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Trigger Mechanism

Trigger is a device used to release or activate a mechanism. It is can be a switch, a button or sensor. When a power is supplied to the trigger, it will activate other mechanism. They are different with respect to shape, size and their triggerring method.


In a voice application, the most commonly used triggers found on the sound modules are push botton, slide button, LDR and motion sensors. Depending on the the type of of the applications, different kind of trigger can be used. Here we will describe three commonly used triggers in a voice application.

Push Button

The push button, shown in Figure 1(a), is the most commonly used trigger mechanism. The button has to be physically pressed to ensure the connection between the two points. This type of trigger is frequently used in toys or stuffed animals. The voice module is placed inside the toy. With proper wire length, the push button can be placed in a visible location. Whenever the button is pressed, the sound would play. The limitation of the push button is that a person needs to physically push the button whenever they want to listen the sound. Similar types are the slide switches.

Motion Sensor

Passive infrared (PIR) sensor, shown in figure 1(b), is one of the types of sensors used in motion detector circuits. Hence, it is also known as motion sensor. When there is movement in the view area, it will trigger an action. One example to use this type of trigger is to place the Voice Module with the motion sensor in front of a Christmas tree or Halloween props. Whenever someone moves in front of the tree, the PIR sensor gets activated and the sound plays.

All PIR sensors require an initial calibration if the power was turned off. To do so, place the voice module in a place where there is no motion or very less motion, so that the sensor can differentiate between stationary and moving objects. For more information, see How to use PIR with Aplus voice IC.

Light Sensor

Light Dependent Resistor (LDR), shown in figure 1(c), is also known as light sensor. It is ON when light falls on it. When it is dark or no light, it is OFF. The two leads of the LDR are connected to the trigger and the voltage pin of the voice IC. This type of trigger is often used in gift boxes. You can place the voice module with LDR light sensor inside a gift box cover with an object. Leave a small hole or opening for light to fall on light sensor. Whenever a person opens the gift box, and the light sensor is exposed to light and the sound plays. One limitation is that it cannot be switched OFF unless there is no light. However, stopping the playback can be done with trigger options when programming the voice IC.

How to connect the triggers

For the Aplus OTP voice IC, one pin of the these triggers must be connected to the trigger pin and the other one to the VDD or VSS pin of the voice IC. The sound will play when VDD voltage is applied. For the Recordable ICís, the sound will play when VSS voltage is applied to the trigger pin.

For more information about these triggers, please contact us.

See also What is sample rate?

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    Tech Notes
  • FAQ
  • PCM vs ADPCM
  • Sampling rate
  • Triggers Mechanism
  • Triggers Options
  • Rec vs OTP vs MTP
  • APR2060 ROSC value
  • OTP Comparison

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