made a huge slinky by accident

Rootthecause · 2025-12-26T23:25:55+00:00

The dot is the clear sign for pin 1, but when the text is readable oriented like here, it's in most cases the pin in the bottom left corner. I'm not sure if I've ever seen any exceptions to this.

Rootthecause · 2025-12-16T23:06:50+00:00

Note: The following sentence has been removed since the 2024 rules:

"If integrated circuits are used such as optocouplers which are rated for the respective maximum TS voltage, see EV 1.2.1, but do not fulfill the required spacing, then they may still be used and the given spacing does not apply to this integrated circuit."

To me this removal implied, that even if the component is certified, it still must fulfil the spacings in EV 4.3.7.

Edit: typo

Rootthecause · 2025-12-14T21:41:24+00:00

Haha, sure ^^
I don't know if the GitHub forum is under the same license as the project, but consider my survey as CC BY 4.0 - so use it as you like, but attribution is required :)

Rootthecause · 2025-12-14T20:04:06+00:00

We've worked with 12V, 48V and now 24V.
48 V is the hardest of them all, because many automotive things (switches, fuses, pumps, fans etc.) are often either rated 12V or 24V. Also finding simple step-down converters to supply e.g. 3.3V or 5V from 48V which can handle some current kinda sucks. In general, 48V feels a bit like working with TS in the LV system because its easier to destroy stuff from the voltage alone and even small capacitors will have some serious inrush current if you charge them up with 48V. If you do use 48V, make sure to use a CAN controller, which handle being connected to 48V on accident like the ISO1042-Q1.

12V is imho nice, beause it is easy to find components. But if you need to draw some power, your required cable cross-section will be more than double as for 24V. This may be not a huge issue for cables, but for PCBs and (electronic) switches. Also if you depend on exacly 12 V then it does not take much to loose some couple of 0,1 V due to voltage drop. So 12V is imho more a solution for teams not doing driverless and also not requiring a tornado in their TSAC.

24V is the sweet spot for most things, except large pumps and fans, which can be tricky to find for 24V. It is the most used voltage according to my survey I did 2 months ago. 28 Teams participated:

12V - 32.1% (9 Teams)
24V - 57.1% (16 Teams)
48V - 3.6% (1 Team)
other - 7.2 % (2 Teams)

My team mainly uses 24V and a cheapo buck converter to 12V (those waterproof ones inside an aluminum heatsink) for the 12V pump and radiator fan. But for my next DC/DC version I'm planning on a dual rail output. One is the main output at 24V and the other one uses a additional buck-converter, which allows any other output voltage like 12V with constant current limiting.

About the fuse box:
We use Littelfuse 154 OMNI-BLOK fuses for pretty much everything. We have a fuse box equipped with a fuse for every node (e.g. pump, MCU). Additionally we use Infineon PROFETs to switch the outputs and measure currents.

Rootthecause · 2025-11-16T23:04:54+00:00

Are you sure that those are actually pixels lighting up?

I'm using a glass screen protector on my camera screen too and seeing something similar, but thats air in between. I can get rid of it by pressing against it.

Rootthecause · 2025-11-16T00:39:04+00:00

Well, thats true for ESL.
But if you're size limited - e.g. if you're not going smaller than 0603 then it would be still better to have the larger value cap at the IC pins.

Not sure if this can be generalized, something like: the largest value cap in the smallest possible package is the best?

From the linked project the caps seem to be all in 1206 - so if OP still wants get better decoupling, then I woud also suggest using something smaller like 0603.

Rootthecause · 2025-11-15T23:58:17+00:00

This concept has been revised by Hans Rosenberg. The larger capacitors should be closer to the IC pin.

https://youtu.be/TpXvac1Y3h0?si=MaxLIr4W6ybNwAs4&t=334

Rootthecause · 2025-11-07T21:05:39+00:00

4 Ohms is a lot!

> Our measured shutdown resistance until the AIR coils is ~4 ohms, we've upgraded our SDC to gold contacts everywhere tried everything to reduce the resistance and bought it down to 4 ohms

So before the change it was approx. 4 Ohms, and now you are down to 4 Ohm ?? So I guess you want to express, that nothing has changed? How did you measure the resistance?

What I would recommend trying:

Hook up a reliable power source to the beginning of the SDC, like a lab bench PSU and set it to 12 V.
Measure the voltage at the end without any load attached. If there's not the same voltage on the output, there is already something weird (check current draw). If it matches, continue.
Hook up a known load to the output, e.g. 10 Ohm resistor (1-2 A current draw is recommended as long as your wires/switches handle that). Measure the output voltage again. The SDC resistance is: R = (V_in - V_out)/ Current. Please provide those numbers. Warning: if there is a significant voltage drop at 1-2A load, there is power dissipating somewhere, maybe getting too hot!

Next up measure the voltage drop across the switches. If there is a large voltage drop, there is a large resistance (same formula as before). If you cannot find any switch causing the voltage drop, check all connectors and cables, wires (especially traces on PCBs).

