Newbie questions galore


 
S

Shaun Stelley

New member
Hey all, found this place after some googling around for a DIY Big Green Egg controller. I'm pretty excited about putting one together but have some questions to ask first. I apologize if they have been answered before, but I've tried to read the Wiki thoroughly, as well as search the forums.

1. rPi B+ support? Is it coming down the pipe at all? Even just software/firmware support? I've got no problem jury-rigging the connection between the boards with a ribbon cable or the like. Just wondering if I should be patient for a few months or go full steam ahead now.

2. RTD support? I'd like to dual purpose my HeaterMeter as a sous vide controller as well, but would prefer to use an RTD for that due to accuracy, and the fact that I already have a submersible RTD. I know it's a little trickier due to the constant-current supply, but thought maybe somebody had figured something out. Hard thing to search for on the forums.

3. J7, J8 headers. Are these actually needed for the standard version? They appear to be for expansion/extension I think.

4. Navigation switch alternate. Is there a perfect solution right now? Would the 5-way version work (SKQUCAA010) Adafruit has some stock of it. Or is the SMT alternate the only real option. I also see OnlineComponents has some stock of the thru-hole version, but then it's an $8 switch with shipping. Anybody tweaked the board layout for SMT pads?

That's all I can think of for now. Thanks in advance for answers and I apologize if anything was easy to find and I missed it.
 
1) It should work fine with the B+ if you wish to use a ribbon cable.

2) Thermocouple and thermistor support are all that are supported. I think you can submerse the Thermoworks thermistor "pro" probes and I've certainly submersed my thermocouple

3) J7 and J8 don't get populated on a standard build

4) The SMD version of the navigation button looks to be the suggested alternative
 
1) as of NOW, no B+ support, A+ is supported on V4.2 if you mount one transistor on the other side of the board (so it doesn't interfere with the extra pins on the A+ header). Bryan would have to comment on future B+ support, I know is has been tossing around layout ideas for it but the double USB header takes up a lot of space on the edge of the board, leaving little space for the HM board to have I/O there. Since boards need to be designed, sent out for fab, built and tested, refined, restart process prob couple times before a HM release comes out I wouldn't wait on rPi B+ support.

2)Hmm, RTD's, I think there was some discussion here about them but I have nothing reliable to add here. Seems like the HM should be able to support them since they are resistive devices? Another one for Bryan I guess...

3)Yes, optional. 7 for connecting optional RF transmitter for wireless probe, 8 for optional?? Data to and from ATMega=rPi? At any rate, on a standard build they are not used.

4)Right now the surface mount version of the switch is the best solution. The pads on the SMD version of the switch lay right on top of the through hole solder joints, someone recently posted that is was very easy to solder the SMD switch in place of the through hole, and it lined up in the 3D printed case just fine... That said, I think Bryan has the through hole switches to go with all his kits so if you order from him there is will be no switch issue.
 
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ah, yes, if you are looking at RTD simply for submersible probe support Thermoworks does indeed have a submersible version of their Pro series probe, and as Steve_M pointed out there are waterproof thermocouples as well.
 
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So B+ should work fine with a cabled solution? I thought I found some thread that indicated it wouldn't quite work for some software reason.

I'm looking at RTDs because they are more accurate (single degrees matter when you are cooking certain things sous vide), and because I already own one not being used.

Any thoughts on the alternate switch from Adafruit that adds the push-in function?
 
I think the B+ would work with some sort of cabled solution, cause the A+ does work. The header on the A+ and B+ is longer but the first bunch of pins match up fine with the HM. I fumbled around looking for something on hand that I could use to mate my B+ to the HM and came up empty handed so I never got to try it...
 
RalphTrimble said:
I think the B+ would work with some sort of cabled solution, cause the A+ does work. The header on the A+ and B+ is longer but the first bunch of pins match up fine with the HM. I fumbled around looking for something on hand that I could use to mate my B+ to the HM and came up empty handed so I never got to try it...
Click to expand...

Cool. I'd probably replace the Heatermeter connector with male pins and then go with something like this:

https://www.samtec.com/technical-specifications/default.aspx?SeriesMaster=SMSD


Or go ribbon with something like this

https://www.samtec.com/technical-specifications/default.aspx?SeriesMaster=HCSD
 
I don't have a lot of time but quick comments:

1) B+ is not supported hardware-wise. They simply do not fit together. As Steve pointed out, you can use a ribbon cable to connect them and it works fine, but you can't mate them back to back like you could before.

2) No RTD support. PT100s and the like requires specialized differential circuity like the thermocouple does. I do not know how to design this like the commercial PID people do so it works with all the different types at once so we're stuck with thermistor probes for FOOD1-3 and thermistor or thermocouple for PIT (but not interchangeably).

3) J7 and J8 are for adding on if you want them.

4) I have never tried the center push version but I think it will work, the footprint is the same and we don't connect the extra pin so... probably?

Regarding a board that fits the A+/B+ I'm halfway done with the first try at a board that fits this. Suffice it to say that a v4.2.4 HeaterMeter is the smallest device we can make that fits a Pi. The A+/B+ I decided to grow upwards. It is bigger and more expensive and only just as functional as existing hardware. It is also unproven, and is at least 2 months, more if it takes more than one attempt. It also might not ever happen if I don't like how it feels!
 
