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Kalpak Dabir
03/31/13 10:28
Read: 2348 times

#189591 - Wrong circuits in Mazidi's "8051 Microcontroller....."
The relay driving circuit (Fig 17-2 in the Indian 2nd edition) in the motor control chapter is wrong.
There is a pullup resistor shown at the pin.
During reset when the pin unable to sink current, the pullup will switch the transistor on and hence the relay.
The correct way is a pull down to prevent spurious switching of relay, and a darlington if the drive from the pin is insufficient.

Same mistake is repeated for the stepper motor, where each ULN input has a pullup (Fig 17-9 in the Indian edition), so at reset, all the motor coils will switch on.

List of 11 messages in thread
Wrong circuits in Mazidi's "8051 Microcontroller....."       Kalpak Dabir      03/31/13 10:28      
   I wouldn't expect too many comments      Richard Erlacher      04/01/13 14:20      
      my most painful "textbook experience"      Erik Malund      04/01/13 15:35      
      RE: "that book probably isn't widely popular outside India"      Andy Neil      04/01/13 16:02      
         Is it possible that one institution or teacher is the cause?      Richard Erlacher      04/01/13 19:28      
            Probably the author's own institution?      Andy Neil      04/02/13 02:41      
         The reason for my post      Kalpak Dabir      04/10/13 04:48      
            Have you fed-back to the authors?        Andy Neil      04/10/13 11:10      
   clicking relays      Erik Malund      04/01/13 15:37      
   Website - contact here?      Andy Neil      04/02/13 02:43      
   More problems with that book      Andy Neil      04/02/13 08:38      

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