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Thread: Bluetooth Pressure Gauge for the Sage/Breville Barista Express.

  1. #1
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    Post Bluetooth Pressure Gauge for the Sage/Breville Barista Express.

    Gene Cafe Coffee Roaster $850 - Free Beans Free Freight
    Hello Everyone!

    I was thinking about replacing the pressure gauge on the Barista Express with a Bluetooth Pressure Transducer and writing an iPhone App for it.

    Does anybody know the connection type for the pressure gauge (NPT/BSP etc.) ?
    What is the numeric range equivalent for the original gauge output ?


    Thanx in Advance!

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    150psi would just cover it. 175psi would be better.
    You will probably want to T into a pressure pipe somewhere, so thread doesnt really matter as you will be welding fittings to suit your application

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    The gauge in the 6910 looks about 1/8

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    I was thinking 200psi (20 bar) for the transducer, there are several alternatives out there like the M5600 from TE Connectivity.
    With that device it would be plug and play, just need to write the software, as long as the connector fits.

    My initial thought was to "replace" the pressure gauge with the transducer.
    That is "digitise" the output from the analog pressure gauge.

    Doesn't the outlet for the front pressure gauge reflect the "brew pressure" ...
    and the water temperature close to what the temperature is at the group head?

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    M5600 comes in every thread imaginable. They also run off a button cell battery so no need for power. Downside is 5 sec sample rate. Maybe can change that?
    So it outputs to a app that graphs the result.

    $245 makes this a pretty big investment. Pretty cool too!!

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    I dont know your other answers.
    Pop the covers on your machine, and check it out yourself.
    I would think you are best to put the transducer not at the end of the little thin coil of tube, although that would reduce the temperature that it sees and allow mounting flexibility.

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    Quote Originally Posted by Jackster View Post
    M5600 comes in every thread imaginable. They also run off a button cell battery so no need for power. Downside is 5 sec sample rate. Maybe can change that?
    So it outputs to a app that graphs the result.

    $245 makes this a pretty big investment. Pretty cool too!!
    The sample rate can be adjusted down to 100 ms via software, however it will eat up the battery.
    The workaround is to implement pressure change detection (and phone proximity) and ramp up the sampling during extraction
    and than reset to standby when done.

    And the pressure change could also be used for starting and stoping a "shot timer".

    Here in Sweden it's more like 190 USD... the good thing is that it can easily be moved to any machine
    with a bit of "plumbing" and can even be used on a portafilter with an adapter...

    Actually waiting for some answers from a TE Connectivity Rep. cause according to the data sheet the operating temperature is max 85C
    and the compensated temperature range is only up to 60C, so depending on what the Total Error Band is at 100C it might not be suitable for this application.

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    Well use the coiled thin wire. That will reduce the temperature considerably.

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    Progress in the project... went the DIY route not the M5600.


    I will use a the following parts:


    - SiLabs BLE112 Bluetooth Module
    - Honeywell PX3 Series Pressure Sensor
    - TI LM35DT Temperature Sensor


    By using the BLE112 module and making a custom circuit board,
    costs are greatly reduced and the modular design makes it easy to
    use whatever sensors one have or can afford.
    Dimal likes this.

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    Under the hood in the Barista Express... (before the modification)

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    The pump over pressure valve in this machine only operates as a safety valve (opens at a set point to prevent pump or machine damage) rather than a traditional OPV (opens at a set point to regulate pressure within a set range).

    There is no benefit in knowing the pump pressure in this machine. You could install an OPV from a Breville Dual Boiler but this won't make a whole lot of difference to the in-cup taste. I've tried it before and it's not worth the effort for such little result.

    It's a cool project though and certainly could be of benefit in other machines in the future.

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    Quote Originally Posted by noidle22 View Post
    The pump over pressure valve in this machine only operates as a safety valve (opens at a set point to prevent pump or machine damage) rather than a traditional OPV (opens at a set point to regulate pressure within a set range).

    There is no benefit in knowing the pump pressure in this machine. You could install an OPV from a Breville Dual Boiler but this won't make a whole lot of difference to the in-cup taste. I've tried it before and it's not worth the effort for such little result.

    It's a cool project though and certainly could be of benefit in other machines in the future.
    Well, there is a pressure gauge on this machine, the outlet for this gauge sits on the top of the group head.
    Correct me if I'm wrong but my understanding is that by digitising that pressure one would get the actual "brew" pressure ?

    IMG_0353.jpg
    Last edited by xandmann; 16th March 2018 at 05:18 PM.

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    Yes, you get brew pressure on the gauge. But it is only regulated by the grinds. If its like the 6910 and 6900 i think it will just stall out at max pump pressure. There is a bypass thing on the output of the pump, but on inspection its a vacuum breaker, not a pressure relief.
    So a opv will regulate pressure at its setting, and then drop as the puck wets out.
    Without the opv, its only the resistance of the puck regulating the pressure. Even if you know the pressure, you cannot change it other than by the grind.

