Decide Direction for the Rev-E Enclosure

[eyuan-creare]

• [x] Determine what the stackup height is. @biomurph is planning to solder the Teensy to the Tympan
• [x] How do users access the SD slot?

Here is the existing enclosure for the Rev-E with AIC shield

• [x] What plastic do we use? The white plastic from Rev-D has shown yellowing under UV light

• [x] Consider which screws we choose (such as plastite screws).

• [x] Provide access to the reset button

[biomurph]

@eyuan-creare do we need the belt clip? Do you have a part number for it? I'm thinking it would be loose in the bag for users to apply if they want. So it could still rest on the table-top.

[eyuan-creare]

@biomurph it's a bit pricey for what it is: BELTCLIP MCS-661BP.

I'll upload the CAD for the triple stack design that has the whole assembly. What SW version are you working with?

[biomurph]

Here's one that is a bit cheaper. belt clip but it has a different shape for the mount surface...

I use FreeCAD. I don't do much with it. I'm not a versatile CAD user. I also use TinkerCAD, which I find useful for making small changes and simple forms.

[eyuan-creare]

@biomurph I like the idea of designing it so that anyone can print it with PLA. Is there a UV protecting finish you could apply?

Also, the print from WanShun turned out nicely. I wonder if it would be worth quoting these out for a production run later.

[biomurph]

I will look into uv safe filament. Would be better not to do a coating. That sounds messy.

Yes, the wan Shun models are good. I reworked them in tinkercad to make them print better on my machine

[eyuan-creare]

Oooo.. Can you share any photos of your printed earpieces? What wall thickness can you do?

[biomurph]

Oh, I'm sorry I misunderstood. I'm not talking about the earpieces I'm talking about the Rev D enclosure.

I have not printed the earpieces. Not worth it, since I figure the resolution will not come out well enough to use.

[eyuan-creare]

• Go with (7) design from the SD Card issue #18 using Adafruit 2000mAh Li-poly battery
• Consider sliding case and front-screwed bottom
• Consider leaving extra height for battery (so no accidental reset button presses) and accommodate other batteries
• Leave holes for PCB mic (with funnel shape), LEDS (GPIO, BT, Charging)
• Consider "ASA Special Edition" embossing
• Note that Joel's printer can do 0.080" down to 0.040". Joel to look into UV stable filament
• Aim for cases to be complete before June 21
• New changes to PCB include the reset button and Quic connector

[biomurph]

Here's a shot of a prototype Dosimeter case print. Think it was done with a fast setting (lower resolution). I'm going to find a similar blue to the one you have

[biomurph]

Here's the blue that I'm getting to work the prototypes and first cases with https://www.matterhackers.com/store/l/pro-series-pla/sk/MFEFY96W

[biomurph]

Your changes should reflect that

1. The Rest Button is added to the TOP of the Tympan between the mic jacks
2. Added quick connector on the BOTTOM near the rout for the battery wire
3. That 3 pin header connector is actually the dial pot

Please see photos below from Circuit Hub

Final Assembly Top

Final Assembly Bottom

[eyuan-creare]

@biomurph What is the standoff between the Tympan and Teensy? I show a gap of 0.150in.

• NVM: I have a board here. I measured .155"

[eyuan-creare]

Also, which part are you using for the Quiic connector?

[biomurph]

I think that the Qwiic connector might have miss hit the BOM in our repo. It is listed in the Circuit Hub Part List in this case, it is a SparkFun part sold by Mouser.

I can confirm your measurement of 0.155" +/- 0.008" tolerance is enough wiggle room.

[eyuan-creare]

Thanks. I was able to source CAD for those two parts. The Sparkfun Quiic connector is actually JST BM04B-SRSS-TB.

@biomurph Can you take a quick look to confirm I have all the important components on board?

[biomurph]

Stand by

[biomurph]

On the bottom, you have the Qwiic connector in the wrong orientation. It should be a Right Angle part. With the opening toward the edge of the board. Here are the production photos. Those links above don't work

[eyuan-creare]

So this is not the correct part?

It must be this RA then?

[eyuan-creare]

I'm going to leave this issue open so I can post progress of the model.

[eyuan-creare]

Here is a general shape I am heading towards. I thought it might be nice to taper on the opposite end of the SD card. Let me know what you think.

I know the SD card access is still tight. I'll work on that next. I plan on pushing the wall in to provide a nice indentation where your fingers can grab the card.

[biomurph]

Oh dang, I wanted to get the Right Angle Qwiic connector, but I got the Vertical instead!

I have to verify that the pin-out is in the right direction for the Qwiic and Stemma plugs.

