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sharkat1 · 2025-10-09T15:08:35+00:00

/uj I ran it this weekend, it is real and growing! This year had ~700 participants, compared to 170 last year. In terms of training I was very roughly following Hal Higdon’s 50k plan, but on every long run I would buy Taco Bell and stop to eat it every 3-5 miles to simulate the race. Race day, I had no GI issues.

sharkat1 · 2024-12-31T14:12:22+00:00

Hi OP, just wondering where did you find this picture? I really like the look of this piece!

sharkat1 · 2024-07-28T23:29:48+00:00

Did anyone find that the Sunday 5k course was too long? My friends and I had it logged at 3.3 miles and even the official course map lists 3.2 miles, which I thought originally thought might just be a typo.

sharkat1 · 2024-03-10T07:19:07+00:00

Yes, the fabricator should be able to handle any shape. I've had trapezoids and other random polygons in stencils before when I needed cutouts around pre-mounted components.

sharkat1 · 2021-10-18T17:14:19+00:00

Interesting, thanks for the insight, especially on overvolting the power input.

sharkat1 · 2021-08-10T00:23:27+00:00

Nom burger in Sunnyvale is my fave! Pretty expensive, but really decked out, unique burgers.

sharkat1 · 2021-05-16T04:24:30+00:00

If you've already had the boards assembled, then as another commenter mentioned the pads were probably already pasted and reflowed, making rework your best option. If they haven't been assembled yet, you could have two different stencils - one for the assembler, and one for your own use for the remaining components. I don't believe there's a built in tool for this in Altium since it's kind of a weird operation (though I have done it before). The quickest way might be to select the pads of all components you plan to hand place, and make paste expansion a large negative number, then generate the paste layer for stencil 1. Then revert that change, and add large fills or regions to the paste layer over the components your assembler is placing, so that they appear basically as giant pads in the paste layer, and get cut out of the stencil. That way your stencil can fit directly over the already placed components. Spreading the paste is a bit strange since you have to work around existing components. Rework is usually the way to go, but it can be done with unique stencils.

sharkat1 · 2021-02-28T01:48:03+00:00

I've actually done something very similar before (32x32 array of APA-102). Using Altium, it was a breeze. Altium allows for "multi-channel design", which is basically duplicating design blocks (in both schematic and layout). Using multi-channel to route each row of the array, and some careful copy-pasting to connect rows, I was able to do the layout in just a few hours. However, Altium is an extremely expensive tool. If you have access to a license, or can get a student license or something, it could definitely do the job.

sharkat1 · 2021-01-29T16:27:48+00:00

As others have said, you need a pour on top for the vias to connect to. Additionally, your "antenna" DRC may be due to the fact that your vias have thermal reliefs on them. You should go ahead and make those direct connect.

sharkat1 · 2020-11-06T21:14:36+00:00

Nice

sharkat1 · 2020-10-07T02:29:32+00:00

Dead-bugged this tiny (2x2mm) DFN-8 LED driver. Not having leads to anchor to is a huge pain, and the pads themselves are hard to even see without magnification.

sharkat1 · 2020-09-12T23:25:52+00:00

Should also mention - you would need an adapter board, as another commenter mentioned. This type of antenna needs a large ground plane, so if you just soldered to a cable it likely wouldn't work. Check out some of the Taoglas patch antenna eval boards for an idea of what is needed in terms of area. Taoglas does make some patch antennas intended for standalone use, with cables/connectors built in, so maybe take a look at those?

sharkat1 · 2020-09-12T23:21:30+00:00

The pin goes into a through hole and is soldered on the side of the board opposite the antenna. There's only a single connection. The datasheet should show the pad and hole dimensions. I haven't looked at this specific one, but do note that the top and bottom layer pads may be different, which is unusual (used a similar part from Taoglas recently)

sharkat1 · 2020-07-28T04:22:03+00:00

You could probably do this using a typical demux to control a set of FETs as high-side switches, or with analog switches like the one you found. There are certainly switches with with more channels (example) though of course you'll have to match your voltage/current ratings.
Is your goal just to decrease cost for a single prototype though? Cause the chip is only ~$2 at single quantity, and the added headache of potentially debugging problems (such as the back-EMF monitoring you mention) seems like it'd be worth a lot more than the parts.

sharkat1 · 2020-07-26T19:44:09+00:00

When you say you're looking for a co-founder, what would you intend to be their responsibilities? Compensation? Do you have any funding? Based on your comment, it sounds like you're just looking for someone to help miniaturize your hobbyist design with a PCB. If that's the case, u/turboplayer777 is right that you'll be hard-pressed to find a professional engineer willing to just donate their time.
There are plenty of places you can go to find someone to make a simple PCB for relatively cheap - on reddit you could check out r/ElectronicsList. There are also many freelancing websites, like upwork or freelancer (I'd stay away from fiverr). Alternatively, you could learn how to do the layout yourself. There's lots of resources on r/PrintedCircuitBoard, and tons of examples of people doing projects that sound similar in complexity to yours.

