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

[Hero999]

The calculation for R2 doesn't look right to me, the correct calculation can be found in the Wikipedia article I linked above.

With R1 = 10k and R2 = 4k7 the trigger voltage will be 1.6V.

As for RV and RL: I don't think you've given this enough thought, you're not supposed to copy the schematic parrot fashion but understand it and apply it what you've learnt to the problem.

 

[FYP]

for R2...i did get 1.6V from this equation...but the thing is the nearest resistance value that can be found in market is 4k7 (i guess) thats why i wrote  R≈4.7k.
regarding RL...well i think its the load thats going to b connected (i.e. motor)
Rv is represents that input device. rit ?

 

[Hero999]

for R2...i did get 1.6V from this equation...but the thing is the nearest resistance value that can be found in market is 4k7 (i guess) thats why i wrote  R≈4.7k.

That's pretty far out.

What value did you calculate?

regarding RL...well i think its the load thats going to b connected (i.e. motor)

Look at the datasheet for a comparator IC such as the LM393, do you really think it can directly control a motor?

Rv is represents that input device. rit ?

Yes.

 

[FYP]

im very sorry..i think i used the wrong equation...ok R1= 3.3k R2= 2.2k

i went through the datasheet...well im not that good at reading datasheets...i get really confused. but i guess ur point is the motor can't be connected directly to LM393 without motor drive. rit ?
i hope you dont get angry or bored of me, im under real stress these days.
thank you

 

[Hero999]

That's right, you got there in the end.

 

[FYP]

hello again

recently im facing s problem in the Ultrasonic sensor that im using,
the ultrasonic im using is LV-Maxsonar-EZ1, its a great sensor that can give different types of outputs like Analog and digital outputs. here's the datasheet of the sensor:
http://www.wrighthobbies.net/datasheets/MaxSonar-EZ1-Datasheet.pdf

the problem that im facing is that the analog output of this sensor is proportional to the distance of obstacle detected...which means when the object is at 3m distance the value (lets say) 3V, and at 0.5m the value is 0.4V.
i want it to be inversely proportional to the distance, in order for the vibrator (which is connected to the output of the sensor) vibrates strongly when an abject comes near by instead of the opposite.
any idea how to overcome this problem ?

 

[Hero999]

It should be fairly simple.

What do you have in mind for the vibrator, a motor with a weight attached to the end fo the shaft?

It should be fairly easy to use PWM to vary the speed.

 

[FYP]

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

 

[Hero999]

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.

 

[FYP]

Hello

recently im doing the software part...is it ok to put my software problems here or should i open a new topic ?

thank you

 

[Hero999]

Post them here or in the microcontrollers section, probably here is best because you have the background.

Don't expect much help from me though as I'm not a software person.

 

[FYP]

;D
then i think its better for me to go to the microcontroller section.
i have feeling this topic wont stop here

you helped me a lot...thank you

 

[ec]

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.

 

[Hero999]

Yes but have you read the entire thread first? If not then it's the first thing you should do.

 

[ec]

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 

 

[Hero999]

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

 

[ec]

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 

 

[Hero999]

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.