Thursday, February 4, 2010

The DDC: An Ongoing Saga

Some of you may have heard about Laing introducing a new motor control PCB for their line of DDC pumps to allow for support of PWM impeller speed control and you may have also heard that these new boards cannot be modified in the same way as the original DDC-3.1/3.2 control boards could to toggle pumps between DDC-3.1 and DDC-3.2 spec.  Well, it's true.  I haven't had the opportunity to experiment with one of the new pumps yet to see if there's a workaround but, in the meantime, here are some thoughts of mine regarding the original DDC-3 control PCB pulled from a conversation on XS:

If you do feel like reverse engineering one of the pumps yourself, this may be of some use (it's a link to the datasheet for the microcontroller that Laing used in the standard DDC-3.1/3.2 pumps). ST Microelectronics model 7FLITE35F2M6

I do have a bit of concern over whether or not Laing would have moved the RPM ceiling value into the microcontroller's programming for the PWM version (e.g. a different programmed ceiling for each model, rather than a switch/solder pad to toggle between operating modes). I'd have to do some experimenting with one, I suppose... but it would probably make more sense from a cost control standpoint to keep the method of the toggle as simple as a bridged solder pad.

For anyone who's interested, here's a picture of the original DDC-3.1 PCB:

...and the datasheet for those Fairchild FET's can be found here (pretty sure it's right, closest match I could find).

We can make guesses and experiment by feeding the microcontroller different inputs, but it will always be a "black box" of sorts without the code they programmed it with. So, really, there's only so much reverse engineering that we can do (not to say that a toggle for the newer pumps couldn't be found).