Most modern designs include at least one LED. But before you solder the LED into the circuit, you somehow need to determine that the color and brightness meet your needs. And then calculate the correct resistor value. The proposed microcontroller tester has a current-limiting LED testing principle, as well as a display that shows:
A 9V battery was chosen for power supply for many reasons:
So, this circuit is based on the LM317 DC regulator (), but with additional components to support the measurements. Calculating the voltage across a 47 ohm resistance determines the current through the LED under test. For example, 0.94 volts into 47 ohms = 20 mA.
LEDs are divided into indicator and lighting. Indicator ones have less power and are used in backlighting of device displays as indicator sources of light signal. Lighting - more powerful (power more than 1 W), used in the design of lighting devices, which can be produced in the form of lamps, strips, spotlights.
The service life of such sources is tens of times longer than incandescent lamps. However, lighting elements last much less than indicator elements. Sometimes there is a need to check them; this can be done with a multimeter or a special tester.
To operate the LED, a low voltage constant current is required. To obtain it, various devices are used, which are miniature power supplies that are elements of the design of lighting devices. It is not always possible to carry out verification by actually connecting to such blocks. In this case, you need to use a multimeter.
Considering the features of the device, you can easily understand how to check the LED with a multimeter. Since it has a semiconductor junction in its structure, then, by analogy with a conventional diode, it must pass current in a certain direction. If the current is sufficient, the LED will emit light.
To check the LED with a multimeter, you need to switch the device to the diode ringing mode, then:
Similarly, you can check an LED with a simple tester, which is an open circuit consisting of a piece of conductor, a DC source and a test lamp.
A situation is possible when, in the process of checking a powerful lighting LED in the manner described above, the voltage is reflected on the display, the element lights up, but when connected to the circuit, the brightness is not strong enough. This is determined by the naked eye without any measurements. In this case, most likely there is a crystal defect. This LED needs to be replaced.
You can check the LED with a tester without removing it from the circuit. It is enough to release one of its contacts.
Currently, special devices - LED TESTER - are being produced and sold. Each such device is an LED tester, made in the form of a device with a built-in power supply and a set of connectors for testing devices of various types.
An LED strip is a light source consisting of many elements. They are spaced evenly along the length of the tape and grouped in threes. This allows you to cut the LED strip into pieces of almost any length without compromising its performance properties. The main thing is that the cut does not fall in the middle of a group of three elements.
Testing the tape involves applying current to the power contacts. If the tape lights up, it is working. If the entire strip does not light up, the fault must be looked for in the supply wires. To do this, you can ring them with a tester. You can measure the resistance with a multimeter to check the integrity of the wires.
If, when the power is turned on, individual groups in the strip do not light up, the problem is not in the supply wires, but in a specific segment with LEDs. In this case, they are checked using the method described above, and the resistor (there is only one for the entire group) is also checked for compliance with the specified resistance value.
For the convenience of consumers, the production of lamps based on LEDs has now been launched, which have a geometric configuration similar to the already familiar incandescent lamps. This makes it possible to install LED lamps in ordinary lamps powered by a 220 V network.
A special current converter – driver – is built into the design of such a lamp. This device is assembled from parts that have parameters that differ in each individual model. This circumstance makes it impossible to use this type of diagnostics, such as checking an LED lamp with a multimeter.
The LED lamp is tested using a special tester. It is a device, inside of which a circuit is assembled that allows you to check the performance of lamps of various types. For this purpose, the body has several connectors for the most commonly used lamp bases. The test result is displayed in the form of a sound signal.
Testing an LED with a multimeter is the easiest and most correct way to determine its performance. A digital multimeter (tester) is a multifunctional measuring instrument, the capabilities of which are reflected in the switch positions on the front panel. LEDs are checked for functionality using functions present in any tester. Let's look at the testing methods using the DT9208A digital multimeter as an example. But first, let’s touch a little on the topic of the reasons for the malfunction of new light-emitting diodes and the failure of old ones.