Bryan Mayland said:
I don't have a lot of time but quick comments:
2) No RTD support. PT100s and the like requires specialized differential circuity like the thermocouple does. I do not know how to design this like the commercial PID people do so it works with all the different types at once so we're stuck with thermistor probes for FOOD1-3 and thermistor or thermocouple for PIT (but not interchangeably).
Click to expand...

Hmm. I think all you need is a constant current supply, a few resistors, and an instrumentation amplifier set with the appropriate gain to get in the range of your ADC. Maybe a couple 0 ohms/jumpers to enable it vs. thermocouple or thermistor. If you have any interest in adding it to v5.0, I could work up a quick schematic and parts. Granted, I'm just a dumb ME who did some work on an RTD circuit researching a previous DIY sous vide controller.
 
Oh I know what the circuit is supposed to look like for an RTD, there are plenty of examples on the internet. But chinacheap PID controllers support RTDs, thermocouples, and some thermistors as well and I've looked inside and they do not have all the parts you'd think they would so that's the mystery to me. Instrumentation amps are also pretty expensive given the overall cost of the project, with just one chip (low quantity) adding like 20% to the parts cost.

Adding the ability to choose your own input for four inputs would make a GIANT device unless it was all done SMD. This project is for beginners so that's out.
 
You mention this being a project for beginners... Which I am totally onboard with, I personally would not like to see a move to more SMD than necessary for the TC support. This brought to mind, however, what if there were a basic HM for beginners and a separate advanced HM that has more SMD and more of these features packed in? I guess that's double work for you so I can see why you wouldn't want to do that. Perhaps someone else could take your schematic and create an SMD layout and add in some of these extra features like RTD, support for 4 TC probes etc... I guess the software support would still fall on you, so might not be something you'd be eager to move on either...
 
RalphTrimble said:
You mention this being a project for beginners... Which I am totally onboard with, I personally would not like to see a move to more SMD than necessary for the TC support. This brought to mind, however, what if there were a basic HM for beginners and a separate advanced HM that has more SMD and more of these features packed in? I guess that's double work for you so I can see why you wouldn't want to do that. Perhaps someone else could take your schematic and create an SMD layout and add in some of these extra features like RTD, support for 4 TC probes etc... I guess the software support would still fall on you, so might not be something you'd be eager to move on either...
Click to expand...

I actually like the idea of an beginners type board and a board for the advance type of board.
 
I think an all SMD version would benefit Bryan if there was a demand for turn-key heatermeters. The cheaper parts and the ability to solder most of the components in a few minutes in a toaster oven would drastically reduce the overall build time.
 
Yah, seems to make sense... The basic version is mostly through hole aimed at people with basic skill level, and the SMD version has more features and can be built by advanced users or purchased in a complete turn-key fashion from Bryan. Sounds like a good set of options....
 
Steve_M said:
I think an all SMD version would benefit Bryan if there was a demand for turn-key heatermeters. The cheaper parts and the ability to solder most of the components in a few minutes in a toaster oven would drastically reduce the overall build time.
Click to expand...
I dunno about how dramatically it could reduce it. I can put together a HeaterMeter about 45 minutes if you don't count the big through-hole parts that probably wouldn't reflow correctly in a toaster like the LCD, jacks, and button. Between spreading solder paste, placing 76 components, and toasting you're probably looking at maybe 20+ minutes and the chance of a component getting knocked out of position goes up the more boards you try to do at once.

That said, an SMD version could be a lot smaller and cost less and can be fabbed assembled as well to take no time at all! That's what I was going to work on next (after the store) when this whole Pi B+ thing started. I'll be revisiting this once 5.0 looks stable!
 
The idea of a through hole and SMD versions of the board is a great idea. I think the major difference would have to be size instead of function. If there is a large function difference I am sure people will pick the advanced just because they want the ability to do everything (even if they won't necessarily use it). People may try to jump into a SMD board who are not prepared for the level of skill needed. The trap with SMD is that it looks easy to the uninitiated.
 
Well, I don't completely agree Curtis. I don't think many people would attempt to build the SMD version just because it say supports RTD probes, or has the option to use 4 thermocouples... Most people don't know what RTD probes are and have no need for them, and standard food probes work well enough, not really worth adding like $30 in parts to get TC on the last 3 probes to most people. And I also disagree that people will take the SMD soldering lightly, most people balked on doing the SMD work on the HMv4.2 TC amp, that's why Bryan made the boards available with the SMD stuff already soldered onto them. Some might like the idea that the HM could be smaller, personally I like the size of the HMv4.2 and wouldn't want it smaller, there comes a point in miniaturization where things get too small to work with. Finally, if someone wanted the features of the SMD version and didn't want to do the SMD work they could buy the board with all the SMD stuff already soldered onto it, then they just need to solder in the probe jacks etc and they'd be off to the races in no time....
 
Good points Ralph. I may have over estimated male ego in my previous post. Plus it is awesome that Brian is able to offer board with the SMDs mounted for people.
 
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