Many AC driver work with V dimming, like we went over above. This is helpful as it allows LEDs to work with very popular residential dimming systems like Lutron and Leviton. The maximum number of LEDs you can run from a single driver is determined by dividing the maximum output voltage of the driver by the forward voltage of your LED s.
When using LuxDrive drivers , you determine the maximum output voltage by subtracting 2 volts from your input voltage. This is needed because the drivers need a 2 volt overhead to power the internal circuitry. For example, using the Wired mA BuckPuck driver with a 24 volt input, you would have a maximum output voltage of 22 volts.
This leads us to finding what input voltage we need for our LEDs. Input voltage, after all, equals our maximum output voltage for our driver after we take into account the driver circuit overhead voltage. Make sure you know the minimum and maximum input voltages for your LED drivers.
In finding what your input voltage should be for an application you can use this simple formula. This determines the minimum input voltage you need to provide. Now this helps us make sure the voltage works, but in order to find the right power supply we also need to find the wattage of the whole LED circuit.
The calculation for LED wattage is:. Overworking the power supply can cause the LEDs to flicker or cause premature failure of the power supply. Just calculate the cushion by multiplying the total wattage by 1. So for our above example we would want at least The closest common power supply size will be 25 watts so it would be within your best interest to get a 25 Watt Power supply with a 24 Volt output.
The FlexBlock LED drivers are boost drivers which means they can output a higher voltage than what is supplied to them. This is extremely helpful in applications where your input voltage is limited and you need to get. As with the BuckPuck driver , the maximum number of LEDs you can power with a single driver in-series is determined by dividing the maximum output voltage of the driver by the forward voltage of your LEDs.
The FlexBlock can be connected in two different configurations and varies when it comes to input voltage. You find the maximum output voltage of the driver in this mode with this formula:. Now with AC input drivers they give off a certain amount of watts to run so you need to find the wattage of your LEDs. The fusing portion of the fuse element is visible through a clear window. The amperage ratings are also listed on the fuse element.
Circuit breakers are used in place of fuses for the protection of complicated power circuits such as the power windows, sunroofs and heater circuits. Three types of circuit breakers exists: The manual reset type - mechanical, the automatic resetting type - mechanical, and the automatically reset solid state type - PTC.
A circuit breaker basically consists of a bimetal strip connected to two terminals and to a contact in between. Manual circuit breaker when tripped current flow beyond its rating will open and must be reset manually. The circuit breaker contains a metal strip made of two different metals bonded together called a bimetal strip. This strip is in the shape of a disc and is concaved downward. When heat from the excessive current is higher than the circuit breaker current rating, the two metals change shape unevenly.
The strip bends or warps upwards and the contacts open to stop current flow. The circuit breaker can be reset after it is tripped. When a circuit breaker is opened by an over-current condition, the circuit breaker requires reset.
To do so, insert a small rod paper clip to reset the bimetal plate as shown. This type of circuit breaker is used to protect high current circuits, such as power door locks, power windows, air conditioning, etc. The automatically resetting circuit breaker contains a bimetal strip. The bimetal strip will overheat and open from the excess current by an overcurrent condition and is automatically reset when the temperature of the bimetal strip cools.
A cycling circuit breaker contains a metal strip made of two different metals bonded together called a bimetal strip. When heat from the excessive current is higher than the circuit breaker current rating the two metals change shape unevenly.
The strip bends upwards and a set of contacts open to stop current flow. With no current flowing the bimetal strip cools and returns to its normal shape, closing the contacts, and resuming the current flow.
A Polymer PTC is a special type of circuit breaker called a thermistor or thermal resistor. A PTC thermistor increases resistance as its temperature is increased. PTCs, which are made from a conductive polymer, are a solid state device, which means they have no moving parts.
PTCs are commonly used to protect power window and power door lock circuits. In its normal state, the material in a polymer PTC is in the form of a dense crystal, with many carbon particles packed together. The carbon particles provide conductive pathways for current flow. This resistance is low. When the material is heated from excessive current, the polymer expands, pulling the carbon chains apart. It resets only when voltage is removed and the polymer cools.
PTCs are used to protect power window and power door lock circuits. Control devices include a variety of switches, relays, and solenoids. Electronic control devices include capacitors, diodes, and switching transistors.
Switching transistors act as a electronically-controlled switch or relay. The advantage of a transistor is its speed in opening and closing a circuit. Control devices are needed to start, stop, or redirect current flow in an electrical circuit. A switch is just a connection in the circuit that can be opened or closed. Most switches require physical movement for operation while relays and solenoids are operated with electromagnetism.
A switch is the most common circuit control device. Switches usually have two or more sets of contacts. Switches are described by the number of Poles and Throws they have. This switch has a single input pole and a single output throw.
A single-pole input, double-throw output switch has one wire going it and two wires coming out. A Headlamp dimmer switch is a good example of a single-pole double-throw switch. A Headlamp dimmer switch sends current to either the high-beams or low-beams of the headlight circuit. These switches move together to supply different sets of output contacts with current.
An ignition switch is a good example of a multiple-pole multiple-throw switch. Each switch sends current from different source to different output circuits at the same time depending on position.
The dotted line between the switches indicates they move together; one will not move without the other moving as well. The momentary contact switch has a spring-loaded contact that keeps it from making the circuit except when pressure is applied to the button. A horn switch is a good example of a momentary contact switch.
Push the horn button and the hold sounds; release the button and the horn stops. A variation of this type is the normally closed not shown which works the opposite as described above. The spring holds the contacts closed except when the button is pressed. A mercury switch is made of a sealed capsule that is partially filled with mercury. In one end of the capsule are two electrical contacts. As the switch is rotated moved from true vertical the mercury flows to the opposite end of the capsule with the contacts, completing the circuit.