A feature of any emitting diode is its low reverse voltage limit, which is only a few volts higher than the drop across it in the open state. Any electrostatic discharge or incorrect connection during circuit adjustment can cause the LED (abbreviation for Light-emitting diode) to fail. Ultra-bright, low-current LEDs, used as power indicators for various devices, often burn out as a result of power surges. Their planar counterparts (SMD LEDs) are widely used in 12V and 220V lamps, strips and flashlights. You can also verify their serviceability using a tester.
It is worth noting that a small proportion of defective LEDs (about 2%) are supplied from the manufacturer. Therefore, additional checking of the LED with a tester before mounting it on a printed circuit board will not hurt.
The simplest method, which is most often used by radio amateurs, is to check light-emitting diodes with a multimeter for performance using probes. The method is convenient for all types of light-emitting diodes, regardless of their design and number of pins. By setting the switch to the “continuity check, open circuit check” position, touch the leads with the probes and observe the readings. By connecting the red probe to the anode and the black probe to the cathode, the working LED should light up. When changing the polarity of the probes, the number 1 should remain on the tester screen.
The glow of the emitting diode during testing will be small and on some LEDs in bright light it may not be noticeable.
To accurately test multi-color LEDs with multiple leads, you need to know their pinout. Otherwise, you will have to randomly sort through the terminals in search of a common anode or cathode. Don't be afraid to test high-power LEDs with a metal substrate. The multimeter is not capable of disabling them by measuring in dial mode.
Testing an LED with a multimeter can be done without probes, using sockets for testing transistors. Typically, these are eight holes located at the bottom of the device: four on the left for PNP transistors and four on the right for NPN transistors. The PNP transistor is opened by applying a positive potential to the emitter “E”. Therefore, the anode must be inserted into the socket labeled “E”, and the cathode into the socket labeled “C”. A working LED should light up. To test in the holes for NPN transistors, you need to change the polarity: anode - “C”, cathode - “E”. This method is convenient for testing LEDs with long and solder-free contacts. It does not matter in what position the tester switch is located. 
Checking an infrared LED occurs in the same way, but has its own nuances due to invisible radiation. At the moment the probes touch the terminals of the working IR LED (anode - plus, cathode - minus), a number of about 1000 units should appear on the device screen. When changing polarity, there should be a unit on the screen.
To check the IR diode in the transistor testing sockets, you will additionally have to use a digital camera (smartphone, telephone, etc.). The infrared diode is inserted into the corresponding holes of the multimeter and the camera is pointed at it from above. If it is in good condition, then IR radiation will be displayed on the gadget’s screen in the form of a glowing blurry spot.
Testing high-power SMD LEDs and LED matrices for functionality requires, in addition to a multimeter, a current driver. The multimeter is connected in series to the electrical circuit for several minutes and the change in current in the load is monitored. If the LED is of poor quality (or partially faulty), then the current will gradually increase, increasing the temperature of the crystal. The tester is then connected in parallel with the load and the forward voltage drop is measured. By comparing the measured and passport data from the current-voltage characteristics, we can conclude that the LED is suitable for use.
Read also 
To check an LED and find out its parameters, you need to have a multimeter, a “Tseshka” or a universal tester in your arsenal. Let's learn how to use them.
Let's start with a simple one, how to ring an LED with a multimeter. Switch the tester to transistor testing mode - Hfe and insert the LED into the connector, as in the picture below.
How to check the LED's functionality? Insert the anode of the LED into connector C of the area marked PNP, and the cathode into E. In PNP connectors, C is the positive terminal, and E in NPN is the negative terminal. Do you see the glow? This means the LED has been checked; if not, the polarity is wrong or the diode is faulty.
The connector for testing transistors looks different, often it is a blue circle with holes, this will be the case if you check the LED with a DT830 multimeter, as in the photo below.
Now let's talk about how to test an LED with a multimeter in diode testing mode. First, take a look at the test diagram.
