LED lights testing

Test equipment and approach

Photometry and flickering test

The photometry test was performed using Opple Light Master 4 (Amazon), (AliExpress).

This device is capable of measuring a number of important light characteristics: Lux, Ra, R9, color temperature, CIE x, and y coordinates, duv value, and flickering. All these characteristics were measured for each testing subject.

Photometry parameters:

Lumen - is how much light is given off.
Lux - is how bright your surface will be, it is a measure of the light density. 1 lux equals 1 Lumen/m2. Lux and Lumen - What's the difference?
CRI Ra - color rendering index. It is a quantitative measure of the ability of a light source to reproduce the color of different objects faithfully in comparison with an ideal or natural light source. Scale varies from zero to 100. It is considered that for applications where the correct display of color tones is important (shop window lighting, art and design workshops, photo studio, kitchens) the Ra value should be more than 90, ideally >95.
CRI R9 - ability to emit red light (>600nm). It is a very important parameter, especially in photography, kitchen, and medical facilities which has a great influence on the correct display of skin tone. What is CRI R9 and Why is it Important?
CIE X and Y coordinates and Duv value - The coordinates represent color from CIE 1931 color space, while duv describes its distance from color emitting by the black body at a certain color temperature. Here you can find more information about it.

Flickering parameters:

Flicker index - considers the area of the waveform above and below the average light output.
Modulation depth (flicker percent) - is the measure of the maximum light vs. the minimum light in a cycle.
Frequency - the majority of humans do not detect flicker frequency >90Hz, but unconsciously through optic nerves, light frequency <400Hz has an impact on the human body.
Risk (IEEE Standard PAR1789) - Integral risk assessment including the above-mentioned indicators
More information about flicker and its impact on humans you can find in this article.

You may also find useful information from European standard EN 12464-1 regarding illumination intensity and Ra parameters recommended for different working environments.

Is the brightness test accurate?

In order to collect and approximate emitting light despite the angle of light emission, the test stand was built using a mirror sphere with a hole at one side where a photometry device was installed.

In order to get accurate brightness measurement results as precise as possible it was needed to calibrate the test stand.

For calibration, it was used the LED Nichia 519A 4000K with defined characteristics. This LED has 635 lumens (this is the approximate value between several sources measured on this chip) at 2A of current.

Then the LED brightness was measured in Lux using photometric tester Opple LM4 and the result was 21000 Lux. So these measurements provide a possibility to calculate the conversion coefficient Lux/Lumen = 33.07 for my test stand and I can calculate Lumens for all other LEDs I am testing.

LED Temperature measurement

To perform an LED temperature test the Infra-red camera Xinfrared InfiRay P2 Pro(Amazon) (AliExpress) is used.

Making temperature tests is important because high-power LEDs should be protected by a heatsink in order to dissipate excessive heat which is harmful to LEDs.

It's good practice to keep a majority of commercial LED under 60C if possible, but not more 85C as it may reduce LED lifespan. Some LEDs can tolerate up to 150C but we shouldn't suppose that heat tolerance level in mass-market LEDs.

How much energy is supplied to an LED?

LED is a semiconductor device and can work under different voltages which higher than its voltage drop characteristic, but the current must be limited because the current-voltage curve of an LED is parabolic and the LED will be burned out quickly if the current is not limited.

If you are working with an LED strip or LED bulb, they have already either a current-limit resistor or an electric circuit for current regulation and you need only to supply a defined voltage

But if you need to work a single LED, then you need to know how much current you have to limit to power your LED. Usually, this information is provided by the manufacturer in the datasheet or on the product page, but it's not always available or you have got a random LED so sometimes you have to deal with LED without such information.

What you can do?

In order to find a current limit, you need to light the LED at forward voltage without any resistors in series which may limit a current for a relatively short period of time because keep feeding an LED for a long period of time without any current limits is dangerous for LED as the current flows through the LED tend to increase over time and eventually will damage the LED.

So once you light the LED at forward voltage, check the current flows through the circuit. This is the current value you are looking for.

