craftbeerpi- are expansion boards necessary?

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Thedutchtouch

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I've been slowly building/researching a raspberry pi based brewery controller (3vessel eHERMS), and plan to use crafteerpi to run it... I've seen it mentioned in a few places that the expansion boards etc are necessary in order to not fry components... but on the craftbeerpi.com site, there's a wiring diagram that shows SSR's connected directly to the Pi GPIOs. I already have 40a SSR's that can take 3v input, contactors, switches, etc. just need to wire it up... any reason to NOT forge forward with this build as planned?

Or am I not understanding the difference and the terregady boards have a different purpose?
 
I think some people have had problems with the SSRs connected directly to the GPIO pins and the Raspberry Pi 3v firing some SSRs - especially the cheaper Chinese SSRs.

I went with a Terragady board (though the 4.2v from a while ago). I like the fact that when assembled as intended, the voltages and connectors to the Raspberry Pi are all taken care of for me. The Terragady board runs on 12v DC, which is more in the middle voltage range for control of the SSRs (and my little pump also runs on 12v DC).
 
ok. I went with mager/ MGR SSR's from Amazon, for my 2 elements (240v) and my pumps (120v chuggers) so hopefully they work Of with my Pi GPIO's as the 12v doesn't really benefit me otherwise. Unless anyone else weighs in with different reasons, I'm going to move forward with my build, and if I have issues with the SSR's then i'll debate better SSR's vs one of these boards, I should have room in my box if i need to add a board or something else down the line (saving some room for possible arduino expansion as well)
 
I run SSRs directly off of RPi pins. The add on boards just add an extra layer of complexity, IMO. I couldn't get knockoff Fotek relays to work, but Auber SSRs run fine on 3.3v. I also run the SSR + line through relays and set up software AUX shutoff switches for My heaters.
 
depends on the SSR's trigger voltage.
There are arduino relay boards that are opto-isolated that can handle up to 10 amps and run right off the rpi gpio.
You can use those to trigger larger SSR's with a higher voltage power brick.
Or you can skip the low power relay board and use a transistor circuit with a power source high enough to trigger the SSR.

either way works.
but you have to pick one to trigger most high power relays or buy an addon board that does it all for you.
 
golfindia said:
If you want to save money and keep things simpler, JBtek 5V relays will work fine for pumps and things less than 10a.

https://www.ebay.com/p/JBtek-4-Chan...ry-Pi-DSP-AVR-Pic-Arm-520361134553/1730687799
Click to expand...

i know, i was initially going to use those , but decided on SSR's for the elements and pumps so that i'd have redundancy in case i fried an element SSR during a brew day... very easy to switch over wiring, I'd lose control over a pump (building in mechanical switches as well because.. well... (pointless?) redundancy) but save a brew day. likely unnecessary, but they're already purchased. the main thing i need now is free time to actually assemble the dang thing.
 
didnt understand the "dont switch SSR's with electromechanical relays"... I'm not planning on doing that. by redundancy above i meant, if i fry an element SSR, i can use a pump SSR in it's place. i don't have any electromechanical relays, just the pi, switches (controlling the contactors), contactors, and SSRs
 
BrunDog said:
My comment was in response to @NitrogenWidget. Those EM relay boards have a transistorized front end to power their relays which means the input current requirement is well suited to chip-level outputs. However their relays are mechanical and can switch up to 10 A which are not well matched to switching SSRs’ inputs.
Click to expand...

Max current for the relay board i'm using doesn't come into play if i'm just triggering a bigger SSR.
It only matters if the potential load i'm putting on it will spike above 10 amps which is not needed to trigger any SSR's we'd be using.

I chose this board because it is cheap, optically-isolated and can be powered by the RPI if your power supply is up to snuff.
just an easy alternative to wiring up a bunch of darlington arrays on a bread board.

I've been triggering a mechanical contactor for a 220v heater element and an SSR for a 110 dual speed pump with my relay board and rpi on my hot tub for yrs without issues.

Plus I have extra space for adding deck lights ect.
I control it all with my phone.
Not a brew setup but it's basically the same thing.
 
I think my point was not conveyed properly... it is not about current loads though I did mention the 10A capacity. An SSR input might only need 20 mA @ 5V, so clearly the EM relay can handle much more. But the SS in SSR means Solid State, means electronic. The RPi is SS also. So the "amplifying" circuit, aka higher current switch should remain solid state. SSRs are primarily used to avoid mechanical contacts, since that circuit may be switched on/off once per second. In an hour that's 3600 times. So my point is do not interrupt a solid state path with an electromechanical one. An interim "SSR" (transistor, darlington, etc.) should be used. Will it work? Of course, but its not a proper design.
 
ok.
I see what you are saying now.
I haven't done an electric brew setup yet.

What I have works just fine for my hot tub because the relay only fires maybe 4 times a day even when it's really cold out because it's so insulated and only a few times when the top is off and i'm using it.

didn't realize the heating element would be constantly triggering to maintain temp for say 5 to 10 gals of water.
 
