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Analog Input, is there an easy(cheap) way?

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  • Analog Input, is there an easy(cheap) way?

    I'm mulling over the idea of buying an 8/8/8 phidget, but its serious overkill for my application. I have an analog humidity sensor, and an analog temperature sensor that I want to put in my car, but I don't think they warrent the 100$ phidget input device. So my question is: Is there an easy way to get the analog resistive value from my sensors into my computer? Any parallel, serial, usb hacks I can look at? The sensors are roughly in the 200kΩ range.

    I've searched high and low, but to no avail. Any help is much appreciated!

    -Jared

  • #2
    You don't have any programming or electronics experience to speak of do you? If you do, it is pretty easy to get a microcontroller (just a few dollars a piece) to start dumping information out.

    I'm working on one myself, actually. In the end, just the analog part should cost about $20. But, it will take programming, and microcontroller knowledge.
    2000 Subaru OBS

    Dell P3 @ 900 Mhz
    7" Lilliput TS w/DigitalWW in-dash mount
    80GB External HD

    I am Zero Bitrate....

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    • #3
      Tossing USB in there gave you that impression, I bet. I'm not inept, but I don't have the greatest knowledge in electronics.. especially microcontrollers. I can follow instructions and adjust things to my needs, but starting from scratch... not happening. I'm a tweaker.

      Heres a dirty little design I found that seems promising.. but attaining a programmer to insert the code into the PIC, and all that jazz goes beyond the scope of getting a value representing those sensors into my pc.

      I'm not looking to become a hardware developer. I just want to get some sensor values into my PC in an easy way that won't break my bank.

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      • #4
        That PIC design you found will do it. But if you don't want to mess with programmers etc, there are all sorts of ADC chips one of which may fit the bill nicely. Look through ADC ICs on digikey or something.

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        • #5
          How much programming do you know? I just found some nice parellel ADCs that may work for you. In order to use them, you would need to poll the parellel port for inputs though. There might even be some source code for it somewhere. Didn't search for that though.
          2000 Subaru OBS

          Dell P3 @ 900 Mhz
          7" Lilliput TS w/DigitalWW in-dash mount
          80GB External HD

          I am Zero Bitrate....

          Comment


          • #6
            I haven't checked on the parts availability, but after a quick Google search ("parallel" "port" "adc") it popped up this:

            http://margo.student.utwente.nl/el/pc/ad_da/lpt-adc.htm

            It's pretty much mushin's suggestion already done. You have a single ADC chip you buy off DigiKey and then wire it up to your parallel port. Whoever wrote up the DIY on that link went into WAY too much detail writing out assembly code and such to poll the port. Seeing as the DIY was written in 1995, I'm not surprised.

            Don't hesitate to ask if you need any help. Hell, I might just make one for you if you ask nicely (and finance the parts with some beer)!
            Real Genius Designs, Inc.

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            • #7
              I'm a VB6 kinda guy. :P C and ASM scare me. I looked into some ADC's and they're exactly the kinda thing I need. You guys are really freakin terrific and helpful. I love these forums.. I think what I stumbled upon on these very forums to be much more interesting than an ADC alone.

              While looking around, I found something VERY interesting in Ricky's old Relay/Input card thread. Curiosity has designed and implemented a rediculously simple USB interface using the 18F2455 PIC loaded with some marvelous code hes created. Parts to build one sourced from mouser cost about 9$usd, INCLUDING THE PIC! The really interesting thing is that you can change the function of the inputs/outputs on the fly, using windows software hes written. So you can change some of the I/O's to control Relays, input analog data, or input digital data.. whatever suits you best! The only thing keeping me from ordering the parts this very instant is I'm not sure how I'd program the PIC.. it doesn't seem to be offically supported by very many PIC programmers, or programming softwares.. the ones that do support it appear very complex.. what I'm thinking of doing is trying out the ultra cheap n' easy programmer described here, or JDM Programmer described here. The chips they program seem quite similar to the 18F2455, and a forum post here makes me think that this would work. I'm getting excited now. Thoughts on this are very very much appreciated.

