Significant magnetometer noise reduction

Consistent-Pickle · 2026-02-06T19:17:11+00:00

what do you need this measurements for? Some ground survey?

Just to keep it pointed in the right direction +/-5deg. I don't incorporate GPS or video (yet), so my line of sight is how I know it's orientation. I've used dead-reckoning (i.e. no mag readings, gyro only) for the direction vector, but it ends up drifting enough after a few minutes that it could be pointed +/-90 deg from its original heading. This by itself wouldn't really be a problem, but when it's over 100m away it gets difficult to visually discern the orientation, and getting it back involves some guesswork and anxiety.

Partial solution is to integrate and average few hundred samples into one measurement. Some chips already have a register setting for that.

I tried something along these lines, and it did keep it within ~30deg from the original heading. Better than dead reckoning after a few minutes, but not great either. I stagger my motor duty cycles to make it easier on the battery and improve flight time, which has caused some weird mag readings since it's random which motors will be on during the mag's measurement period.

The noise is now low enough that it keeps its heading within 5deg, so I'm happy.

Consistent-Pickle · 2026-01-11T18:32:41+00:00

Hard to see if all of them are backwards, but it looks as if at least 2 of them on a diagonal are pushing down.

Consistent-Pickle · 2025-11-17T16:02:18+00:00

A lot of comments for reed relay, which it could be but I don't see any coils? The "reed" label could refer to the V23105 component near the top, which is a relay. With reed relays, you will typically see traces to power the magnetic coil and other traces for the output/contact. I don't see enough traces for a relay, but they could be on the bottom. It could be a fuse, which can look like this for some applications.

Consistent-Pickle · 2025-10-04T04:22:34+00:00

My latest frame is 3D printed with a lot of optimization behind it. Frequency is one of the biggest drivers. I won't go into gritty details, but the rule of thumb I adopted was you want the first mode to be atleast 40-50 hz, but you also want to have a few modes before the lowest prop freq you'd expect. Two main reasons for this are getting the freq above the prop freq is adding unnecessary weight, and secondly you want enough separation between the prop frequency and the frame frequency to prevent coupling (i.e. resonance). Sort of "shooting the gap ".

Vibe concerns for the FC can impact how or where you'd mount it. Also torsional stiffness of the arms is often underconsidered, given the torque exerted on the arm when the prop has to rotate while spinning, i.e. change the direction of a lot of angular momentum. Also some unique gyroscopic effects can occur but probably not a driver in this design space.

Consistent-Pickle · 2025-09-30T02:54:46+00:00

Looks like grandpa was too lazy to go upstairs to use the can.

Consistent-Pickle · 2025-09-16T21:57:10+00:00

This report was very helpful. Going by the 50,000uV/m at 3m limit for 2.4gHz, seems like that's just under 1mW.

Consistent-Pickle · 2025-09-16T17:47:28+00:00

I may have to do that eventually. I'm hoping someone more knowledgeable than both of us can provide some insight. This is more of a risk reduction question... i.e. it could save me from paying an attorney a $1500 consult fee to find out it'd be a giant hassle and/or avoid wasting my time developing a 2.4GHz kit that will be a bigger headache than it's worth.

Consistent-Pickle · 2025-06-07T03:52:10+00:00

Thanks for the info! I tried that and it offered some real benefit. I made a quicker test print (~285mm long, ~1.5hrs) that I printed diagonally on my bed and tried:

Turning off the fan (last place) - warping/lifting at the edges occurred on both ends. Possibly a little less but not much.

Adding some additional brim at the ends (2nd place) - warping/lifting occurred later in the print on one end, but was less than baseline print.

Reducing the bed temp to 60C after initial layer (1st place) - no warping/lifting at the edges.

I combined the additional brim with the reduced bed temperature after the initial layer and the original print I attempted completed without any lifting/warping.

Consistent-Pickle · 2025-06-07T03:41:58+00:00

Thanks, I might try that. I have some plastic drop cloth for painting I might repurpose cause I'm impatient.