Thedutchtouch said:
I've been slowly building/researching a raspberry pi based brewery controller (3vessel eHERMS), and plan to use crafteerpi to run it... I've seen it mentioned in a few places that the expansion boards etc are necessary in order to not fry components... but on the craftbeerpi.com site, there's a wiring diagram that shows SSR's connected directly to the Pi GPIOs. I already have 40a SSR's that can take 3v input, contactors, switches, etc. just need to wire it up... any reason to NOT forge forward with this build as planned?

Or am I not understanding the difference and the terregady boards have a different purpose?
Click to expand...

Do you have a schematic you wouldn't mind sharing? I'm doing the same setup and would also like to include (possibly pointless) mechanical switches. TIA!
 
This may be a stupid question but only having played around with the Raspberry Pi and CraftbeerPi for a short while as I'm building my panel I have to ask.
I see a lot of folks here recommending that the Pi not be directly connected to SSR's and relays and a number of people make shields that offer protection to the Pi as well as allowing the use of a higher voltage power supplies to trigger SSR's etc. I also see on the various Pi forums that many people use various Darlington array IC's such as the UNL2803 or UNL2804 between their Pi's and relays. These would seem to serve many of the same purposes as the CBPi shields I've seen. Since all the shields appear to use individual transistors, diodes, resistors, etc for each GPIO going to the SSR's and relays instead of the IC which would seem to be much simpler from a wiring standpoint I assume there must be some drawbacks to using a ULN2503 or 4 in the CraftbeerPi environment. Is this the case? Or could I use something like the attached photo with a separate power supply and be good to go?
PiConnections2.jpg
 
For the record those relays are 50ma... The 2803 probably draws the same current :^) I think more people have burnt up Pis by wiring addon boards wrong than by just connecting relays to the GPIO.
 
That was my experience. I have a Terragady board. It just added a lot of unneeded complexity to my build. I fried two Pi's before I got the thing working. Unless you need 12v I would recommend skipping it.
 
golfindia said:
For the record those relays are 50ma... The 2803 probably draws the same current :^) I think more people have burnt up Pis by wiring addon boards wrong than by just connecting relays to the GPIO.
Click to expand...
That isn't the relay board I'm actually using. The picture is from the raspberrypi.org site and was one of the ways that were recommended for using a relay board with the Pi.
According to the data sheet the ULN2803 only requires 1.5mA from each GPIO pin connected to it so it would seem you could safely use all 8 of the IO's without exceeding the 50mA maximum recommended across all GPIO pin on the Pi.
I was just curious why the folks on the Pi forums often recommend using these ULN IC's while the CraftbeerPi shields all seem to use individual transistors, diodes, etc for each GPIO. Not being very familiar with the Pi or circuit design, I'm sure there are reasons I'm just not seeing. In the end my only real concern is wiring my Pi into the control panel in the safest way possible. Thanks for the replies.
 
Most likely the discrete implementations were simply scaled from simple, proven designs.
There's a certain comfort in just using "more of the same"...

Cheers!
 
The 5v rail on the Pi is limited to 50ma??? that is news to me. My research lead me to believe its only limited my the PS capacity. I run 6 relays straight from a Pi board with a 5a PS.... No problems. I know that the 3.3v rail is limited due to the converter. But why use 3.3v?
 
NeoBrew said:
That was my experience. I have a Terragady board. It just added a lot of unneeded complexity to my build. I fried two Pi's before I got the thing working. Unless you need 12v I would recommend skipping it.
Click to expand...

Agree 100%, if you need 12V, it is a good way to get 5v from the 12v...

Suggestions if you decide to not use a board:
Make a 'harness', not individual single pin connectors...
Firing the SSR's can be done by putting the same transistor, diode, and resistor in shrink wrap instead of on the board.
the resistor for the DS18B20 can also be put in heatshrink and you can make daisy chain connectors for q-d connectors on your panel
use a 5v relay board with the little opto-isolator chips on it, and feed the board power direct from PS.
USB power supply can be used for test and real simple implementations, but a real 5V supply connected to the header is wise
 
Thedutchtouch said:
I've been slowly building/researching a raspberry pi based brewery controller (3vessel eHERMS), and plan to use crafteerpi to run it... I've seen it mentioned in a few places that the expansion boards etc are necessary in order to not fry components... but on the craftbeerpi.com site, there's a wiring diagram that shows SSR's connected directly to the Pi GPIOs. I already have 40a SSR's that can take 3v input, contactors, switches, etc. just need to wire it up... any reason to NOT forge forward with this build as planned?

Or am I not understanding the difference and the terregady boards have a different purpose?
Click to expand...
I’m doing a similar build and was curious which route you decided to take and how it’s working out.

Did you connect the SSR's directly to the Pi GPIOs or did you use an expansion board?
 

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