[biomurph]

I have confirmed that the distance between the Tympand E PCB and the Teensy 4.1 PCB is actually 0.165" Also, the board edges on the USB end line up perfectly.

And yes, I did get the production Rev E delivered today!

[eyuan-creare]

@biomurph Thanks for taking measurements. What do you mean by "board edges on the USB end line up perfectly"?

• The RA Quiic would have been nice, but it's a bonus feature. Are you saying they came with vertical connectors?

[biomurph]

@eyuan-creare When I say that the board edges line up perfectly, I mean that the edge of the Teensy board that the USB is on lines up right with the edge of the Tympan board below it. They are in alignment.

• NOTE the Qwiic connector placed is not the Qwiic connector that I requested in my BOM.

Please proceed under the assumption that we are using the correct, RA Qwiic connector. I am working with Circuit Hub to address the issue.

[eyuan-creare]

SD Slot Access

• Let me know what you think of this SD slot. @biomurph If you are up to printing a preliminary shape, I'll put rudimentary holes for all the connectors then send you a model that's just split in half. Then we could check how hard it is to remove the SD card.

[biomurph]

This looks great! Yes, please upload STL or OBJ files and I will do a test print to see how the parts fit and the holes line up.

[eyuan-creare]

So you are saying the edges of the PCB (on the side the USB is on) are aligned:

And that the gap between boards is 0.165" instead of 0.15in?

[biomurph]

@eyuan-creare Yes. That's exactly it. I think the board to board spacing is likely variable. There is some room on the pins to shove the plastic spacer closer to the Tympan, but it's tricky and a pain. Best to leave them and call that dimension 0.165"

[chipaudette]

@eyuan-creare , be aware that the way that you've drawn the battery wires requires that we bend the wires back on themselves in a way that goes against the way that they're soldered.

The batteries in my hand have their wires soldered on so that the wires extend lengthwise off the end battery. In your drawing, the wires are bend back to pass over the battery itself. As a result, we have to bend the wires back against the way that they naturally want to lie. When I do that bend on the battery in my hand, it all happens where the wire is soldered to the battery. This will stress the solder points quite a bit.

I'm sure that we can live with it, but we should be aware of it.

[chipaudette]

@eyuan-creare , I don't know where you're going to split the case to enable the board to be placed in the enclosure, but it looks like you're giving yourself a tricky design challenge!

The conflict that I'm seeing is how one will simultaneously slide the PCB sideways into the headphone-end of the case while also having female headers poke up vertically through the holes in the top of the case. Those vertical headers will try to prevent the side-ways sliding.

You've made this work in the past, so I have confidence that you're on it...but hooo-weee, you're setting yourself up for a tricky design task!

[eyuan-creare]

Re: Batteries Good point. I was going off of how the 1200mAH battery is packaged. I'll check how the new ones I ordered look.

[eyuan-creare]

Re: Splitting the case The items that need split are the audio jacks, the P/S & pot, and the USB jack. I could probably tilt the PCB in to omit the split at the audio jacks.

I'm assuming the SD card must be removed before installing the Tympan. I always forget this step and stress out the SD slot. There's a possibility I could split the case at the SD slot. But that would take some wrangling. The bottom case would have to slide over the USB slot. @chipaudette let me know if this is worth pursuing:

[chipaudette]

I think that no one will remember to remove the SD card from the slot prior to removal, so it's great that you're considering that scenario. But...

In the RevE, the SD slot is built-into the T4. The T4 slot is much more robust the slot on the RevD. So, the RevE will be more tolerant to failing to remove the SD. I think that we'd be fine without having to do the split at the SD slot.

So, I don't feel the need for you to pursue the alternative concept unless you yourself liked it better for a bunch of other reasons.

[biomurph]

As far as printability, the first design, with the part on the audio jack might be easier. Also, parting on the jacks and the USB makes it easy to remove the board by lifting the USB end, thus 'sliding' any SD card out.

@eyuan-creare Let's print both! I've got the filament, and I'm ready to go! That way we can have some empirical evidence.

[eyuan-creare]

Enclosure for Test Print

• Will export these parts for a test print on Monday. And see if I can add some height to accommodate the new batteries @biomurph found (10.3 x 34.5 x 52 mm). Also the 2000mAh battery is too tight. Will work on that.
  

Perhaps I was influenced by my 5yr-old, who just discovered eyebrows :)

Should I punch a hole in the case for the Quiic connector? Hoping I don't have to as it would leave an ugly gap in the case.