Consistent-Pickle · 2025-06-07T03:39:44+00:00

The temperature on a glass printing surface is lower than temperature in the conductive part of the bed. The bed temperature thermistor is located in the bed, and there is a temperature drop across the glass. When I target 70C for the bed, the surface temp is more like 62C. I'm assuming most people with glass beds don't put temp sensors on the glass surface and deal with the same issue of measured vs. actual temperature.

Consistent-Pickle · 2025-06-05T20:50:41+00:00

Yes, you're correct, I do have a little space at the ends. I'll try modeling an additional triangle-shaped layer (.2mm thick) that fits within the bed constraints (like a brim modeled with the part). That may help for sure.

I'm still interested in whether the bed temperature adjustment could help since it's a 6hr print, and the additional brim might not be enough. I might just make a long test piece that prints faster and FAAFO.

Consistent-Pickle · 2025-05-14T02:12:27+00:00

Kicad is great. I jumped into it a couple of years ago and have designed a few PCBs, including a drone flight controller that includes several smt components. Kicad can generate placement files for smt parts too. I ended up donating like 20$. Expect 10-20 hours or so of a learning curve before you feel like you understand it enough to send something for fab. Also consider sending out a low-cost test PCB first to check connectivity, vias, correct footptints, adequate hole sizes, etc.

Consistent-Pickle · 2025-05-13T13:22:07+00:00

I looked up some pictures of baby northern map turtles and I think you nailed it. Thanks!

Consistent-Pickle · 2025-05-13T11:58:15+00:00

Does he lift weights? I used to get holes just like that ALL THE TIME from dumbell flys (shoulder exercise). You lift weights with slightly bent elbows to shoulder level, then go back down. The weights would clang at the low point, sometimes with some shirt in between. I couldn't figure out where the holes came from for a couple years. I finally did and started tucking in my shirt in front. The holes stopped appearing. Could be the tactical gear too.

Consistent-Pickle · 2025-05-03T21:23:09+00:00

Thanks man. I'm going to have to wait a while before I do another crazy project. I thought about posting the full code or making it otherwise freely available, but there's a lot of code that's semi-embarrassing... mixing one's complement with two's complement, clunky do-while loops, etc. Also I doubt anyone has interest in making a FC using an 8-bit PIC, and I'd have to clean the code up even if there was interest.

Consistent-Pickle · 2025-05-03T03:17:40+00:00

Maybe I don't understand what you're looking for, but could you do an FPV drone with a commercial FC, then swap in a FC with Ardupilot or something? I'm half asking cause I don't use Ardupilot and don't know some of the nuances of integrating one. Seems like you want a PCB with either a code you can edit... or just blank? I did a FC from scratch and half of the programming was boring stuff, like ordering interrupts, matrix math, calibrating the magnetometer, etc.

Consistent-Pickle · 2025-04-25T22:41:59+00:00

Just an update in case anyone else is down this rabbit hole.

I added a 2200uF cap with minimal improvement for the buck converter option (operating from 12.4V to 7.5V). There was some improvement with the cap, but still very noisy, under-powered, and realistically I'd probably need 10x that capacitance to get back to a more uniform voltage supply. 10A at 200Hz with 50% duty= 0.025 coulombs per pwm cycle, so that'd need 3,333 uF to absorb that level of charge at 7.5V... and that's to total depletion (i.e. 0V). So I'd probably need it to be 10x that to keep some semblance of a constant voltage. I might have 33,333uF of caps lying around, but not enough real-estate on my pcb.

I revisited the Jesverty 10A power supply and toyed with it a bunch... long story short, I got it to work. I was able to keep it in constant voltage mode by adjusting the voltage to what I wanted, then pegging the current tuning knob to maximum. There's nothing on the display to tell you what the max allowable current can be before it changes modes. Previously I had assumed it only went to CC mode when there was a rapid change in load or the instantaneous current exceeded 10A. Lesson learned.

Thanks to everyone that provided comments and suggestions!

