• A review of LocoPCB's service

    2 days ago 0 comments

    Story till now: LocoPCB was offering 5 100x100 mm boards for $2 + shipping. Gerber files were uploaded and after one to and fro with the customer rep, it was sent to processing and then manufacture. I misunderstood the difference between those two stages, read the Job Status section below. It has now shipped. Now waiting for the boards to arrive, I guess in a few weeks. So there will be a hiatus in this log until then.

    LocoPCB

    I saw ads from LocoPCB on PCBShopper many times and when I saw that they were offering 5 100x100 mm boards for $2 + shipping I decided to give them a try because they offered V-cut panelisation for free. Their office is in Shenzhen but the factory is in inland Guangzhou.

    The loco refers to locomotive as you can see from their logo. I wonder how people react to the name in Spanish speaking countries. I suppose it's still publicity.

    Board

    The board is actually under 100x48 mm so I made 2 panels per board by using the Append PCB operation in pcbnew, then adjusted the outline (Edge Cut). V-cuts must be from edge to edge. Both top and bottom of the PCB are scored, leaving about 1/3 FR4 material. Should be interesting to see how hard it is to separate the halves compared to breaktabs and mousebites.

    To ask for V-cuts in the form you tick the Customer Panel option, and the V-cut should be an edge to edge line in the Edge Cuts layer. This confuses the 3D viewer once added, as the outline is no longer a closed polygon, so you will not be able to view the board outline there, though the rest can be viewed. One complication is that I wanted to preserve the rounded corners so I had to leave 2 mm bays so that the router could cut that. Here's what the board looks like:

    Ordering

    While consulting their support pages for requirments I found that the images wouldn't display in Chrome. The reason is that the page are served by https but the images are served by http. Chrome considers this insecure. Firefox will display it with a warning in the location bar. I sent a bug report to their IT department.

    Like other fabs you fill in the form and upload the Gerber archive. You have to pay (Paypal or Visa) before it is checked.

    I had noted that unlike many other fabs they want PTH (Plated Through Hole) and NPTH (Non-PTH) in one file. This is an output option in Kicad/pcbnew. But I had failed to note that Include Extended (X2) Attributes should not be selected. And Protel file extensions of course. Must be older software that they are using. As a result, the customer rep asked me to resubmit. The redone archive worked. So to summarise:

    • Protel file extensions
    • Enable PTH and MPTH in a single file
    • Disable Include Extended (X2) Attributes

    Job status

    First the status showed processing. I thought this meant it was being made, but it turns out that this is probably just the stage where they prepare the design material such as files to drive the machinery.  It stayed in this stage for 3 days.

    After that it went into manufacturing. This should be where they actually make the board, i.e. the chemical and mechanical processes. It spent 2 days here, in line with their advertised 48 hours.

    After that the status changed to ready to ship, and then changed to shipped.

    This status line was the only progress indicator I saw, where some other fabs actually show you the part of the process it is going through. Spending 3 days in processing isn't what I expected 48 hour turnaround to mean. I think this is because for cheap orders there are engineers who try to fit the order on the unused parts of the large board containing many other, probably higher value orders. Well, I can't really complain for the $2 price and really I'm not in a hurry.

    I chose the cheapest shippng option E-packet so it will be at least 2 or 3 weeks before it gets here.

  • A review of 3 electronics bazaars in China

    11/18/2019 at 13:36 0 comments

    Revisions

    2019-12-06: Added a placeholder section for Banggood.

    2019-12-04: Aliexpress/Shipping: Aliexpress uses a single number for orders combining > 1 seller.

    2019-12-01: LCSC/Specifications: Symbols and footprints for Kicad can be obtained from the LCSC product pages. Explain how to extract information.

    Introduction

    First of all let me define the topic of review. By electronics I mean things that makers use, for example active components like chips, as well as passive components like resistors, electromechanical and optical devices, as well preconstructed modules like MCU platforms. But I exclude consumer electronics like phones. I also include materials and tools for working with electronics, like heat shrink tubing, soldering stations, multimeters, and so forth. Services like PCB manufacturing and assembly are also found in these bazaars. For these sites if you search under electronics, you end up seeing phones and that sort of thing. Usually it's the industrial category you want.

