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Offline Ncartmell

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Home Build
« on: September 19, 2017, 01:17:22 PM »
I have just received some PCB's for the Scout and OP Sound from china (SEEED). Very good boards, 10 boards @ $4.90 plus $10 shipping, so total cost of $20. That is effectivelly $1 each and the boards have also been electrically tested.

You can also order a solder stencil but I wanted to see the quality of the boards.

The question, can I vary from the BOM.

For instance will non surge 1/10W resistors be ok?

The flash memory is W25Q128FVSG acceptable?

What parts can't be changed?

It also may be of interest that SEEED will manufacture fully populated boards.

I tried to get a price but was unsure if it was complete as there was a warning that all parts were not recognised.

It may be worth pursuing for a production run.

Best Regards

Neil

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Offline LukeZ

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Re: Home Build
« Reply #1 on: September 19, 2017, 02:46:24 PM »
Yes, you can substitute many components with comparable parts, especially the passives such as resistors and capacitors. Obviously some substitutions are not good, as Hobby King discovered, if you have questions about specific components just ask.

W25Q128FVSG should work just fine, but note the sound card doesn't presently implement the flash memory at all. You can choose to leave it off along with R8 and C3. The flash memory was an idea I was playing with but so far it doesn't seem we will need it.

The important parts on the Scout are the thermistor, diodes, MOSFETs, motor driver, microcontroller and crystal, and the LDO (voltage regulator). Even among those, if you were careful and knew what you were doing you could substitute the thermistor, diodes  and LDO but just use the parts specified to be safe if you can.

The important parts on the Sound card would be the LDO, the micro-SD socket (get the wrong one and the footprint won't line up), and obviously the amplifier IC as well as the Teensy.

I agree SEEED is a great supplier. As for manufacturing, lots of places will manufacture boards but they all seem to want to be paid for it. :) Production runs are extremely expensive and I am not rich. I also don't believe there is any substantial profit to be made from selling RC tank electronics given the size of the market so I don't feel it makes economic sense for me to invest in this financially beyond what the development costs have been (which were considerable). So for manufacturing that really only leaves us with entities willing to shoulder the financial burden themselves... which is a small list indeed.
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Offline LukeZ

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Re: Home Build
« Reply #2 on: September 19, 2017, 02:47:21 PM »
Also as you build your boards please post over in the Assembling Boards by Hand thread to ask questions or share your experience.
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Offline johnnyvd

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Re: Home Build
« Reply #3 on: October 05, 2017, 04:37:52 AM »
I have just received some PCB's for the Scout and OP Sound from china (SEEED). Very good boards, 10 boards @ $4.90 plus $10 shipping, so total cost of $20. That is effectivelly $1 each and the boards have also been electrically tested.

Hi Neil, i'm very curious on how the boards look from Seeed. i have some experience with them because i ordered my flow controller boards with them. I solved this by changing some layer names..

I also tried to order the TCB from them, but as i had to convert Eagle to Gerber files i started losing the bottom silkscreen.

When i look at the price of the boards i guess you did not order with ENIG coating on the pads? OSHpark does that when you order the TCB with them.. Would it matter if we used the standard HASL coating instead?

Could you share some pictures with us? And could you share the Gerber files so ordering them would become easier?

I attached my version of the TCB in Gerber format. I have to remark that the file was never ordered OR reviewed & tested!

(Maybe someone could take a look at it?)

Cheers, John
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Offline LukeZ

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Re: Home Build
« Reply #4 on: October 05, 2017, 10:54:01 AM »
I haven't gone through the SEEED process so I haven't verified this information. But in the case of OSH Park, they provide an Eagle CAM file for creating the Gerbers. I see that SEEED does as well at the bottom of this page.

They give their Gerber files different names than OSH does, and arrange the files somewhat differently. I've gone through each layer and most of the default SEEED selections are fine, except for the silkscreens (as John discovered). But you can always adjust the layers yourself before generating the Gerbers.

In Eagle board view, go to File -> CAM Processor, then File -> Open -> Job and select the SEEED CAM file. Now you will see a bunch of tabs on the CAM Processor form that represent each Gerber to be exported. On each tab you are able to modify which layer belongs to that Gerber file.

For the Silk top we need to add layer 121 _tsilk

For the Silk bottom we need to add layer 122 _bsilk

All the other layers should be fine as-is.

For simplicity, I have attached SEEED Gerbers for all three Open Panzer projects to this post (the Scout is an odd case that removes layer 25 tNames from the top silkscreen because there isn't room for them, but we still need 121 _tsilk).

