Design Your Circuit. Part X – Voice recorder

Voice Recording chips are now available to record voice and sounds and to play it for a short time. These chips are ideal for the gadgets like Toys, Door phone, Alarms, Automatic answering machines etc. These chips have a recording memory from 20 to 60 seconds and the memory lasts for many years if the chip is properly maintained. The advantage of the chip is that, it requires no software and microcontroller for its operation. Let us build this tiny voice recorder.

APR 9301 V2 is the chip in the circuit. This IC has a non volatile memory with 100K recording capacity and around 100 years of memory retention capacity. The IC utilizes the Invox proprietary analog / multi level flash non volatile memory cells that can store more than 256 voltage levels. The IC can operate in a single 5 volt supply and consumes only 25 mA current.

1. Recording
The LED indication gives when the IC records the voice. A single voice message up to 20 seconds can be recorded. The IC remains in the recorded mode as long as the RecL pin 27 is grounded. Recoding will be terminated with the last memory when 20 seconds is over. The Speaker driver will automatically mutes in the recording mode. By changing the value of the OscR resistor R1 it is possible to increase the recording period as follows

A. R1 52K 20 Sec.
B. R1 67 K 24 Sec
C. R1 89 K 30 Sec.

Press, switch S1 and speak through the MIC or record music. LED will glow in the recording mode. Open S1 after recording. Use a small condenser MIC.

2. Playing the recorded message

By pressing the play back switch, the play mode starts from the beginning of the message. The input section will be muted during play back. Close S2. Recorded message will be heard from the speaker. Use a 2 inch 8 Ohms speaker.

3. Standby operation

After completing the Record or Play back function, the IC will enters into the standby mode.

4. Sampling frequency
A. 20 Sec 6.4 KHz
B. 24 Sec 5.3 KHz
C. 30 Sec 4 KHz