The forward voltage value depends on the emitting light wavelength (emitting color) of an LED. Here is the reference for LED without phosphor coating:

Infrared (IR) - 1.5V
Red/Orange/Yellow - 1.8V
Green - 2V
White/Blue//UV - 3.2V

Sometimes you might see an LED chip coated with a yellow surface. This is phosphor(luminophore) coating on top of a blue LED because blue LED is the most energy-efficient LED and phosphor re-emits light in other wavelengths, giving a more rich light spectrum. The majority of LEDs that are used as a source of light looks like that.

An LED can withstand bigger voltage (and current), but you should avoid it as the LED becomes less energy-efficient, generates more heat at its maximum, and degrades quickly. You might even consider to reduce current in order to reach higher Lumen/Watt ratio and prolong the LED lifespan.

Once you decide which electrical current for your LED is optimal (taking into account its brightness and efficiency), you will need either to set the defined current limit on your LED power supply or build a circuit installing a current limiting resistor in series with the LED. You can use this online calculator to define the resistor value.

It is worth noting that you can power your LED by any voltage with the correctly chosen resistor, however as bigger the difference between forward voltage and power supply voltage will be, then the overall circuit efficiency will be lower because more electrical power will be dissipated on the resistor.

I performed several tests under different voltages (and current respectively) so you can compare how efficient and bright LEDs are under different conditions.

What is COB LED?

A CoB LED (or chip-on-board LED) is a single device with many LED chips mounted on a thermally efficient substrate placed below a uniform phosphor coating. As practice shows, such assemblies are less energy-efficient compared to individual LEDs, but give more uniform lighting and reduce the effect of a point light source, which is reflected in the design.

Opple Light Master 4

Mirror sphere test stand

Test stand under the mirror sphere

Nichia 519A 4000K

Xinfrared InfiRay P2 Pro

5/3mm signal LED typical forward voltage

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Issues with the use of car LED bulbs

Some car owners may encounter a problem when replacing ordinary incandescent(halogen) bulbs with LED bulbs. The problem is that the LED bulb either does not turn on or blinks. At the same time, some cars with this problem may show an error on the dashboard that the bulb does not work.

This problem occurs in some modern cars that have a burned-out/absent bulb detection function.

The on-board computer of such cars measures the resistance of the area where the bulb should be installed, and if the resistance is significantly higher than that of an incandescent bulb, or no current is flowing at all, the computer registers the problem, shows an error and interrupts the current supply to the bulb. The difference in resistance value arises because the incandescent lamp consumes significantly more current than LED (2-7 times), and the value of current consumption depends inversely on its resistance (the higher the resistance, the less current flows).
At the same time, cars that do not have such a function (determination of the burned-out lamp) perfectly and without any problems use LED lamps instead of classic incandescent lamps (I confirm by my own experience).

If your car has such a problem, there are several ways to solve it:

Disable the detection of burnt-out bulbs in the on-board computer (the most reliable way, but requires the participation of an electrician)
Install a resistor in series in the circuit between the power wire and the lamp (before or after the lamp - it does not matter). This will “cheat” the onboard computer because the resistance in the circuit will be higher and similar to the resistance of the incandescent lamp. The resistor should be powerful enough (50W, 6-10Ohm) to dissipate heat and not overheat. The resistor has no polarity, and installation is not a difficult operation (you need to cut the wire and install the resistor in the break), but the presence of the resistor in the circuit reduces the energy savings that could be obtained using only an LED bulb. There are also adapter kits with which you don't have to cut the wires, they are inserted between the base and the bulb. In general, solving the problem by installing a resistor (or an adapter kit with a resistor) is not a guarantee that the bulb will work correctly in your car because some cars measure resistance quite accurately and a small deviation may be considered an error, and some deviation is unavoidable because the resistance of LED bulbs varies, but in most cases, the problem is solved this way.
Some LED bulbs have built-in canbus error-free circuitry. No one can say with certainty that the implementation of this circuit in a particular LED bulb is guaranteed to solve the problem with your car and LED lamp because the implementation of this circuit may vary and the causes of such a problem with LED bulbs also vary from car to car.

