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Hi,

Would anyone help me and point me in the right direction for the correct power supply for the below LED decoder.

I've got 10 X 5m RGB LED strips connected to it and a 12v power supply however it flash's when powered until the strips are dimmed via DMX to about 50%...

Please bare with me I'm new to this and doing it for a project (a project I wish I never said I would do now)

Thank you for any help in advance.

http://www.ebay.co.uk/itm/151824745044? ... EBIDX%3AIT

Danmcr,

I am going to try to help here, but up front I am no expert. I just started to dive into these things myself.

Power draw is dependent upon the number of LED's you are attempting to light. We know that each strip you have is a 5M strip (pretty common) but we need to know what density you purchased. The strips actually come in 30, 60, 120, and sometimes 240 LED's per strip. Each color on the LED will use 6.67 mA, meaning that each LED could use up to 20 mA per LED (Red, Green, Blue each using 6.67 mA, totaling 20 mA per LED on full brightness).

So, as an example, lets say you purchased a 5 meter strip, w/30 LED's per meter. Each meter will pull 600 mA (or 0.6 amp per meter) x 5 (total number of meters) = 3 amps per strip.

A 60 LED per meter strip would use 6 amps for a 5 meter run. (1.2 amps per meter) as a further example.

Now, the next question is your power supply. Usually rated in wattage. Presuming you are feeding 12v into the line. You would multiply the voltage (12) x amps (first example of 3 amps) for a total of 36 watts needed, per strip. In theory, you would need 360 watt power supply (minimum) to run the 10 strips. See next note.

NOTE: It is usually stated that you do not want to go over 80% of a rated power supply, as it will start running hot and cause issues. for a circuit that needs 360 watts of power, you would want a 450 watt power supply.

NOTE 2: One other thing. While all of my above calculations are based upon 20 mA per LED, it seems that many of the strips I see on Amazon (by far the cheapest) rate the amperage slightly less than that. a 60 LED/meter strip is coming out to 1 amp per meter (rather than the 1.2 amp/per meter). If this hold true, you can reduce the wattage a bit.

Adafruit (an electronic project website) talks about the amperage calculations. It gets a little confusing as they talk about segments, rather than each LED. They have three LED's per segment (each segment can be cut as an independent run):
https://learn.adafruit.com/rgb-led-strips/current-draw

There are a lot of sites that talk to this as well.

Good luck...

Just to point out the spec sheet shows a maximum of 2amps per channel (for safe reliable operation you ideally want to be lower than that. Those calculations above show a draw of 3 amps which if it held anywhere near true would certainly explain your problems, and also potentially lead to the decoder overheating.

You need to also link the specs for the LED strips themselves, or confirm that each 5m strip consumes less than 2 amps.

Spudd11 makes a point.

I thought about mentioning that, but then as I dug deeper into this DMX decoder, it actually says each "channel" is good for up to 2 amps. Each color is one channel, so, in theory, each strip would be good for up to 6 amps (2 amps for red "channel", 2 amps for blue "channel", and 2 amps for the green "channel").

That said, your strip would need to consume no more than 6 amps for a 5 meter strip.

Of course, it's hard to say how valid the manufacturer information (or poster's information) is. a 60 amp capable DMX decoder would be something pretty serious, IMO. I usually see no more than 30 amps when looking through Amazon for a decoder.

If the amperage became the limitation issue here, you would need to "double feed" (I think it is called) additional power on the distant end of the strip as well, but you would need to investigate further the way to do that. I've seen it discussed, but not tried myself.

Actually it's worse than that. lower than 2 amps per channel.... 360W max total across all 30 at 12v would translate to 12W (1 amp) per channel.

So like danmcr mentioned you might need a split power supply (if your led strips have their own power input line), but it all comes down to seeing a link to your led strips and their requirements before we can say anything concrete or helpful.

Hi guys,

Thanks for the above replies, interesting read.

I'm still no closer to resolving the power issue and at the point where I'm tempted to ditch the decoder and move back to multiple 3 channel decoders to achieve what I'm looking for.

I purchased a power supply which the seller of the 30ch decoder pointed me to, it blew up once all connected!!!

Thanks for your time and replies it's been helpful.

Daniel

spud1511 wrote:Actually it's worse than that. lower than 2 amps per channel.... 360W max total across all 30 at 12v would translate to 12W (1 amp) per channel.

So like danmcr mentioned you might need a split power supply (if your led strips have their own power input line), but it all comes down to seeing a link to your led strips and their requirements before we can say anything concrete or helpful.

Going off your post i changed the power supply and I'm now up and running.

Thanks to everyone for your time and post.

Daniel