Finalized PCB Parts List

[Nathan Ray]

This is a rough draft of the Digikey Order and Finalized PCB Parts List I've been working on. It is missing several key components and prices. I want Ian to help look over it as we comb through the PCB's. I hope to have this list finalized and ready to submit by this Saturday. 

If you think it would be easier on both of us to either have this on Github or to start a google doc instead of passing around an excel file just let me know.

[Ian Brech]

I'm all for a Google doc at the moment. We'll just need to make sure that everyone that needs to gets added in on it. I'll start looking this over and see what I come up with.

Also Nate, I'm sorry but I told you the long way of doing it. A little late now, but if you choose "values" instead of "parts" when creating the BOM, it actually gives you the quantities. Hope you figured that out.

Also, Digikey says it has 31 of our 3.3V DC/DC converters in stock. Based on what we've heard from some other teams, we should call them to verify that they actually have enough of them. Might be a little motivation for us to get these lists finalized too.

[Ian Brech]

Here's an updated version of the parts list. I went ahead and modified the one for the primary PCB. There were quite a few parts missing. Another thing to note for that board is that I was trying to get samples of the optoisolators, but after filling out two requests I have not heard back from the company. I think I'm going to try calling them tomorrow. I'm assuming a final list on Google docs or git has not been made yet.

A couple notes:

1.) 0.1uF = 100 nF (check part numbers)

2.) some components may have the same value, but different part numbers. This is for a reason (see 10 uF caps on primary board)

3.) pin/JTAG headers are typically going to be your through-hole, no-load connectors, and should not be on this list.

4.) we need to double check if we need other hardware (like dip sockets) from the other parts list before we finalize this. Honestly, it might be easiest to use that parts list (since it's laid out really well already) for our final complete list. This one will be good for figuring out which parts go to which board(s)

I think that's it for now. 

[Ian Brech]

After thinking about it again, I'm just going to upload this to our PCB repo on git, since these are the parts for the PCBs. That way we have everything in one place, and anyone who needs to can access it easily. Any objections?

[luke.renaud]

I would rather NOT see it on the git. As a binary document I'd like to avoid pushing it as it will have multiple revisions. Use the google documents system for sharing for now, but until it's a item describing everything that was used, I'd prefer if we keep it off of the git repo.

[Ian Brech]

Just as an update, the 4 pin firewire headers seem to be absurdly difficult to find. Digikey has none that are stocked, and the one we found from Cypress (CC1394-32006-201) is $4.20 each. For 6 of them, we're looking at another $25.20, plus $33.99 for shipping. I'm not sure what our other options for this are at the moment, but I will keep looking.

On a brighter note, I just got a package today with 5 samples of our dual optoisolators. Evidently they don't notify you that you are getting samples, so I may or may not have another order of 5 coming.

[Ian Brech]

I've been going through the master list and realized that I never checked the current rating for the 3.3V power supply we are using on our main PCB. It's rated for 1.2A. Our microcontrollers are rated for a maximum Vdd current draw of 300mA. We should not be maxing out the microcontroller, so I'd like someone to help verify the current draw of the design. According to the PIC32 datasheet, we should be drawing about 15 mA per microcontroller, plus whatever the sensors, 3.3V LEDs, and other 3.3V devices are drawing. Plus if we factor in the Thruster Feedback LEDs, each segment will draw 25mA, or 0.5A for two LED bars being on at the same time. Add the bar on the Primary board, and we're up to 0.75A for 3 LED bars. Is this something I should be checking, or are we confident that the total current draw will be within this range?

[Ian Brech]

Attached is the BOM for the EE parts in its present state. I have not yet removed unnecessary components, nor have I yet combined our entire BOM onto a single sheet. I plan on doing this tomorrow morning. There are a few things on the Google Doc BOM that need verification before we finalize orders. I would also like to verify that the pins listed under the KK connector section are the correct pins.

