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Parallel vs Serial Was: NEWBIE - Hooking up multiple power supplies to a circuit

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  • csakima
    Yeah, me too. I would go the Parallel port route. It s easier ... more direct. I ve connected relays (thru drivers) to my parallel port ... and had QBasic
    Message 1 of 1 , Nov 29, 2002
      Yeah, me too.  I would go the Parallel port route.  It's easier ... more direct.  I've connected relays (thru drivers) to my parallel port ... and had QBasic programs control them.
       
      To really do a good "serial" job would be to run maybe a PIC microprocessor with it's UART going to your PC's serial port.  The PIC would then interpret the characters coming over the serial line and determine what your PC wants to have happen.   Then, the PIC can turn ITS output ports on and off in response .... turning your devices on and off
       
      Curtis
       
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      ----- Original Message -----
      Sent: Friday, November 29, 2002 8:08 AM
      Subject: RE: [Electronics_101] NEWBIE - Hooking up multiple power supplies to a circuit

      Hello,
       
      First of all, you can't hook up your serial port directly to your transistor. You need to build a RS232 interface.
      That interface could be made with a microcontroler or with discrete logic part.
       
      On a other way, it would be a lot easier to do this by using your parallele port.
      You simply need isolation between the port and the transistor. You can use a 74hxxx buffer or any other isolating device.
      Then, a simple program accessing the port or even ASCII comment sent directly to the port through hyperterminal would do.
       
      Regards,
       
      David
      -----Original Message-----
      From: ridiculicity [mailto:ridiculicity@...]
      Sent: Friday, November 29, 2002 2:49 AM
      To: Electronics_101@yahoogroups.com
      Subject: [Electronics_101] NEWBIE - Hooking up multiple power supplies to a circuit

      Hey there everyone,

      I have a very basic question but I can't figure out the answer.
      Basically, I want to use a transistor as a switch on a 12V DC motor
      and I want some kind of digital signal ( most likely a line from my
      serial port ) to control the on/off functionality. I'm not sure how
      to hook this up.

      I'm assuming that the +12V source goes on the collector of the
      transistor and the negative goes on the emitter. Then the line from
      the serial port would connect right to the base. That's where my
      question pops up. Shouldn't there be a ground for the TTL signal? Is
      it possible that the TTL signal just switches the transistor and then
      vanishes? Shouldn't there be a way for the signal to go from computer
      to transistor and then back to computer?? I just don't understand..

      If anyone could help me, I'd sincerely appreciate it.
      Thanks!!!
      Mike

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