LM324 - IR Sensor

Feb 07, 2006 2 Replies

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Manimozhi Baskaran 20 years ago

I built the circuit below with the IR sensor on the bread board

A large bowl of snow was brought inside the house to the sense the snow

Varied the 50 K pot (20 turns on the pot)

No buzz output from sensor

Any suggestions on what is going wrong?

Thanks

---+-------+----------+----------- +5 --------VoutLM785 (NTE equivalent one) (Vin) +9V- --------- |

| | | |

| | 100K |

| | | |

| | +-----[22K]-------+ |

50K pot | | 1/4 | |

| |\\| | |\\ 324 | |

ref(A)+-----|+\\ +------|+\\ | |

IR in | | >--. | | >-----+-+--|| |

-------|-----|-/ `-| | |/| 1N914 | | |/ | +| |

| | 100K +----[100K]-' | |

| 1/4| | | | |

100K 324| | === 0.2uF (B) | |

| | | | | |

-----+-------+----------+---+----------------+--------------------------------------------- GND

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ehsjr 20 years ago

-----+-------+----------+---+----------------+---------------------------------------------

I tried to clean up your diagram, which was not clear, and came up with this: ------ ---+-----+----------+--------- +5 ------Vout|LM7805|Vin--- +9V | | | ------ | | | | | | 100K | | | | | | | +-----[22K]-----+ | pot 50K | | 1/4 | | | |\\| | |\\ 324 | piezo | ref(A)+---|+\\ +------|+\\ | 5V-9V | IR in | | >--. | | >-----+-+--|| | -------|---|-/ `-|

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John Fields 20 years ago

(Vin) +9V- --------- |

-----+-------+----------+---+----------------+--------------------------------------------- GND

With the 50k pot cranked to zero ohms the reference input to the opamp will be 5V, and since: E1R2 E2 = ------- , R1+R2 with the pot cranked to 50k the reference input will be: E1R2 5V * 100kR E2 = ------- = -------------- = 3.33V, R1+R2 50kR * 100kR So there\'s no way you can get to 0.8V, no matter how much you crank the pot. What you need to do is change this: +----------+----+5V | | [50k]--[--|---------|-/ | | [100k] | | | +----------+----GND to this: +----------+---+5V | | [100k] | | | +---------|+\\ | | >--[--|---------|-/ | | [50k]------+--[--|---------|-/ | | [50k]

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