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Low MCLR Voltage on PIC

  1. Jun 9, 2013 #1
    Hi everyone,

    I have built a circuit with a PIC micro-controller (16F877A). I have connected +5 V supply to the MCLR pin through a resistor of 4.7 kΩ. All I saw in sample designs were 4.7 kΩ or 10 kΩ but my circuit doesn't work. When I measure the potential difference between the ground and the MCLR pin I read a 4.40 V value.

    I have two questions now.

    1) Do I have to use a smaller resistor?
    2) Why all the sample designs with 4.7 kΩ are OK and mine is not? What can I be missing? What may cause this huge potential drop (About 0.70 V)?

    Some additional information found by mistake:

    1) Once the PIC didn't fit to the socket well and the MCLR pin was not plugged in. When I measure the potential difference, it was about 5 V.

    2) While I was trying to measure current I put one of the probes on MCLR and the other one to the OSC1/CLKIN by mistake (It is a multimeter with two probes) the circuit worked.

    With the help of the additional information could you please comment on what my problem can be?
    Last edited: Jun 9, 2013
  2. jcsd
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