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Friday, May 4, 2012

CryoBUG Controller PCB Layout

I made a few more changes to the circuit design, so this now brings it up to Rev 1.2 (the design is now locked in). The changes mainly consist of adding another CD4013 Dual RS Flip-Flop IC chip and some discrete support circuitry to enable "Fault Identification" LEDs.

Rev 1.2 Schematic (page 1 of 2)  -- Click Image to Enlarge --

Rev 1.2 Schematic (page 2 of 2)  -- Click Image to Enlarge --

Page 2 of the schematic shows the additional latch circuits that retain the state of the last fault, and display which safety (via an LED indicator) caused the actual fault condition. Was it a high liquid line temperature fault, or an under/over pressure cutout? By knowing which condition caused the fault, it allows for a better response to correct the problem. Typically a high liquid line temperature would be caused by a clogged or blocked air cooled condenser, or perhaps a fan motor malfunction. A low pressure cutout would primarily be caused by a loss of charge due to a leak. And a high pressure cutout could be indicative of an excessive load condition.

I lumped the pressure faults together because quite frankly it was more easily accommodated with only one extra IC chip. And secondly, pressure faults will rarely be a problem. It is far more likely that an overheat condition may occur due to a neglected condenser cleaning.

These two fault LEDs will be mounted so as to be visible from the CryoBUG's control panel, along side the remote connector.

I was able to squeeze all of this circuitry on one 3.8"x2.5" MiniBoard (ExpressPCB's 3 for $51 deal). Although I'll probably opt to go with their MiniBoardPro which is a full production version having solder mask and silkscreen.

Here is the completed PCB design, although I still need to double check that I got everything connected, and that all the components will fit properly.

Rev 1.2 PCB Layout  -- Click Image to Enlarge --

When I'm ready to place my order, it's as simple as making a few selections in the program, give em my credit card info, and about 2 days later they're suppose to arrive at my doorstep. Pretty awesome!

BTW this controller can be set-up for either 115V or 230V operation just by changing the jumpers (W1-W3).


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