you, he may nibble you, but you will know you were bit.


    Technologically challenged individual, Please have pity.
  • PatMPatM Posts: 72
    edited 2008-01-02 19:56
    bambino said...
    (Are my eyes deceiving me? Does this ADC accept negative input signals while needing only a single supply? In other words, if I have a +5V to -5V volt signal to measure I can set this to bipolar and it will read it even though it has only a +5V and 0V supply/ground?)
    Not only that, it can tolerate voltages somewhat higher without frying. I'll admit, It's a bit pricey just to add a perihperal to the propeller to learn on, but it's very forgiving if you not experienced with hooking up sensors to measure stuff.
    I just ordered two from Newark (only company besides Digikey that ships in canada as if it came from canada, no broker fees to collect). I would get it from Digikey but they don't have the ferric ram from Ramtron. I only have one left so I got 4 more of those too.

    One of the bane's of my work is sensors that span negative to positive voltages. I need a negative voltage generator (icl 7662) and two opamp stages (one to buffer the adjusted negative offset voltage) and the other for gain and adding the offset so the output becomes all positive. So if I have a 5V ref on the ADC, I add roughly -2.5V to the negative input (instead of ground) which gives a +2.5V output when the positive input on the opamp os 0V.

    Much simple to use a single opamp to set gain and not worry about positive offset.
    ·
  • bambinobambino Posts: 789
    edited 2008-01-02 21:16
    PatM, Glad to see It helped.
    Just an idea though! If your not concerned with duplicating the neg Voltage: you could read the signal with the adc, convert the result to Pos integer, then output that with a DAC. Depending on the Dac you may accomplish a smaller footprint in you circuit.
    With 8 inputs you could also do some feed back from your dac to see that your output is in fact what you wanted.
  • PatMPatM Posts: 72
    edited 2008-01-03 00:09
    bambino said...
    PatM, Glad to see It helped.
    Just an idea though! If your not concerned with duplicating the neg Voltage: you could read the signal with the adc, convert the result to Pos integer, then output that with a DAC. Depending on the Dac you may accomplish a smaller footprint in you circuit.
    With 8 inputs you could also do some feed back from your dac to see that your output is in fact what you wanted.
    Trying to understand what you're suggesting. I just need to convert the +/- sensor output to an integer. With the Max ADC I still need a negative voltage for an op-amp so I can add gain (output of +.414v to -.414V). With 10x gain I can get a bit more than 80% of the ADC range. I'll see if I can figure out·a resistor combination for 12x gain (1k + 11k? Hmmm, is there an 11k? I have 11.5 here). and that would give me nearly 100% range with the 1270's +5/-5 setup.).

    Even without the gain I still need an opamp. pH sensors put out miniscule current. At the far extents its pico-amps. I monitor swimming pools so its typically between 0v and 0.05916V. The input impedence has to be at least a couple of giga-ohms and even that is a huge load. The 1270 has about 16 k-ohm input impedence so it would be almost like a dead short. I buffer the signal though an LMC6482 opamp with > 10 tera-ohm input impedence.

    Its still a nice improvement - I get to lose the LM3851.2 reference, a pot, and the extra op-amp stage for buffering the negative offset voltage.

    ·
  • bambinobambino Posts: 789
    edited 2008-01-03 12:40
    I mis-read your post.
    Yes, the Dac would be redundant. What kind of sensor are you using to measure ph.?
    Not many pools around here, but a lot of interest in soil ph.
  • PatMPatM Posts: 72
    edited 2008-01-05 13:47
    I use Acutrol, Strantrol, and Hanna probes. I don't think any of these would work for soil though. Not familiar with the methods used to measure soil pH.
    ·
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