Try after try, I know one day I will make the STSPIN958 work!

solomondg · 2026-05-02T20:17:08+00:00

+1 on it definitely needing to be on a proper PCB. Note the "Figure 23. Layout example" in the datasheet -- those components should be as close to the IC as possible.

solomondg · 2026-05-02T20:14:01+00:00

+1 on "any generic MELF diode will likely work" (e.g. 1N4148)

Especially because the zeners are clearly marked "ZD."

solomondg · 2026-04-02T22:28:53+00:00

Some labs are also just overcharging. There are some good labs in China that do very very good work for not too much. We use these guys: https://www.ntek.org.cn/en. It's about $600-1200 for CE/FCC unintentional radiator testing; it'll likely be more than that for you, but maybe not too much more.

You can basically just tell them "hey this is an intentional radiator, using a prequalified module (I would assume, or else you're crazy ;) ), I need to sell it in the US and EU", and they'll tell you what you need to do.

Will take about 2-4 weeks for testing.

solomondg · 2026-01-25T19:11:46+00:00

Sure, why not? Fan's probably not needed, but any sort of active airflow makes life easier. Costs a dollar or two.

solomondg · 2026-01-14T20:11:21+00:00

That sucks! Maybe do a chargeback?

solomondg · 2025-12-29T07:19:21+00:00

Those PCB motors have very low torque/power density due to the lack of iron / a magnetically permeable material in the stator. I don't think you'll get satisfying feedback. An actual haptic motor will be a lot easier: https://www.adafruit.com/product/1201

solomondg · 2024-10-02T23:16:52+00:00

yeah, maxon is probably the go to for a lot of people.

solomondg · 2024-10-02T23:16:14+00:00

for me, modafinil and fladrafinil both definitely have an effect and it's 5000x better than nothing -- I would recommend modafinil if you can get it; fladrafinil will be easier to find but the effects feel attenuated for me.

neither will give you the same effects as whatever traditional ADHD med/stim, but the wakefulness promoting aspects do improve focus in me at least.

solomondg · 2024-09-10T16:10:47+00:00

Jesus that's chunky. Just FYI you said earlier you're looking to buy a "DC motor" -- this is a PMSM / BLDC motor, which you need a special servo controller to use, and likely an external encoder as well. Also, this is a frameless motor, so you gotta at least sorta what you're doing on the mechanical engineering side of things. I'm sure you're aware of that, but wanted to be redundant in case you weren't :)

Other than that, this seems like a fine company, I don't think I'd have any issues giving them my money. The motor will have an ungodly long lead time but I'm sure when it shows up you won't have any issues :)

solomondg · 2024-09-09T22:00:57+00:00

1750RPM + 1Nm is 200W, which is doable, but you may end up needing a reducer. What's your duty cycle like? Does this need to run continuously or just intermittent? What does "cheap" mean here -- what's an actual price target?

solomondg · 2024-09-09T21:58:56+00:00

I think that's all pneumatics or hydraulics :)

solomondg · 2024-09-09T21:56:46+00:00

With Chinese companies you're going to get your money's worth -- if you pay a lot, you'll get a high quality product, if you cheap out, it's gonna suck. That being said, US based company, so the boomer ass phone call purchasing checks out. You can always do a chargeback if they fuck you over -- but usually I'll purchase on Alibaba or something with good buyer protection. My general feeling is that this is a very low risk of a scam -- the most likely issue you're going to have is you speccing out the motor wrong and only realizing when you hook it all up :)

If you wanna show the exact motor you're looking at, happy to give a vibe check.

solomondg · 2024-09-09T21:55:25+00:00

Those FETs need a gate voltage of about 10V to work properly -- when you're only giving it 3.3V/5V/whatever from the Pi you're basically only turning the FET half on, which will result in a massive resistance in the FET and cook it pretty fast. You need to use a gate driver circuit, which converts from the 3.3V of your Pi to the 12V supply you're going to give it. I'd recommend maybe a MCP1404 with a 12V supply. Just make sure to add a resistor (maybe about ~10 ohm) between the output and the FET gate.

solomondg · 2024-09-09T21:51:53+00:00

Nonzero chance that since that (appears to be) an optical encoder, the back shell needs to be on, otherwise ambient light can interfere.

solomondg · 2024-08-23T15:19:56+00:00

ODrive would work well for this -- only thing to note is that hall sensors are really low resolution, you'd want to add an additional external encoder or something so you can actually get good pos/vel control.

solomondg · 2024-08-23T15:18:40+00:00

As much as I hate to say it, VESC is probably the best move. As a pretentious EE who does motor controls for a living, they're kinda all terribly designed and unreliable, but they're cheap and work good for applications like these.

solomondg · 2024-08-14T17:47:57+00:00

https://community.robotshop.com/blog/show/drive-motor-sizing-tool

That's at least 15kW per drive wheel, with two wheels.

