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Using Relay To Replace Pushbutton on a Handphone. — Parallax Forums

Using Relay To Replace Pushbutton on a Handphone.

azmax100azmax100 Posts: 173
edited 2006-11-21 11:25 in General Discussion
Hi all,

I am doing a project to program a relay to replace the push button on a handphone.
If i asign a pin to each of the button I will need 17 I/O pin. that's not enought from BS2.
maybe i have to sacrifice few buttons to make it posible.

Do anybody knows how to replace· pushbutton without using relays.This is the only method I
know cause I am newbie.

I would very much appreciate if you can tell me how.

· Azmi.

Post Edited (azmax100) : 11/17/2006 2:47:10 PM GMT

Comments

  • Bruce BatesBruce Bates Posts: 3,045
    edited 2006-11-17 15:37
    azmi -

    What you need is a keypad encoder. Here is one but it's limited to 16 keys whuch is usually an ample number:
    http://www.allelectronics.com/cgi-bin/item/EDE-1144/search/KEYPAD_ENCODER_IC_.html

    Regards,

    Bruce Bates

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  • azmax100azmax100 Posts: 173
    edited 2006-11-18 03:45
    Thanks Bruce for your reply.

    I already take a look at the link and download the datasheet.

    What I understand after readind the D/sheet that the encoder is use to send signal to the stamp.

    Actualy what I am going to do is instead pressing the h/phone button I want to program the stamp to dial

    or use the function in the phone.For instance I want to use the MP3 from the phone so I will program BS2 to

    press the button for me. I was thinking to combine this function with a remote control (IR Remote By Andy Lindsay).

    Is it can be done with the encoder?

    Maybe I miss something or not really understand what I've read from the D/sheet.
  • Bruce BatesBruce Bates Posts: 3,045
    edited 2006-11-18 09:34
    Azmi -

    The keypad encoder is only used for READING a keypad, that's it.

    If you're looking to send touch-tone signals, you want to use the DTMFOUT command.

    Regards,

    Bruce Bates

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  • GadgetmanGadgetman Posts: 2,436
    edited 2006-11-18 10:39
    The problem with not enough I/O can be addressed by using a 'serial-in-parallel-out' shift-register.
    A popular one is the 74HC595.

    As for how to connect to the keys, that depends on the phone, really.

    It may be possible to drive it with a transistor, or even directly from the outputs of the 595.
    (difficult to tell without experimenting with the phone in question)

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    Don't visit my new website...
  • azmax100azmax100 Posts: 173
    edited 2006-11-18 11:28
    Thanks to Bruce & Gadgetman for your reply.

    Actually I already done some expeiment with the relay and it's work fine.

    I got the schematic from this thread http://forums.parallax.com/attachment.php?attachmentid=39247

    I dont mind to follow Gadgetman suggestion to use the 74HC595 to get the extra IO.However

    I don't like to use the relay cause i don't like the tick sound·and will take lot of space.

    I want to make my project as small as posible. If I have to drive it directly from the 595 how am I going

    to connect it. Can you provide me a schematic for that. I would very much appreciated for your help.

    Thanks & Take care.

    Azmi.

  • GadgetmanGadgetman Posts: 2,436
    edited 2006-11-18 11:57
    I don't know how the phone you're using is wired up, so I can't give you any specifics.

    What you should do is look at how it works.
    I assume one side of each switch is connected to some sort of IC in the phone, but the other side?
    Is it driven low(Gnd) or high(+5V/3V/whatever)?
    And what voltage does it need to consider it a keypress?
    (Try a large Potentiometer, say 10Mohm or more, across the terminals and adjust it down while measuring the voltage across it until it registers a keypress)

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  • FranklinFranklin Posts: 4,747
    edited 2006-11-18 19:42
    While looking for info on a solution I found this site and thought it would be a good resource for us all.
    www.allaboutcircuits.com/vol_3/chpt_7/9.html

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  • azmax100azmax100 Posts: 173
    edited 2006-11-20 05:06
    Hi all.

    Thanks Franklin & Gadgetman for your reply.

    Gadgetman,

    I will do as what u suggest and will let u know about the progress. I will do it this evening and let

    u know. ( Malaysia time now is 1.00 pm) Hope u will keep on looking·at my post.

    Thank you very much.

    This forum need a lot of people like you.

    ·==============================================

    Edited:

    I·already made a·measurement with multimeter·on the pushbutton. It seem there's no·current flow

    to complete the circuit. maybe its from·-tive·side.The circuit functioning even i connect with 10K resistor.

    (that is the highest·value·resistor I have).

    Hope u can guide me towards my project.

    Thank you & take care

    p/s·attached photo are the keypad. I have to peel the·button layer to solder the wire to the relay.

    17·button·x 2 wires. It will look messy isn't it?


    Post Edited (azmax100) : 11/20/2006 12:43:39 PM GMT
    Phone Button.jpg
    640 x 480 - 145K
  • azmax100azmax100 Posts: 173
    edited 2006-11-21 11:25
    anybody have any idea?

    Please.
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