--- "DO IT YOURSELF" ENTRY ------- PURPOSE: Helping Eyes is a "visual aid" which can be mounted to any apparel to prevent injury to the visually impaired. It uses an ultrasonic range sensor to "sense" objects and sends vibrations to warn its wearer of the incoming object (or wall/ceiling). As an object comes closer, the vibration's intensity increases.
MATERIALS USED: Attiny85 (with socket), HC SR-04, SPST Slide Switch,Two CR2032 batteries (with holder),NPN transistor,1N4007 Diode, Perfboard (5cm by 7cm), DC Vibration Motor (I salvaged mine from an Xbox controller), A mounting surface (i.e. a hat).
The schematic can be broken down into three parts:
3.DC Vibration Motor.
The power supply consists of two CR2032s, a diode, and a SPST switch. The CR2032s in series will give us a voltage of about 6v (provided that we are using relatively "new" batteries). From the attiny's datasheet, you will find that the absolute maximum operating voltage of an attiny is 6v. Since batteries can produce higher voltages than their rated amounts, just connecting two CR2032s in series could give us voltages higher than 6v (which would damage the attiny). To lower the voltage, I added a diode in series with the batteries. This will drop the voltage down 0.7V, to ensure our attiny never receives any voltage higher than 6v. To complete the power supply, add a SPST switch to act as an on/off switch for our circuit.
Connecting the HC SR-04 is rather straightforward. Just connect VCC to our positive voltage supply, the GROUND to ground, TRIG to the attiny85's pin 2, and ECHO to the attiny85's pin
3. (The TRIG and ECHO connections are dependent on the attiny's programmed code).
1.The DC vibration motor requires a transistor, and an attiny pin to function. First, connect the base of an NPN transistor to the attiny's physical pin 5. Then connect the collector to our positive voltage supply and the emitter to the positive connection on the DC motor. Finally, connect the DC motor's negative side to ground. A transistor is used to operate the DC motor because the attiny's pins do not supply enough current to power our motor, so instead we use a transistor so we can supply more current to the motor.
2.Before we solder, let's make sure we use our perfboard space wisely to avoid having to move components later. Here are some things to consider while planning your perfboard layout:
Give the DC vibration motor room to spin.
Make the SPST switch easily accessible.
Mount the HC SR-04 straightly with nothing obstructing its view.
3.Before soldering any components to the perfboard, be sure to hot glue your DC motor to the board. This will protect any wires from being disconnected later on.
To begin soldering, I connected all the major components to the board first (such as the motor, attiny socket, hc sr-04). Then I made the necessary connections after. However, any way you soder your circuit will work, of course.
This circuit shouldn't need too much troubleshooting since there aren't many components, but if you run into problems be sure you connected two batteries and your diode since this circuit needs more than 3v to function (due to the voltage drop of the DC motor). Refer back to the schematic, and your breadboarded circuit for help troubleshooting.
4. Next we can mount your new Helping Eyes to your mounting surface.
5.Since this device is so small, it can be mounted to many surfaces (such as clothing, hats, belt buckles, etc.). I chose to mount mine to a hat to prevent against accidents involving low ceilings in homes. Because if the varieties of mounting surfaces, I will give you a list of ways to mount your Helping Eyes:
Use Hot Glue or Epoxy
Make the circuit using an arduino lilypad and sow it into clothing.
Attach using Velcro.
Screw it into your mounting surface.