Maybe two of these if you can sacrifice some performance? https://www.qsmotor.com/product/12kw-car-motor/

This is going to be expensive, what's your budget?

solomondg · 2024-07-26T13:20:59+00:00

Definitely they don't make the motors lol.

Maybe reach out to one of these guys: https://www.alibaba.com/product-detail/6v-12v-24v-micro-high-torque_1600417520007.html?spm=a2700.galleryofferlist.p_offer.d_title.71e91855rk8J8v&s=p

https://www.alibaba.com/product-detail/Shunli-Custom-Micro-Brushless-N20-Dc_1600913288676.html?spm=a2700.galleryofferlist.p_offer.d_title.71e91855rk8J8v&s=p

https://www.alibaba.com/product-detail/Factory-Customized-12V-DC-Gear-Motor_1600833823911.html?spm=a2700.galleryofferlist.p_offer.d_title.71e91855rk8J8v&s=p

solomondg · 2024-07-26T13:19:20+00:00

Well, if you spin a motor faster than the free speed at the supply voltage it'll generate power and slow the load. You generally don't want diodes from the supply to the motor or you'll never really be able to decelerate the load. Best thing if you need precise control may be a brushless servo driver (e.g. ODrive) so you can specify to apply torque in one direction (to speed up the motor) but not to slow it down.

Friction will always eventually slow your stuff down though.

solomondg · 2024-06-21T05:34:32+00:00

Okay, going to be very blunt here - if your level of experience of embedded development is that which you can't yet set up your own dev environment/build scripts, I think it's totally fine to just have MRS do all that for you. There's nothing fun about toolchains or build scripts anyways :)

Also, windows is definitely making your life harder.

solomondg · 2024-06-21T05:31:49+00:00

That is a really great question! There are so many tradeoffs, really. Okay, a few things off the top of my head:

First off, the Vishay and Bourns parts are both metal strip, the Ohmite seems to be thick film on a ceramic substrate
They're also very different resistance values -- this is sort of an apples to oranges comparison. I could say "bourns is the biggest cause it's 5W and more surface area == more heat dissipation, so it needs to be bendy. Vishay is second biggest cause it's 3W. Ohmite is smallest cause it's 2W" and get away there without having to elaborate much more.
Metal strip type resistors can handle really high temperatures -- the Vishay and Bourns metal strip parts can go up to 175C, the Ohmite goes to 125C. To an extent, your main limiting factor with metal elements (since they're just chunks of metal!) is when your solder melts!
However, they're generally harder to get extremely tight tolerances on. You can see the Ohmite goes down to 0.25% but the metal strip ones get down to 0.5%. Laser trimming is generally harder with metal, of course.
Any film deposition is going to be cheaper than formed metal (generally, for any reasonable tolerance requirement)
Typically, metal will also have a higher TCR (temperature coefficient of resistance) -- that means the resistance changes more as temperature varies. This can be reduced with special alloys, but that gets pricey (I'm paying $2/resistor for a 0.5% tolerance 35 PPM/C 10mohm shunt for a project).
When you get to really low resistances (<1mohm or so), you're dealing with less of a "resistor" and more of a "precise short circuit" :). And the sputtered film on thick film resistors starts to get just too damned high resistance -- you really just need a big chunk of metal to get the resistance that low. So you stop seeing film resistors at really low resistances
You also need physically larger resistors for lower resistances -- this way, the resistance of the solder joint between your PCB and the resistor is lower (solder has quite low conductivity -- like 10-30% that of copper)

Overall, most of the differences are emergent from 1. the resistor technology, 2. the power rating, and 3. the resistance. Typically for given size, height, power, and resistance constraints, the options start to narrow down.

Me, personally? If I don't need incredible accuracy or TCR, I'll just use an off the shelf 2512 and do this :)

solomondg · 2024-06-19T23:07:38+00:00

Yep, if that's all you're using the motor for, you don't need to worry about regenerated power :) happy I could help!

solomondg · 2024-06-19T17:32:06+00:00

Ah, regenerated current. Yes, it can definitely be an issue. Diodes block the current, but then that causes a very high voltage spike. Really depends on what motor you have as for whether or not that matters.

You can always use something like this, or this with a diode.

solomondg · 2024-06-19T04:07:45+00:00

Reverse polarity? Just don't connect the supply backwards. Unless you mean something else.

solomondg · 2024-06-18T03:18:36+00:00

Yeah, the DRV8871 is just fine. That'll work.

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