Mercury switches are often used to detect motion, such as the one used in the engine compartment on the light. Other uses include fuel cut off for roll-overs, and some air bag sensor applications. Mercury is a hazardous waste and should be handled with care. In an engine coolant temperature switch, when the coolant reaches the temperature limit, the bimetal element bends causing the contacts in the switch to close. This completes the circuit and lights the warning indicator on the instrument panel.
A time delay switch contains a bimetal strip, contacts, and a heating element. The time delay switch is normally closed. As current flows through the switch, current flows through the heating element causing it to heat, which causes the bimetal strip to bend and open the contacts. As current continues to flows through the heating element, the bimetal strip is kept hot, keeping the switch contacts open.
The amount of time delay before the contacts open is determined by the characteristics of the bimetal strip and the amount of heat produced by the heating element. When power to the switch is turned off, the heating element cools and the bimetal strip returns to the rest position and the contacts are closed.
A common application for a time delay switch is the rear window defroster. A flasher operates basically the same as the time delay switch; except when the contacts open, current stops flowing through the heating element. This causes the heating element and bimetal strip to cool. The bimetal strip returns to the rest position which closes the contacts, allowing current to flow through the contacts and heating element again. This cycle repeats over and over until power to the flasher is eliminated.
Common uses for this type of switch are the turn signals or the four-way flasher hazard lamps. A relay is simply a remote-control switch, which uses a small amount of current to control a large amount of current.
The image to the right shows an example: To wire a series circuit like the one shown, the positive output from the driver connects to the positive of the first LED and from that LED a connection is made from the negative to the positive of the second LED and so on, until the last LED in the circuit. Finally, the last LED connection goes from the negative of the LED to the negative output of the constant current driver, creating a continuous loop or daisy chain.
Here are a few bullet points for reference about a series circuit:. The loop concept is no problem by now and you definitely could figure how how to wire it, but how about powering a series circuit. This means you have to supply, at minimum, the sum of the forward voltages of each LED. Lets take a look at this by using the above circuit again as an example and lets assume the LED is a Cree XP-L driven at mA with a forward voltage of 2.
The sum of three of these LED forward voltages is equal to 8. So theoretically, 8. In the beginning, we mentioned using a constant current LED driver because these power modules can vary their output voltages to match the series circuit. For a deeper understanding of LED drivers take a look here. Some drivers require inputting slightly more to account for powering the internal circuitry of the driver the BuckBlock Driver needs a 2V overhead , while others have boosting FlexBlock features that allow you to input less.
Hopefully you are able to find a driver that can accomplish your LED circuit with the diodes in-series, however there are circumstances that might make it impossible. The segments are marked by metal contact pads and sometimes have a scissors icon screen printed right on them love those! The strips shown here are segmented in 5cm and 10cm lengths, each segment containing 3 LEDs.
Usually strips use 30, 32, 60 or LEDs per meter, which will change price and power consumption. For each segment the LEDs are wired in series, which means the operating voltages are added up, giving the higher voltage needed. All of the segments are wired in parallel, so they get all get the same amount of voltage all the way down the strip, but the current draw adds up depending on the length of the strip.
For more information on how to power your strip, skip to step 3. The LEDs that fade and blink together, stay together. All the LEDs on the strip will act as one, they are non-addressable. One way to tell by sight is that they do not have any driver chips that you can see on the strip that would be digital! These are also called individually addressable or just addressable.
Shown here is a strip using the LPD driver. They too come segmented, where they can be cut down to bite-size lengths. These strips take 5 volts, so they can run straight off a microcontroller.
They will power up when attached to 3. You will want to use a microcontroller with these to program cool patterns and make them reactive to sensors and switches. Most of the work is in the software, the hardware set up is simple and will be gone over in a later step. Digital strips get their information from one data-in pin or two data-in and clock-in pins, dependent of what strip is used.
Make sure to check the datasheet for the pinout diagram, voltage ratings and other useful information. The neat thing about addressable strips is that each LED can do it's own thing. It can be any color it wants at any time.
The makes blinking patterns and color swirls possible, and so much more. To keep your LED strip project glowing brightly with the appropriate power, you will need to know how much current your project draws and it's operating voltage.
Once you know those two things, you can choose a power supply. Keep in mind that current draw can be a tricky thing to figure out. Here we will take information from the datasheet and plug it into some simple equations to get the max current needed, since the information from the datasheet are if the LED is on at full brightness.
The number of LEDs per meter lpm factors in the power calculation as well. Strips can be 30, 32, 60, or more per meter. As an example let's look at the white strip's datasheet. We can see the operating voltage is 12V, which should also be screen printed on the strip itself at the cut line of each segment. What we are looking for is the current draw measured in milliamps mA.
It tells us that each segment made up of 3 LEDs draws 60 mA. To make the calculations easier, the current draw can be divided by 3 totaling 20mA per LED. If one meter is being used with 60 LEDs per meter we have this information:. Another way of calculating current draw is using the power consumption per LED.
The power consumption can also be used to find current draw if the power consumption, measured in watts per LED is known instead. The datasheet tells us. First divide. We now know that we want to use a a power supply that can provide 1. Keep in mind that the current draw per LED is at full brightness. If the strips are dimmed through a PWM pin on the Edison, it will take less current.
Going by the max amount is still a good guide to know if you have enough to begin with. Battery life is based on current draw of, again it will fluctuate, especially with the digital RGB strips when patterns and colors are dancing along it. Current draw will fluctuate dependent on the color and brightness the LED is outputting.
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