Thread starter purcer Start date Mar 7, I am trying to cascade three counters inorder to light 27 leds and have them constantly run. I have found WEB sites on one but nothing on how to cascade them. I am using a timer for the clock pulse.
Electrical Engineering Stack Exchange is a question and answer site for electronics and electrical engineering professionals, students, and enthusiasts. It only takes a minute to sign up. The LEDs should blink only one at a time.
I found a circuit with 2 s which does 16 LEDs - see here. It says the design can be expanded "indefinitely" by adding more s but it is not clear to me how to do it.
Also, it the "reset" circuit part necessary? If they can all be on the same amount of time, I'd just use lots of shift registers. There are several types.Cascading 4017 Decade counter - 0-99 counter
For example TI Display drivers. A SIPO shift register can be chained together by driving them all from a common clock, and connecting Serial Out of one device to Serial In of the next device. They may also have an enable which trasfers the shifted bit pattern into the LED drivers. Initialisation, power on, must clear all of them to zero usually a RESETand initially load a 1 to the first shift register.
A datasheet for which shows a schematic for cascading three and hence more in Figure 12 page Sign up to join this community. The best answers are voted up and rise to the top. Home Questions Tags Users Unanswered. Asked 5 years, 6 months ago. Active 5 years, 6 months ago. Viewed 3k times. Kozuch Kozuch 5 5 silver badges 17 17 bronze badges. Combine the timer from your linked diagram as the clock to this electro-tech-online.
LED ‘Graph’ Circuits
What if I want my row of LEDs to run in a loop? Active Oldest Votes.Last August, the U. Although lamps that are almost as efficient have been available for more than a year, the prizewinning design is just now going on sale. Like the backlights in modern cellphones and computer monitors, these lamps use light-emitting diodes to generate white light. They offer long lifetimes, pleasing colors, and most important, phenomenal energy efficiency. But prices are dropping, and performance is improving fast.
Why are LED-based lamps superior, and what makes them so tricky to engineer, anyway? You might imagine that the answers would hinge on the subtleties of solid-state semiconductor physics that govern high-brightness LEDs. They do, but only up to a point. Like it or not, incandescent bulbs are a dying breed.
Australia and the European Union started phasing out traditional incandescents in The United States is haltingly moving in the same direction, and China is aiming to eliminate incandescent bulbs by The reason is simple: Old-fashioned lightbulbs squander enormous amounts of electricity. In truth, some can be dimmed, but their range is usually limited.
Also, CFLs are slow to light up, and because their bulbs contain mercury vapor, they present an environmental hazard. Even with recycling opportunities available, millions of these bulbs end up in landfills every year.
These nominally white lights, in fact, contain blue LEDs, along with a phosphor coating that converts the narrow wavelength light they emit into something the human eye perceives as white. With the appropriate mix of phosphor materials, designers can set the tone of the light from cool to warm, depending on the application they have in mind. Next to their high energy efficiency, the most attractive quality of LED lights is their longevity.
Such long lifetimes reduce one of the hidden costs of lighting, especially for commercial and industrial users: maintenance and replacement costs. That, and the energy savings that accrue, explains why large-scale users have been the early adopters.
Really, the only thing holding such businesses back is the high up-front costs—and the prospect that LED lighting technology will soon improve and become an even better deal. The operating voltage of a standard white-light LED is usually in the range of 3 to 3.Hello Luther.
The circuit is very simple. And a power supply. The magic that makes the snowfall effect is in the software. If you're new to electronics you'll need to learn how to program microcontrollers and to have a programmer such as the PICkit 2 or PICkit3 to build this circuit.
The software also called firmware that drives the micrcontroller is the long code I posted above. You'll also need the mikroC compiler if you're going to use the above code. Welcome to the fascinating world of electronics :. Hi again. Yes you can use other PICs as well. To simplify matters use a PIC that has an internal oscillator. The formerly popular PIC16F84 does not have this internal oscillator and so you'll have to put in a crystal or resistor-capacitor pair.
Using ordinary LEDs only allows for a very narrow angle at which the light can be seen. Commercially available cascading lights use LEDs that that have a very wide spread and so the light is visible from practically any angle.
