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Help Minimum voltage for pulsin ? — Parallax Forums

Help Minimum voltage for pulsin ?

jbalatjbalat Posts: 96
edited 2009-08-04 23:39 in BASIC Stamp
In DC my incoming square wave goes between 1.2v to 5.3v

In AC I have measure Vpp=3.9v but also as low as 3.17v

I have noticed that in some cases the input frequency is not properly detected..

Just wondering how pulsin works.. ie what is the min and max it will work with ?
or is it purely based on votage difference in which case what Vpp will it fail ?

Comments

  • agfaagfa Posts: 295
    edited 2009-08-02 12:52
    The BS2's input threshold is 1.4 V (1.4v to 5v = logic 1) according to the Robotics with the BOE Bot manual.· I tried to find a link to it but couldn't find it, the manual is available for download @ Parallax's site.· I believe this threshold may vary slightly with different BS2s and different Vdd values.· I believe you need condition the input to avoid anything above 5v or negative voltage ( of AC).· A simple level shifter could be made from a transistor to increase low level pulses.· A diode could be used to protect against a negative input.

    Post Edited (agfa) : 8/2/2009 12:59:04 PM GMT
  • jbalatjbalat Posts: 96
    edited 2009-08-02 23:54
    I am just guessing here but from what I have observed my dc wave can vary. It must be oscillating between (Lo approx 1.2) and (Hi approx 5v)

    So you are saying if my 1.2v DC Low goes over 1.4v then it would register as a HIGH also...!!

    seems like I need to reduce my signal by about 1v so that the signal ranges from 0.2v to 3.5v (assuming a 3.5v high would give a reliable Hi Reading ?)

    My electrical skills are very minimal... Could I just make a simple voltage divider to reduce the voltage ?
  • $WMc%$WMc% Posts: 1,884
    edited 2009-08-03 00:05
    jbalat

    Take a look a TTL logic!

    _______$WMc%_________

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    The Truth is out there············································ BoogerWoods, FL. USA
  • sam_sam_samsam_sam_sam Posts: 2,286
    edited 2009-08-03 01:58
    You could use a optic sensor might work for you

    I had a project that I need to do something along the same line

    and if you have ac or dc then you could something like H11AA1

    Here is the data sheet

    http://www.vishay.com/docs/83608/83608.pdf

    and here where you can buy some

    http://www.mouser.com/Search/ProductDetail.aspx?qs=sGAEpiMZZMteimceiIVCB1Lm4ynvmRGvs%252bwYP8Brkno%3d

    you can put a pot on the out put to adj you max voltage

    If you need a drawing of how to do this let me know

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    ··Thanks for any·idea.gif·that you may have and all of your time finding them smile.gif

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    Sam

    Post Edited (sam_sam_sam) : 8/3/2009 2:18:17 AM GMT
  • jbalatjbalat Posts: 96
    edited 2009-08-03 02:35
    Thank you very much for the help

    YES PLEASE with the Diagram !!
  • agfaagfa Posts: 295
    edited 2009-08-03 02:41
    jbalat said...
    I am just guessing here but from what I have observed my dc wave can vary. It must be oscillating between (Lo approx 1.2) and (Hi approx 5v)

    So you are saying if my 1.2v DC Low goes over 1.4v then it would register as a HIGH also...!!
    If your signal is 1.2v to 5v·it should detect it with PULSIN.· If the signal exceeds 5v you should take precautions.· I would think that·a voltage divider would work, be sure to adjust for the highest possible voltage.· No matter what, I would use a current limiting resistor on the input.


    Heres the link I was trying to find.

    ·http://www.parallax.com/Portals/0/Downloads/docs/books/edu/RoboticsV2_2.pdf
    ·
  • jbalatjbalat Posts: 96
    edited 2009-08-04 23:39
    Looks like someone has beat me to it for the frequency converter project.
    www.youtube.com/watch?v=P4Edv-Oc3SQ

    No worries.. will try to get the signal conditioned better for the 1.4v threshold. (ref page 210 of robotics pdf)

    If it doesnt work I may have to use the opticoupler if I can figure it out.

    Post Edited (jbalat) : 8/4/2009 11:55:47 PM GMT
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