This is a mains 230V AC load current indicator and is a LIVE CIRCUIT, so take care. The Resistors have to be a fusible ceramic wire wound.
More at Mains Voltage and Power Circuits
This circuit has been drawn from my memory and i have not tried it out again, just see if it is ok and then try. You should use the fuse of 1A a slow blow if you want but it is very important. You can design the shunt R3 and Fuse rating as required by your load.
Note that this circuit is to be put in series with the load like an ammeter. If you put it across the supply like a voltmeter it will fuse out or burn out. This circuit has to be enclosed in a plastic sealed enclosure to avoid contact.
The 555 Astable generates a clock for this circuit, an oscillator giving a square wave output at pin 3 which is counted by 4017 to give a running lights effect.
Digital Timers Counters and Clocks
The decade counter-divider CD4017 has 10 outputs, for every low to high transition at the clock input, rising edge, the counter advances one LED. After going one full circle the the first LED lights again and it goes on. You can vary the value of R2 100K Linear potentiometer to make LEDs run fast or slow.
The frequency of oscillation of astable 555 is given as f = 1.44 / ((R4 + 2 * (R2 + R3)) * C3)
The 10 outputs have 10 green LEDs. The current thru the LED is limited by R1, the current can be calculated like this (9V – 1.6V) / 1K = 7.4mA this is within 20mA which is the danger limit of the CMOS output. You want it to be bright use transistors for every output.
The cap C1 is a filter and C2 is to prevent noise at pin 5 influencing the output as it is a control voltage point.
You can cascade or chain many more counters with the CO or carry out pin 12 of 4017. The pin 15 reset is kept at low for counting, on high it will reset the counter but is not used in this circuit.
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This is a easy to build LED lamp circuit for Learning and building skills. This is the first draft schematic V 1.0. It will need improvements for Higher Power Lighting.
Perpetual Candle Project
I will give a short summary, The LM317 here configured for around 6.4V DC. The Q3 BC547 limits the current, you can select R3 to suit, make it 1/2W. The Ni-Cd battery pack 1.2 * 4 will not get Over-Current or Over-Voltage due to this circuit.
The IRF540 Mosfet or any other equivalent you have around, along with Q2 BC547 forms a current source for the parallel 12 LED array. Ultra-bright White LED at 20mA each or use a 1W ready LED Chip. R4/R6 can be selected for the Max LED current. The voltage of LED is around 3.1 and 20mA * 12 = 240mA is the max current. You can Tweak the design for even 5A or more but then you will need a DC/DC High frequency converter in place of LM317. The Current source also needs to switch to improve efficiency. A PWM on the mosfet gives brightness control. The entire solution (switching) can be found in many chips with semiconductor vendors today.
One Single High Current LED may work well. 12 Matched LEDs also can be used. In LED Array some are dim, put min. resistor (3.9 ohm) for all 12 for current sharing. The resistor addition will impar the ability of Candle to work at lower battery voltages. Also resistor is less green, It wastes power, so use PWM and Single Die high current LED. Ni-Cd system may last over 5 Years if Candle is allways on Mains. Sealed Lead Acid system may go upto 2-3 years life but will have more punch. A SuperCap system may last more than 12 Years, i feel.
Source in Cadsoft Eagle format – candle.zip
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.
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.