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During my RGB led fan project I accidently bought common ground rgb leds while my circuit was disigned for controlling common anode rgb leds.
Now that I have run out of common anode RGB leds I tried to come up with a solution to somehow connect common ground to common anode.
After a few tests I came up with the circuit below. Using 3 pnp transistors it inverts the R-, G- and B- to R+, G+ and B+.
In order to create ground for the led's I connected 3 rectifier diodes to R-, G- and B-.
I am very happy with the results of this circuit and the fact that I don't need an additional wire for ground to drive the common ground leds.
I added the eagle files including the circuit and board. (NOTE: on the board I used BEC PNP transistors)
Now that I have run out of common anode RGB leds I tried to come up with a solution to somehow connect common ground to common anode.
After a few tests I came up with the circuit below. Using 3 pnp transistors it inverts the R-, G- and B- to R+, G+ and B+.
In order to create ground for the led's I connected 3 rectifier diodes to R-, G- and B-.
I am very happy with the results of this circuit and the fact that I don't need an additional wire for ground to drive the common ground leds.
I added the eagle files including the circuit and board. (NOTE: on the board I used BEC PNP transistors)
http://www.ebay.co.uk/itm/12V-10A-MUSIC-SOUND-CONTROLLER-RGB-LED-STRIP-LIGHTS-/270899518388?pt=UK_HomeGarden_Lighting_Lamps_Lighting_SM&hash=item3f12de9bb4
I think the easier option to use controller as signal generator would be better for novice, i have had the controller open and its easy to remove the board once i know what im looking for to find the ground plain. thanks for your help.
i will do some more research. What components will i need just to build the signal generator and what would I connect to the ground plain (once ive found it).
The option of using the audiocontroller as signal generator is indeed easier but not necessery as your controller is high rated so it should be able to drive the load u want it to power.
I see that the controller has 2 groups meaning u need to make 2 converters with half of the rates I jusr calculated as each group will drive only 75 leds.
By signal generator I mean using the controller to drive power transistors that power the led strip in this way the current driven by the controller is many times smaller then your actual output current.
there are a total of 150 smd rgb leds (75 each 2.5m strip).
My local electronics store (maplins.co.uk) would have all the bits i'd imagaine, its just how they all go together and is the actual green board specific for the components or just a generic board.
As you can tell, ive never attempted anything like this before, soldering wires together has been my limit.
150 * 20 * 3 = 9000 mA = 9A minimum for rectifier diodes
Transistor you need to look for is something like this:
http://www.dz863.com/datasheet-815751563-BD436_Bipolar-Power-C77-Pnp-Transistor-4a-32v/
Rectifier diodes should be 10A + like this one:
http://parts.digikey.com/1/parts/1567259-rectifier-50v-10a-r-6-10a01-t.html
The pcb I used is a double layer prototype board but u can use any prototype board.
However u should check the soundcontroller maximum output cause 12v * 9A = 108 watt of power if your not sure it would be much better to go with other circuit that uses your controller only as signal generator and not as a driver.
This circuit is also easy te build.
my problem is i ordered an rgb led strip and a separate led sound controller.
while the sound controller has a positive + line and ground r g and b lines, it turns out the actual strip is ground on the + line and positive on the r g b lines.
wouold this circuit solve my issue ? thanks.
To calculate the amps, count the nummer of segments your strip has. Ussualy they are marked with a scissor icon. Each segment uses about 20ma for each color. This means the pnp rated mA should be higher then (number of segments * 20). the rectifier diodes should be rated higher then the total mA consumed by the strip so (number of segments * 20 * 3).
if u don't mind having a 5th wire u could also directly connect the ground of your strip to ground of sound controller but this means opening it up and finding the ground plane. When u start soldering be sure too keep the datasheet of the transistor nearby to make sure u use the right pins. Not doing so could harm the led strip, the controller and the circuit your are building.
if you don't now what parts u need or need help leave a comment and ill help you as much as I can.