Some cars may have a problem with signal lights and DRLs (Daily Running Light) that use single-pin 21W bulbs instead of dual-pin 21/5W bulbs, and PWM dimming is used to control the brightness. PWM (Pulse Width Modulation) is the interruption of the power supply to the bulb at a specific frequency and duration, which allows for adjustment of the visible brightness and power consumption of the bulb. Some LED bulbs cannot operate correctly in this mode, resulting in noticeable flickering.

Solution: there are adapters that smooth out the PWM effect and eliminate flicker in LED bulbs by using high capacitance capacitors, but this approach, while eliminating flicker, does not allow dimming in the way a car tries to do. Often such adapters come with a built-in resistor. A better solution may be to select a lamp that is capable of PWM control.

Conclusion: if you have not used LED bulbs before (interior lighting, license plate lighting, signal lights, daytime running lights, low/high beam), it makes sense to try a bulb from a store that will allow you to return it, in case the bulb will not work on your car or you will not be able to solve the problem of compatibility with LED bulbs. The same applies to the use of adapters and resistors.
I want to note once again that the described problems are individual problems of certain car models. On my 2008 year Peugeot 308, the interior, running lights, and signal LED lamps work perfectly well without any problems and resistors.

Car LED resistor kit

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12V Car signal&marker lights test (60 lights test!)

This test will come in handy if you are planning to replace standard halogen lights in your car with LED lights/bulbs/lamp designed for cars with the same socket type. Such a replacement makes sense if you want to either reduce the car's energy consumption (energy consumption is reduced by 4 or more times at the same brightness level) and/or increase the brightness of the lighting.

All test details that were performed in this LED category can be found in this google-document ("Car Signal/DLR Light" sheet).

The testing is ongoing so the light list and recommendations will be updated over time by adding new test subjects.

All lamps for further testing were purchased by me personally with my own money.

Type of sockets (plugs) of the tested lights:

This test category involves lamps used as signal or marker lights:

- Turn Signals/Indicators

- Brake/Tail lights

- Daytime Running Lights (DRLs)

- Reverse Lights

The most common types of socket (plug) for these lights are:

P21/5W, (socket: 1157, BAY15D, BA15D) - 2 contacts (High/Low beam)
P21W (white), PY21W (yellow),(socket: 1156, BA15S, BAU15S) - 1 contact
W21/5W, (socket: T20, 7443, 7443 SRCK, W3x16q), - 2 contacts (High/Low beam)
W21W, WY21W (socket: T20, 7440, W3x16d) - 1 contact
P27/5W (socket: 3157, T25, W25x16q) - 2 contacts (High/Low beam)
P27W (socket 3156, T25, W25x16d) - 1 contact

Some of the LED light makers use the same light head but different socket types or change the color of the LED installed (white, yellow, red), but there is no difference in the performance of a light bulb with different socket types. The color of the light however may have some influence on brightness.

In my tests, I mostly focused on P21/5W type of bulbs in this car lights category.

Primary color definition

The majority of the test subjects are White LED bulbs, however there are some Yellow and red LED lights. When I define LED color, it is important to define a primary color (the color tone is the secondary, if the tone is important for you, then turn attention to the measured "Color temperature" value), because for the "Turn light" the primary color must be Yellow, as well as some "Brake/Tail lights" the color must be bright Red (unless light assembly requires white/transparent light bulbs). This primary color is also defined and noted in the the google-document.

