Looking for feedback on brewing shield with touchscreen

Nope, I have only used his Gerber Viewer.
I used to order at Hackvana, but now order via a local company that manages outsourcing PCBs to China.
I already fixed some crooked lines, will do the annular rings after a meeting. I noticed that myself too and I fully agree.

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Allright, I think I am near a final version. I replaced and edited all footprints for a more reliable reflow process.
Diode is now PMEG3030 in a sot-128 package.
Added another set of mounting holes.

Analog input is 100nF again, because I predict 99% of customers won’t use it.

I don’t remember if I did anything else.

So, this should be a final version. Nitpick please :slight_smile:

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I used the jack plug from the shield shield, but the DC jack seems to have only tiny drills. I need to look into that.

@elco Nice work! This looks great, what about protecting your input with a MOSFET reverse polarity circuit?

@mtnscott, I have used it on other boards, but didn’t think of it this time.

The diode gives a 350 mV voltage drop, but a MOSFET could do better.
I don’t think the 350mV drop will be a problem, because the things behind it on 12V will be PC fans or motorized ball valves. They will work fine at 11.7V. For evertyhing on this board, the voltage will be dropped anyway by the LDO.

The boards behind it will have optional external power I think. I think I can only use a diode in that case: get power from the bus, unless your external power is higher. 2 diodes? Or can you think of a nicer solution?

If I am not mistaken, the MOSET circuit does not protect the power supply when the load is powered from elsewhere. This could happen, because I bring 12V out on the RJ12 connectors. This could be a benefit of the diode.

When you get this board, or even before if you have parts, stuff J1, D4 and F1… then short VIN to GND and see what happens :slight_smile: Good test to see if your FUSE and reverse polarity diode are correctly designed. Ideally you’d want to repeat this test at the two extreme temperature ranges that this product will be rated for. Also, try loading VIN to MAX current that all of the devices should typically pull, and make sure D1 and/or F4 do not overheat.

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Will do that @BDub!

Files are ready for production, I will sent them to Eurocircuits tomorrow so will have boards in 7 working days.
Their PCB Visualizer is totally awesome. It will check your PCB for errors and visualize it. I highly recommend it for a final check on any PCB.
So here is the final version in PCB Visualizer:

And here are 2 of the first expansion boards.

An OneWire to SSR board, which can be screwed to an SSR.

A OneWire valve controller, with a DS2408 onewire addressable switch (8bit) and an SN754410 H-bridge.
I will use 5 wire valves, that have 2 wires to drive the motor and 3 wires for feedback. They have 2 switches that are closed when fully open or fully closed.

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@Elco, I bought a spark core for a brewing project exactly like what you are proposing. I just started doing the work on the onewire DS18B20 temperature sensors. It was inspired by brewpi. My regular life has interfered and the project has floundered.

I would be interested in being an early adopter. My 10g brew rig is all manual valve but ready for retrofit. Please let me know how I can get involved…

-Sean

this is awesome @Elco !
are you looking for any beta testers? happy to pay for my unit! i am a home brewer, and very good at breaking stuff :smile:

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Update: I got the PCBs, waiting for the last parts that will hopefully arrive tomorrow.

I misjudged the space needed below the display. The bottom entry headers do not work well with the standard length headers on the display and the increased space between display and PCB.
I used the bottom entry headers so all components were on the same side of the PCB, which is cheaper to assemble, but unless I can get the display with longer headers, it won’t work.

These 10 PCB’s can still be used for prototyping, but I need to figure out a new solution for the next prototype.

If anyone can suggest another display with touch screen that is easy to interface with SPI, or a controller chip on the PCB, please respond!

A flat cable connector on the board would be good option as well.

It would also help a lot if I could figure out who makes this display. In that case, I could just order it with longer headers.

I’ve been using that display for a while because it’s the largest SPI I could find. If it helps, I’ve measured the board to board spacing for a couple header sockets. One was 11.1mm (part M20-7821446) and the other was 10.0mm (929984-01-14-RK).

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If you can get the board without any headers, Samtec do various length ones and you can order them online from the website. They have a part number generator and 3D models so you can check they fit.

I know, I have used Samtec headers regularly. Finding the display without headers is the problem.
I can only find this display through re-sellers, who just pick them up at the Shenzhen market I suspect.

What about the matching sockets from Samtec? That would extend it and allow you to dismantle is needed.

Just regular headers are already very long. Male + female = 10.83mm. I can combine this with a board to board spacer of 11.1mm to hold the display firmly in place. The only issue with that is the waste of space.

See the photo below:

With a 6.4mm spacer, the distance looks much nicer, but the display headers do not enter the through board header (from Samtec). Notice that the socket is mounted on top of the board to reduce the space below the board.

To reduce the space I have to either use:

  • Longer pins on the display, through board socket op the top, like photo above.
  • Shorter pins on the display, low profile socket on the bottom.
  • Another option might be a through board header from wurth on the bottom:

This allows the display pins to go through the board a tiny bit, for a total board to board distance of 7.1mm

I almost have 10 boards ready. I don't want to solder many more 0603 resistors by hand :wink:
I would like to make these prototypes available to developers that can write code for it.
Sorry @avidan, I am looking for people that can make stuff, not break stuff now. It is to early for breaking stuff as a lot fo the software still has to be ported.

@BDub, PM me if you want a board.
Others that think they can help significantly with writing the software (LCD/touch screen, OneWire, RS485), send me a PM as well. I will look at your forum activity and code contributions, because my supply is limited.


BTW, already found one design flaw: I need pull down resistors on the 125D inputs. When the pins are set to input on the spark, just looking at the board can enable the buzzer (floating pins). The spark will set them to output of course, but pull down resistors for when the bootloader is active is wise.

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@peekay123
I tried the IL9341 straight from the spark Web IDE.
Worked like a charm! Only had to change the arguments in the constructor to

Adafruit_ILI9341 tft = Adafruit_ILI9341(D4, D5, 0);

I set the reset pin to 0, as it is connected to the spark reset pin. The pin is not used in the library, so it doesn’t matter anyway.

I will send a board and LCD your way tomorrow.

I can probably get the LCD’s without pins. So I can use

and

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Small update:
Got SWD debugging working, see my other thread. Display is working fine. Still have to test the touch screen functionality.

The 5V linear regulator works, but it generates quite a bit of heat.
The board + spark + display draws 250mA. So the LDO has to dissipate (12V-5V)*250mA = 1.75W
This might become problematic when the board is put into an enclosure.

I might have to reconsider the choice to use an LDO and go for a switching power supply instead.

If you do go with a switcher, take care to minimize noise/ripple on the output rail.

If the switcher produces too much ripple (e.g. poor layout, high ESR caps, etc) you can push the on-core LDO into oscillation. Key symptoms of that problem are very high LDO power dissipation (aka, it gets very hot) and/or erratic behaviour of the core.

The core doesn’t need an elaborate or difficult switcher, but it pays to make sure it is at least decent.

@AndyW, I was thinking something along these lines:

http://webench.ti.com/webench5/power/webench5.cgi?VinMin=11.00&VinMax=13.00&O1V=5&O1I=0.8&base_pn=LM2675&AppType=None&op_TA=30&lang_chosen=en_US&optfactor=3

LM2675MX-5.0, with low ESR 47u or 68u output capacitor and 47uH or 68uH coil.
This chip gives a much higher efficiency than the LM2595 (90% vs 82%).

WeBench gives an 8mV output ripple at 260kHz.

Total BOM count is 7, so it is still pretty small. Only 4 more than the LDO.