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Old 03-21-2013, 04:45 AM   #31
theknub
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Feb 2013
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doug, have to say this project seems awesome. i'd be all in if i was looking to go this route. good job and keep it up.
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Old 03-25-2013, 04:14 PM   #32
DougEdey
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Dec 2011
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So one of my friends invested in my control box as a gift for my work:



Whilst the core brewstand is headless, he's given me a Touchscreen (10") and a NEMA box to work with. The cables are hardwired for now (I can't justify the $200++ on the fittings at this point, and the pi is inside and working.

Unfortunately the SSRs he gave me were duds, so I got my old ones back from him and I'm going to be running a cleaning cycle tonight to test everything works.

When I have the inside tidied up (it's a mess at the moment), I'll post some more pictures.

But the next update will provide a UI to manage the config file for first time configuration.

 
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Old 03-25-2013, 10:16 PM   #33
DougEdey
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Dec 2011
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So if you're using this PLEASE UPDATE THE ANDROID APP AND SERVER! I found that updating the PID didn't work at all, so I fixed it today.

Also, I worked some more on my control panel.





I got new SSRs and found one is broken (always on, so I can still use it since the other one still kills the circuit). I'm also waiting for new voltage regulators because the screen power is meant to be centre negative, but it's actual centre positive (not sure if this is a manufacturing fault or a documentation fault), so I blew the Voltage regulator on the HDMI->LVDS board.

 
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Old 04-02-2013, 12:11 PM   #34
yowbrew
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Mar 2011
Ottawa, ON
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Anyone have thoughts on how this could be modified to drive 2 5500 watt elements using contactors?

 
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Old 04-02-2013, 12:24 PM   #35
kal
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You need to use an SSR to drive an element, not a contactor. A contactor (or a relay) is not meant to switch on/off that often.

Kal

 
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Old 04-02-2013, 12:57 PM   #36
yowbrew
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Mar 2011
Ottawa, ON
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Thanks for the reply Kal. I guess I have to do more research. I was thinking about modifying the ebrew supply schematic and replacing the BCS-460 with a Raspberry pi. They show the SSRs driving contactors that are then connected to the elements.

http://www.ebrewsupply.com/designs/5...2-Electric.pdf

 
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Old 04-02-2013, 02:26 PM   #37
kal
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I haven't looked at the schematic but I'm sure it's the SSRs that are turning the elements on/off baed on what the BCS-460 is telling it to do while the contactors are there for safety. The contactors are likely switched through physical switches.

This is a common approach and is what I do.

I explain it in the "How it works" section of my heating elements wiring diagram here: http://www.theelectricbrewery.com/co...part-2?page=13

Quote:

Quote:
At first glance the BOIL and HLT relays may seem redundant: We use a PID which controls an SSR which in turn tells the element when to fire. So why are the mechanical relays needed at all? Why don't we simply use the ELEMENT SELECT 3 position switch between the PIDs and SSRs instead? The reason is safety: The mechanical relays ensure that there is a complete physical disconnect between both HOT lines and the heating elements when the relay is off. This is important as we will often be working or cleaning one kettle while the other is operational.

Doing something similar with SSRs would require 2 SSRs per heating element (one for HOT A and one for HOT B), but even that would not be 100% safe as SSRs have a small amount of leakage current that flows through at all times, even when the SSR is off. SSRs are also known to fail from time to time and when they do, they tend to fail "closed" meaning that the heating element stays on. The mechanical relays provide us with the piece of mind that when we've turned the element off, there is no possibility of it coming on by accident nor is any side of it energized.

So why use SSRs at all? Why can't we just use the mechanical relays? SSRs are Solid State Relays, essentially switches with no moving parts so they are able to switch as fast as required, often many times per second. Regular mechanical relays are not meant for this amount of switching as the contacts would wear out quickly. Whenever frequent switching is required, SSRs are used instead as we've done here. The three 30A/240V DPDT relays we use are only switched once or twice during the brewing session so they are being used in the way that they are designed to operate.
Kal

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Old 04-12-2013, 12:07 AM   #38
DougEdey
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Dec 2011
Ottawa, ON - Ontario
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Sorry for being quiet on updates, I've used this a few times, done some bug fixes, modified some other code, and updated the Android app so it now supports Landscape Layout (this took a while since I've been learning Android layouts).



 
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Old 04-25-2013, 01:55 AM   #39
DougEdey
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Dec 2011
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So some updates should be coming out tomorrow, mainly storing brewing session data on the server to enable better logging in the long run. I've updated the server and android app backends to lay the groundwork.

 
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Old 04-27-2013, 04:16 PM   #40
DougEdey
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Dec 2011
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Updated the repos today, the server now stores and serves the datestamps for starting the day, mashing in/out, sparging, boiling, and chilling, this'll be used at a later date more, but for now, I'm using it as a brew timer (long pressing the inputs on the first page on the android app will update the server, and if you have multiple devices running, it'll update them all)

 
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