A lamp or power supply often says AC or DC. It looks like a detail, but it decides whether your lamp lights up, flickers or does nothing at all. I'll explain it in plain language, with examples from the house, garden and car.
In short
- AC = alternating current. The current keeps changing direction. The wall socket gives 230V AC, 50 times per second (50 Hz).
- DC = direct current. The current always flows the same way, with a fixed plus and minus. Think of a battery, accumulator or LED power supply.
- LEDs themselves always run on DC. A 230V bulb therefore has a small converter (driver) built in. An LED strip gets its direct current from a separate power supply.
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AC and DC at a glance
AC · alternating current
Goes back and forth 50 times per second. Easy to convert to a different voltage, which is why the entire power grid runs on it.
DC · direct current
Always flows one way, with a fixed plus (+) and minus (−). This is what LEDs, batteries and electronics need.
| AC (alternating current) | DC (direct current) | |
|---|---|---|
| Meaning | Alternating current | Direct current |
| Direction | Keeps alternating (50 Hz in the Netherlands and Belgium) | Always the same way |
| Plus and minus | No, can be connected either way | Yes, wrong way round = the LED won't light |
| Symbol on the label | V~ or VAC | V⎓ (line with dotted line) or VDC |
| Where you find it | Wall socket (230V), old halogen transformers (12V AC) | Battery (car, camper, boat), batteries, USB, LED power supply |
| With LED lighting | E27, E14, GU10: run on 230V AC thanks to a built-in driver | LED strips, G4 capsule bulbs, car bulbs: 12V or 24V DC |
How to recognize it on the label
Look at the small symbol after the voltage. It tells you more than the rest of the sticker.
What does this mean for your LED lighting?
🏠 Regular bulbs at home
You connect E27, E14 and GU10 bulbs directly to 230V AC. The driver in the bulb turns it into direct current itself. You don't need to buy anything extra.
View LED bulbs ›✨ LED strips
An LED strip runs on 12V or 24V DC. So you always need an LED power supply that converts 230V AC to the right direct voltage.
View LED power supplies ›💡 G4 capsule bulbs and old halogen
Many old halogen transformers give 12V AC. An LED bulb on 12V DC may flicker or not light up on it. Then replace the transformer with an LED power supply.
View G4 bulbs ›🚘 Car, camper and boat
The battery supplies 12V (or 24V) DC. Car bulbs are made for it. Does a plug-in bulb (such as T10) not light after you install it? Turn it around: then plus and minus will be correct.
View car bulbs ›📩 Handy explanation, isn't it?
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Worked example: which power supply do I need?
- Voltage: choose a power supply with the same voltage as your strip (12V strip = 12V supply, 24V strip = 24V supply). A wrong voltage can destroy your strip.
- Power: add up the wattage of all the meters.
- Margin: take a power supply with at least 20% more power. Then it stays cool and lasts longer.
Handy to grab with it:
RGB LED strip 12V, 5 metres, pack of 10View ›
LED dimmer 12V/24V with rotary knobFor single-color strips, goes between power supply and stripView ›
All LED power supplies › · All LED strips › · Connection materials ›
Dimming? AC or DC matters there too
230V bulbs (AC)
You dim a dimmable E27 or GU10 bulb with an LED dimmer in the wall box. Note: the bulb itself must be ‘dimmable’.
View LED dimmers ›LED strips (DC)
You don't dim a strip with a regular wall dimmer. You place an LED dimmer (PWM) between the power supply and the strip.
View the strip dimmer ›Want to know more? Also read everything about dimmers and compatibility.
Goes with this article
G4 capsule bulb 12V DCReplacement for halogen, warm white 3000KView ›
GU10 LED bulb dimmable5W replaces 50W, warm white, simply on 230VView ›
T10 car bulb, 2 pieces12V DC, daylight white, CAN-BUSView ›
Driver for 12V recessed spotlightsFor up to 12 spots, 36 WView ›
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Frequently asked questions
Can I connect a 12V DC bulb to a 12V AC transformer?
Why does my LED flicker after replacing a halogen bulb?
What happens if I swap plus and minus?
Is 230V alternating current dangerous?
Why does the power grid run on AC and not on DC?
Can I plug an LED strip straight into the wall socket?
Kind regards,
Bas / LEDPLANET.NL