32 Seconds Voice Record Playback Circuit


Project   has been designed around Win bond’s ISD1616 IC (SMD) IC, which is fully integrated, single-chip, single massage voice record and playback device ideally project suited to a variety of electronics systems. Massages are stored in flash memories made in unique Multilevel Storage Technology (MLS). Therefore, voice or audio data are stored directly into the memory in their natural form without any compressions alike digital approach, providing high-quality, solid-state audio reproduction. Project provides high quality audio recording and simple operations.  Massage duration is user selectable in ranges from 10 to 20 Seconds depending on the sampling rates from 4 KHz to 12 KHz adjustable via on board potentiometer (preset), giving the users greater flexibility in duration versus recording quality. Massage recording and playback is easy using on board tact switches. This project can be used in variety of application like, Interactive Games and booths, Light and  sound shows, gaming machines, toys, robots, animatronics, lifts/escalators, warning systems, security systems, audio guide, home appliances. Project work on 5V DC @ 100mA. It consumes minimal current in standby mode typical 1uA to 100ua (Without power LED). The device enters into standby mode automatically once an operation is completed for power saving purposes.



  • Toys
  • Amusement Equipment’s
  • Interactive Games
  • Lifts/Escalators
  • Warning Systems
  • Security Systems
  • Audio Guide
  • Home Appliances
  • Robotics
  • Animatronics
  • Light and Sound Show



  • Power supply input 5 VDC @ 100 mA
  • Power supply spans a range from 2.4 to 5.5 VDC
  • Standby current 1 uA typical and 10 uA maximum without power LED
  • IC Enters in standby mode immediately after record playback cycle
  • Microphone preamplifier with automatic gain control built in IC
  • PWM Class D speaker driver
  • Direct Drive Speaker 8 Ohms or typical buzzer
  • AUD current output to drive external power transistor
  • Onboard microphone
  • Easy operation via onboard tact switches
  • Onboard tact switches for Level trigger Play, Edge trigger Play, and Recording
  • Onboard power indication
  • Onboard preset for sampling rates settings
  • Onboard recording indication
  • Supply input and speaker terminal via header connector
  • Low Noise high quality voice record/playback
  • 100 Year massage retention
  • 100,000 record cycles
  • Speaker is not provided with kit


Testing the Project,

Connect the 8 ohms 0.5W speaker to LS1 (SPK), apply 5V DC to CN1, and make sure polarity is correct otherwise it can damage the IC. CN2 (AUD) is current drive output to connect the project with external audio amplifier.

Record A Message

The device starts recording whenever REC switch pressed or recording pin of IC pulled HIGH to LOW and stays at LOW. Recording stops when the recording switch released or the signal on ICs pin returns to HIGH.  The device starts recording from the beginning of the memory when REC transits from HIGH to LOW and stays at LOW. A record cycle is completed when REC is pulled to HIGH or entire memory is filled up. Then an End-of-Message (EOM) marker is written at the end of message, enabling a subsequent Playback cycle to terminate appropriately. Hence, the device automatically enters into standby mode. REC takes precedence over any playback operations. If REC is pulled LOW during a playback cycle, the playback immediately halts and recording starts from the beginning of the memory. The REC pin has an internal pull-up device


Playing the recorded message

Edge-trigger Playback: A playback operation starts when switch (SW2) PLAYE pressed or PLAYE pin of IC detects a LOW going signal exceeding the specified denounced time

Level-trigger Playback: A playback operation begins when switch (SW3) PLAYL is pressed and playback stops when switch is released. PLAYL pin of the IC detects a LOW going signal and remains at LOW. Playback stops when the signal returns to HIGH


The ISD1616 IC provides record/playback duration from 10.6 seconds to 32 seconds. Sampling rate and duration are determined by on board 220K Ohms PR1 potentiometer connected to the Rosc pin.


Sample Rate Rosc. PR1 Potentiometer Duration
12Khz 60K Ohms 10.6 Seconds
8Khz 80K Ohms 16 Seconds
6.4Khz 100K Ohms 20 Seconds
5.3Khz 120K Ohms 24 Seconds
4Khz 160K Ohms 32 Seconds


D1 (Green LED)

The D1 Green LED goes on during recording, the output pin of IC provides an active-LOW signal during recording, which is used to turn on a D1 (Green LED) as a “record-in-progress” indicator. However, during playback, the D1 LED blinks a few times per second to indicate a “playback-in-progress” operation. It returns to an OFF state when operation stops.



D2 work as power indicator, it is in on state during power is on.

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Classic Timer Based On 555 Timer

Classic AC 230 V Timer project can be used in all application requiring a timer of up-to 3 Minutes to operate or control any AC mains load of up-to 200 Watts.  This project is based on the Classic 555 Timer IC, triggering a TRIAC.  Input and Output is Optically Isolated.

  •  Supply input 12 VDC
  •  Mains supply input 240 VAC or 120 VAC ( Read Note for 120V/230V AC)
  •  Output: up-to 200 Watt
  •  Optically isolated Input / Output
  •  Onboard start and reset tactile switch
  •  Timer On LED
  •  Preset adjustable and jumper selectable for range
  •  Power-On LED indicator
  •  Screw terminal connector for easy mains supply input and load connection
  •  Four mounting holes of 3.2 mm each
  •  PCB dimensions 46 mm x 91 mm










Lux Meter Module – Light Meter Schematic


LUX Meter project has been design to measure the illumination.  Illumination is luminous flux falling on surface area of photo diode.  This illumination converted to corresponding voltage using Op-Amp circuit.

