Sunday, July 20, 2014

Audio Visual User Interface with Ack

This circuit is an User Interface part of a Security Alertness Monitor that i designed decades ago. The circuits are here - Digital Circuits - Part 1 The RAM and RTC part is missing, i will add later. It is without uC or Software. Only CMOS Logic.

555 Buzzer and Pushbutton User Interface

Every Hour "+V UR" Goes High for 120 Seconds. The Buzzer Sounds and a Red LED turns on. The Guard has to respond by Pushing the Switch. The Green Light Flashes and the external Flip-Flop logic brings "+V UR" Low, The Buzzer Sound Stops and Red Light Goes off..

If not pressed the Sound Stops after 120 Seconds and even the Red light goes off then. This records a Non-Alert Hour in the RAM for that Day. The Ram Stores 9 Days alertness status.

You could try porting this project into a 89C2051 for learning product and interface design.

Saturday, July 19, 2014

Display On Timer with 555

This is related to the earlier post. This was done to save battery power. The output of some equipment may be in the form of LED Annunciators In the Security Guard Monitor, an Array of 24 LEDs would show the Status of alertness along with the day, this was scrollable.

Display On Timer with 555

When the "Display Now" is pressed it triggers the Monostable Multivibrator made of a 555. The output "EN" goes high for the time duration defined by C27 and R71.

The 555 output as you know can drive more than 200mA for quite some time without much heating up. Many LEDs can be driven with the current limit resistors. I used CMOS chips to drive the LEDs, this circuit was used for the Logic only.
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This circuit was a part of the user interface like the previous one. You could use it for voltmeters or even backlight for LCD.

Example - When you press the switch the Time of a clock can be seen in darkness for a few seconds.

Wednesday, July 16, 2014

Power Supply with Battery Backup

This is an incomplete version of the power supply used for the Alertness Monitor with hourly LED Display. This circuit used a Dual Color LED. Green meant Alert and Red meant No Alert or acknowledge press.

Power Supply with Battery Backup

I can write here only in "Electronic English". Focus on the tech not grimmer. It may be like Pascal with a touch of Acronyms, codes and circuit axioms.

The top part is a 5V regulator with 0.7 Diode boost, means 5.7 V DC. The battery was floating on this point above the zener Z4, that connection comes from outside. A protection fuse maybe needed in case Zener draws more current. The Zeners were test selected to get above 6V along with the diode.

The second supply is to drive the LED array and Relay. This second battery supply was needed to prevent the RAM from losing data and also the CMOS logic getting reset, when the relay solenoid operates. Even when the Display Now switch is pushed, the current is large and the pulse could reset digital circuit.

The battery was used very less, it worked during the power failures for short duration between mains and generator switching. This circuit is not meant for in situations when battery drains are high.

Circuits by Application

Analog Circuits

  1. Battery Level Indicator
  2. Simple Sample and Hold
  3. Sample and Hold Standby
  4. Voltmeter Attenuator
  5. Precision Current Source
  6. Opamp Supply Virtual Ground

SCR and Triac

  1. Solid State Relay
  2. Normally Closed AC SSR
  3. AC-AC-SSR
  4. DC-DC SSR
  5. 2N2646 based Pulser
  6. Drive SCR thyristor

Mains Power

  1. Flashing Neon Lamp
  2. Dimmer power control
  3. Edison Bulb Life Extend
  4. Mains Current LED
  5. Mains Voltage LED

Digital Circuits

  1. Simple Digital Counter
  2. Running Lights
  3. Frequency Divider
  4. Crystal Oscillator
  5. Simple High speed switch
  6. Differential TTL converter

Measureall DMM

  1. Ohmmeter Measure Resistance
  2. Precision Digital Attenuator
  3. Precision Amplifier

Mixed Circuits

  1. Monostable Multivibrator
  2. Digital to Analog
  3. LM311 Oscillator
  4. PLL using 4046
  5. VCO with LM331
  6. BCD Thumbwheel to Analog
  7. V to F Converter ICL8038
555 Circuits
  1. OR gate with two 555
  2. fixed frequency duty cycle
  3. Pulse width modulation
  4. Astable Multivibrator
  5. uC Reset Generator
  6. LM555 Voltage Doubler
  7. 555 Power Oscillator
Discrete Circuits
  1. Isolated dual supply
  2. Sound to light converter
  3. Water operated relay
  4. Telephone Indicator
  5. Passive volume control
  6. RS232 Opto-Isolation
  7. Voltage Level Indicator
  8. Relay Driver
  9. Constant Current LED
  10. Voltage Doubler
  11. FET Current Source
Opamp Circuits
  1. Three Opamp Differential
  2. Two Opamp Differential
  3. Buffer Opamps
  4. Differential Op-Amp
  5. Inverting Opamp
  6. Non Inverting Opamp
  7. Digital gain control
  8. Square Triangle Oscillator
  9. Dual Polarity Output Amps
  10. Ammeter Precision Rectifier
  11. Voltage / Current 4-20 mA
  12. Current Source for RTD
Power Electronics
  1. Dual Power Supply
  2. Single Power Supply
  3. Battery Backup Supply
  4. 5V 1A Supply LM2575
  5. 5V Power Supply L296
  6. Dual Power Supply
  7. Tubelight Electronic Choke
  8. Voltage Doublers Multipliers
  9. White LED Lamp on Ni-Cd

uC and uP

  1. PC RS232 with MAX232A
  2. Battery Backup SRAM
  3. watchdog uC uP systems
Instrumentation Circuits
  1. Mains monitor LM3914
  2. Simple Mains monitor
  3. single digit voltmeter
  4. High Resistance Meter
  5. Diode Thermometer
  6. Function Generator
  7. Diode Leakage Tester
  8. Analog LED Ohm Meter
  9. Millivolt Source Current Loop
Process Control
  1. AD590 - temperature
  2. Thermocouple Amplifier
  3. Linearizing Thermocouple
  4. Thermocouple Amplifier
  5. 0-1V to 4-20 mA
  6. 1-5V to 4-20 mA
  7. InfraRed - Optical Switch
  8. InfraRed Detector