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Ultrasonic Voice Alert

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Build a simple alert that speaks or chimes when people come within range

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Build a simple alert for when people get too close to keep their distance and wash their hands. As the ultrasonic sensor detects the person getting too close, it will use the record and playback module to playback a pre-recorded message. Use it to remind people to wash their hands or as an alert to keep them at a distance.

Bill Of Materials

Qty Code Description
1 XC4410 UNO board
1 XC4605 record and playback module
1 WC6028 plug to socket jumper wires
1 PH9251 battery snap 9V
1 XC4442 ultrasonic sensor
1 AS3006 speaker 1W round
1 SB2423 9V battery eclipse

Extra Ideas

  • XC4444 use a PIR sensor to detect movement instead, suitable for wider range doorways and rooms.
  • XC3744 increase the volume and play louder messages.
  • XC3748 use the MP3 audio player to play some tunes when people walk in.
  • XC3714 use the 8 digit display to visualise the distance between the person and the device.

How to build

Connecting the speaker module

The speaker is easy to hook up, just get two lengths of wire with an adequate amount of exposed wire on each end, and loop it through the two hoops on the speaker. If you are comfortable with soldering, you can solder them in place so that they don't fall out. Here we used some prototyping wires we had lying around.

speaker connections

Next up, attach it into the module; there's no polarity with this, just one wire goes to one screw terminal, and the other wire goes into the other.

Make sure that the stray ends of your wire don't cross over. If you want, an easy way to make a connection is via using PT4433 to tidy up the wires and attach them into the terminals, but that's not needed for now.

module connections

Pinout connections

The schematic diagram is something like this: schematic

UNO pin Connection Description
A0 PLAYE on playback module triggers the playback
A1 ECHO on ultrasonic receives sonar
A2 TRIG on ultrasonic sends sonar

This becomes a pretty easy connection to do. If you have a look at the front of the ultrasonic sensor, you should find which one is which:

ultrasonic sensor

You can use the plug-socket jumper leads to connect between the playback module, Uno, and ultrasonic sensor, while also connecting GND and VCC pins.

the ultrasonic can be connected to VIN pin with no issue. This pin has 7v from the 9v battery connection.

module connections

How to use

Hook it up to power so it turns on, then hold the record button on the playback module so you can record a short message.

After recording the message, wave your hand infront of the ultrasonic sensor. you should find that when something passes the ultrasonic sensor, it will play back your message automatically.


Problem Possible cause
It keeps playing back the message This could be caused by a few things:\
either the REPEAT switch is kept on, \
or the ultrasonic sensor is not detecting correctly. \
if changing the REPEAT switch doesn't fix it, have a \
look at the Serial monitor for what the ultrasonic is doing
It's not detecting movement Definitely check the serial monitor