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Thread: Kudos to Bryan!

  1. #51
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    Steve,
    Been watching this thread for awhile and like seeing digital controls implemented in a simple device for making expresso. I am sure that some of the manufactures out there are watching your progress and like what they see. I have a couple of tid-bits that might help. Your control circuits common and the stainless/cast aluminum components of the brewer must be bonded. This will reduce and or eliminate noise issue. You found out that using the battery your unit was stable and then when you change to switching power source it would get noisy. I would try bonding the DC common of power source to the metal plate in the brewer. This will bond all the commons to the same rail. If any of the switches and thermos switches in the brewer are currently bonded to the plate on one side of the switch terminal, this would cause an issue and then I would not bond power source common to metal plate. Another thing I will bring up is that most ssr`s will switch comfortably between 20hz and 60hz. Anything higher than 60hz is a no go and will cause oscillation and or just poor control. Thermal controller such as a Omega control always offer 2 types of interface on the back. One for relays and one for ssr`s. When using ssr`s the control loop must work slower to work within the spec of the ssr. Also if your bonding everything together, make sure the thermocouple is not grounded.

  2. #52
    TVWBB Guru Steve_M's Avatar
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    PID controlled espresso machines aren't new, it's just adds more cost to the cut throat consumer market. All of the commercial machines are PID controlled already. There's also off the shelf kits available, like these ones from Auber. I went the full DIY route because it gave me a practical project to work on and I enjoy learning new things.

    The SSRs I'm using are AC load specific, and only switch at the zero crossing of the AC sine wave. At 60hz you get 120 half cycles per second, meaning you can safely cycle things up to 120Hz.

  3. #53
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    Quote Originally Posted by Steve_M View Post
    PID controlled espresso machines aren't new, it's just adds more cost to the cut throat consumer market. All of the commercial machines are PID controlled already. There's also off the shelf kits available, like these ones from Auber. I went the full DIY route because it gave me a practical project to work on and I enjoy learning new things.

    The SSRs I'm using are AC load specific, and only switch at the zero crossing of the AC sine wave. At 60hz you get 120 half cycles per second, meaning you can safely cycle things up to 120Hz.
    Yep no shortages with pids in the espresso world. Pid, infusion, etc.

    Not to mention it really doesn't even matter on most consumer machines . they don't have a large enough boiler or enough Mass on the boiler or group head to give you temperature stability that's needed. you can try to improve these defects with a PID but it's still going to leave you wanting a much better pro-sumer machine. So it's pretty much pointless except on a few machines that are high quality.

  4. #54
    TVWBB Guru Steve_M's Avatar
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    The brass grouphead on the Gaggia Classic is a good hefty chunk of brass. It takes about 8 or 9 minutes for temps to stabilize after turning it on. I use the web interface on the PID controller to verify if the unit is ready. If I see PID output hovering around 5% then I know that it's simply maintaining the setpoint. I've also added code to turn the boiler off after 3 hours as well as the ability to tell it do switch back on or off as needed. This lets me start things up remotely and by the time I arrive home, I can grind some beans and pull a shot without having to wait!

  5. #55
    TVWBB Guru Steve_M's Avatar
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    Still no "proper" PCB, but I'm one step closer to getting the controller mounted inside of the machine. Found these Hi-Link AC to DC PCB mount transformers and they're working out well.

    I've ditched the OLED display for now since I was never really looking at it. It's easy enough to add back into the mix by adding 4 pins to the board.

    I really need to figure out how to make a proper PCB for this now that I've got the final design sorted out.

    Last edited by Steve_M; 01-27-2019 at 03:28 PM.

  6. #56
    TVWBB Guru Steve_M's Avatar
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    Used EasyEDA for this. It's a work in progress, but pretty happy with the results so far!

    Last edited by Steve_M; 01-31-2019 at 08:36 PM.

  7. #57
    TVWBB Honor Circle Bryan Mayland's Avatar
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    Nice! Never head of EasyEDA before, that's a neat browser-based PCB design system. When you joined this forum 5 years ago did you think you'd be designing circuit boards? :-D
    I'm that HeaterMeter guy what ruins everybody's free time.

  8. #58
    TVWBB Guru Steve_M's Avatar
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    Nope, I sure didn't. The HeaterMeter really opened my eyes to microcontrollers and circuit designs. I've always been a pretty technical person, using linux since '95 and always being in a systems / ops role dealing with servers and data centres and jumped on the RasPi bandwagon pretty much on day 1.

    The HeaterMeter allowed me to break things down to bite sized pieces that made more sense to me. Seeing how all the stages worked 12v > 5v > 3v > microcontroller and then how the input and outputs to/from the microcontroller worked was what I needed. Kinda like breaking it down into lego blocks that you can stick together.

    Coming back to the title of this thread, kudos to you for making a cool product that allowed me to learn something new!

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