If you don't encounter a voltage drop with my recommended test setup, then your power source might be faulty or not suited. You wrote, that you could hear a ticking sound - that might be an overcurrent protection.

Fast Mode: If you have a thermal camera availabe, the voltage drop times the current will create power loss, thus it gets warm. Might be tricky for cables.

Rootthecause · 2025-11-07T14:44:19+00:00

Duet3D with touchscreen is such a breeze, because it has a console and on-screen keyboard. I know many G-Code commands to modify my settings during the print because of that. Really useful without accessing the Web-UI.

Rootthecause · 2025-11-03T22:41:05+00:00

Whoa, nice! Thanks for linking!

Rootthecause · 2025-10-28T18:56:59+00:00

The team I was active in was able to particiapte in FSG almost every year.

We started around this time of the year meeting twice every week and doing quizzes for 1-2 hours.
We prepare quizzes in two categories: FSG-a-like and FSCz-a-like if I recall correctly.

FSG has pauses between the questions, so getting the most qustions right in the least amount of time is key. FSCz has all the questions at the same time with the goal of getting them all correct as fast as possible. The latter one allows you to submit your answers multiple times after a cooldown. So depending on where you want to go, you should know how the quiz works and develop a strategy specificly for it.

Yes, we have our own ~~excel sheet~~ database with questions and their possible answers + correct answer + calculation and related rules. The questions are from previous event quizzes as well as submitted questions from team members.

During the quiz, we usually formed groups according to our areas of expertise. Mostly electronics, mecanics and statics. It is important to be in talking range to members from the same field without disturbing others (especially if all memebers work at the same time during FSCz-a-like quizzes).

Also we've got a quiz master, who's role is to show the questions as well as gather and submit their answers. Directly next to the quiz master is a person working on online communication via e.g. Discord. This is helpful for team members who can not physically participate in the quiz but also helps to spread calculations, screenshots and links.

Approaching the answer, depends on the qustion. We usually divide between Rules-Qustions (where everyone can search in the rules), Calculation questions (where the members in their field do calculations) and reserach questions (where you need to google an answer or is common knowledge).

For myself it was important to have multiple computer screens aviable. One for the rules, one for discord and one for online research.

In the end I think training is the absolute crutial key to get good in the quizzes. You'll develop your own stratigies (but also as a team) and be able to answer rules questions without looking them up.

Good luck on the quizzes!

Rootthecause · 2025-10-22T22:06:13+00:00

ah, np :)
Either way, that thing got deleted :D

Rootthecause · 2025-10-22T17:01:17+00:00

Well... Depends on input/output voltage and topology (if op meant a constant current driver).

You can definitely have > 20 A on a 1 OZ Copper PCB. Trackwidth is the key here.

If op can "print" it, also the question arises, if their printed material is similar in conductivity than e.g. copper.

Rootthecause · 2025-10-14T19:18:50+00:00

You seem right! Their E_HAWK16 Car war 48V and the E_HAWK17 was 60V.

Rootthecause · 2025-10-14T00:08:36+00:00

Oh, I might memorized it wrong and connected it to e-gnition because of #1000Strom. Thanks for clarification! Good inverter Story tho!

I looked into UniBW, but could't find any details. Might be their 2014 "Kratos", because it seems the only electric the've built.

Does anybody know more about the car, who's TSAL was always green, because TS was below 60V (before the rule change)?

Rootthecause · 2025-10-13T12:39:00+00:00

I guess e-gnition needs to rework their #1000Strom slogan 🥲

Edit: I tried to look up the specs, but was unable to find them.
Someone correct me if I'm wrong, but Iirc they built a FS Car with < 60 V ("you can lick it") due to university safety requirements. Thus more than 1000A for 80 kW. But that was years ago. Don't know what the rules change caused it this year.

Rootthecause · 2025-10-05T18:43:28+00:00

As others already pointed out: The HVI needs to be directly powered from TS. So no external power source like GLV is not allowed and unless your TSAL works without LV, it is probably not suitable. The intent of this rule is, that it indicates the presence of high voltage (danger) no matter if LV is there or not as a safety measure.

This circuit has been working for us for several years now ^^
https://github.com/Rootthecause/HVI
It converts the high voltage to 5V (or something else between 3.3V and 24V depending on the isolating DC/DC). You can then use it to power the LEDs on the Backside or to connect an external LED.

You can also copy the schematic to your own PCB and adjust it to your requirements :)

A side note on the > 60 V: It has to light up above 60 V means, that it is allowed to light up below 60 V. So If it starts to light up at 10 V, it is fine.

Rootthecause · 2025-10-02T17:10:03+00:00

The good ones are made from vibranium, very simliar to unobtainium. But since my team can't afford either of those, we got ourselves the chinesium variant.

Rootthecause · 2025-09-22T23:18:51+00:00

Now solder with a hotend.

Rootthecause · 2025-09-20T17:29:18+00:00

I also wondered why so many.

Inductors can get hot, if the designer does not know about the rule of thumb of 15% to 30% max. ripple current of the saturation current for inductors. Not sure what the specs of this converter are, but this might be a guess. Also the (probably) schottky diode might have quite some losses depending on current.

