Electronics > Electronics

Help about Sharp IR sensor GP2D120

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suren:
seems like they dont need any external circuit to control and it gives a analog output voltage corresponding to the distance.
In my project i need to detect a surface in the range of that sensor..i dont really need to measure the distance..I just need to see whether the surface is present or not..
and i am implementing my motor control by using parallel port ..(i dont want to use any microcontroller)..is it possible to take input from parallel port(with a bit of external circuit ,if required like Analod to digital converter etc)??Plz reply at earliest..
Best Regards,
Suren Kumar

KambeiX:
you don't need an ADC for that task. You can do it with a 7414 TTL IC (schmidtt trigger). It will go high when the threshold (I think it's 2.5v) is reached and vice versa (the thresholds are different).

If you need a specific distance to be reached (specific voltage) you can use an OP amp for this task.

As the inputs for the OP amp, use the target voltage in the inverting input (using a pot for calibration) and the sensor output connected to the non-inverting input.

When the sensor voltage goes higher than the target voltage, the op amp will go high.

suren:
thanks for your reply..
I think using a comparator like LM339 would be a good bet for this..and it comes really cheap.Do u have any info on the cost for the thing you are proposing??

KambeiX:
well a comparator, op amp or 7414 won't cost you more than 0.5 and 2 resistors or a pot will cost less than that so the total won't be more than $1 =P

the comparator of course would be the best solution, but on the inside is basically an op amp, so you can use one if you have one and don't want to buy a comparator.

Brandon121233:
you can get comparators as free samples from Maxim, and they give you free 2nd day shipping  8)

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