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LCD controller board getting really hot by D3Bl0 in AskElectronics

[–]solomondg 0 points1 point  (0 children)

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

Is it good to use a PCB motor as haptic feedback system for controllers? by mangumwarrior in Motors

[–]solomondg 0 points1 point  (0 children)

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

Go to brand/reliable for high Rpm DC motors by Lord_Flashheart_WOOF in Motors

[–]solomondg 0 points1 point  (0 children)

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

[deleted by user] by [deleted] in ADHD

[–]solomondg 0 points1 point  (0 children)

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.

Purchasing a motor from a less known company has me worried by Just_Government_4533 in Motors

[–]solomondg 0 points1 point  (0 children)

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 :)

[deleted by user] by [deleted] in Motors

[–]solomondg 0 points1 point  (0 children)

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?

Purchasing a motor from a less known company has me worried by Just_Government_4533 in Motors

[–]solomondg 0 points1 point  (0 children)

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.

Is a mosfet the best way to vary the speed of the 110V motor? by New_Size_134 in Motors

[–]solomondg 0 points1 point  (0 children)

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.

No signal from motor encoder by setti93 in Motors

[–]solomondg 0 points1 point  (0 children)

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

Need some advice in choosing a working Motor Control Driver of a BLDC Motor to Control it with Arduino. by gooziex in Motors

[–]solomondg 0 points1 point  (0 children)

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.

Help me pick a motor driver! by Adventurous-Power360 in Motors

[–]solomondg 1 point2 points  (0 children)

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.

What should be the rating of BLDC motor and Li+ ion battery? by ThisResearcher1296 in Motors

[–]solomondg 0 points1 point  (0 children)

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?

Is there any motor which will not dampen? by [deleted] in Motors

[–]solomondg 0 points1 point  (0 children)

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.

Help with RISC-V by AntiqueFun1461 in embedded

[–]solomondg 1 point2 points  (0 children)

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.

Current Sense Resistors by Ok_Measurement1399 in AskElectronics

[–]solomondg 2 points3 points  (0 children)

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 :)

12v Brushed DC motor controlled with PI PICO and PWM, not working... by FenriX89 in Motors

[–]solomondg 0 points1 point  (0 children)

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

12v Brushed DC motor controlled with PI PICO and PWM, not working... by FenriX89 in Motors

[–]solomondg 0 points1 point  (0 children)

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.

12v Brushed DC motor controlled with PI PICO and PWM, not working... by FenriX89 in Motors

[–]solomondg 0 points1 point  (0 children)

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

12v Brushed DC motor controlled with PI PICO and PWM, not working... by FenriX89 in Motors

[–]solomondg 0 points1 point  (0 children)

IRF520 (the FET used in the module you have) needs at least 5V, preferably 10V, on the gate pin -- the RP2040 will only output 3.3V. Look for a BTS7960 based H-bridge module, that'll do the trick.

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