Does anyone get tired of buying expensive voice recorders? then this Voice Recorder and Playback Circuit show how to make easy one at home!
Also, we can use it to record small message for family or friend, by just pressing two button one for record and other one to listen.
Note: This project is little bit hard but its too very useful for one to try for.
What is a Voice Recorder and Playback Circuit:
Voice recorder and playback circuits record voice and play it later and these types of circuits are useful for many applications such as voice message systems, doorbells, announcements, and other systems where short audio needs recording and playback.
Moreover, 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:
| Components | Quantity |
|---|---|
| Resistors (All resistors are 1/4 watt) | |
| 52k | 1 |
| 1k | 1 |
| 100k | 1 |
| 10k | 1 |
| 10k to 30k adjustable resistor | 1 |
| 1k to 10k adjustable resistor | 1 |
| Capacitors | |
| Ceramic 0.1μF | 2 |
| Ceramic 0.01μF | 1 |
| Electrolytic 22μF 25V | 2 |
| Semiconductors | |
| Transistor 2N9304 | 1 |
| IC1 APR9301 | 1 |
| LED (any 5mm, 20 mA) | 1 |
| Record push button | 1 |
| Play push button | 1 |
| Electret MIC | 1 |
| Speaker 16Ω | 1 |
This voice recorder uses special record and playback device, which can record clear sound for 16 to 30 seconds.
Also, people use it in auto phone answer machine, doorbell, train announcement system.
Here, the circuit have transistor 2N3904, 16 ohm speaker, electret mic, one record-playback IC (APR9301) and some more parts.
Furthermore, the APR9301 V2 is a very good IC for sound recording and playback and a 52k resistor connects to pin 7 to control how long the message can record.
Recording Mode:
When we press record button, LED start blinking and that show recording has begin, so wee can speak message in mic (electret microphone).
Also, IC1 continues recording as long as you hold the record button, keeping pin 27 connected to ground.
Hence, 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 and if pin 6 is high then power is in down mode starts with less than 1µA use or no record/play.
How it Work:
First, 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 the PCB, check for mistakes and ensure the power supply is +6V with 0V ground.
Also, the LED lights when we press the record button, which shows that IC1 is working properly.
Formulas:
When making a voice recorder and playback circuit, we must place all parts correctly so the APR9301 IC works properly.
Here, is simple way to make circuit with formulas:
Voltage Divider (for Adjustable Resistors):
Use adjustable resistor to set voltage or bias level, so 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 the 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 with basic parts; also 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:
- First, use circuit diagram to place all parts on PCB and start putting parts like IC1, 2N3904, speaker, MIC, resistors, capacitors, LEDs and switches.
Soldering Components:
- Now, before solder check solder point is clean and tight and be careful with parts that have polarity like capacitor, LED and IC.
Connect Wires:
- Also, use wire cutter or stripper to cut wires for connection and connect all parts using good wire and follow the circuit diagram.
Adjustable Parts:
- Then change resistor or other part if we want different record time and also use preset resistor values like 38k, 52k, 67k, or 75k ohm depends on how long we want to record.
Check Connections:
- After that, check again all connection on PCB and ensure no part is missing or are bad solder.
- Next, before putting power ON check voltage is in correct range and check voltage at pin 14, 15 and 28 is correct.
- Also, after pressing record button see if LED turns ON, that means IC1 is working.
Test Record and Play:
- Now press record button and speak in MIC to record and after recording time finish then release record button.
- Also, now press play button to hear message from speaker.
Last Check:
- After record and playback circuit must go back to standby mode and check record, play and standby all are working correct.
Conclusion:
To conclude, this Voice Recorder and Playback Circuit is good for when we need simple and low cost audio message; also people use it in message systems, security and more.