The diode test mode is indicated by a graphical representation of the diode, more details about the designations in. This method is suitable not only for LEDs with legs, but also for checking an SMD LED.
Checking LEDs with a tester in dialing mode – is shown in the figure below, and you can also see one of the types of connectors for testing transistors, described in the previous method. Write in the comments about what kind of tester you have and ask questions!
This method is worse; the tester produces a bright glow from the diode, and in this case, a barely noticeable red glow.
Now pay attention to how to check the LED with a tester with an anode detection function. The principle is the same; if the polarity is correct, the LED will light up.
Indeed, almost every home has such an LED. They have found wide application in remote controls. Let's imagine a situation where the remote control has stopped switching channels, you have already cleaned all the keyboard contacts and replaced the batteries, but it still does not work. So you need to look at the diode. How to test IR LED?
The human eye does not see the infrared radiation in which the remote control transmits information to the TV, but your phone's camera does. Such LEDs are used in night illumination of video surveillance cameras. Turn on the phone's camera and press any button on the remote control - if it is working, you should see flickering.
The methods for checking an IR LED and a regular one with a multimeter are the same. Another way to check if an infrared LED is working is to solder a red LED parallel to it. It will serve as a visual indicator of the operation of the IR diode. If it flickers, it means signals are being sent to the diode and the IR diode needs to be replaced. If the red does not flicker, then the signal is not being received and the problem is in the remote control itself, and not in the diode.
In the remote control circuit there is another important element that receives radiation - a photocell. How to check a photocell with a multimeter? Turn on resistance measurement mode. When light hits a photocell, its conductivity state changes, then its resistance also changes downward. Observe this effect and make sure it is working or broken.
How to check an LED with a multimeter without desoldering? In the principles of its verification, everything remains the same, but the methods change. It is convenient to check LEDs without soldering using probes.
Standard probes will not fit into the connector for transistors, Hfe mode. But it will fit sewing needles, a piece of cable (twisted pair) or individual cores from a multi-core cable. In general, any thin conductor. If you solder it to a probe or foil PCB and connect probes without plugs, you will get such an adapter.
Now you can test the LEDs with a multimeter on the board.
How to check the LEDs in a flashlight? Unscrew the lens unit or front glass on the flashlight, carefully unsolder the board from the battery pack if the length of the conductors does not allow it to be easily examined and studied.
Any electrician has “ringed” an incandescent lamp many times, but how to check an LED lamp with a tester?
To do this, you need to remove the diffuser; it is usually glued. To separate it from the body you need a mediator, or a plastic card, it needs to be inserted between the body and the diffuser.
If you can’t do this, try warming the gluing area a little with a hairdryer.
How now to check an LED light bulb with a multimeter? In front of you will be a board with LEDs; you need to touch their terminals with the tester probes. Such SMDs light up dimly in diode testing mode (but not always). Another way to check serviceability is to test the battery with a Krona battery.
The crown produces a voltage of 9-12V, so check the diodes short sliding touches to their poles. If the LED does not light up with the correct polarity, it needs to be replaced.
First, take a look at which LED is installed in the spotlight, if you see one yellow square, as in the photo below, then you won’t be able to check it with a tester, the voltage of such light sources is high - 10-30 Volts or more.
You can check the performance of this type of LED using a known-good driver for the appropriate current and voltage.
If many small SMDs are installed, checking such a spotlight with a multimeter is possible. First you need to disassemble it. In the case you will find a driver, moisture-proof gaskets and a board with LED. The design and testing process are similar to the LED lamp described above.
There is a whole article on our website about this, here we will look at express verification methods.
I’ll say right away that it won’t be possible to illuminate it entirely with a multimeter; in some situations, only a slight glow is possible in Hfe mode. Firstly, you can check each diode individually, in the diode test mode.
Secondly, sometimes it is not the diodes that burn out, but the current-carrying parts. To check this, you need to put the tester into continuity mode and touch each power terminal at different ends of the area being tested. This way you will identify the intact part of the tape and the damaged one.