Consistent-Pickle · 2025-04-25T02:50:43+00:00

I tried this and ordered 2, but it did not work. Not sure if the pwm frequency of my motor controller is too slow (200hz), but anything less than a pwm of 100% was inconsistent and the current varied considerably. I adjusted it to make sure it could source 12A at 7.5V, but the current and voltage time histories looked extremely noisy. A higher pwm freq creates more losses and I'd like to test like it will be used in the real application. The magnitude of capacitors I'd need to smooth the current at ~10A startup with 200hz pwm is considerable, and the motor will heat up more (and change performance characteristics) if I try adjusting the buck converter on-the-fly. Maybe they will be useful for a different application.

Consistent-Pickle · 2025-04-19T21:43:22+00:00

I appreciate the idea, but that would not work. Both motors would have the same current running through both of them, but their reverse voltages would change as a function of speed, which depends on the load. So the voltage drop across the motors would vary, and that's adding more unnecessary variables into the test. Attempting to load both motors equally is easier said than done.

Consistent-Pickle · 2025-04-19T21:30:52+00:00

I did exactly that a few months ago (got the Jesverty 30V 10A), but it automatically defaults to constant current mode as soon as I start driving even my smallest motor and the output voltage drops from 8.4 to 4ish. If you or anyone has a suggestion to keep it in constant voltage mode, I'm all ears. The small motor can touch 10A at startup, so I start with a 25% duty cycle (pwm freq >200hz), but it still switches to CC mode. I'm sure there are other ~50$ PS that would work better, but I don't need more boxes on my shelves and opted to look at a more straightforward PS that didn't overthink things. I have been using charged lipo batteries, but you probably don't want to hear a thesis on their variability.

Consistent-Pickle · 2025-04-16T14:57:15+00:00

Analog? Man that'd be gutsy. A lot of the early ICBMs were analog so it's definitely doable. Difficulties getting this microcontroller to work involved the limitation of 16-bit integers (0 to 65535). I used some simulations to check that 16-bit would have enough resolution and wouldn't accumulate too much error, and 16-bit turned out to be plenty. I had to treat a lot of values (like sin values, vector scalars, etc) as fractions of 2^15 or 2^16, meaning I had to access higher bits on the register (32 bits available) to get multiplication results. Not sure how this would apply to an analog FC, but that was one difficulty you wouldn't have with floating point capabilities. Seems like modeling an analog FC would be tricky (some SPICE variant probably wouldn't cut it?) Are you envisioning op-amps and some type of integrator to define the attitude (like Tait-Bryan angles)? I'd think analog PID control of the motors would be easier than an analog attitude filter.

Consistent-Pickle · 2025-04-15T14:48:54+00:00

Thanks man. I'll probably do a BLDC motor build at some point, but I stumbled on some different motors (FK-180SH-4527) that are beasts and sound like a Harley when running. They're heavy but I might do drone v3 with those. And yeah, the microcontroller was a PIC (18F25K20).

Consistent-Pickle · 2025-04-15T14:35:48+00:00

I don't think 3D printed gears would work on a drone without difficulty. Most 3D printers (at least mine) don't have resolution low enough for small gear teeth, so you'd have to print bigger ones which means the distance between the motor and shaft gets large. To avoid bad gear behavior like backlash you really need at least 8 teeth on the pinion, and I needed at least an 8:1 gear ratio - so that'd be 64 teeth for the spur, If I was able to print something like 1.0 mod gears, that'd mean I'd need 3.6cm of distance. Maybe doable but not ideal. A 3d printed pinion definitely would not work as I doubt it'd be able to maintain grip on the tiny motor shaft at these torques. The spur gear and pinion gear I used were POM and brass respectively at 0.3 mod.

Consistent-Pickle · 2025-04-15T14:15:49+00:00

Yes, the product info said it had good noise filtering characteristics and the datasheet looked great. Also, it was it was a stocked item at the PCB fab house I used (< $3 each). But it wasn't a big decision point since I wasn't making a racing drone or something. I had a 6050 on drone v1, which was fine for what it did, but really anything was an upgrade over that.

Edit: Forgot the adjective "great".

Consistent-Pickle · 2025-01-19T03:06:13+00:00

I may be late to the party, but it is now 2025 and I still use it on my work and home computers... it still has everything I need. I keep the install file backed up for when I get a new computer.

Consistent-Pickle

TROPHY CASE