  • Supply 9 VDC PP3 Battery @ 20 mA
  •  Onboard Photo Diode
  •  Onboard preset for calibration
  •  Range selection via jumper 10mV/LUX, 1mV/LUX, 0.1mV/LUX
  •  Interfacing is via berg connector
  •  Power-On LED indicator
  •  Four mounting holes of 3.2 mm each
  •  PCB dimensions 53 mm x 38 mm


The project is designed around Texas instrument Op-Amp TLC271 which can operate from single supply with low bias current, here op-amp act as current to voltage converter.  5000 LUX (approx) can be measure with a voltmeter having 5V range.  Meter is not provided.



  • J1 Jumper : 10mV/Lux
  • J2 Jumper : 1mV/Lux
  • J3 Jumper : 0.1mV/LUX
  • PR2 Preset : To Calibrate the meter
  • PR1 Preset : Fine Gain adjustment for 10mV/Lux
  • CN1 Connector : Supply 9 VDC (PP3 9V DC Battery Ideal) and Output Voltage
  • D2 LED : Power Indicator
  • D1 LED : Photo Diode (Sensor)

Standard incandescent 100W lamp should be used for approximation calibration.  To make Calibration select the 1mV/Lux J2 Jumper, move the preset full in CCW.  Connect the accurate voltmeter having range of 5V. Adjust the distance between the photo diode and Lamp so that voltmeter reads 0.38V0.  At this point, illumination on photodiode surface is about 100 Lux (aprox).  And then adjust the PR2 so that voltmeter reads 1V.  Calibration has now been complete. This project is based on Hamamatsu Photo Diode Application








99 Seconds 2 Digit Count Down Timer


2 Digit Count Down Timer is a utility Count Down timer project for upto 99 seconds of countdown time.  This project can find many uses in your shack and home.  The relay output remains on during the Count Down period, allowing you to interface load or alarm that you want to keep it on for a certain amount of time (in seconds).

  • Micro-controller based design for greater accuracy and control
  • Power supply input 12 VDC 200 mA
  • Two 0.5″ display segments to display time
  • 12V SPDT (Single Pole Double Throw) relay for alarm use
  • Single key start and dual key alarm time set function
  • Power and Relay-On LED indicator
  • Terminal connectors for connecting power supply input and relay output to the PCB
  • Onboard regulator for regulated supply to the kit
  • Crystal resonator based design for better accuracy
  • PCB dimensions 72 mm x 81 mm



This is a micro-controller based 2 Digit (99 Seconds) Count Down Timer.  This Count Down Timer is very easy to use and easy to configure.  This project can find a lot of application areas where you need a device to remain ON (or OFF) for a certain period of time (upto 99 Seconds).  Power to the circuit is applied at CN1 (12 VDC).  D1 provides the reverse polarity protection to this kit.  LED D2 confirms DC Power Supply to the board.  S1 and S2 displays Count Down time.  J3 provide an easy way of connecting external switches to this board.  LED D4 confirms the relay status.

Operating Instructions:

The setting up of countdown period and START Function for this project is accomplished with the help of 3 tactile switches shown as SW1, SW2 and SW3 in the schematic and labeled as UP, DOWN and SET on the PCB respectively.


  1. Setting Time : The default value is shown on display S1 and S2 respectively. You can change this value by simply pressing the UP and DOWN key.
  2. Start : You can start the Count Down by pressing SET key. When the Count Down starts the relay is energized, indicated with the glow of LED D4. Once the Display (S1 and S2) reaches 0 the relay is de energized.


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Dark Sensitive LED Light

Dark activated LED light is a simple project which operates a LED when the light falling on the LDR goes below a set point.  The circuit is built using LM393 comparator, LDR as light sensor, preset (potentiometer) for sensitivity adjustment, transistor to drive the LED. The project can also be considered for use in energy saving application.

  • Input – 12 V @ 1A
  • LED 12V 500mA Maximum (6W)
  • Onboard Preset for Level Adjust
  • Operation LED Indicator
  • On Board Power LED
  • Header Connector for Power Supply and LED
  • PCB dimensions 55.45MM X 12.70 MM











16 Channel Infra Red Remote Control

16 Channel Infra-Red remote controller is based on PIC16F73 Micro-controller from Microchip. The receiver part follows RC5 (Philips) Code Format. Tiny receiver provides 16 latch outputs or 8 Latch + 8 Momentary outputs by closing Jumper J1. All outputs are TTL and can drive Relay board or solid state relay. The circuit uses TSOP1738 Infra-Red receiver module which provides high degree of noise immunity against interfering light source.

  • Supply Remote Transmitter RC5 Philips 2XAAA Battery
  • Supply Receiver 7V to 12V DC
  • Modulation 38Khz
  • Philips RC5 Code Format
  • Operating range up to 20 feet
  • 2 Pin Screw Terminals for Supply Input
  • On Board Power LED
  • Onboard VT (Valid Transmission) LED
  • All Outputs TTL Level provided with Header Connector
  • Jumper (J1) for Mode Selection
  • J1 Open 16 Latch Outputs
  • J1 Closed 8Latch + 8 Momentary
  • Robotics
  • Lights
  • Fans
  • Home Appliances
  • Remote Door closer
  • Remote Curtains
  • Security Systems







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