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final year project: a blind stick that uses different sensors, help needed

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well i was thinking about using the analog output since its straight forward, but then i found out its reversed all over. about the PWM...do i have to use microcontroller to make it work as i want? is there's other way i could use to deal with PWM instead of software implementation ?
thank you

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If you're using a microcontroller, then why aren't you using the digital output?

Look at the section of the datasheet referring to the PW output, if you want to do PWM it's your best bet but you might need to tweak it to give the output you desire.

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Heck, I'd do this the analogue way because it's easier and cheaper: a VCO connected to a speaker or piezo buzzer, could monitor the voltage and increase the frequency of the tone or pulsed tone as the object is approaching. Don't bother with an expensive VCO IC, it's easy to make one from a couple of op-amps.


i am b.tech third year student and i have been given a project to develop a walking stick for the blind using piezoelectric sensors.could you please guide me along these lines and also suggest some references which can guide me from the grass root level.

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hi again

I have read this thread. i have thought of making my blind stick with the help of a ultrasonic sensor, a comparitor and finally a piezobuzzer. however the sensor requires a 5 volt power supply which has to be provided by a piezoelectric material. so i need to know if there are any piezo ultrasonic sensors that could work without any power supply and if not, then how should I go about it since the sensor would require a constant power supply.

thanks  :)

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Please post a link to the sensor you've found which requires a 5V supply.

I don't see why requiring a power supply should be a problem for you: if the transducer were passive (doesn't require a power supply when receiving, which is normally the case) you'll still need a power supply for the ultrasonic transmitter, an amplifier, comparator beeper etc.

Here are some transducers which don't need power to receive but you'll obviously need power to send as I said above.
http://www.rapidonline.com/netalogue/specs/61-1520.pdf
http://www.rapidonline.com/netalogue/specs/35-0175.pdf

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actually i want a blind stick which doesn't need any power supply. so what i plan is to first convert the pressure into electrical energy using a piezo pressure sensor. so that when a person hits the stick on the ground the pressure will be converted into electrical energy and then I can use this electrical energy to operate ultrasonic sensor and comparator. But the problem is for the comparator circuit i will need a constant power supply and also for the ultrasonic sensor. I planned to use the sensor posted in the above posts the MaxSonar EZ1 but the requirement of constant power supply is posing a problem.

Can you suggest a way to over come this constant voltage problem. may be some sensor which doesn't require a constant power supply or anything else 

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It's not possible because the amount of energy you'll generate by simply banging the stick on the ground won't be enough to power an ultrasonic transmitter. You need a real power supply such as a battery, hand cranked generator or a solar panel.

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