The red and blue lines highlight the stripes that should ring from the very beginning to the end of the LED strip.
How to test an LED strip with a battery? The power supply for the tape is 12 Volts. You can use a car battery, but it is large and not always available. Therefore, a 12V battery will come to the rescue. Used in radio doorbells and control panels. It can be used as a power source when testing problematic areas of the LED strip.
Let's look at how to test an LED with a battery. We will need a battery from the motherboard - size CR2032. The voltage on it is about 3 volts, sufficient to test most LEDs.
Another option is to use a 4.5 or 9V battery, then you need to use a resistance of 75 Ohms in the first case and 150-200 Ohms in the second. Although from 4.5 volts, checking the LED is possible without a resistor by briefly touching it. LED's safety factor will forgive you for this.
Build a simple circuit to measure the characteristics of an LED. It is so simple that you can do it without using a soldering iron.
Let's first look at how to find out how many volts our LED is with a multimeter using such a probe. To do this, carefully follow the instructions:
However, it is extremely difficult to determine the change in brightness by eye and bring the LED to the nominal mode; you need to have a lot of experience. Let's simplify the process.
To reduce the likelihood of burning a diode, determine by its appearance which type of LED it is similar to. There are reference books and comparison tables for this; refer to the reference rated current when carrying out the characterization process.
If you see that at the nominal value it clearly does not produce the full luminous flux, try to briefly exceed the current and see if the brightness continues to increase as quickly as the current. Monitor the heating of the LED. If you supply too much power, the diode will begin to heat up intensely. Conventionally, a normal temperature will be at which you cannot hold your hand on the diode, but if you touch it it will not leave a burn (70-75°C).
To understand the causes and consequences of performing this procedure, read.
After all the work done, check yourself again - compare the readings of the devices with the table values of the LEDs, select the closest suitable parameters and adjust the circuit resistance. This way you are guaranteed to determine the voltage, current and power of the LED.
A 9V crown battery or a 12V battery is suitable to power the circuit; in addition, you will determine the total resistance for connecting the LED to such a power source - measure the resistance of the resistor and potentiometer in this position.
Checking a diode is very simple, but in practice there are different situations, so many questions arise, especially for beginners. An experienced electronics engineer will determine the parameters of most LEDs by their appearance, and in some cases, their serviceability.
💲 GET MONEY BACK FROM ONLINE PURCHASES, REGISTER goo.gl/IOOKLO ◄
VKONTAKTE GROUP: vk.com/chipdip31
★ PRODUCTS FROM VIDEO ★
1 goo.gl/7gCvJ7 (LED tester)
2 goo.gl/lt1V8l (ESR meter)
3 goo.gl/xOVhUu (ESR meter)
4 goo.gl/a4NQNW (LCR tester)
5 goo.gl/xCdsKA (Tester)
6 goo.gl/6ruVNu (Infrared, air soldering stations, soldering irons)
7 goo.gl/yphbSF (Soldering stations)
8 goo.gl/hXqqLS (Electronic modules)
9 goo.gl/wiFAe8 (Modules and components)
10 goo.gl/J4bQoK (Electronic components)
11 goo.gl/mZNUmR (Multimeters)
▰▰▰▰▰▰▰▰▰▰▰▰▰▰▰▰▰▰▰▰▰▰▰▰▰▰▰▰▰▰▰▰
PLEASE WRITE TO ME IN THE COMMENTS IF THE LINK IS NOT WORKING OR THE PRODUCT IS OUT OF RANGE!
▰▰▰▰▰▰▰▰▰▰▰▰▰▰▰▰▰▰▰▰▰▰▰▰▰▰▰▰▰▰▰▰
Review of Chinese LED tester. LED Tester For 5mm 3mm 10mm LED Light Lamp. In this video I disassemble and test the Chinese LED Tester. The device is designed to test the performance of LEDs under various current values. #LED, #Tester.
