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Olivetti M24 / AT&T 6300 Keyboard Emulator

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    #31
    Interesting progress. Three questions:

    - why not using, like original M24 keyboard, using the +12V supply with a voltage regulator?
    - what is the usage of the mini-DIN keybard connector?
    - M24 keyboard mouse emulation, please...?
    <album>

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      #32
      Originally posted by 1ST1 View Post
      - why not using, like original M24 keyboard, using the +12V supply with a voltage regulator?
      The reason is that it did not seem necessary to me - 12V are not directly needed anywhere, and 5V are already provided on the keyboard connector, so why not use that? It saves at least 2 components (the regulator itself and the upstream capacitor), and it uses less power (the regulator would be a linear one, so it dissipates the excess voltage as heat).

      Originally posted by 1ST1 View Post
      - what is the usage of the mini-DIN keybard connector?
      It's to connect keyboards with a PS/2-style connector. The keyboard protocol for AT and PS/2 keyboards is the same, only the connector is different (DIN-5 for AT keyboards, vs mini-DIN-6 for PS/2 keyboards), so the emulator should be able to work with both. On the PCB I wanted to keep the option of choosing one connector or the other.

      Originally posted by 1ST1 View Post
      - M24 keyboard mouse emulation, please...?
      Working on it...
      Last edited by Valerio; November 18, 2018, 01:23 PM.

      Comment


        #33
        Originally posted by Valerio View Post
        The reason is that it did not seem necessary to me - 12V are not directly needed anywhere, and 5V are already provided on the keyboard connector, so why not use that? It saves at least 2 components (the regulator itself and the upstream capacitor), and it uses less power (the regulator would be a linear one, so it dissipates the excess voltage as heat).
        Maybe the 5V is too weak for the emulator, modern keyboard & mouse... I think you should make it configureable, so the user can choose if he wants to use 5V, or install an 7805 and use this one...
        It's to connect keyboards with a PS/2-style connector. The keyboard protocol for AT and PS/2 keyboards is the same, only the connector is different (DIN-5 for AT keyboards, vs mini-DIN-6 for PS/2 keyboards), so the emulator should be able to work with both. On the PCB I wanted to keep the option of choosing one connector or the other.
        Ok, I understand, good decision.
        Working on it...
        Yeah!


        As it has USB connector, will it also be possible to 'remote control' the M24 from another PC over USB (mouse and keyboard)? That would be cool!
        <album>

        Comment


          #34
          Originally posted by 1ST1 View Post
          Maybe the 5V is too weak for the emulator, modern keyboard & mouse... I think you should make it configureable, so the user can choose if he wants to use 5V, or install an 7805 and use this one...
          There is no mouse yet and with emulator and keyboard it works fine off the 5V line, even with the voltage drop. However you have a point - let me get to the bottom of the cause of this voltage drop.

          Originally posted by 1ST1 View Post
          As it has USB connector, will it also be possible to 'remote control' the M24 from another PC over USB (mouse and keyboard)? That would be cool!
          This is already possible today with the current version of the emulator - minus the mouse. Just use PuTTY or any other terminal app of your choice that supports serial over USB, and you can control the M24 as if you were typing on its own keyboard. Not all keys are available but it's pretty usable.

          I'm not sure how I would support a mouse-via-USB though - even if the emulator did emulate the M24 mouse (which should not be hard), I'm not familiar with how (or even if!) terminal apps send mouse movement (and click) information down a serial line...

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            #35
            Originally posted by Valerio View Post
            Nice! Can I ask what keyboard you tested it with? Or did you use the TTY-via-USB feature?

            Also, did you power it via the USB cable or from the AT&T 6300 keyboard port?

            Thanks!
            I used a Dell model RT7D5JTW PS/2 keyboard which is rated at 75mA.

            I am currently using the 5V pin from the keyboard port, which in my case is providing 4.85V. It works fine to power the Arduino and a PS/2 keyboard. I am planning on adding a voltage regulator and using the 12V pin before I attempt to use my IBM Model F AT keyboard. My Hi-Tek XT/AT keyboard draws 300ma, so I can only assume that the older capacitive keyboards probably draw more.

