Voice Recorder and Playback Circuit

Anyone tired of buying expensive voice recorder?

This Voice Recorder and Playback Circuit show how to make easy one at home!

We can use it to record small message for family or friend.

Just press two button one for record and other one to listen.

Note: This project is little bit hard than other one.

What is a Voice Recorder and Playback Circuit:

Voice recorder and playback circuit are used to record voice and play later.

This type circuit are useful for many thing like voice message system, doorbell, announcement and more where short audio need record and play again.

Circuit mostly have one IC for record and playback, one mic for input, one speaker for sound out and some more small parts.

Circuit Working:

Parts List:

This voice recorder uses special record and playback device.

It can record clear sound for 16 to 30 seconds.

People use it in auto phone answer machine, doorbell, train announcement system.

Circuit have transistor 2N3904, 16 ohm speaker, electret mic, one record-playback IC (APR9301) and some more parts.

APR9301 V2 is very good IC for sound record and playback.

One 52k resistor connect to pin 7 it control how long message can record.

Recording Mode:

When press record button, LED start blinking and that show recording has begin.

We can speak message in mic (electret microphone).

IC1 keep record as long as pin 27 is connected to ground and record button is press.

After 20 seconds with 52k resistor recording stops and LED stop blinking and pin 25 goes high.

Resistor value change record time:

38k ohm = 16 sec

52k ohm = 20 sec

67k ohm = 24 sec

75k ohm = 30 sec

Playback Mode:

To hear message just press play button for few seconds and sound come from speaker.

Standby Mode:

After record or playback finish pin 6 of IC1 stay low to keep standby.

If pin 6 is high then power is in down mode starts with less than 1µA use or no record/play.

How it Work:

Press record button for time depend on resistor like 52k for 20 sec and after that press play to hear sound.

Making and Testing:

We can make PCB and check for mistake.

Be sure power supply is +6V with 0V ground.

The LED lights when we press record button, it shows IC1 is working OK.

Formulas:

When making voice recorder and playback circuit all parts must be put correct way so APR9301 IC works good.

Here is simple way to make circuit with formulas:

Voltage Divider (for Adjustable Resistors):

Use adjustable resistor to set voltage or bias level.

We can use this formula:

Vout = Vin × R2 / (R1 + R2)

where:

• R1 is resistor in series with moving resistor R2
• Vin is supply voltage
• Adjust R2 to get wanted Vout

LED Current Limiting Resistor:

To find value of resistor for LED use this formula:

RLED = (Vcc − VLED) / ILED

where:

• Vcc is 6V for supply voltage
• VLED is 2V for LED forward voltage
• ILED is 20mA for LED for our current need

Circuit Design:

This design is easy to build voice recorder and playback circuit using APR9301 IC and basic parts.

Final working depend on which parts we use and what we need.

How to Build:

For building a Voice Recorder and Playback Circuit following are the connection steps one should follow:

Put Parts on PCB:

• Use circuit diagram to place all parts on PCB.
• Start putting parts like IC1, 2N3904, speaker, MIC, resistors, capacitors, LEDs and switches.

Soldering Components:

• Before solder check solder point is clean and tight.
• Be careful with parts that have polarity like capacitor, LED and IC.

Connect Wires:

• Use wire cutter or stripper to cut wires for connection.
• Connect all parts using good wire and follow the circuit diagram.

Adjustable Parts:

• Change resistor or other part if we want different record time.
• Use preset resistor values like 38k, 52k, 67k, or 75k ohm depends on how long we want to record.

Check Connections:

• Check again all connection on PCB and ensure no part is missing or are bad solder.

Testing:

• Before putting power ON check voltage is in correct range.
• Check voltage at pin 14, 15 and 28 is correct.
• After pressing record button see if LED turns ON, that means IC1 is working.

Test Record and Play:

• Press record button and speak in MIC to record.
• After recording time finish then release record button.
• Now press play button to hear message from speaker.

Last Check:

• After record and playback circuit must go back to standby mode.
• Check record, play and standby all are working correct.

Conclusion:

This Voice Recorder and Playback Circuit is good for when we need simple and low cost audio message.

People use it in message systems, security and more.

References:

Audio recording and playback

Datasheet IC APR9301