Checking LED Bulb with Multimeter

Since the bulb of the LED bulb is not transparent, it is not possible to visually determine which of the chips have burned out. This also applies to the other elements. To check an LED lamp, you use a multimeter - a device for measuring resistance and current. You will also need it to check the cable for breaks.

To identify a fault, you should learn how to use a multimeter, learn how it works, and familiarize yourself with the modes and rules of preparation for use. There are analog and digital multimeters. Experts advise to buy the second version because of the more accurate indicators in diagnosis.

Preparing the multimeter for the test

Before the test, you need to carefully inspect the multimeter for damage. The cover of the battery compartment should close tightly. Next, it is worth checking the probes and the wires going to them. If it is necessary to insulate, electrical tape or heat shrink tubing will do. There should not be any chips on the probes, otherwise they should be wrapped in the same way.

The mode should be switched to 200 Ohm resistance before operation. Connect the black cable to the "Com" socket and the red cable to the measured values. A one should appear on the screen. If the reading is different, the multimeter is broken or does not work correctly. Then the probes are crossed with each other, after which 0 should appear instead of one.

Fig.1 - multimeter.

This reading tells you that the tester is working correctly. If the image on the display is pale or the numbers are flashing, most likely the batteries are running low. To check the LED lamp it is necessary to select the "breakage search" mode on the toggle switch. It is indicated by a chip icon.

Steps to test the LED lamp 220V

To test the LEDs in a 220V lamp with a tester, you need to do the following:

• check the toggle switch and set the chip test mode;
• connect the wires to the tested diode;
• check the polarity.

If everything is done correctly, the indicators on the screen will change. Another way of diagnostics is to check the transistors. In the pnp section, the cathode is connected to port "C" and the anode to "E".

Testing of individual LEDs

To wire individual LEDs the multimeter has to be switched to the Hfe transistor test mode. After the diode is inserted into the connector as in the picture.

Fig.2 - testing of chips through the Hfe mode.

These pins are the minus and plus electrodes that make the diode glow. It is important not to mix up the polarity, as the LED will not light up. Just in case, you can swap the pins of the chip to make sure it is faulty.

Before testing the diode determine, Where is the anode and cathode of the diode. Multimeters can have different specifications and designs, and the test slots are sometimes different. But each one has all the slots you need.

Testing the LED illuminator

Determine the type of LED. If it looks like a yellow square, you will not be able to check it with a multimeter, because the voltage of such a source sometimes exceeds 30 volts. In this case, a working driver is used to test driver with the appropriate voltage and current.

Fig.3 - illuminator with one high power LED.

If the illuminator has a board with many SMD chips it can be checked with a multimeter.

Fig.4 - illuminator with board and SMD LEDs.

Inside the housing there is a driver, gaskets to protect against moisture and a board with diodes. After disassembly you should proceed in the same way as when checking the LED lamp.

Checking the LED bridge

It is not possible to illuminate the entire bridge with a multimeter. Sometimes you can get a slight glow in Hfe. In the diode check mode each chip is checked separately.

Fig. 5 - current-carrying parts of the strip.

If you check the current-carrying parts, the tester should be put into the test mode and go through each power lead at all ends of the tested area. This way you can find the damaged part of the bridge. In the photo, the blue and red stripe shows the zones that should be tested from the beginning of the strip to the end.

How to check without unsoldering the diode

LEDs mounted on the board are checked with a stylus. But standard tools may not fit through the connector for the transistor. A thin conductor will be needed here. These can be:

• sewing needles;
• A piece of cable or strands of stranded wire;
• office paper clips.

The conductor will have to be soldered to a foil stylus or connected without a plug, obtaining an adapter. If a foil plate with soldered wire pieces is used, you have to insert it into the appropriate multimeter slot and use homemade probes.

Why do LED bulbs fail

An LED is a semiconductor devicethat looks like a standard diode. They have a small reverse voltage limit. An electrical discharge or improperly adjusted circuit can cause the chips to burn out. Low-current bright diodes, which serve as power supply indicators, most often burn out due to unstable mains voltage.

It is advisable to watch video: How to check the LED in the LED lamp with a multimeter.

The most common causes LED lamps burn out - are:

• Incorrect amperage. In the characteristics prescribed on the package, the maximum life is indicated. But this parameter at the optimum current of about 20 mA. Chinese bulbs are rarely of high quality, as manufacturers install cheap chips in them, often used for backlighting gadget displays. These elements are designed for 5 mA and burn out quickly;
• Low quality of diodes. In order to save money, manufacturers often install in the lamp chips made with outdated technology, namely with a transparent p-contact. This option is the most economical and used for backlighting smartphone screens. When heated, the life of such LEDs is significantly reduced. Therefore, they should not be used in luminaires;
• heat generation. Sometimes the bulb burns out due to overheating. This can be provoked by a poor combination of the housing with LEDs. For example, if the chip is designed based on the latest technology, it will be difficult to work in the chip housing of past generations and will burn out quickly. In most cases, this is due to the size of the seating slot.
• low-quality assembly. Due to stiff competition, manufacturers are trying to put as many devices on the market as possible. Therefore, the control of the assembly is reduced, which becomes the cause of diode degradation.
• Improper use. Overheating of the bulb can occur not only because of violations of assembly technology. Sometimes it is advisable to buy a lamp from Russian manufacturers, as they are adapted to the local network and better tolerate voltage fluctuations.

Fig. 6 - low-quality diode lamp.

LED strips should be installed only on the aluminum profile. If the lamp constantly burns out regardless of the manufacturer, you need to check the wiring.

We recommend studying: Repairing Led bulbs at home.

Conclusion

A multimeter is one of the best options for checking the performance of an LED bulb. The only thing required of the handyman is to learn how to use it and set it up. Improper setting of the tester can lead to incorrect results.