    Next, the caveats:

    • My assessment is individual. I am a hobbyist and just want to get adequate quality materials at acceptable cost. Projects that have more stringent requirements will have to do more homework. I can write about only my experiences. Feel free to comment and add your experience.
    • The situation varies a lot depending on where you live, payment methods, shipping costs, customs procedures, import duties, shipping times and so forth. I can write about only my situation, be sure to check yours. Again feel free to contribute.
    • The situation varies by time too, exchange rates go up and down, special sales may benefit you.
    • These are not the only 3 sources for electronics from China, there are many others. I may extend my review in future.
    • China is not the only place to buy components, but probably is the largest source. Also you may prefer to patronise a local shop for one reason or another, e.g. quick delivery or consumer protection laws.

    The three sites I review are eBay, Aliexpress and LCSC. The first two are seller platforms that host many shops while the third is a major component supplier to the trade and makers.

    eBay

    Usually this is the first place people head for as it's well known. Chinese sellers are well-represented here. They are usually based in Shenzhen, Shanghai and other coastal cities. Some have operations in Hong Kong. A few are found inland. But it really doesn't matter, for more than the obvious reasons.

    Choice: You will be spoilt for choice. Competition is cutthroat and prices often differ by a few cents. Besides price I also look at how many stars the shop has acquired, and the rating. I also tend to prefer shops that specialise in the kind of stuff I'm looking for. To some extent this is self-adjusting; you are less likely to see a home lighting shop sell Arduino workalikes, but they may sell bulk bags of LEDs. However the caveat is choice is good only for items in demand. The sellers here don't like holding inventory that doesn't move quickly. If you want that specialised chip you will need to go to a well-equipped stockist.

    Specifications: One problem with listings is that it's often difficult to work out exactly what you are getting. Does that WiFi dongle have a Linux driver? You may have to look through several similar listings before you see mention of the chip used which you can then go check for compatibility. This sort of research is time-consuming, sometimes a little enjoyable, but it comes with the territory.

    Price: eBay allows you to sort by price+postage lowest first. However many shops counter with the trick of advertising several items in one listing, and it turns out the cheapest price is for some related item. For example an Arduino board listed for $1 may turn out to be the price of an USB A-B cable, and you see that the Arduino costs a few $ in the dropdown. It's annoying to find $1 and up listings cluttering the first 20 pages of the results. You could...

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  • Why pcbnew

    10/23/2019 at 18:01 2 comments

    Why you should learn to use Kicad/pcbnew even if you don't plan to make an etched board

    I have found that even if you implement your circuit on perfboard instead of manufactured board, it's worthwhile taking your schematic which you drew in Kicad/eeschema and going through the PCB design process, but not generating Gerber files.

    The reasons are:

    1. By assigning footprints to all your components, you can get a realistic assessment of how much board space you need, and how the finished board will look.
    2. By strategically adjusting the placement of the components you can reduce the wiring required. You can even go back and make adjustments to the schematic, e.g. change the assignments of functionally identical units of a component, such as a multi-gate IC, to reduce the wiring complexity.
    3. An autorouter such as freeRouting (which I described here) can indicate the complexity of the routing. If you end up with lots of vias, you might want to adjust the placement.
    4. If you decide to manufacture a PCB in future you are in a good starting point.
    5. It's good practice for pcbnew. :)

    Some examples:

    DTL binary clock:

    5371 clock:

    One aspect is that with perfboard you can bend the component pins a little, but you can't reflect this in the footprints, which assume the official courtyard. You can see an example in the 5371 clock board above where I bend the LM7805 ground pin backwards. In the footprint the pins are in-line. To do this properly this you would have to design custom footprints. I just make do with some annotations on the layout on the "front silkscreen" layer. You aren't going to take this to a PCB fab house anyway but just print out the schematic and layout to follow.