8:1 Multiplexer Interface

Discussion in 'General Electronics Chat' started by ajitnayak87, Nov 17, 2014.

  1. ajitnayak87

    Thread Starter New Member

    Dec 30, 2013
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    Dear all.

    I am using Arduino board for programming and 3 analog 8:1 mulitplexer. My main agenda is i wanted to read 24 channel indivully connected via hall sensor. each channel are connected to hall sensor and output is connected to analog pins of arduino. For testing purpose i used potentiometer , instead of hall sensor.Basic circuit added below. HS1-Hs24 connected to potentiometer .

    Intially tested indivually where i can able to get proper result.if vary the pot i can found changes in output. Now i i connected all together . But this time , i found that VCC pins instead of 5v dropped down to 4.5v . & keep flactuating because of which i can't stable out put. circuit remain same . change made is scaling from 1 to 3 MUX. all Ic get 5v and connected to common ground of arduino.


    Problem i found that when selective pins so,s1,s2 are non connected , voltage remain constant 4.9v. as soon as connect slective pins it start fluctuating. i wanted to know what reason behind flactuations
     
  2. GopherT

    AAC Fanatic!

    Nov 23, 2012
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    3,703
    The Enable pin (pin 6) is hard wired to ground in your drawing. Do you have each chip connected to a different analog pin on the arduino? If you use the Enable pin to enable and disable the chip, you only need one bus line to make the connection.

    What power supply do you have and double-check that you done have a short circuit come where to cause your power supply to drop to 4.5 volts. Each ship should only take 5 to 10 mA.
     
  3. ajitnayak87

    Thread Starter New Member

    Dec 30, 2013
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    I have sorted out problem. Intially I given 5v to Mux IC from arduio VIA USB. Now i given via SMPS 5v regultated. Now Power @ IC remaining @ 5.10v Constant. Now i can able to get proper value. Is there any other way i can do it. Where i can connect 24 Sensor instead of analog multiplexer???
     
  4. ScottWang

    Moderator

    Aug 23, 2012
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    You may did something wrong with the Inh pin.

    You want to have 24 channels then you will need 3 bits for the Channel selection, the Inh pin to do the enable and disable as below:
    1. Input Channels -- IO-0~IO-23, Mux1 : 0~7, Mux2 : 8~15, Mux3 : 16~23
    2. Channel Selection -- ARD_D15,ARD_D16,ARD_D17
    3. Chip selection -- ARD_D14(011), ARD_D13(101), ARD_12(110), never use 000 or any two 00 for Inh here.

    110 - to Select the Inh of Mux1 chip, ARD_D14, ARD_D13, ARD_12
    101 - to Select the Inh of Mux2 chip, ARD_D14, ARD_D13, ARD_12
    011 - to Select the Inh of Mux3 chip, ARD_D14, ARD_D13, ARD_12
     
  5. ajitnayak87

    Thread Starter New Member

    Dec 30, 2013
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    0

    Since They connected indivually to analog sensor, I didnt find any problem. I am not getting what are you are trying to say here. My code enable Ao port of mux 1,mux2, mux3 once output being read by a0,a3,a5 analog port respectively. Next switching cycle A1~A7 . So there will no interface problem here.
     
  6. ScottWang

    Moderator

    Aug 23, 2012
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    767
    If your 24 inputs are related to the same output, but as your 3 outputs will need 3 datas memory to memory them, if their datas are separated for 3 parts then it's ok, otherwise they have a little problem that you need to conquer it.

    So what you said about the 24 inputs that the output is n't the same?
     
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