Hope that helps. Well if the 16F84A is what you have at the moment then it'll do. Download the datasheet. Go to page 23 and look at the Fig. It provides the schematic as well as the recommended values for the resistor and capacitor. If you want to use a crystal check out Fig.
Because it doesn't have an internal oscillator, the number of pins for output is limited to So that's 13 LEDs instead of You'll also have to make sure to set the configuration word properly.
If you're going to use mikroC that'll be easy. That compiler has a menu that allows changing the values. There's one minor problem. The 84A has only one timer. In the program I use two timers-- timer 0 and timer 1. The 84A only has timer 0. Take your time learning. Getting firmware to work can not infrequently be frustrating but it's all part of the game. I just remembered that some of these older PICs have what's known as "open drain" pins. They're analogous to an open bipolar transistor collector.
Simply means these pins can only sink current, they cannot source current. And sure enough the 84A has one open drain pin-- RA4 which is pin 3.
The only way to use this pin is to reverse the anode and cathode of the LED so that current flows into the pin.In this project, we will build few simple LED Circuits.
Nowadays, people are investing more in LEDs due to their energy efficiency. Home lighting, office lighting, Automobile lighting, Street lighting etc.
Students, hobbyists and makers often work with LEDs in different types of projects. LEDs are very sensitive components with respect to voltage and current and they must be provided with rated current and voltage values. Wrong voltage or current to LED will burn them off.
But as the complexity of the circuit increases, choosing the right resistor with right wattage is important. The circuit diagram for this circuit is shown below.
The following image shows the setup of single LED connected to a 12V Supply and a current limiting series resistor.
The important component other than the LED of course is the Resistor. So, selecting the right resistor with the right wattage is very important. First, we will calculate the resistance. The value of the series resistor can be calculated using the following formula. Substituting these values in the above equation, we can calculate the value of Series Resistance as. Now that we have calculated the resistance of the series resistor, the next step is to calculate the power rating of this resistor.
Power Rating of a Resistor specifies the value of power that a resistor can safely dissipate. The Power Rating of a Resistor can be calculated using the following formula. Here, V RES is the voltage drop across the resistor and.
So, the Voltage Drop across the Series Resistor is.
4017 Cascade, One more try
The current through the Resistor is same as the current through the LED as they are series. So, the current through the Series Resistor is. Substituting these values in the above formula, we get the power dissipated by the resistor. Once the right resistor is selected, we can connect the resistor in series and give the 12V Supply to the LED.
The following image shows the circuit diagram of the LEDs in Series. Since the LEDs are connected in Series, the current through all of them will be the same i. Coming to the power rating of the resistor, it is equal to 1. Once all the components are selected, we can connect them on a breadboard and power on the circuit using a 12V Supply. All the three LEDs in Series will light up with maximum intensity.
This means that the voltage drop across the Resistor is 8. This current will also flow through the resistor.This is my first instructable, hope you will like it. I have been playing around with LEDs for a while and I realized that I am pretty much limited with Arduino pins and can not make huge projects which requires a lot of pins. This is small project with main focus to drive LEDs by using Arduino pins as less as possible and it demonstrates how to add infinite number of pins.
In this particular project the 16 LEDs are driven with just only 3 Arduino pins. The key element is shift register. Each 74HC shift register can drive up to 8 LEDs and by daisy chaining registers it is possible to extend Arduino 3 pins to infinite number for great number of registers, there could be problem with clock which is required for shift registers.
Did you use this instructable in your classroom? Add a Teacher Note to share how you incorporated it into your lesson. Connect the second shift register exactly the same, but connect the DS pin 14 to first register pin 9. After that connect pins: 1, 2, 3, 4, 5, 6, 7 and15 from both registers to LEDs. This connection makes all the pins always active and addressable, however when the Arduino is powered up some of the LEDs may be turned on.
