LEDs buzzing

Svetlana January 01 2022

What does buzzing mean?

Buzzing can be heard as a high-pitched sound coming from the speaker. The buzzing noise is caused by a resonance due to the fact that it vibrates at a particular frequency. In some cases, Buzzing has been noted as sounding similar to blowing air against an object, or as a bee's hum. It is not known if being exposed to loud frequencies can result in permanent damage over time, however, this page will investigate the main causes of buzzing and what you can do about them:

Hissing:

A hissing noise may occur when there is a lack of power (too little current) and enough voltage for your device; one cause of this issue would be the use of underpowered resistors or capacitors causing voltage drops due to high resistance. This issue can be solved by:

  • Increasing the current on your power supply (ex: increase battery voltage and/or add a second cell)
  • Using higher rated resistors or capacitors that have lower resistance and higher current rating respectively.

Buzzing:

A buzzing noise may occur when there is enough power (enough current ) but not enough voltage for your device; one cause of this issue would be insufficient decoupling capacitors, such as ceramic disk capacitors or surface mount electrolytic capacitors; this microphonic effect happens because these types of capacitor change their value slightly after each pulse of current goes through it, thus creating large swings in frequency response and thus making them microphonic (they act as a microphone, converting sound to electricity and back).

This issue can be solved by:

  • Replacing electrolytic capacitors with larger value ceramic disk capacitors or using tantalum capacitors.
  • Use more decoupling capacitors after your voltage regulator (ex: place 100nF capacitor between V+ and GND of Voltage Regulator IC).

Is it normal when LED buzzles?

In most cases, LED buzzing is not normal. In fact, it is usually caused by a design flaw in the circuit. Most LEDs have a diode built-in to the legs to prevent reverse current flow from damaging your microcontroller or other devices powered by the LED itself.

Because of this, it becomes important that no part of the circuit has a voltage that would allow current to flow back towards your device or something could get fried. This issue can be solved by:

  • Fixing software bugs that may cause this resistance to change generates unwanted sounds.
  • Removing unnecessary resistors generating noise.
  • Replacing some components with others of larger value (ex: using 100nF capacitor instead of 1uF).

How much noise should we expect from an LED?

There isn't really a simple answer to that question since it depends on many factors: Voltage level used to power up LEDs (1V or 3V), type of diode (LED diodes are generally less noisy than others), circuit configuration (many capacitors required for low-impedance sources such as switching converters) and so on...

But if you take a close look at the example circuits below, you will probably see that in most cases noise levels are significantly below 100mV.

Is it OK to power LEDs with unregulated voltage?

Yes, it actually can be done and usually does not require any additional electronics other than simple resistors which do not introduce significant noise at all.

It is still recommended to use capacitors on both ends of the resistor but they should only keep the voltage stable and not reduce noise coming from your circuit or source you're powering up your LED with. A voltage regulator may be required when using high currents (more than 1A) or very long wires where voltages drop significantly.

Do dimmers make LED bulbs buzz?

An LED is a diode and so it only works one way: Current can flow from the positive terminal to the negative one, but not in the opposite direction. A normal light switch on your wall works by changing the connection between your house current and whatever you want to control with it electronically (your lamp). What happens when you turn off such a switch is that no current flows through whatever's controlled. It's just like unplugging it, but without having to get behind the couch to pull the plug out of its socket.

When you dim an LED by reducing voltage instead of the current, nothing changes about how electricity flows through your lighting setup; since there is no difference in voltage supplied (just lower amperes) there won't be any difference in resistance and therefore no reverse current will take place.

That said, dimming doesn't make LEDs buzz; but reducing voltage to an LED may make it look drastically less bright (reduce flux) because the human eye perceives brightness logarithmically: If you reduce voltage by half your LED's brightness will halve. However, since most circuits don't go under 3V or so, there should be no noise issues associated with this process.

Do old LEDs buzz?

Noise problems can occur when a motor or a high-power light is powered on relatively slowly. While this is not always the case, many motors have coils that store energy for milliseconds before being activated fully, while some lights slowly warm up to full brightness. Since many old LEDs are used for these types of devices, noise problems may occur with them as it is more difficult to keep coils or circuits completely shut off until they are fully activated.

This is done by placing larger values of capacitors on voltage regulators near the LED in question since the capacitor will charge faster than almost any other part of a circuit and can be thus made switched on and off faster. Sometimes it's also possible to use different components which have larger value resistance compared to normal resistors placed before or after the regulator itself.

Can buzzing bulbs be dangerous?

Yes, it can. If this sound has enough power and is at the right frequency, it can cause local electromagnetic interference or other problems with nearby equipment. Depending on the voltage and current involved in such a situation, there might be a higher chance to get an electric shock as well.

