Analogue Electronics Mini-Instrumentation Project

Discussion in 'The Projects Forum' started by Fnixer, Jun 2, 2015.

  1. Fnixer

    Thread Starter New Member

    Jun 2, 2015
    3
    0
    Hi,

    I have been tasked with creating a circuit using a sensor of my choice, I chose a LDR, and was going to use a LM324 op-amp to activate a LED when light is shone on the LDR. I have a 5v and <250ma limit on the imput and the output must be proportional to the variable level being monitored, clamped to a range of 0V to 3.3V (ranging from at least 0.1V to 3.2V), with appropriate anti-aliasing filtering.

    Any help would be appreciated and suggestions how I would go about this and circuit diagrams.

    Thank you
     
  2. AnalogKid

    Distinguished Member

    Aug 1, 2013
    4,546
    1,252
    What you describe is pretty simple, and can be done with 1/4 of an LM324 using only 20-25 mA of your current budget. Your comment about anti-aliasing makes me wonder if there is an intent to use a more complex system. What is this for?

    ak
     
  3. crutschow

    Expert

    Mar 14, 2008
    13,056
    3,245
    Anti-aliasing filtering is needed when you a going from an analog value to a digital value for the signal.
    Is that your intent?
     
  4. Fnixer

    Thread Starter New Member

    Jun 2, 2015
    3
    0
    As far as I know I just have to display a 3.3v output with a light shining on the LDR and a LED activating.
    I was advised to use a low pass filter to clamp. Generally I am very bad at analogue electronics and don't really know where to start, thank you for the help so far however.
     
  5. Fnixer

    Thread Starter New Member

    Jun 2, 2015
    3
    0
    Anyone any ideas?
     
  6. AnalogKid

    Distinguished Member

    Aug 1, 2013
    4,546
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    Your question is not very clear, which is why you aren't getting responses. Let's clean up the question a bit.

    1. Do you need an output that is proportional to the light input? An example of this would be an LED that gets brighter as more light hits the LDR.

    2. Do you need a digital output? That is, a signal that snaps from GND to approximately Vcc when the light on the LDR exceeds a trip point value.

    3. What is the LDR? Manufacturer, part number, light resistance, dark resistance ... anything?

    4. Do you have a partial schematic, block diagram, or anything to show your work up to now?

    ak
     
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