Solution for this is to connect MR pin 10 and OE pin 13 to Arduino directly, but it this way you have to sacrifice 2 Aurduino pins. To add more shift registers connect them like the second register. If you want to regulate the brightness of LEDs then connect potentiometer as shown in picture above to control resistance for all LEDs. However it is optional and you can get along without it. As a software developer it is unacceptable for me and I am used to make everything as dynamic as possible with no limitations.
Simple LED Circuits
I redesigned the existing code samples to allow you to use unlimited number of shift registers. See code below:. In the final code I added several effects for those 16 LEDs. The effects are demonstrated in the video above. If you want to add more LEDs, connect more shit registers as described previously and change the value of numOfRegisters in the code Also adjust logic for effects.
You can also use this code not for just LEDs only, if you simply want more pins for your Arduino use the regWrite int pin, bool state function to write state for any pin and there is no limit how much shift registers you are using, just change the value of numOfRegisters and every thing else is automated.
LED Troubleshooting - Wiring
I soldered up the project on a prototype PCB. Thank you for this example! The code is very clean and it is so easy to expand the number of shift registers. In my project, I just need the ability to turn on or off a specific LED. I just noticed that the pins connected to the second shift register are numbered 0 - 7 and the pins on the first shift register are numbered 8 - Is there a way to change the code, so that the pins on the first shift register are numbered 0 - 7 or maybe 1 - 8 and on the second 8 - 15 or 9 - This way, by adding more shift registers, the numbering would just continue and there would be no need to change the code for the already assigned pins in the loop.
Again thank you very much for you effort! Reply 9 months ago. Reply 1 year ago. Reply 2 years ago. Think ints. Reply 3 years ago. Question 1 year ago on Introduction. Question 1 year ago. Hola, muy buena idea!! Question 2 years ago. HI there!Practical graph circuits may be designed to generate either a bar-graph or a dot-graph display. Figure 1 illustrates the bar-graph principle, and shows a line of 10 LEDs used to represent a linear-scale V meter that is indicating a 7V or b 4V; the input voltage value is indicated by the total number of LEDs that are illuminated.
Figure 2 shows the same meter operating in the dot-graph mode; the input voltage value is indicated by the relative position of a single illuminated LED.
A number of special ICs are available for operating general-purpose LED analog-value display systems. For many years, the best known ICs of this type were the U etc.
But the first two of these families have now ceased production, and only the LM family remains. The LM family are popular and versatile ICs that can each directly drive up to 10 LEDs but can easily be cascaded to drive larger numbers of LEDs and can drive them in either bar or dot mode.
IC-driven bar-graph displays make inexpensive and, in some ways, superior alternatives to analog-indicating moving-coil meters. Their scales can easily be given any desired shape. They are moderately complex but highly versatile devices, housed in pin DIL packages and each capable of directly driving up to 10 LEDs in either the dot or the bar mode. The family comprises three devices, these being the LM, the LM, and the LM; they all use the same basic internal circuitry see Figure 3but differ in the style of scaling of the LED-driving output circuitry, as shown in Figure 4.
Thus, the LM is a linearly-scaled unit, specifically intended for use in LED voltmeter applications in which the number of illuminated LEDs gives a direct indication of the value of an input voltage or of some parameter that is represented by a proportional voltage. The LM, on the other hand, has a log-scaled output designed to span dB to 0dB in 10 -3dB steps, and is specifically designed for use in power-indicating applications, etc.
Finally, the LM has a semi-log scale that spans 23dB, and is specifically designed for use in VU meter applications. All three devices of the LM family use the same basic internal circuitry, and Figure 3 shows the specific internal circuit of the linear-scaled LM, together with the connections for making it act as a simple LED The IC contains 10 voltage comparators, each with its non-inverting terminal taken to a specific tap on a floating precision multi-stage potential divider and with all inverting terminals wired in parallel and accessible via input pin 5 and a built-in unity gain buffer amplifier.
The output of each comparator is externally available, and can sink up to 30mA; the sink currents are internally limited, and can be externally pre-set via a single resistor R1. The IC also contains a floating 1. In Figure 3the reference is shown externally connected to the internal potential divider pins 4 and 6. Note that pins 8 and 4 are shown grounded so, in this case, the bottom of the divider is at zero volts and the top is at 1.