How to Make a Simple Reverse Forward LED Light Chaser Circuit Using IC 4017 Posted by hitman
LED light chaser circuit typically refers to an electronic configuration able to generate or illuminate a group of LEDs in some predetermined sequence. One popular IC 4017 is very commonly employed for making this type LED sequencer circuit. The IC basically is a Johnson's 10 stage decade counter/divider and can be used for many interesting light pattern generations, and may be used for various decorative purposes. We all have probably learned a lot regarding circuits using the above IC for producing chasing light effects, effects , however making the IC create "reverse" "forward" "chasing" pattern with LEDs is something many of us might not be acquainted with. Here we will learn how to make a simple yet effective to and fro or reverse forward light chaser circuit. But before that let's take a brief look at the IC 4017 pin out details. The IC 4017 is a 16 pin dual in line (DIN) IC. The IC has 10 outputs which generate the sequencing high outputs in the order of the pin outs - 3, 2, 4,7, 10, 1,5, 6, 9, 11. The sequencing takes place in response to a frequency applied at pin 14 of the iC Pin 16 is the positive supply input, pin 8 is the negative supply input or the ground line. Pin 13 is used clock inhibit inhibit and will stall the circuit if connected to positive supply terminal, however connecting it to ground makes everything normal, so we connect it to ground. Pin 12 is the clock carry out, not required for single 4017a applications, so we leave it open. Pin 15 is the reset pin, pin , and it resets the output to the start pin in response to a positive response to it. The pin 15 of the IC is connected to the second last pin 9 of t he IC, which means the output resets every-time the sequencing reaches pin 9m,and the moment this pin goes high, the IC repeats the action by resetting the system. Pin 14 is the clock input and requires to be fed with a square wave frequency, easy obtainable through any astable oscillator made from ICs like IC 555, IC 4049, transistors etc.
Looking at the figure, we see that basically the IC is arranged in its normal sequencing or chasing mode, however the clever introduction of the diodes at the outputs of the I C make the sequencing appear to be reversing and forwarding from start to finish and v ice versa. The diodes just make the outputs of t he IC align in a to and fro manner by forcing 5 outputs to move in a forward chasing pattern, while the following 5 outputs are redirected toward the same LEDs but in t he opposite direction, making the pattern look like a to and fro chasing motion. Parts List R1 = 1K, R2 = 4K7, R3 = 1K,
R4 = 100K pot, linear, C1 = 10nF, C2 = 4.7 uF/25V, IC1 = 4017, IC2 = 555 =
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How to Make an Efficient LED Emergency Light Circuit The article describes a very simple homemade emergency light circuit that can be used during power failures and outdoors where any other source of power might be unavailable. The circuit uses LEDs instead of incandescent lamp, thus making the unit very power efficient and brighter with its light output. Moreover, the circuit employs a very innovative concept especially devised by me which further enhances the economical feature of the unit.
Let’s learn the concept and the circuit more closely: The concept: We know that LEDs require a certain fixed forward voltage drop to become illuminated and it is at this rating when the LED is at it’s best, that is voltages which is around its forward voltage drop facilitates the device to operate in the most efficient way. As this voltage is increased, the LED starts drawing more current, rather dissipating extra current by getting heated up itself and also through the resistor which also gets heated up in the process of limiting the extra current. If we could maintain a voltage around an LED near to its rated forward voltage, we could use it more efficiently. That’s exactly what I have tried to fix in the circuit. Since the battery used here is a 6 volt battery, means this source is a bit higher than the forward voltage of the LEDs used here, which amounts to 3.5 volts. The extra 2.5 volts rise can cause considerable dissipation and loss of power through heat generation. Therefore I employed a few diodes in series with the supply and made sure t hat initially when the battery is fully charged; three diodes are effectively switched so as to drop the excess 2.5 volts across the white LEDs (because each diode drop 0.6 volts across itself). Now as the voltage of the battery drops, the diodes series are reduced to two and subsequently to one making sure only the desired amount of voltage reaches the LED bank. In this way the proposed emergency lamp circuit is made highly efficient with its current consumption, and it provides backup for a much longer period of time than what it would do with ordinary connections.