Short or loose wires can cause buzzing in LEDs. Sometimes LED is just too sensitive for its own good. If you have your circuit set up in such a way that power supply wires are placed very close to the LED legs, it may generate noise that can be heard in form of buzzing, crackling, or other strange sounds. This may not happen with every type of wire so there's no 100% sure-fire solution here but keeping your cables well apart from each other should do the trick most often.

Can digital watches cause LED buzz? It is possible if a proper voltage source is used and something goes wrong with the circuit design, however, this would be more likely caused by a shorted or incorrectly connected capacitor than a problem with a watch itself.

In order to check this, you would need to open your watch and check what type of power source it uses (usually a battery, solar cell, or an electromagnet). If you have access to this power source it is possible to use a multimeter to see if there's any voltage coming from it. Alternately, you could just try using different power sources with the same circuit design in order to identify which one works for sure.

So, how can you solve it?

Humming and buzzing can result in various problems, so it's important to try and see what the main cause is. A shorted capacitor or an incorrectly connected one can be fixed by simply re-soldering your circuit components.

Buzzing LEDs is usually not a problem with the LED itself but with current passing through it. Many times this can be fixed by adding larger capacitor(s) on power lines just before the voltage regulator in question or by placing some inductors (optional) between the regulator and LEDs themselves. If that doesn't fix the issue you might have bigger problems than just buzzing LEDs; faulty components, reverse polarity connections... etc.

If you believe there's something wrong with your circuit design, sure you document all connections properly and use common sense, but if you can't seem to figure out what's wrong it may be time for you to check some other circuits and designs on the internet. It is always better to learn from somebody else's mistakes than your own and there are many different ways and ideas which might prove useful for your problem at hand.

Do other bulbs hum?

It depends on the circuit design of a given bulb. It would be best to consult with some schematic for this if you have one available.

How can I test my LEDs?

There are various ways to do that, some more involved than others. You could use a multimeter to wire it into a breadboard or simply turn on your LED and slowly increase brightness wirelessly from another device while monitoring voltage levels on power supply lines in order to see if anything changes when you do so.

If there's no significant change in voltage levels over time then most likely nothing is wrong with the circuit itself and all you've got to deal with is either faulty components or shielding problems which can usually be fixed by adding capacitors (optional) or changing positions of your LED.

Can LEDs damage hearing?

The threshold for human hearing is around 20 kHz, but some sensitive devices can pick up sounds in the range of 80 kHz or higher. If laying your hand on a circuit doesn't decrease noise levels significantly, there's no need to worry about it causing any permanent problems with your ears... assuming you do not use excessive force while working with it and follow all safety guidelines, that is.

If you are worried about it then stick to using common sense when soldering LEDs or other electronics components - don't solder wildly while the circuit is turned on, avoid creating short circuits, etc.

Buzzing and humming can be artifacts of some bad design decisions, however, if you get the same kind of noise from other electronic devices then this time it's best to just leave it alone and not mess with it. If that were not the case then most likely there would be serious safety concerns and negative effects on performance for sure.

How do I shield my circuit and LEDs against RF and EM interference?

It is possible by adding metal sheets or even simple aluminum foil around your circuit - these can be adjusted in order to shield your LED(s) only while blocking out any potential forms of interference which could damage or destroy them in the process. You should also try using insulated materials instead of simply soldering directly onto copper tape whenever possible, however, this will usually mean more work and less efficient design.

Moreover, keep in mind that shielding some circuits might be extremely dangerous and can even block signals from life-saving devices such as walkie-talkies! If you are not sure about your design then it is best to consult with somebody else and verify everything first before implementing it and testing it on the field.

How can you check the wiring?

That depends on the circuit and schematic you use. If you have a logic analyzer then it should be fairly simple to check if your wiring matches the requirements of the schematic - you just need to compare them and see whether there's any discrepancy between given pin numbers, voltage levels, and such which could mean that some lines are connected with each other or not properly isolated from outer interference like stray capacitors, etc.

On the other hand, if it is only an LED then you can safely assume that all connections are done properly - what matters in most cases is the voltage level (it should match about ~3 V), polarity (if using LEDs), and a correct number of pins used for this purpose.

Please note: A lot of these problems arise from the incorrect use of Arduino boards, which is a common mistake by beginners - they simply connect RGB LEDs to PWM pins or even analog inputs instead of using dedicated digital outputs that drive several LED cathodes at the same time.

These kinds of mistakes lead to all kinds of problems with multiple consequences and one can even end up frying their Arduino board if they're not careful enough during such experiments.

Bottom line

If your circuit is faulty then you can either fix it or replace certain parts of it. If LEDs are making strange sounds for no apparent reason, most likely there's nothing wrong with them - this could be caused by some interference outside of the device you are working on which may interfere with its wiring. Either way, make sure to double-check everything before testing it on the field!