[biomurph]

@eyuan-creare That is really great looking work! I will be shipping with the Adafruit batteries in the near term so no need to change the vertical dimension in that regard. Also, I am removing the Teensy program push button to avoid any chance of random resets. Don't bother putting in the quick connector hole yet. Let's get the prints made and see how it fits first

[chipaudette]

Looks pretty good!

How are the bottom and top held to each other?

[eyuan-creare]

Right now, by magic SW-glue. 😊

I intend to bolt the PCB Assy to the lid. I will try to use as few screws as possible, but I may need separate screws for the PCB Assy.

Going to correct a few features then export it for a test print to see if the parts fit. Then work on holes for mics and LEDs, then add screw bosses, then a lip.

[eyuan-creare]

@chipaudette How should I handle the microphone port? Having the port so narrow can create high-frequency resonance. However the header and audio jacks are close by, so it would be difficult to drop the height of the case.

Should I port the mics out the side?

Also, should I look into a gasket to seal the mic port? Or keep the design simple?

[chipaudette]

..and adding "tympan" on it somewhere, like your previous builds? :)

...and possibly saying "RevE" somewhere? Maybe? Maybe not?

...and consider adding a flat smooth spot for a sticker for the BT ID, like you've done on some of the earlier units. That's always a super-helpful piece of info to have written on the case.

...and no need to be stingy with the size of the holes for the PCB mics. Big holes is good acoustically. Also, drawing attention to the locations of the mics is a benefit, not a curse. I do agree, however, that aesthetics are important, too...and big holes might not be very attractive. It's your call how big/small to make the mic holes; I just wanted it clear that I'm not specifically asking for them to be tiny.

[biomurph]

Are the on-board mics used that much for 'real' audio work? I seem to remember that @chipaudette said once they are only used for proof testing and rarely used for any real recording?

Super psyched to print this thing!

[eyuan-creare]

@chipaudette So narrow mic ports are okay, and no need to side port them? I'll shoot for Ø0.125"~0.15"

[biomurph]

Just got notification that the Tympan Rev E.2 arrived at your location

[chipaudette]

I think that the on-board mics are most useful as something concrete that people can understand while they try to wrap their minds around the more abstract things that Tympan can do. "Oh, it has microphones! I understand what that sentence means!" It can be an anchor point for their mind.

So, along those lines, I feel that there is some benefit to making them visually obvious as a way to help draw people towards this anchor point. It might reduce the time that they spend being confused about what Tympan is.

The on-board mics are also good for quick demos, for sure.

But for proper recordings, yeah, there are weird acoustics by being inside the enclosure. That's not great. As a result, people would bring their own external microphone for any proper work. But, like me, I bet they'll end up using the PCB mics a lot more than they'd like to admit...they're there and they're easy to use. It's hard to argue with that.

[biomurph]

I kind of like that two-tone blue top and bottom... I have a couple different colors of blue filament here. Might come out nice!

[eyuan-creare]

@biomurph Here are STEP and STL files for the test print. (Note that there are no holes for screws or a lip for the split case parts.) I will update these files as I add new features.

https://github.com/Tympan/Tympan_Rev_E_Hardware/tree/master/Enclosure/Exports

I left Ø0.150" for the mic ports:

[eyuan-creare]

@biomurph : The Tympan mounting holes are Ø3mm. #4 screws are too tight a fit, so I think I will go 2.5mm machine screws. okay?

[chipaudette]

Thanks for adding the mic holes.

Based on looking at the CAD rendering, I think that you've added tubes going down to the mics, as opposed to just cutting a couple holes in the top surface. That's fancy! While this seems like a good idea to have those tubes (and it could be!), there's always the question of what happens to the acoustics. By having the tubes, it might end up making it sound like, you know, that you're listening at the end of a tube.

Unfortunately for us, the other option isn't obviously better, either....if you were to just have holes in the top of the enclosure, you'd end up hearing the resonance of the whole inside of the enclosure. (I'm hearing everything through a seashell! Ick!) But, we also know that laying a piece of foam in the enclosure helps cut down on the enclosure's seashell resonance. So, maybe top holes can be made to sound better than listening via a tube.

Or not.

One really doesn't know until one listens through a prototype. So, let's print and listen!

[biomurph]

@eyuan-creare I will print the models now. When I imported them into my slicer software (Cura, Lulzbot Edition) the size of them was super duper tiny. I think maybe it's an inch - mm problem? I opened the STEP files in FreeCAD and was able to export them as STLs and they do appear to be the right size. Print will take 2.5 hours to do 1 top and 1 bottom.

@chipaudette the Rev D enclosure does not have 'tubes'. I lay in a piece of foam during assembly.

[eyuan-creare]

Good to know. I am about to add screw bosses that could interfere with inserting the battery. Will update the CAD around 3pm.