As it stands, our current cost for the EE materials is $809.16. This include the $345.26 crimper for the KK connectors as well as the DC/DC regulators.

[Ian Brech]

Attached is a master list of our BOM. I have included the "ideal quantities" that I think should be ordered. I'd like everyone's feedback on this as well. I'll put this in the Google doc as well so that we can get everyone's opinion on how many of each part we should order. I'm waiting to finalize the prices until we know our exact quantities, so that we can try to get the best pricing available.

I still need some clarification as to which 22uF capacitor is being used on the 5V and 12V regulator boards (the MFN and DPN are for different 22uF capacitors; one has a 5mm pitch, the other is 2.5mm, and it looks like the boards use a 5mm pitch?). Also, we still need to find 4 pin firewire headers and thermal compound.

[Nathan Ray]

Ok I've looked things over.
-The price of the Blue LED's are just inherently more because of blues placement in the EM spectrum. That's the cheapest one there is don't worry about it
-the breakaway header under the CONNECTORS section needs a QTY: probably 6.
-Have we not decided to try and buy those IEE 1694 std 4 pin firewires? I know they were a bit pricey but, I don't think there are any other options.
-I looked into some thermal paste. This one has a thermal resistivity ~16 deg C/W at 50C. Looks like it changes as a function of Temperature (about 32 C/W at 100C). But it seemed good enough for our purposes as the cheapest one had 56 C/W (this isn't the one I'm recommending) and we want as low a thermal resistivity as possible without breaking the bank . Here's the info:

DGN
473-1096-ND
MF
MG Chemicals
MFN
8615
Price:
6.29
QTY Recommended:
1



Oh and just use the 5mm pitch caps. Looks like they are the ones that fit the 5v/12v Power PCB's.

[Ian Brech]

Here's the updated BOM. Any preferences for quantities?

[luke.renaud]

The only thing I'll note is there are a few parts that are already duplicated for a second board in the list (e.g. stepper drivers) while a few other parts don't have any extras (e.g. optoisolators). As an minor aside, resistors are all priced at minimum quantity of ten (although we can by smaller volumes) but this will reflect itself as a few dollars higher final price. This isn't worth correcting in this sheet, it's just something to note when we do our final P.O.

Thoughts:

- Breakaway headers are 40-pin, so we can order far fewer if we want. I'd be in favor of cutting quantity from 6 to 3.

- I'd favor having a few spares of the wire-headers for the sherlock and KK connectors just in case. They're easy to lose, and I feel it's worth having a few extras just in case. I leave final call on this to the greater team though.

- We don't need the coil switching relay. Part No. PB647-ND

- Bump optoisolators from 3 to 6 for backup board. And on this note is 8 the correct number of 8 pin dips sockets?

 

When this order is finally submit, I recommend submitting it as a printout of a DigiKey cart, with the P.O. form simply having a single item saying something to the effect of "attached parts list" and the total cart cost rather than itemizing each item on the sheet in a secondary P.O.

@Nate, how did you compute the thermal resistance of the thermal paste. I've run some numbers from the data sheet and it looks good, but your findings aren't readily apparent. They provide sigma ~ 3 across temperature, and given an approximate area of .1"x0.5" (which I hope is worst case) and a thickness of 2mm, I'm figuring ~20ºC/W. Am I missing something?

[luke.renaud]

Also, is the separate order for the power poles from Mouser nearly ready as well? It's less time critical, but we want that out before break as well if we can.

On that same note, has anyone looked at fuses/fuse holders for inside the battery tube? They aren't necessarily something we have to get from Digikey, but it'll be needed on a similar timeline to that of the power poles.

[Ian Brech]

I have not had a chance to look into the power poles yet, but I was planning on doing that tonight. Are we still wanting ot only get the 10A pins and try to trade with the HAM Radio club, or just get the higher current pins as well? I can look into a fuse and fuse holder as well. Does someone know how much current we should rate those for? I want to say I saw something written about 60A-70A, but I can't remember where that was or if it's for the battery.

