During our months-long beta test, we encountered many users who didn’t qualify for the beta and yet would like to have the capabilities afforded by the Storm PWM Controller. These users didn’t qualify because they ran systems that required 0-10V PWM signals, often using Meanwell “P” series drivers such as the ELN-60-48P or the ELN-60-24P. The Storm controller supports 0-5V PWM but not 0-10V PWM. We decided to pursue development of a version of the Storm that could accommodate the 0-10V requirements of some LED drivers.
Adding 10V PWM support involves adding quite a bit of circuitry. The original Storm boards share 5V operation between all of the computational circuitry and the PWM circuitry, and adding 10V would mean that we need to translate the signal level from 5V to 10V. This is usually done via a transistor, which is pretty straightforward in itself, but it also means that we need to support a stable 10V supply on board to supply the transistor. So in order to add 10V PWM support we need to supply a 10V regulation circuit as well as transistors for each of the six PWM channels. That’s what we’ve done.
We’re currently waiting for the PCBs to be manufactured, after which we’ll do some testing to make sure everything is up to snuff. Will update everyone once we’ve verified that the board is working as designed. Contact Us if you’re interested in the Storm 10V.
We’ve received the prototype PCBs and soldered up a Storm 10V for testing purposes. As you can see, at its core it is still a Storm LED Controller, but its outputs are boosted up to 10V PWM levels. The boost chip we are using is the ULN2003A Darlington Transistor Array, which is designed to handle enough power/current to drive small stepper motors. What we discovered is that the voltage drop across the ULN2003A is a little higher than we want. What it means is that instead of outputting a solid 10V signal, the signal is reduced by the voltage drop which can be up to 1.6V!
The 1.6V figure is from the ULN2003A Datasheet at a max current of 350mA which is far higher than you’d need to drive PWM drivers (you could run motors at that current). More realistically we’d expect to see a voltage drop up to 0.5V, which would result in a PWM amplitude of 9.5V. This should be good enough to run any PWM driver that requires 10V PWM signals, as the threshold voltage for the driver is usually set back from the actual stated voltage.
Because of the voltage drop problems associated with Darlington Transistor Arrays, we decided to go another route – the add-on board. On this add-on board we’ll use discrete NPN transistors that have a much lower saturation voltage. The NPN transistor we are using is the KST2222A from Fairchild Semiconductor, and the saturation voltage behavior as given in the datasheet are below.
As you can see from the figure, the Vce voltage drop that we are concerned about is about 0.05V for low-current applications. This will allow us to get extremely close to the 10V PWM signal that we seek. With that we’ve designed the PWM add-on board as well as a 0-10V analog add-on board. The analog portion follows easily from the PWM design by simply adding a resistor-capacitor low pass circuit that converts the digital signal to analog.
These two boards will be able to plug directly in to the outputs of the CORALUX Storm Controller and convert the outputs to either 10V PWM or 10V Analog. We are now waiting for the PCBs to come in for verification. Stay tuned.