Though I've been an analog electronics tech for 60 years, I'm now tackling my first major digital project using an array of SR04 ultrasonic ranging devices controlled by an Arduino Mega to drive an array of mechanical button buzzers which will be in contact with the skin of a blind wearer to give him/her a much more advanced "view" of his/her immediate environment than the old white cane. Since I'm new to this stuff, I don't know how to convert the output of the rangefinders into a variable level vibration with the closest reflections producing strong vibrations, mid distance reflections producing light vibrations and reflections from 8 or more feet producing barely discernable vibrations. Each buzzer draws 60MA at 5V so I believe I'll need to take the TTL output from the Mega and use a single stage transistor current amplifier to actually drive each buzzer. Doing so will give me 4.4V max to drive the buzzers. Of course I'll need reduced voltage for mid and long distance reflection data. I also plan to stagger the transmit bursts and need to take the range data from each SR04 and direct it ONLY to its buzzer. Since this project will be entirely open source, both the physical design and software, and I'll encourage anyone who wishes to copy it and/or improve on my design. I'm seeking assistance and possible participation of those in the Arduino world. I'm shooting for a cost of under $200 for the finished device and hope to have a fully functional prototype by fall of this year.
Each buzzer draws 60MA
60mA, milliAmp, perhaps? 60 MegaAmp would be a lot.
4.4V max to drive the buzzers
Use Low Rds, Logic Level MOSTETs, with 5-10mOhm on-resistance, nearly the full 5V will be available.
Of course I'll need reduced voltage for mid and long distance reflection data.
I would think you could use varying levels of PWM instead; or perhaps different frequency - slower for farther, little faster for nearer, really fast for close.
Got links to specs for the buzzer and range sensor? Will range sensor be mounted on a headband, chest plate, etc? How many sensors are you thinking? Are they wide angle, narrow angle, etc?
Sounds interesting overall.
A guidance system of similar design was published in Circuit Cellar magazine Nov. 2014, by a couple of engineering students. The code and design files are available on line.