    You could set up pressure profiling though...use the pressure gauge to regulate the pump. Maybe pid the pump?

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    Done with the first revision of the PCB for the sensor module. Will send it to the fab. house next week.
    Pretty happy with the size 30 x 45 mm so it fits perfectly in a Hammond 1551 plastic enclosure.

    senSTAT_v1_0_Front.png
    senSTAT_v1_0_Back.png

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    Quote Originally Posted by Jackster View Post
    Yes, you get brew pressure on the gauge. But it is only regulated by the grinds. If its like the 6910 and 6900 i think it will just stall out at max pump pressure. There is a bypass thing on the output of the pump, but on inspection its a vacuum breaker, not a pressure relief.
    So a opv will regulate pressure at its setting, and then drop as the puck wets out.
    Without the opv, its only the resistance of the puck regulating the pressure. Even if you know the pressure, you cannot change it other than by the grind.

    You could set up pressure profiling though...use the pressure gauge to regulate the pump. Maybe pid the pump?
    Maybe, but for that I really need to take the machine apart to see what is possible to do.

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    If you don't mind a bit of manual tweaking, there are easier (and cheaper) ways to control brew pressure than via pump speed adjustment:
    https://www.instagram.com/p/BKInEJFB6WP/

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    A inline restrictor in the brew path doesnt sound like a good idea. You may as well have a double wall basket. Probably a double wall basket would be a better restriction
    Or is the restrictor going as a bleed screw and dumping off pressure where a opv would go?

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    UPDATE:

    The first batch of components have arrived for the project. Also got word from the FAB house that the PCB:s are manufactured and sent.
    Done with the firmware for the BLE112 module, and the first version of the iOS App for iPhone.

    Actually I will be testing several alternatives for temperature measurements. The module will have both analog and I2C inputs.

    LM35DT
    MLX90614
    TC74

    Below the "cheaper, no name" 1.5% FS accuracy Pressure Sensor, have also ordered a Honeywell PX3.

    Sensor.jpg
    Last edited by xandmann; 29th March 2018 at 05:05 PM.

  19. #19
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    Quote Originally Posted by Jackster View Post
    A inline restrictor in the brew path doesnt sound like a good idea. You may as well have a double wall basket. Probably a double wall basket would be a better restriction
    Or is the restrictor going as a bleed screw and dumping off pressure where a opv would go?
    It is upstream of the basket (in fact, in my case its on a bypass line around the pump). No coffee passes through it, not comparable to a double wall basket at all.

    Also, you can't "dump pressure" - you can divert flow though
    Dimal likes this.

  20. #20
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    Ok. Bypasses around pump. Its a poor replacement for a opv. Imo.
    If your grinds determine a 12 bar extraction and your valve is adjusted to 'dumping pressure' to 10bar, then you are dumping 20%. Midway through the extraction, when the pump could be delivering 10bar, you are still bypassing 20%, so delivering only 8bar to the puck.
    Even in the link if you check the pics the poster was unhappy with the arrangement and was trying to mechanise the tap operation. It looks like he gave up on that as well and was going to try something else.

    Maybe the bypass in conjunction with a solenoid to shut the bypass when pressure drops. But a opv isnt that expensive or hard to set up.

    Sorry to divege from the op topic.
    Looking forward to seeing this work out as a cool project

  21. #21
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    Quote Originally Posted by Jackster View Post
    Ok. Bypasses around pump. Its a poor replacement for a opv. Imo.
    If your grinds determine a 12 bar extraction and your valve is adjusted to 'dumping pressure' to 10bar, then you are dumping 20%. Midway through the extraction, when the pump could be delivering 10bar, you are still bypassing 20%, so delivering only 8bar to the puck.
    Even in the link if you check the pics the poster was unhappy with the arrangement and was trying to mechanise the tap operation. It looks like he gave up on that as well and was going to try something else.

    Maybe the bypass in conjunction with a solenoid to shut the bypass when pressure drops. But a opv isnt that expensive or hard to set up.

    Sorry to divege from the op topic.
    Looking forward to seeing this work out as a cool project
    I assure you, the poster is still using the setup. Whilst not perfect, it's far superior to an OPV, which is a poor replacement for a control valve (and is still fitted to the machine BTW).

    You can't adjust the flowrate mid-shot with an OPV...

  22. #22
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    That is true mr.Jack.

    The guy is obviously a brainiac. I looked through his post web page and instagram. Pity he has no article about the bleed valve on his bz99. Would love to learn more on this subject

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    UPDATE:

    Still waiting for my PCBs, seems they got stuck in Swedish customs. But the iPhone App is coming along nicely.

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    UPDATE:

    Just got delivery from the Fab. House and DigiKey.
    Will assemble the module this weekend, than "fine-tune" the firmware and we should be in business.

    The iOS App is ready, will be sent in to Apple for review the coming weekend.

    IMG_0540.jpg
    MrJack likes this.



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