MAKE AN RGB CONTROL KNOB.
This is a knob based colour changing controller that uses a custom programmed microcontroller to pack a lot of features into a small affordable kit. The module can drive up to 5A per colour at up to 30V to drive surprisingly large arrays of LEDs. This version of the RGB controller uses a knob to scan back and forth through a spectrum of strong colours for mood lighting. If you can't decide what colour you want, then just press the knob in for two seconds and when you release it the unit will start fading between random colours itself. To keep things sensible the unit uses a pallete of 1536 colours. Rotating the knob sweeps smoothly from red to orange to yellow to green to cyan to blue to violet and back to red. This makes it perfect for use as a mood light controller.
As a kit it's very easy to build due to the small number of components, clear markings and large chunky pads and tracks. I've deliberately chosen good quality components for this module including professional quality rising clamp terminals, beefy MOSFETs with a low on-state resistance and the chip is supplied in a good quality gold-contact turned pin socket. Fixing hardware for mounting it in your chosen application is also included.
Using the unit is simple. To turn the lights on you push the knob once and they fade gently up. You then turn the knob in either direction to scan through the rainbow. The knob response is ballistic, if you turn it slowly you can step one increment at a time, while if you turn it faster it moves through the colours in progressively larger steps. The knob can keep be rotated at up to 60 RPM.
To activate auto mode just press the knob in for two seconds while the unit is in manual mode and release it again. The unit will then use its integrated 8 million bit randomiser to select colours and gently fade between them, pausing on each one. To turn the lights off just push the button and they will fade out. To go from auto to manual mode just click the knob in to turn the unit off, then again to turn it on again.
When it is powered up, the controller remembers the last setting from when it was powered down. If the lights were off they will stay off, if it was in random mode it will start fading between random colours and if it was on a selected colour it will light up in the last stored colour. The knob selected colour can be stored by pressing the knob to turn the lights off and then on again.
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Here's a picture of the complete assembled module ready to go. As you can see it's a fairly straightforward design and you should be able to assemble it quite quickly. Here's a complete step by step assembly guide.
The circuit board is designed to seperate into two parts to let you mount the knob remotely. It's entirely up to you if you want to do that. I've allowed generous pads for the use of a connector or directly soldered wires if you do split the PCB. In most instances I guess the circuit board will be built as a single unit, but it can be carefully cut into the two parts afterwards if desired.
The first things to install are the links. These are important. Without them the red and green channels won't work!
They're simply offcuts of wire soldered in to form a small bridge.
Then we solder in the diode. This is a general purpose 1A type because it's easy to source and is robust and easy to work with. It's a polarity sensitive component and must be installed the right way round. The PCB position is marked 1A and has a line at one side to show which side the little silver band should be mounted.
Now we solder in the resistors, which are actually arrays of resistors in SIL (Single In Line) form. Each of these little black packages contains four resistors. Normally it's important to put these in the correct way round, and there's a dot on the package to mark pin one. However, in this instance I've designed the PCB so you can put them in any way round. Much easier!
The smaller type both contain four 10,000 ohm resistors and are used to pull floating inputs and outputs to a known state. There are integrated pull up resistors in the controller chip, but I chose to add lower value external ones.
The bigger type both contain four independent 1,000 ohm resistors and are used to protect the chips inputs and outputs, and also limit current through the power indicator LED
Take care soldering these components in, as their pads are very close together and it's possible to bridge them with misplaced solder.
Now we solder in the two little 100nF (0.1uF) capacitors. These are decoupling capacitors and go into the positions marked "D". Their job is to filter any glitches on the processors power supply.
These components are not polarity sensitive and can be soldered in any way round.
Next is the power indicator LED. This indicates when the circuitry has power and will only work if it's installed the correct way round. The longest lead is the anode and goes to the hole nearest the "+" symbols.
If you chop off the leads and then forget which pin is which, then there is a small flat on the body of the LED next to the negative lead. This corresponds to the flat side of the PCB symbol.
Now we fit the little three pin voltage regulator (78L05) which goes into the position marked 5V as shown.
Its job is to give the controller a nice steady regulated 5V supply.
You have a choice in mounting the electrolytic capacitor. You can either leave it standing up on the PCB or lay it down flat. As you can see, I chose the latter. Make sure that the longer lead goes to the side marked with plus symbols. The negative stripe printed on one side should face away from the diode as shown. If you fit that component in the wrong way round it might go POP!
The MOSFETs will need their outer leads bent slightly to make them fit in the PCB holes. This was done to allow much bigger pads and tracks to be used.
Now the three MOSFETs get soldered into position.
The six way terminal block gets fitted with the wire ports facing away from the MOSFETs. This is an extremely good quality rising clamp terminal block. It's rated for professional use.
If you've every used cheaper versions you'll appreciate it.
I deliberately designed the PCB with the main current carrying track to the MOSFETs kept clear of solder resist. This means you can flow solder along it to make it beefier if desired. Note the gold plating on the exposed copper. It takes solder well.
Be extra careful in mounting and soldering the rotary encoder. This is a fairly high resolution gray code unit and has a lot of small contacts inside it. Once you've carefully jiggled the large support pins and the five small connector pins into the PCB, solder the big support pads first, then carefully solder the five other pins without lingering on them with the soldering iron for too long.
Now the controller chip gets fitted. This is a custom programmed microcontroller that decodes the knobs output and pulse width modulates the RGB outputs. It is supplied pre-fited into a socket. You can either solder it in while still in the socket, or take it out the socket and re-insert it once the socket has been soldered.
Observe the correct positioning. The end of the chip with a notch is marked on the PCB.
Finish the controller by adding the knob to the encoder and the four support feet. There are six holes for the support feet to allow for whether the knob is on board or mounted remotely.
To mount the knob on the shaft it is necessary to pop the lid off the top of the knob (it can be pushed through from the other side) and make sure the internal nut is loosened to allow the collet to slide over the encoder shaft. Don't push it onto the shaft so far that it stops the knob being pressed in, since the encoder contains a push activated switch too. To lock the knob onto the shaft, tighten the nut then replace the lid. The shaft diameter is standard, so you can choose to use other styles of knob too.
The knob itself has six components! Apart from the grey plastic knob and lid there are four metal components as follows.
From left... The bush has an indent that aligns it in the base of the knob. It's tapered hole should face out. The collet then sits through that bush so that as it's pulled in the taper pushes it's jaws shut to grip the encoder shaft. On the other side of the knob the collet is held in place and tightened with a washer and then nut. The plastic lid then hides the nut.
Here's a view of both sides of the knob as assembled.
The controller is connected to your power supply and LEDs as follows:-
"B" The output for the blue LEDs. Pulls down to 0V to illuminate the LEDs.
"G" The output for the green LEDs. Pulls down to 0V to illuminate the LEDs.
"R" The output for the red LEDs. Pulls down to 0V to illuminate the LEDs.
"-" The circuits negative (0V) supply.
"+" The circuits positive supply from 9-24VDC.
"+" Common +ve connection for the LEDs.
This controller is compatible with most common anode RGB LED arrays including the modules on this site.
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