              Posts from Ricky's Thread by Curiosity regarding his device:


              Originally posted by Curiosity
              Wow. All this time and not much happening? Just to add more noise to the thread, here's some code for the 18F2455
              http://curioustech.home.insightbb.com/cario.htm
              You can set any of the 19 I/O pins as input or output and up to 10 analog inputs from software without changing the firmware. If it wasn't for the PIC programming part, it would cost under $10 for a basic unprotected USB I/O board to start adding relays or whatever you want to it.
              Originally posted by Curiosity
              Yeah, it's all been tested with LEDs, relays, buttons, switches, pots. Everything works. Don't worry too much about using a VID/PID as long as Windows doesn't recognize it. Most manufacturers don't use all 65K product IDs either, so it's not likely that you'll get into trouble if it's not a commercial product.

              There are no jumpers. It's all software configurable and saves the TRIS, ADC, etc. registers to EEPROM so no need to waste valuable ports for configuring.
              Originally posted by Curiosity
              I was thinking maybe people would be interested in something cheap that they could do their own thing on, like perfboard. All you need is a crystal, 4 caps, PIC, socket, USB jack, a little hookup wire, and it's running. Something like this. The rest would be up to them. Buy a few thermistors and have 10 thermometers, or steering wheel controls. 19 LEDs + resistors? 19 relays would be a bit harder to hook up though if they aren't 5V with built-in diodes. In comparison the Phidgets it would be much cheaper, just with less protection unless you know what you're doing.

              His page with the source code for the pic, and to control it through windows:
              http://curioustech.home.insightbb.com/cario.htm

              LegoGT. Next time you're in Montreal gimme a message, and we'll grab some drinks.

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              • #8
                Originally posted by Fusion-One
                what I'm thinking of doing is trying out the ultra cheap n' easy programmer described [URL="http://home.vrweb.de/~lotharstolz/stolz.de.be/lvpc/index.html"]
                I recommend the ICD2 clones, build this one >>>
                http://www.mp3car.com/vbulletin/showthread.php?t=43981

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                • #9
                  http://www.members.aon.at/electronic...pgm/index.html is what I use, with the very simple LV-ISP hardware. I've only used it with the 18F4620, but it says it supports the 18F2455.

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                  • #10
                    Originally posted by mushin
                    http://www.members.aon.at/electronic...pgm/index.html is what I use, with the very simple LV-ISP hardware. I've only used it with the 18F4620, but it says it supports the 18F2455.

                    I've decided to build this programmer, it appears to be perfect for what I want to do... and simple. The only part I'm having trouble with tracking down is the 74ALS05D.. I'm ordering from Mouser.com and would like to keep my order there.. but the closest thing I can find is this. Which, from checking the datasheet appears to be the piece I need.. its just the part# isn't exactly what the schematics call for.

                    Any word on the part I found compared with what is needed in that schematic? Same thing, same function?

                    You guys rock.

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                    • #11
                      Same chip. Slightly different package. Thats it.
                      2000 Subaru OBS

                      Dell P3 @ 900 Mhz
                      7" Lilliput TS w/DigitalWW in-dash mount
                      80GB External HD

                      I am Zero Bitrate....

                      Comment


                      • #12
                        Originally posted by Fusion-One
                        I've decided to build this programmer, it appears to be perfect for what I want to do... and simple.
                        Does it support to PIC you want to use? The apps will show you if it does so get hold of it first, run it and see if the PIC you want is listed.

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                        • #13
                          Sure does. It actually supports a ton of different pics, the link mushin posted has all the details for both the software and the device. Really a terrific little peice of kit, considering how simple it is.

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                          • #14
                            I built Curiosity's Cario device, and all i have to say is: its perfect. Using his test program, everything works exactly as it should.. inputs, outputs, everything. Super simple to build, super simple to use.

                            Now I just need to figure out all this c code, so I can somehow judo grip wrestle it into a dll I can use in my vb apps.

                            Here's some shots of the device.... and yes, I know I could use a little soldering practice. ;d This one is going to be controlling my entire room... hell, I might even plug my computer into it, so I can make my computer commit suicide by cutting its own power. Muah. Muah. Muah. But really, this device is the real deal.

                            My hat is off to Curiosity, threefold.





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                            • #15
                              I don't understand. What is your project?
                              CarPC #3: 99% Complete
                              Pentium M 1.7Ghz, 1GB DDR2 RAM
                              DVD/CD-RW installed in dash below monitor
                              OEM LCD relocated for 7" Touchscreen
                              Wi-Fi, GPS, PS2 controllers...
                              500+ full albums
                              4,000+ video games
                              music videos, movies, & more!
                              old carPC

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