Cable for Sensirion SFM3300-D

[fpdotmonkey]

https://www.mill-max.com/products/new/rugged-4mm-pitch-spring-loaded-connectors

[fpdotmonkey]

https://www.nxp.com/products/interfaces/ic-spi-serial-interface-devices/ic-bus-repeaters-hubs-extenders/i2c-bus-extender:P82B715

[mechatroniks-git]

Attempted to use https://www.digikey.com/product-detail/en/avx-corporation/009155004201006/478-4684-1-ND/1687183 Contacts slip off the pad when compressed.

[mechatroniks-git]

This Samtec part is better, but interferes: https://www.digikey.com/product-detail/en/samtec-inc/SIB-104-02-F-S-LC/SAM10715-ND/2664704

[mechatroniks-git]

Going with this part should work: https://www.digikey.com/products/en?keywords=821-22-004-10-002101

[fpdotmonkey]

Seems like this tab doesnt extend out far enough

[Burhan-Q]

@fpdotmonkey Just curious, did you try clipping it from both directions? Happy to extend that tab, let me know what Δ you're seeing as needed.

[mechatroniks-git]

@hydronics2, here is the PCB DXF Sensirion PCB.zip

[mechatroniks-git]

The step file: Sensirion PCB Assembly Mockup.zip

[fpdotmonkey]

@Burhan-Q looking at it closer, I think the issue is actually the fillet on the inside corner of the part stopping it from fully engaging. That said, it is clipping on and staying affixed.

[fpdotmonkey]

It could also be a print quality issue.

[Burhan-Q]

@fpdotmonkey I can make that a sharp corner if you'd like to check for a better fit. Let me know what you'd like to do.

[fpdotmonkey]

Sure sounds good

[fpdotmonkey]

Also what's the part number on this?

[hydronics2]

@mechatroniks-git you're cutting it kinda close here. I'd recommend moving the connector 1-2 mm outboard or just trimming the PCB 1-2mm. Any input?... I usually let those connectors hang off the board anyway to allow more PCB space... but I don't want to mess with dimensions too much if you're designing a clamp thingy too...

[hydronics2]

this is just a general note to remember for later... The P82B715 level shifts the i2c signals to 5V. If we end up putting the 2nd chip on the master board, be sure it level shifts back down to 3.3V or take other action as needed.

[hydronics2]

@mechatroniks-git do we need jumpers? I figure either the P82B715 is landed or it's not. Cheap small boards easy to switch between those with the P82B715 and those without. right? I can put them on no sweat just thought I'd simplify things as needed.

[Burhan-Q]

Also what's the part number on this?

@fpdotmonkey just now logged it on the Hardware Parts List as P-TET-000027

[hydronics2]

@mechatroniks-git for review

[hydronics2]

@mechatroniks-git for review

[hydronics2]

@mechatroniks-git for review

[mechatroniks-git]

@hydronics2 Can we add a parallel cap on the IC? Datasheet calls for .1 and 1uF. Also, add a pullup on SDA1. Thanks

[hydronics2]

@mechatroniks-git I made the changes... why only a pull-up on the SDA line and not an SCL line? .... never mind, I see it on the TI data sheet now. The crazy thing about the TI data sheet is it shows no pullups on the SCL line!... I think I got everything I need Patrick.. I'll add a few pull-ups and we can either populate them or not.

[hydronics2]

@mechatroniks-git @fpdotmonkey @Burhan-Q I submitted a pull-request. Here are the files. https://github.com/hydronics2/project-tetra/tree/master/02_Development/FlowMeter/Sensirion_connector_board I estimated the pogo pin distance in the step file. The pogo pins stick out 5mm (0.197") from the board and the stroke is 1.39mm (0.055").

[fpdotmonkey]

@Burhan-Q @hydronics2 ping me on slack when you have the board and the clip ready for me to print

[hydronics2]

@Burhan-Q @hydronics2 ping me on slack when you have the board and the clip ready for me to print

I posted a step file tin the link above. Check it out and see what you think.

