Feedback on PCB design for kegerator


I’ve been working on this for a while and I need some feedback on this design. I’m a programmer by trade so I outsourced the PCB design.

The PCB drives an NFC chip which is used by an app to authorize your pour. It then opens a 24v solenoid and tracks the flow with a flowmeter. It also tracks the temperature inside the kegerator.

I have the temp sensor, flow meter, and solenoid attached to the RJ45.

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I hate to double post but I would really appreciate some feedback on this design… Any EEs here?

Hi @jlkalberer

There are a lot of EEs here! You posted a lot of material and folks are busy, but I took a quick look.

  • A general comment: your design does not have a lot of EMI protection so you might consider adding some components that you can stuff or not, depending on how the cabling works to the RJ-45. At least a cap to ground and a series inductor per input. You can stuff the inductor position with a zero ohm resistor of the same size if you don’t need it. On the output side, consider how you might add a snubber network to the solenoid drive with a cap and resistor to ground.

  • Your flow sensor appears to be +5V device with open-collector output. You could avoid all the level shifting stuff by just using a 5V tolerant input. You might still want some extra input protection like back-to-back 5.6V zeners or similar, again depending on the cabling and input protection for EMI.

  • For your MOSFET to drive the solenoid with the level shifter, you could just use a 2.5V Vgs MOSFET and avoid all the level shifting.

  • You have a mixture of 1% and 5% resistors spec’ed. Sometimes I see a voltage divider where you might want 1% but in the level shifters (if you use them) that is not needed unless you are planning to buy fewer unique component types.

Good luck with your project!


@jlkalberer, to add to @bko’s excellent comments, you could increase the resistor values to the RGB LED unless you need them to be very bright. You chose a 7805 to regulate Vdc to 5V but with a maximum of 24V input, the regulator could get very hot depending on the flow sensor current draw. I assume you considered this. Finally, I wonder if an opto-isolator would be better for the interface to the MOSFET driving the solenoid? :smile:


I would spend some time looking at the whole supply voltage scheme. The solenoid fly-back can be a problem on the 7805. There are other methods to dampen the fly-back. Adding to the other comments the MOSFET drive looks a little to complicated for a simple solenoid drive.

The floe sensor - A opto-isolater can be real simple to implement and it will provide isolation. All you have to do is have the flow sensor control the LED in the opto…

Happy Brewing - Got a Winter Ale and Pumpkin Stout fermenting…


Thanks for all the feedback. You guys are awesome.

any chance you want to make a few copies of the board? id be happy to buy one from you…im thinking about setting this up for a kegerator authorization system for a coffee/beer lounge i want to set up

Sure man. I’m prototyping soon and will be doing a kickstarter at some point. I have a few startups in shared spaces who will be beta testing for me (people are stealing their beer) so I planned on making a few extras.

The PCB has been manufactured and we are about to start testing. I’ll post a new thread once I have the board and have printed out an enclosure. Here are some pics :slight_smile:

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Wow, that looks awesome! love the tag connect for programming… i just put one on the latest version of my custom board. the cables are very good quality and so easy to use.