Running simulation in Tina circuit simulator??

Discussion in 'General Electronics Chat' started by spinnaker, Nov 19, 2009.

  1. spinnaker

    spinnaker Thread Starter Senior Member

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    I downloaded the free fersion of Tina.

    http://focus.ti.com/docs/toolsw/folders/print/tina-ti.html

    I built a basic 555 timer circuit but can't see any way to run it.

    I checked help and form the looks ogf it, there is supposed to be a Run command on the menu but I am not seeing it.

    I loaded one of the sample simulations and don't see a run command either.

    How do I run the simulation?
  2. SgtWookie

    SgtWookie Expert

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    On the Menu Bar, click on Analysis, then Transient...
    Set your start time (0), and End Display time, usually in uS or mS.
    Clicking "Use Zero Values" will be necessary when simulating oscillators and astable multivibrators (such as free-running 555 timer circuits)
  3. spinnaker

    spinnaker Thread Starter Senior Member

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    Sgt,

    As always thak you.

    I tried this and I get operating point not found.

    Could it be that this sim is a little over my head right now? Are there any other easier ones that are free?
  4. SgtWookie

    SgtWookie Expert

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    OK, maybe you have connected things up improperly.

    Why don't you post a screen print of your schematic, and if possible your schematic itself?
  5. spinnaker

    spinnaker Thread Starter Senior Member

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    The files are attached. The txt file is actually a tsc file for tina. You will need to rename the file.

    Attached Files:

  6. SgtWookie

    SgtWookie Expert

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    OK, how did you come up with those values for R1, R2, C1?

    How fast were you expecting the LED to flash?

    You know that the output of a bjt 555 timer when high will be about 1.3v less than the supply, right? Since your supply is 5v, that means your maximum output on pin 3 will be around 3.7v. Figure that the CQX35A LED will have a Vf of 1.6v @ 20mA. That LED is rated for an absolute maximum 50mA.
  7. SgtWookie

    SgtWookie Expert

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    Just a little bit about selecting the value to use for R1:

    When using the "standard" 555 timer schematic like you have, you need to keep in mind that in order to discharge the timing capacitor C1, pin 7 (the discharge pin) is shorted to ground. Pin 7 is the open collector of a transistor; the emitter is tied to the ground pin.

    I have yet to find a published maximum sink current for the discharge pin. However, I suggest that you really don't want to go over 10mA sink current via R1; as the more current pin 7 sinks, the higher the Vce gets, and the hotter the 555 timer IC gets.

    So, a rough "rule of thumb" for the absolute minimum value of R1 is 100 Ohms per volt of Vcc.
    1v / 100 Ohms = 10mA.
    Since your Vcc is 5v, your minimum is 500 Ohms. You're really better off to at least double or triple that minimum, especially if you're running from batteries.
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