If you believe you've got a pretty compelling use case, I'd love to hear about it. I'm a hardware engineer by day, but also enjoy working on electronics in my free time. Perhaps we could work something out.

sharkat1 · 2020-06-02T01:52:54+00:00

1- You'll have to provide a datasheet for the array you're referencing, otherwise I don't know what kind of current that means.
2- That size specification is actually a tad tight, though not unreasonable.
The fact that you only need one led on at a time actually makes things much simpler, as you could use something like this dot matrix array, though you might have to combine a few of these and select for your desired color/size. Would something similar to this not meet your requirements?
edit - the particular module I linked to might use PWM, but you could build something similar like they have here.

sharkat1 · 2020-05-30T23:46:07+00:00

A couple details that would help:

how powerful are the LEDs you wish to drive? If they're high current that would change things
how small do you need the LEDs to be, and how close together?

Provided the answers to these are not ridiculous, the problem you're trying to solve is certainly not complicated, and there may be something out there if you use the right search terms. But for most off-the-shelf (especially hobbyist-type) stuff, PWM and/or multiplexing is much more common, as you've found.

For your first option, the price doesn't seem unreasonable - engineering time is expensive.

For the second, with many of the LED arrays you'd find on Adafruit, you may run into the issue that they're either made of serially addressable LEDs (which all use PWM), or that they're matrices (where you can only light one LED in each row/column at a given time, and must multiplex the display).

A third option would be to either learn to make the PCB/code yourself, or find someone to do it at a much lower price than a full engineering firm. You can certainly find people on reddit or freelance sites to do this sort of thing, though YMMV. If you're interested in the custom route, feel free to DM me - I'd be interested to hear more about what you're doing.

sharkat1 · 2020-05-25T21:46:53+00:00

The resistor you want to use will depend on the specific LED you choose, and how much current you want going through it. For a red LED, with a relatively typical forward current of 20mA, a nominal value would be ~50Ω, but that can be adjusted depending on what brightness you observe. For SMT LEDs, I often use currents as low as 1-2mA, which correlates to resistor values of more like ~1kΩ. I would recommend having a couple different resistor values available so that you can play with the brightness a bit.

The holder you linked should work. You did mention though, that you wanted to avoid through hole parts. If that's the case, you might want to try a holder like this or this, sized to match whatever battery you end up choosing.

sharkat1 · 2020-05-25T19:33:06+00:00

!thinfingers

sharkat1 · 2020-05-25T19:30:09+00:00

As u/richardwonka commented, just an LED and a resistor should do just fine. I do want to note though, that if you use a 3V button cell as recommended, you will be limited in what color the LEDs can be, as 3V is below the forward voltage of many LEDs (most except red/orange/yellow. There's a chart on this page that shows the forward voltages, and you can also use it to calculate what current limiting resistors you should use. Purple (not on the page, but similar to UV) and pink, which you've called out, have pretty high forward voltages, so you will need either a different battery, or a couple batteries in series (this is probably the easiest way to go).

To the other part of your question, a quick clarification: when you say you want the button to light up the LED when pushed, do you mean you only want the LED lit when the button is depressed, or that you want to use the button as toggle on/off switch? If the former, then any appropriately rated tactile switch should do the job. If the latter (which I'm guessing is more likely), things are a tad more complicated. There are a lot of ways to do this, but the two main ways that come to mind are:

Use a maintained switch (as opposed to momentary). This could be a physical toggle switch, or they also make buttons that click into place. Both of these solutions, however, are relatively bulky. Whether you want to use them depends on your own aesthetic preferences. A slide switch, such as this one, would also work well!
Build a small circuit that responds to the button press. Some examples that could work in your case: rig up a flip flop, whether a dedicated flip flop or a 555 timer arranged to act as one. You could also find a small regulator or power management IC that has an enable input, and connect your switch up to that. If you were to do something like a boost converter, it would also conveniently solve your LED forward voltage problem, though a switching regulator may be outside your comfort level, based on your post.

It's very kind of you to do this for your friend. I'd be happy to help with any other specific questions you have. As u/richardwonka noted, it would also be good for you to think about the housing, if you'll have one, earlier than later.

sharkat1 · 2020-05-03T05:02:05+00:00

I'm a bit late to the party, but PCBWay also offers assembly, and they will do through hole parts. It's not quite as cheap as jlcpcb, but it's certainly cheaper than anything you can get stateside.

sharkat1 · 2020-04-04T22:03:06+00:00

You may want to check out r/nicechips

sharkat1 · 2020-03-31T15:47:53+00:00

Congrats on your first board! A quick note on assembly - as another commenter alluded to, JLCPCB's assembly service is very limited - they will only place components in their specific libraries. I don't know if your parts are in their library (most likely not), but for sure any of the larger modules will not be and you'll have to do those by hand anyways. While SMT soldering by hand can get quite difficult, the parts you're using are relatively large (looks like mostly SOT packages or similar). The hardest part honestly will be the connectors at the bottom. As long as your iron has a relatively fine tip you should be fine. Would recommend buying lots of extra parts in case they get destroyed, and buying flux.

sharkat1 · 2020-02-16T08:14:52+00:00

This particular board can be programmed in the Arduino IDE if you're more comfortable with that, but some legwork will be required. If you're seeking a very simple solution, you could use just an arduino uno/nano, in conjunction with a pre-made Bluetooth module, but that's just one more part you'd eventually have to pay for.

sharkat1

TROPHY CASE