As far as the optoisolators go, I have 5 already from a sample order, so should we still increase that to 6 on the Digikey order (for a total of 11)? We want to number of 8 pin sockets to match the total number of optosiolators, since that's all they are going to be used for.

How many more KK and Sherlock connectors are you thinking? I'm getting anywhere from 3-8 more of each, are you thinking we want somewhere around 10-20 extras of each (both male and female headers)?

Ok, I have a preliminary  Digikey cart put together. I had to change the blue led because the part we had selected was non stock and only reported as having 2 available.

[Ian Brech]

I really haven't changed a whole lot on this list other than the blue LEDs and the quantities of the breakaway headers. I did update the quantities to what I currently have in the Digikey cart. the total cost in the cart is less than what is in this document by ~$30 because of quantity discounts. Any final opinions?

*Side note, I did up the quantity on those SMT PFETs, just because they're really small and possibly something we'll lose a few of.

[Ian Brech]

Here is the finalized list as it currently stands in the Digikey Cart. I'll be emailing this to Luke shortly.

[Ian Brech]

Here is the initial sheet for the Mouser order. It's all powerpoles right now, but we may want to look at fuses an fuse connectors as well through them. Check what Luke said above to double check what all else we need.

I've attached what I've looked up for the powerpoles. We have red and black shrouds, but I'm not sure if we want more of those or not. I've included numbers for both purple and orange shrouds, though I don't know that we need more. The pins Luke gave me the number for are listed as 30A tolerant, not 10A. I'm also not sure what currents these need to be able to support (or where they are going for that matter), so I've included 15A, 30A, and 45A pins. According to the datasheet, the PP15/45 series shrouds should be good up to 55A. Also, I have no idea what quantities we are looking to get.

Nate, if you can look into this further I would greatly appreciated it.

[luke.renaud]

With regard to power poles:

We'll need a pair for both sides of each thruster. So that's 12 black + 12 color for the full motors minimum. We could double this if we want to put a power pole near the h-bridge and a separate one near the bulkhead to allow us to easily remove the wire connecting the thrusters completely and make building the wires easier as well.

We'll need 4 black + 4 color for the battery input power minimum, possibly more depending upon the exact pinout that the mech-e's give us through the bulkhead.

If we want we could also power pole the relay's at various points. This is probably a call that merits a brief meeting between a few people to quickly decide where we want to put connectors formally in the power routing system. Ideally this should happen before everyone ships out. If you guys decide shortly after spring break, I can still try to process paperwork when people are out of town. A decision on preliminary wiring as well as any choices of color convention just needs to be made while it's easy to talk face to face.

As an aside, a few companies make products like this (http://www.powerwerx.com/powerpole-power-distribution/ps-6aa-inline-6-way.html) that allow you to easily bus the power distribution. We only have a couple of splice points so I really don't think buying one is worth it, but if we think that's a good way to mechanically connect things, we can talk with the MechE's about possibly machining some sort of frame or 3D printing a structure to hold them. Then again we can always just manually splice wires and heat shrink them.

-Luke

[Nathan Ray]

I've talked it over with James and he really wants to pursue the splitter route. Sorry I haven't been able to work more on the Mouser order over the break, I felt that a meeting between a few of the EE's about the specifics of power poling the relay was needed before we submitted one anyways. Once we all get together we can finalize this (hopefully) last order and include all the fuses and fuse holders we need as well.

     The timeline we are looking at should make us fairly busy for the next 2+ weeks. From what I can tell the only things we need to add are the automotive fuses/fuse cutout, and the power distribution array. Did I miss anything? 

                          MFPN                           MPN

 15A Fuse     0297015.WXNV          576-0297015.WXNV
30A Fuse      0297030.WXNV          576-0297030.WXNV
40A Fuse      142.6185.5402            576-142.6185.5402

Vertical Mount  01530008Z                  576-01530008Z