Again - I've not ordered these from SEEED so I can't promise the results. But they should be correct.

EDIT: I've removed the attachments from this post and put the SEEED Gerbers on the Downloads page instead. This way they are all in one place and I can keep them up-to-date. For those that can I still recommend buying boards from OSH Park, that will be easiest (OSH Park links are also on the Downloads page).
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Offline Ncartmell

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Re: Home Build
« Reply #5 on: October 26, 2017, 04:20:08 AM »
Hello John,

Sorry for the delay but I have not logged on for a while.

As far as uploading to SEEED I just got the zip files from OSH and then uploaded them to SEEED.

The boards seem ok and I just used all the default settings as this was the first time I have ever ordered boards.


I showed them to someone at work and they were impressed with them.

He says they have been electrically tested as well as he can see the small indentations from the probes.

Apparently they have to pay extra for testing when they buy their boards from another supplier.


I did notice the silkscreen was slightly out.

The only issue I had was getting the stencils made.

If you try and get SEEED to do the stencils then the postage goes through the roof, I think it is a fault with their system.

So I got the stencils made by OSH.

There is an issue with sourcing the parts, the H Bridge is now obsolete VNH2SP30.

There is a replacement VNH3SP30 however it does not have the CS pin, is this an issue Luke?

Ali-express still has the original chip available but only from limited sources.

I will take photos of the boards and upload them.

Best Regards

Neil

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Offline LukeZ

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Re: Home Build
« Reply #6 on: October 26, 2017, 08:03:11 AM »
There is an issue with sourcing the parts, the H Bridge is now obsolete VNH2SP30.

There is a replacement VNH3SP30 however it does not have the CS pin, is this an issue Luke?

Ali-express still has the original chip available but only from limited sources.

The VNH3SP30 is a pin-compatible part but in function is inferior to the VNH2SP30. If you already have the PCBs and are unable to find the 2SP30 anywhere then you can use it, but the PWM frequency will need to be lowered to 10kHz in code (so it won't be completely silent) and the current-sensing function will be disabled.

The functional replacement for the VNH2SP30 is actually the VNH5019 however the pins are in a slightly different order so minor alterations to the board must be made. I have intended to do this but the last time I checked the original chip was still widely available so I have not got around to it. It does look as though now the supply is dwindling so I will post a new version of the board soon.

In the meantime as Neil says the original chips are still available on AliExpress and eBay.
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Offline Ncartmell

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Re: Home Build
« Reply #7 on: October 26, 2017, 11:33:41 PM »
Hello,

Pictures of the SEEED boards
20171027_072203.jpg
Home Build 20171027_072203.jpg
Views: 103

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Offline Ncartmell

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Re: Home Build
« Reply #8 on: October 26, 2017, 11:36:08 PM »
Second picture
20171027_072140.jpg
Home Build 20171027_072140.jpg
Views: 104

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Offline LukeZ

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Re: Home Build
« Reply #9 on: November 01, 2017, 09:36:54 AM »
The functional replacement for the VNH2SP30 is actually the VNH5019 however the pins are in a slightly different order so minor alterations to the board must be made... I will post a new version of the board soon.

I've posted Revision 11 of the Scout ESC board to the Downloads page, the only difference is the replacement of the VNH2SP30 with the new VNH5019 chips. Some minor re-routing had to be done so Rev 10 and 11 PCBs and stencils are not compatible with each other, but other than the two motor driver chips the bill of materials is exactly the same.

I've left the Rev 10 files up for those who are building it, but for anyone contemplating a new design go with the new version so you don't have a problem sourcing chips.

I have parts on order to build a Rev 11 board myself just to make absolutely sure the design works, but the changes are so minimal I'm not expecting any issues.
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Offline LukeZ

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Re: Home Build
« Reply #10 on: November 01, 2017, 05:01:56 PM »
Also FYI, I've started posting Gerbers specifically for SEEED PCBs for all designs on the Downloads page, and I will keep them up-to-date. For those that can I still recommend ordering from OSH Park so you don't have to mess with Gerbers and you will get a known good, and very purple, board. I believe OSH ships overseas as well. But for those that want to go through SEEED, this should help.
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Offline Ncartmell

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Re: Home Build
« Reply #11 on: November 02, 2017, 12:37:33 AM »
Hello Luke,
I was purchasing parts for the Scout and OP Sound from DigiKey and several were out of stock.