[fpdotmonkey]

@hydronics2 in application, are the header pins in the model you posted going to be replaced by the sprung pins like what Patrick suggested?

[hydronics2]

Yes that's right. I put some header pins in their and tried to size them to 5mm to represent the pogo pins that will stick out 5mm from the board according tonl the data sheet I referenced (uncompressed)

[fpdotmonkey]

@Burhan-Q so I tried filing out that fillet, and that didn't do anything. However, I bent it a little so the internal angle on it is a bit smaller, and now the fit is a bit better.

[fpdotmonkey]

It basically looks like the cross section picture you sent me, so I think it's good. Time to add a feature for the terminal block to go through I suppose.

[Burhan-Q]

Moved to Blocked. See notes here. PCB revision required to address issue shown in image @fpdotmonkey @hydronics2

[hydronics2]

haha.. that's funny. I didn't move that part I swear.... but I can certainly move it outboard as many mm as necessary... say start with 5mm?

[mechatroniks-git]

We have a mystery to solve, last I left it, the connectors were 8.43mm (center to center distance from the row). Pushing it out 5mm would work, give me the center to center distance, and I can check.

[Burhan-Q]

Perhaps it's the spacing from the front edge of the board to the phoenix connector thru holes? [both measurements captured in Fusion, from 'front face' of board to center of thru hole]

@mechatroniks-git board measurement {M}

@hydronics2 board measurement {H}

Profile view with phoenix connector visible, looks like there's a difference in phoenix connector position/length.

@mechatroniks-git {M}

@hydronics2 {H}

[Burhan-Q]

@Burhan-Q so I tried filing out that fillet, and that didn't do anything. However, I bent it a little so the internal angle on it is a bit smaller, and now the fit is a bit better.

@fpdotmonkey do you mean that I should decrease the angle of the clip section like this?

[hydronics2]

@mechatroniks-git @Burhan-Q So it looks like the pogo pins are fine but the large connector exact position needs to be resolved. I can put it wherever it needs to be. This is the latest revision...

[Burhan-Q]

Blocked by #113

• [ ] adjust position of phoenix connector pins

[fpdotmonkey]

@Burhan-Q the design for the clip is good no need to change it

[Burhan-Q]

@fpdotmonkey clip updated with cut out for PCB. Ready for testing

P-TET-000027-0.zip

[Burhan-Q]

@fpdotmonkey clip updated with cut out for PCB. Ready for testing

@fpdotmonkey please move to card to Testing bucket on project board and add Testing Label to the Issue once you begin printing.

[fpdotmonkey]

First print of the clip didnt turn out so well. The hook that grabs the ledge nearest the PCB broke off while i was removing support material. Im going to try printing it with the PCB face down to see if that helps at all

[fpdotmonkey]

This is how I'm orienting the next print

[fpdotmonkey]

The previous print was just like this one, but on the other outer face of the clip

[fpdotmonkey]

Ok so the connector is nominally working!! The clip connects to the sensor perfectly, and the PCB slides right in. That said, i feel like its really easy to break the PCB-side hook while removing support, and the features for retaining the PCB didnt resolve super well in the print.

[fpdotmonkey]

Also, the clip has a good bit of slop along the sensor's axis (~.075"). I'm concerned that this could cause a short between pins.

[fpdotmonkey]

It also only takes a hair of pressure to remove the PCB. Granted we'll see how hard it is to inert and remove when we have the actual board, but I think an iteration before then could be good

[Burhan-Q]

Also, the clip has a good bit of slop along the sensor's axis (~.075"). I'm concerned that this could cause a short between pins.

@fpdotmonkey could you get me two photos of the extremes of the motion you're seeing, with the Sensirion facing the other direction? I'd looking to see how the harness is moving relative to this feature

[fpdotmonkey]

Full right Full left

[fpdotmonkey]

You can most easily see the difference looking at the right edge of the clip. I measured the displacement to about .075"

[Burhan-Q]

@fpdotmonkey What's the inside distance you measure on the Sensirion here?