The prototype is based on these parts:
- Arduino Uno
- Adafruit Data Logging Shield
- Panasonic Motion Sensor AMN32111
- Microchip MCP4821 DAC
- Texas Instruments LM386N-1 (Replaced by the TDA 7052 in the final Version)
- A small speaker 0.2W 8Ω
- A dual color LED green/red
- Various resistors and capacitors.
- Small SD-Card
The “Arduino Uno” is a cheap microcontroller board based on the ATmega328. It has already everything necessary to build a device. Read all details about the controller here.
Adafruit Data Logging Shield
The microcontroller itself has only 32KB of flash memory, which is not enough to store all voice samples in a good quality. To get more storage I use a SD-Card to store all the samples. Actually SD-Cards go really well with microcontrollers, because they support the SPI protocol. The only problem is the different voltage. The “Data Logging Shield” from Adafruit just adds a SD-Card and a RTC to the Arduino microcontroller. Read all details about this shield here.
Panasonic Motion Sensor AMN32111
The sensor is of the “slight motion detection type”, which is actually true. It signals at even a very small motion in the specified range. You should find details about the sensor here.
Microchip MCP4821 DAC
There are many different ways how to realize sound output for the Arduino controller. But most produce a really low quality sound output, especially the projects which just use the PWM feature of the controller.
I decided to use a cheap DAC chip which is connected via SPI to the Arduino. The output of this chip is impressive accurate. The version I am using has an internal voltage reference. Here I could improve things by using the version with external voltage reference. The chip also comes with a handy DIL-8 package.
Texas Instruments LM386N-1
This is a low voltage power amplifier. It takes ±0.4V input and converts this into a signal to drive a 0.2W 8Ω speaker. It can take an input voltage from 4-12V, which is perfect to power the amplifier directly from my power source, using 9V. It also comes in a handy DIL-8 package.
In the final version of the project, I replaced this chip with the TDA 7052. See this post for details and reasons.
Small 0.2W Speaker
The speaker I use is a really small and cheap one. The data-sheet of the speaker praises the features of this speaker, but actually the sound is very poor. I plan to replace the speaker and amplifier with a 1W one to have some margin left.
Dual Color LED Green/Red
I actually use a LED from “Everlight”, it has the same forward voltage for both colors which would allow a single resistor after the cathode. But I use two different resistors to equalize the brightness of both colors.
Resistors and Capacitors
There are many resistors and capacitors I use. I do not list them here, you find the exact values of them on the circuit plans.