Type of measurements performed for each light bulb:

Brightness measurements and power consumption were performed for 4 different voltages:
- 14V (car engine on),
- 13V (for the sake of test),
- 12V (basis),
- 11V (for the sake of test),
- I measure additionally a starting voltage (minimum voltage which lights the LED)

The photometry test and flickering measurements were performed for 14V (car engine on) as it is the main operational voltage for the lights.
LED temperature test. There are 3 measurements performed:
- 10 seconds - for the sake of test.
- 30 seconds - to check whether an LED is suitable to be used as signal light within the 85C threshold.
- 60 seconds - to check if the LED can be within the temperature limit of 85C in order to be used as a DRL (Daily Running Light).
- If the temperature is within limits I did an optional 90sec temp test.
- If a bulb has a glass or plastic cover, it's impossible to correctly measure the LED chip temperature, in this case, I measured the hottest part of the bulb, usually its housing and its temperature is usually 25-30C lower than the LED chip for plastic housing it could be even lower due to the bad heat dissipation.
Most of my tests are done for 2 contact socket bulbs (High/Low beam) P21/5W. The power consumption difference between High/Low beams was noted in the additional parameters section in the google-document - "Car Signal/DLR Light" sheet. The brightness and photometry tests are performed for the High beam mode.

Other LED lights qualities and recommendations approach:

Some bulbs have aluminum shell/housing which is a very good feature because it is used as a heatsink/radiator for heat dissipation and prolongs LED lifespan.
Some of the bulbs are more powerful than others. If a powerful bright bulb does not have a very good heatsink, it quickly overheats, brightness drops and LED degrades quickly. You may install high-power hot bulbs as brake or turn lights as they light occasionally and may cool down between flashes, but you should avoid using them as DRLs (Daytime Running Lights).
Try not to rely on nominal power (Watt) written on an AliExpress product page, as most of the time (with a very few exceptions) it's not correct, however, you can check the real light bulb power, temperature, energy efficiency, and many other parameters based on my measurements.
My final recommendation was given taking into account a few parameters:
- Structural design/quality, general impression
- Heat dissipation measurements
- Energy efficiency
- Level of brightness and its stability. Brightness level must be at least 75% or higher than halogen "classic" bulb.

LED lights I recommend in this category among 60 test subjects:

CSL_18 (Alternative link)- Very good light, good brightness (89% from halogen), the temperature under limits, impressive energy efficiency, power 4.69Watt. Can be used as DRL. Price - 3USD per bulb.
CSL_25 (Alternative link)- Very good light! Stable good brightness (76% from halogen), stable incredibly low temperature, good ALU heatsink, focused beam with lens, good packaging, power 5.9Watt. Best for DRL. Price - 3.4USD per bulb.
CSL_29 (Alternative link)- Very good stable brightness (103% from halogen), good heat dissipation (ALU heatsink), good energy efficiency, power 6Watt. Suitable for DRL. Price - 3.8USD per bulb.
CSL_32 (Alternative link) - Good packaging, solid structure, ALU heatsink, very bright (156% from halogen), power 9.8Watt, could be used as DRL. Price - 3.6USD per bulb.
CSL_34 (Alternative link) - Solid structure, ALU heatsink, stable very high brightness (171% from halogen), very good power efficiency, power 9.6Watt. Could be used as DRL. Price - 5.2USD per bulb.
CSL_46 (Alternative link) - Solid structure, Aluminum shell, stable good brightness (126% from halogen) on different voltages, 24V support. Good heat dissipation 80C max after 90 seconds, suitable for DRL. Very good power efficiency. Power:7.1W Price: 3.7USD per bulb.
CSL_48 (Alternative link) - Solid structure, Aluminum shell, good brightness (79% from halogen), Perfect heat dissipation (62C max after 90 seconds), suitable for DRL. Good power efficiency. Power:5.5W Price: 6.3USD per bulb.
CSL_51 (Alternative link) - Solid structure, Aluminum shell, good brightness (90% from halogen), very good heat dissipation (70C max after 90 seconds), suitable for DRL. Very good power efficiency. Power:5.5W Price: 6.5USD per bulb.
CSL_53 (Alternative link) - Compact size, good brightness (105% from halogen), good heat dissipation (68C max after 90 seconds, radiator measurement), suitable for DRL. Impressive power efficiency. Power:6.1W Price: 6.3USD per bulb.
CSL_62 (Alternative link) - superb brightness (139% from halogen), good heat dissipation (76C max after 90 seconds, LED chips measurement), suitable for DRL. Good power efficiency. Power:8.6W Price: 3.5USD per bulb.