Efficient, Automatic, White LED Emergency Light Circuit Description: Referring the figure, we see that the circuit is actually very easy to understand, let’s evaluate it with the following points: The transformer, bridge and the capacitor forms a standard Power supply for the circuit. The circuit is basically made up of a single PNP transistor, which is used as a switch here. We know that PNP devices are referenced to positive potentials and it acts like ground to them. So connecting a positive supply to the base of a PNP device would mean grounding of its base. Here, as long as mains power is ON, the positive from the supply reaches the base of the transistor, keeping it switched off. Therefore the voltage from the battery is not able to reach the LED bank, keeping it switched off. In the meantime the battery is charged by the power supply voltage and it’s charged through the system of trickle charging. However, as soon as the mains power disrupts, the positive at the base of the transistor disappears and it gets forward biased through the 10K resistor. The transistor switches ON, instantly illuminating the LEDs. Initially all the diodes are included in the voltage path, and are gradually bypassed one by one as the LED gets dimmer. Parts List
R1 = 10K, C1 = 100uF/25V, D1, D2 = 1N4007, D3---D6 = 1N5408, T1 = BD140 Tr1 = 0-9V, 500mA, LEDs = white, hi-efficiency, 5mm, S1 = switch with three changeover contacts. In response to the suggestion of one of our avid readers, the above circuit has bee modified and improved with a second transistor stage incorporating an LDR trigger system. The stage renders the emergency light action ineffective during day time when ample ambient light is available, thus saving precious battery power by avoiding unnecessary switching of the unit.
Circuit modifications for operating 150 LEDs, requested by SATY:
Parts List R1 = 220 Ohms, 1/2 watt R2 = 100Ohms, 2 watts, RL = All 22 Ohms, 1/4 watt, C1 = 100uF/25V, D1,2,3,4,6,7,8 = 1N5408, D5 = 1N4007 T1 = AD149 or similar, Transformer = 0-6V, 500mA Power Supply Circuit with Emergency Backup The circuit shown below was requested by one of the readers, it is a power supply circuit which trickle charges a battery when AC mains is available, and also feeds the output with the required DC power via D1. Now, the moment AC mains fails, the battery instantly backs up and the compensates the output failure with its power via D2.
When input Mains is present, the rectified DC passes through R1 and charges the battery with the desired output current, also, D1 transfers the transformer DC to the output for k eeping the load switched on simultaneously. D2 remains reverse biased and is not able to conduct because of higher positive potential produced at the cathode of D1. However when mains AC fails, the cathode potential of D1 becomes lower and therefore D2 starts conducting and provides the battery DC back up instantly to the load without any interruptions.
Parts List All Diodes = 1N5402 for battery up to 20 AH, 1N4007, two in parallel for 10-20 AH battery, and 1N4007 for below 10 AH. R1 = volt/charging current (Ohms) Transformer Current/Charging current = 1/10 * batt AH
LED Tube Light Using Transformer, Circuit Diagram Posted by hitman
Using white LEDs for illuminating our homes is becoming popular nowadays, due to the high power efficiency involved with these devices. The diagram shows a straightforward configuration involving many LEDs, arranged in series and parallel.
The LEDs are driven by a general purpose 24 V power supply for illuminating the LED bank very brightly. The power supply incorporates standard bridge and capacitor network for the required rectification and filtration of the supply voltage to the LEDs. The arrangement of the LEDs is done in the f ollowing way: The supply voltage being 24, dividing it by the forward voltage of a white LED which is around 3 volts gives 24/3 = 6, meaning the supply voltage will be able to support at the most 6 LEDs in series. However since we are interested to include many LEDs (132 here), we need to connect many of these series connected strings of LED through parallel connections. That's exactly what we do here. Total 22 strings of LEDs having 6 in each are connected in parallel, as shown in the figure. Since current limiting becomes an important issue with the white LEDs, a limiting resistor is added in series with each of the strings. The value of the resistor may be optimized by the user for adjusting the overall illumination of the LED tube light. The proposed design will provide enough light for illuminating a small 10 by 10 room brightly, and will consume not more than 0.02 * 22 = 0.44 Amps or 0.44 * 24 = 10.56 watts of power. 24 Volt, LED Tube Light Using Transformer, Circuit Diagram
