555-Circuits (Page 4)

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.

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.

Audio Visual User Interface with Ack

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.

This is dual 555 multivibrator like power oscillator. This is my contraption and conception but couple of decades old. It appears to have errors. It worked but the document fixing after design worked, not done. This can be used to make a small inverter, for powering 230V gadgets of low power. The transformer is used in step-up mode. It may make a sound if the laminations are not of good quality.

This circuit can be modified using 7555 and switching transistors like BD139 driving a Ferrite 100 kHz transformer to build a Fluorescent Lamp of 10W to 20W.

From Schematics of delabs

Fluorescent lamps can be fired and lit at high frequency at relatively lower voltages. Experiment both with frequency and pulse width to get nominal lighting at good efficiency. One of the reasons CFL lamps -230V and emergency lamps 12V fail, is failure of the switching devices. These have to be overrated thrice or more, the switching heat dissipation should not be underestimated, during low/high voltage and keep a aging allowance.

Designing a working circuit is no big deal. But making a batch of reliable and robust power electronics products, which are idiot proof and abuse resistant is a challenge for engineering. Then they will need it at an affordable price too… Checkmate !

This circuit shows the voltage doubler working with a 555. LM555 has good drive 200mA, both Vcc and Gnd.

555 has the advantage of having a high drive as well as being a Mixed Design, Analog Programmable chip. That may be a High Title for such humble a chip.

It has the capability of a Mini ADC due to its VCO function. It could form even a simple switching supply. Power Line Modems have been designed using this chip.

Timers, Modulators, Trip Relays and even a Timer for The Humble Bread Toaster. Musical circuits, Piano and Metronome Galore, it drives Speakers directly.

The Star of what we used to Know as Chip as IC. Too small today in the days of ASIC and FPGA. But ideal for Education of Electronics and Simple Real times Solutions.