OP Sound D2 is out of stock so I was going to use the blue LED kitted from the Scout but change the current limit resistor to 560R.
Also a few resistors are out of stock
10K swapped for 11k
2k2 swapped for 2k
1k swapped for 1k1
100k swapped for 110k
Also
BZT52C15S-FDICT-ND swapped for BZT52C15S-TPMSCT-ND
Several caps out of stock but used exact value replacements.

Are these changes acceptable I do not know how critical some of the resistor values are?

Is there a reason why they are Automotive Anti Surge 1/4W?

Best Regards

Neil

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Offline LukeZ

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Re: Home Build
« Reply #12 on: November 02, 2017, 10:41:14 AM »
Neil, sorry these parts are hard to find. I typically select parts based on the stock quantity a Digikey, the idea being that if DK has 300,000 units in stock it is probably a part that is going to be around for a while. But even so it surprises me how much changes in a short period of time.

You can use the Blue LED from the Scout on the sound card just fine but you will want to change the resistor R2 on the Sound Card. Since the Blue LED on the Scout operates at 3.3v and the Sound Card also operates at 3.3v, you really don't need a resistor, but put in a 1 ohm so there is something to bridge the pads:
1 ohm resistor

As for the resistors the "automotive anti-surge" is meaningless, any 0603 replacements will work just fine. On the Scout and Sound Card the resistors don't even have to be 1/4 watt. The values in most cases are not exactly critical but they are all standard values so there is no reason to change them:
1k
10k
100k
2.2k

Your BZT diode replacement is perfectly fine, looks like the exact same part with a slightly different number.

And yes, caps can be replaced with equivalent value parts, they are not critical either.

Also recall that for now there is no need for the W25Q128 flash chip on the Sound Card, you can leave it off along with the 10k resistor R5. It doesn't look like we'll be implementing any functionality based around that chip.
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Offline Lotuswins

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Re: Home Build
« Reply #13 on: November 12, 2017, 06:44:16 PM »
Hi Luke,

Okay, we are just back from vacation so now I'm ready to start assembly of the board.  I have the hot plate you recommended, and have checked off all the parts from digitech and others.  I found the board layout finally that shows where to put which part (initially I thought I'd have to trace back from the schematic...yikes!).  So my first question is how much of the solder paste do you put on? and how is it normally applied, manually?  I was thinking of using a small screwdriver to put the paste on each tang of the part and set it down on the board though not much would be needed (the pads are awfully close together!). 

Thanks...obviously my first time at this!   Jerry

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Offline LukeZ

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Re: Home Build
« Reply #14 on: November 12, 2017, 07:13:55 PM »
Jerry, you certainly can apply the paste "manually" but that would be quite the task and thankfully human resourcefulness has given us shortcuts. But if you were to do it by hand, I would apply the paste to the board using a toothpick, and then place the parts down. I wouldn't apply paste to the parts first, that would be too tricky. Pasting a board with a toothpick is fine for small circuits, but for the Scout I think the effort would be excessive.

What you really need to do is buy a stencil from OSH Stencils. I recently added links to these on the Downloads page, they probably weren't there when you first started your project so I apologize for that (be sure to buy the correct version, there are two revisions of the Scout now listed on the Downloads page, you no doubt have Rev 10).

The stencil will cost about $15. On checkout you can also buy a "jig set" for an extra 5 dollars, which are probably a worthwhile investment. Eventually you end up with a drawer of spare PCBs and those work just as well as the pre-made jigs but when you are first starting you won't have anything so the jigs are necessary.

Included for free with every stencil is a little spreader, which is basically just a credit card piece of plastic. You could also use a real credit card, or a regular spreader from the hardware store.

Here is a video tutorial that basically shows the process. Practice will make perfect, and also different people have different techniques. For example the guy in this video doesn't tape down his stencil while scraping, he just holds it by hand. In my view this is sheer madness, I always tape mine down (you only need to tape it along one edge, then scrape from that edge and away). If you don't like your paste job you can always wipe all the paste off your board and do it again, so you can practice as many times as you want (using rubbing alcohol for cleanup of your board, stencil, spreader, fingers, whatever).

A good spread will leave a thin film of paste on the board no taller than the thickness of the stencil. You really don't need much, less than you'd probably think. You might find it difficult on the ATmega processor to get the pins pasted cleanly so that the paste isn't smeared across multiple pins - don't worry, the paste will separate onto each pin individually during reflow, provided you didn't put too much on. Watching the solder re-flow is a magical experience. But remember not to burn it!

Feel free to ask questions as you go along.


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