LED Test Box LED Tester for Light Emitting Diode Brand New.
New Mini Handy LED Tester Test Box 2~150mA for Light-emitting Diode Bulb Lamp. Mini Handy LED Tester Test Box 2~150mA for Light-emitting Diode Bulb Lamp.
Overview of the Chinese LED tester. LED Tester For 5mm 3mm 10mm LED Light Lamp. In this video I can make out and test Chinese LED Tester. The device is designed to verify that the LEDs at different current values.
#led #ledtester #aliexpress #aliexpress
▰▰▰▰▰▰▰▰▰▰▰▰▰▰▰▰▰▰▰▰▰▰▰▰▰▰▰▰▰▰▰▰
★ SALE! HUGE DISCOUNTS! BEST SELLERS! ★
#ALIEXPRESS BEST PRODUCTS WITH FREE SHIPPING: bit.ly/aliexressbestseller
#GEARBEST COOL GADGETS: bit.ly/gearbestsale
#BANGGOOD BEST PRODUCTS AT LOW PRICES: bit.ly/banggoodsale
#DEALEXTREME PRODUCTS FROM $0.99: bit.ly/dealextremesale
▰▰▰▰▰▰▰▰▰▰▰▰▰▰▰▰▰▰▰▰▰▰▰▰▰▰▰▰▰▰▰▰
★ BEST SERVICES FOR SAVING ON ONLINE PURCHASES, REGISTER AND SAVE! ★
1 LetyShops more than 900 online stores, I RECOMMEND, REGISTER goo.gl/MTXV50
LetyShops Cashback browser plugin: bit.ly/cashbackplugin (DON'T MISS THE BENEFIT!)
2 ePN Cashback: bit.ly/EPNCashback
Browser plugin ePN Cashback: bit.ly/PluginEPNCashback (SAVE MORE ON PURCHASES WITH ALIEXPRESS)
3 Admitad is the best CPA affiliate: goo.gl/EQTD79 ★ VIDEO: goo.gl/wr7SSP ★
💲 DON'T FORGET TO SAVE ON YOUR ONLINE PURCHASES!
▰▰▰▰▰▰▰▰▰▰▰▰▰▰▰▰▰▰▰▰▰▰▰▰▰▰▰▰▰▰▰▰
💲 CHANGE MONEY AT A FAVORABLE RATE!
💲 Monitoring exchange offices: bit.ly/WMZtoVISA
💲 A profitable currency exchanger, I often use it myself: bit.ly/smartwmz
▰▰▰▰▰▰▰▰▰▰▰▰▰▰▰▰▰▰▰▰▰▰▰▰▰▰▰▰▰▰▰▰
║ Did you like the video?! Subscribe to the #MegaGigaVOLT channel: goo.gl/M477sn
║ I will be very grateful if you support me and “LIKE” this video.
║ Also don’t forget to leave comments under the video!
║ Share this video on social media. networks with friends
★ S A S I B O ★
▰▰▰▰▰▰▰▰▰▰▰▰▰▰▰▰▰▰▰▰▰▰▰▰▰▰▰▰▰▰▰▰
★ SOCIAL NETWORKS ★
VK - vk.com/yaroslavshebanov
Instagram - www.instagram.com/belgorodcity
▰▰▰▰▰▰▰▰▰▰▰▰▰▰▰▰▰▰▰▰▰▰▰▰▰▰▰▰▰▰▰▰
💲 YOU CAN SPONSOR THE DEVELOPMENT OF MY CHANNEL:
DONATE TO THE #MegaGigaVOLT CHANNEL: www.donationalerts.ru/r/megagigavolt
HELP RAISING THE AMOUNT AT: yasobe.ru/na/megagigavolt
★ S A S I B O ★
▰▰▰▰▰▰▰▰▰▰▰▰▰▰▰▰▰▰▰▰▰▰▰▰▰▰▰▰▰▰▰▰
