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Covid Alarm...ish circuit design — Parallax Forums

Covid Alarm...ish circuit design

MarV_nMarV_n Posts: 2
edited 2021-04-20 18:04 in General Discussion

I am working on this Project. For a start i would like to use two comparators circuits to mimic the thermistor and feed the comparators into two transistors (making a and gate) but then there is so many ways to go about this can an any one help me with this, is there a better way to go about this from start to finish?

A new COVID-19 “fictional” vaccine will be available at the end of April 2021. The vaccine MUST BE stored between -20˚C and 10˚C. You are tasked with designing, simulating, and breadboarding a storage temperature monitoring device that will produce an alarm if the temperature exceeds the storage temperature range. It has also been requested to add a “test” feature that the user has available which verifies the operation of the device. The following components MUST BE included as a functional portion of the design, meaning that each part contributes to the functionality of the final design:

  1. Must include at least two of following (they can be two of the same component):

a. LM741

b. AD712

c. Diode (any type)

d. BJT Transistor

e. MOSFET Transistor

  1. NTCLE100E3101GB0 (THERMISTOR NTC 100OHM 3560K BEAD).

NOTE: You will NOT actually use the component. This component can be simulated using a variety of methods. DO NOT go out and purchase the thermistor. It is not necessary!

Comments

  • Homework for you to do:
    Research various web based resources such as Electronic Design, All About Circuits, Engineering 360 and many online textbooks with everything you have listed. Enough to integrate into the system meeting your requirements providing you analyze and understand what you find.

  • ercoerco Posts: 19,925
    edited 2021-04-21 00:38

    All those component requirements... is this a school assignment? I'd just grab a 339 or 393 comparator, make 3 voltage dividers (two are reference/calibration pots, and the other uses the thermistor & fixed resistor) and throw in a 10-cent beeper. Cost: $5 or less. Time: about 4 minutes to breadboard and get it working. Then solder it in ten.

    Add a momentary (test) switch to beep the beeper and use 2 series diodes to drop the voltage from a 9V battery. Totally unnecessary but meets the requirements.

    That particular thermistor may be tough or expensive to source, but in general they are cheap. Like 11 cents each: https://www.ebay.com/itm/10pcs-Thermistor-Temperature-Sensor-NTC-MF52-103-3435-10K-ohm-1-High-Qualitju/363309610662 . And that one specs down to -30C.

    Wouldn't your prof be impressed if you wired one up and had it ready to demo?

  • I think your going to need at least a few resistors, maybe a few 0.1uf caps for the OP amps etc. As mentioned above

  • @erco said:
    All those component requirements... is this a school assignment? I'd just grab a 339 or 393 comparator, make 3 voltage dividers (two are reference/calibration pots, and the other uses the thermistor & fixed resistor) and throw in a 10-cent beeper. Cost: $5 or less. Time: about 4 minutes to breadboard and get it working. Then solder it in ten.

    Add a momentary (test) switch to beep the beeper and use 2 series diodes to drop the voltage from a 9V battery. Totally unnecessary but meets the requirements.

    That particular thermistor may be tough or expensive to source, but in general they are cheap. Like 11 cents each: https://www.ebay.com/itm/10pcs-Thermistor-Temperature-Sensor-NTC-MF52-103-3435-10K-ohm-1-High-Qualitju/363309610662 . And that one specs down to -30C.

    Wouldn't your prof be impressed if you wired one up and had it ready to demo?

    Thank yo so much. I made few adjustment and I am finally done and it works as intended. that's what it looks like:

  • ercoerco Posts: 19,925

    Nicely done!

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