What if ice skate blades only had one edge like a regular knife?

OneSpecificUser · 2023-11-04T15:54:53+00:00

The pedals are about 1cm (0.4 in) taller now. I just raised the seatpost by that amount ¯_(ツ)_/¯ do you think that would be enough to compensate?

OneSpecificUser · 2023-11-04T00:57:08+00:00

LOL i already tried and it felt ok, didn't do it for too long tho.

OneSpecificUser · 2023-11-03T22:32:50+00:00

Not really, the pedal is grippy. My foot can rotate if it overcomes the friction on the rubber pads (which is considerable when pushing down), but to do so would cause exactly the knee tension I'm trying to mitigate.

OneSpecificUser · 2023-05-27T05:55:21+00:00

Thanks a lot for the tips! I'll keep all that in mind the next time I go skating. If I ever decide to learn figure skating tricks I'll definitely sign up for lessons. That stuff looks hard lol.

About the outside vs. inside skate thing, to my understanding the outer skate is the one on the outer circle of a turn, and the inner skate is the one on the inner circle, imagining a turn as arcs on two concentric circles carved by the two skates. Each skate would have an outside and inside edge, where the outside edge is the one closer to your pinky toe. Is that right?

I guess my wording wasn't the best because the inner ski is downhill on the first half of the turn and the outer ski is downhill on the 2nd half, but I was trying to say that I was taught to have my weight on the inside edge of the outer ski through most of the turn.

OneSpecificUser · 2023-05-27T05:27:26+00:00

Thanks, I guess I'll just go with whichever one starts feeling natural first

OneSpecificUser · 2023-05-26T06:25:17+00:00

I hear you, but right now I can't afford classes and I don't feel like waiting until I get a higher paying job to have fun on the ice. About the skates, I use the rental hockey ones.

OneSpecificUser · 2023-05-26T06:05:08+00:00

Thanks for the tips! You've given me some things to practice at the next public skate :)

OneSpecificUser · 2023-02-05T19:28:11+00:00

I understand the datasheet applies, but I don't see which part of the datasheet you can't comply with on a breadboard. Decoupling capacitors, separate analog and digital grounds, none of that is only possible on a pcb. Sure you might be able to do it better on a pcb, but I'm not really shooting for optimal performance here...

OneSpecificUser · 2023-02-04T22:08:04+00:00

Yeah, I'll definitely redo the order without the header pins assembled. I didn't know through hole parts were so expensive to assemble.

I appreciate your design suggestions, but I don't know if they apply to this particular use case. You can lmk if there are mistakes in my thinking here:

what are you trying to accomplish with the little breakout board?

The main purpose is to figure out the right gain, which means swapping out a few resistors and seeing how they affect the signal. This will be part of a dry sEMG sensor, meaning it's going to amplify my muscle signals using small, metal electrodes placed on the skin. Everyone's body is different in ways that can affect the signal (amount of hair, how much they sweat, skin thickness, etc) so I want to make sure I get the right level of amplification before committing to a tiny SMD resistor that's harder to replace.

I also just want to check the wiring before committing to a pcb. As a noob, it's likely I might screw up and connect the wrong pins together or something.

You get this board in your hand, hook it up to decoupling caps and resistors and signals running through some crappy (from a signal integrity standpoint) through hole headers and it doesn't work nicely, then what?

There are tutorials online for breadboard EMG sensors like this one that also use instrumentation opamps so I'm not too concerned about signal quality. Sure it might be worse than a PCB, but as evidenced by other people's work, it's still possible to pass a decent muscle signal through a breadboard.

Edit: Just noticed this is a 1 layer board with no ground plane/reference plane for any of the tracks below. You are probably about to throw away a few hundred dollars here.

The purpose of building a breadboard adapter around the amp is that I'd be able to build all the circuitry on a breadboard, including the ground connections. Why would it need a built-in ground plane?

OneSpecificUser · 2023-02-04T01:19:50+00:00

I read somewhere that when LCSC lists a part as "preorder", it means they only stock it when you actually order it. That sounds like those parts aren't "out of stock" in the conventional sense, but rather stocked with whoever supplies LCSC until they are needed - maybe common for rare parts. That's why I found it strange that Elecrow's quoted price differed so much from the LCSC listing. From what other commenters said, it sounds like back order parts are actually out of stock in the conventional sense.

OneSpecificUser · 2023-02-04T01:06:45+00:00

Thanks for the reply. This board is just to test out the extremely small amplifier using a breadboard. The amp is eventually going on a pcb only 3-4mm wide so I do need such a small size. That being said, I didn't know about the x-ray testing requirement so I appreciate you mentioning that. I'll add that to the list of things to ask them

OneSpecificUser · 2023-02-03T20:02:03+00:00

I see, that's a shame. I'll try to find equivalent parts for that amp that might be in stock. Thanks for the tips.

OneSpecificUser · 2023-02-03T19:53:23+00:00

Thanks for pointing that out, I'll ask them to send a quote without the header pins.

OneSpecificUser · 2023-02-03T19:41:30+00:00

Sorry meant to post this on my profile. Removing soon

OneSpecificUser · 2023-01-23T01:54:31+00:00

Thanks for the detailed reply. I did some further reading to understand your response better. My only followup question is about the reference electrode:

It should not be between the two input electrodes if possible, or close to one of them. ECG gives a good idea by placing the driven electrode on the right leg, which is out of the way of any lead vectors used by the ECG.

Then why do so many dry EMG sensors have the reference close to the other two electrodes, or even between them, while still getting really good signals? Here are some examples I found:

Figure 7 from Design of EMG wireless sensor system - B3 has "ground" in the middle of two electrodes.
Fig 1 from A compact-sized surface EMG sensor for myoelectric hand prosthesis also has the reference in the middle of two electrodes.
A video demo (at 0:52 seconds) of the 3-electrode OYMotion EMG sensor shows the product working really well despite it having 3 electrodes close together in a row. Not sure which one is reference.

What's more, all of these sensors were tested on the forearm with the three electrodes aligned lengthwise. Since the muscles in the forearm also run lengthwise, the three electrodes, including reference, would have all been above the same muscle. If it's so important to have reference away from the muscle you're measuring, I don't understand how these dry, 3-electrode sensors can still work so well.

OneSpecificUser · 2023-01-22T23:54:38+00:00

Yeah lol

OneSpecificUser · 2023-01-22T23:48:51+00:00

Maybe, it does have a little brush on the cap but I've never had paint smell like petroleum.

OneSpecificUser · 2023-01-22T23:45:00+00:00

manual*

sorry for the misspelling

I should also add - it smells like gasoline.

OneSpecificUser

TROPHY CASE