            Will

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              #36
              I run a Compaq keyboard, a BluePill ( 32 bit ARM ) and 10 led's on the USB port. It is a PS/2 to parallel but could generate M24 codes as well, by just a change to the lookup table. It could even be used take USB to the M24. The BluePill is cheaper than the Arduino's.
              Such things can be done on an Arduino as well.
              Dwight

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                #37
                Originally posted by JWDW View Post
                I used a Dell model RT7D5JTW PS/2 keyboard which is rated at 75mA.
                If I have that adapter, I would use a newer Olivetti keyboard, like ANK 25-102 or ANK 26-102. They would need more power than 75mA.
                <album>

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                  #38
                  Ok we seem to have a consensus that a regulator is desirable - I will add it to the PCB.

                  Comment


                    #39
                    Edited PCB attached. Looking at the 7805 datasheet it seems that in a TO-220 package it is safe to dissipate (12V - 5V) * 500mA = 3.5W while keeping the junction temperature well within the recommended operating conditions, so I did not include space for a heatsink - let me know if you think otherwise.

                    Also note that the space for the input / output capacitors is approx 9x9mm / 6x9mm - should be enough for ceramics or low-voltage electrolytics.

                    keybem_front.jpg
                    olivetti_kb.pdf
                    olivetti_kb.zip

                    Comment


                      #40
                      I suspect the temperature will stay within operating range but I doubt it will do much to improve its life time. I'd say add a heat sink. There are a lot of variables in what it can take. Things like do the leads connect to a power plane. Will it be mounted vertical or horizontal.
                      Dwight

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                        #41
                        Most places I looked at say case to ambient is on the order of 50 to 60 degrees C per watt.
                        3.5 times 50 is 175. add that to 25 = 200 degrees C. Most to-220 packages are rated at 150 C.
                        At 150 C, I can tell you that touching the package will flatten the finger prints so you can get away with other crimes.
                        Most show the die at 3.5 degrees per C so the die would be another 12.25 C hotter then that.
                        What numbers did you see for package to ambient?
                        Dwight

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                          #42
                          Originally posted by Dwight Elvey View Post
                          Most places I looked at say case to ambient is on the order of 50 to 60 degrees C per watt.
                          3.5 times 50 is 175. add that to 25 = 200 degrees C. Most to-220 packages are rated at 150 C.
                          At 150 C, I can tell you that touching the package will flatten the finger prints so you can get away with other crimes.
                          Most show the die at 3.5 degrees per C so the die would be another 12.25 C hotter then that.
                          What numbers did you see for package to ambient?
                          Dwight
                          Ok, I admit I only checked one datasheet, this one, which gives the thermal resistance as 19 degree C/W for TO-220 packages, which would give T_J = 3.5 * 19 + 25 = 91.5 C, still too hot to touch but below the recommended max junction temperature of 125C.

                          TI's datasheet gives 23.9 C/W, which would bring this to 107, even hotter but borderline ok.

                          However now I see ST's datasheet says 50 C/W ? This would definitely mean it's way too hot, as you say.

                          And Fairchild's even higher at 65 C/W! I am perplexed...

                          Anyway I think I can rotate the 7805 so its back faces the outside of the PCB, so a heatsink can be attached...

                          Comment


                            #43
                            And here it is - with the regulator rotated and on the outside border of the PCB, so a heatsink can be attached.

                            keybem_front.jpg
                            Attached Files

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                              #44
                              And off it goes for production - fingers crossed!

                              JLCKB.JPG

                              Happy Thanksgiving everyone!

                              Comment


                                #45
                                Originally posted by Valerio View Post
                                Ok, I admit I only checked one datasheet, this one, which gives the thermal resistance as 19 degree C/W for TO-220 packages, which would give T_J = 3.5 * 19 + 25 = 91.5 C, still too hot to touch but below the recommended max junction temperature of 125C.

                                TI's datasheet gives 23.9 C/W, which would bring this to 107, even hotter but borderline ok.

                                However now I see ST's datasheet says 50 C/W ? This would definitely mean it's way too hot, as you say.

                                And Fairchild's even higher at 65 C/W! I am perplexed...

                                Anyway I think I can rotate the 7805 so its back faces the outside of the PCB, so a heatsink can be attached...
                                I suspect it is an error in the table. If you look at the text above the table, they say it is 54 C/W. At number that is a little closer.
                                Dwight

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