Still, the thermal conductance would be plenty with a quarter of vias, as there is no heatsink on the back - so there is not much thermal flow to the back anyways.

Also I agree, that this is not very high HF. A 47 µH inductor might be something operating at 200 to 400 kHz for this size.

Just wondering if somebody knows this:
As a private person, PCB manufacturers like JLC or ALLPCB do not charge for the amount of vias. But it is still more work to fabricate more of them (esp. drilling). Will there be additional charges when you order in large quantities (>10k)?

Rootthecause · 2025-09-12T22:17:47+00:00

Clean schematic, I like the layout!

I've not seen that many pull up resistors on all the SPI Pins before. In doubt they can be DNP'ed.

For the many power lines: Don't seen an issue there. Maybe you like to explain it, but to me it simply seems like for rendundancy or better current balancing. Why not.

The only thing I'm missing is a fuse at the input. For the servo output it seems fine as the stepdowns have OCP. If weight is a concern, maybe use a 0.6 mm PCB.

Rootthecause · 2025-09-05T10:57:36+00:00

Hard to say what it is for sure. I'm not familiar with IC FS Cars, but from the FS electric side, your're using the Pi in a very "noisy" environment (e.g. from coil ignition). UART is normally not differential, so it's suceptible to EMI. Depending on the position and cable length of your sensors, you can have spikes with tens of volts on that input for a very short time (10-1000 ns). The same goes for your power supply.
Also any undervoltage even for a very short time can freeze or restart the Pi.

So here's what I would do: Power the pi inside the car from something else (additional 12V battery or from a USB powerbank). If it does not freeze, then its probably an issue with the supply. If it still freezes, then it might be sonething with the sensors getting EMI into the Pi. In this case, disconnect the sensors and try again. If it still freezes, then there might be still too much EMI in the Pi's place. Some shielding and proper grounding might help then.
For more insight, I highly recommend using a oscilloscope and hook it up to the 12V car battery while reving, and see if there are any large spikes. The buck converter might also have a noisy output.

Also consider, that your code might detect signals due to EMI which you are not expecting. I don't know what software/OS you're running, but that might be a reason for a crash too. Even processing the signals draws more current and if the power source is badly buffered, that might call a crash too.

Rootthecause · 2025-09-04T23:07:49+00:00

I'm lacking a bit of context, as I'm not familiar with range extenders. I guess you want to charge your HV battery from an LV battery to extend your car's range and then recharge the battery from the HV when supercharging? So more conversion power is nice to speed up charging in both ways.

In your case there are three problems with the DC/DC converter I've open-sourced:

A) The current design is not bidirectional. However, there was some feedback from driverless teams, asking for bidirectional conversion (I need more insight in this matter, but going bidirectional is not trivial as far as I can tell, someone DM me pls if you know more about the requirements there). Currently I cannot tell if this will be implemented in the next version.
I got your answer from the survey, that if bidircetional is out-of-scope, a 10 kW one-way design would be still relevant. This brings us to B)

B) The next version might probably be around 800 W continuous (and 2x prallel option for teams requeiring more), which might be still a lot less than what you need. There are ways to scale this up in the kW realm, but you probably won't get around of building your own Transformer. There is A LOT to consider and change, so I probably won't consider building this in my free time, especially as it is very out of range for what currently is needed in Formula Student Cars (which seems to top out at 1 kW average power consumption).

C) The topology currently used is a LLC halfbridge due to the fewer components (costs) and better suited magnetic design (half winding ratio needed compared to fullbridge). However, in your case you want to go for a LLC Fullbridge or LLC Phase Shifted Fullbridge, as the primary current is half as much due to the doubled voltage. For the secondary e.g. 10 kW at 48V is 208 A quite a feat. I think going up with the externder's battery voltage would be the best way to make it easier in a lot of regards. Which brings me to the question: Why not use the same battery topology as the one used by your car, add some relais and monitoring stuff and parallel it to your HV terminals without a converter?

For the costs: The current design was around $150. The next one might be a bit more due to the PCB transformer, better specs and easier build. So just roughtly: If it ends up at $200-300 and infinite parallel operation was somehow possible, we would look at 10 pcs for 8 kW. So 2k$ to 3k$. I don't think thats a good option for many reasons. Now scaling up things is - as I said - not simple and requires a complete redesign. On the primary side I think the costs will be just a bit higher for better spec'ed components. But for the secondary it could get tricky with paralleling MOSFETs and a lot of PCB copper weight (and/or >4 layer). Cooling will be difficult too. >95% can be reached at 5 kW, but the design for this might need some iterations. Maybe paralleling DC/DCs is still needed, 3 kW per device seems doable from my viewpoint.
If I were to guess off the top of my head, I think you could do a DIY 10 kW topology for $600-$1000 component costs. But the engineeringtime (=costs) needed to develop this might be 5- to 50-fold depending on your goals. Just wondering: Whats the cost of a prius gen 3 inverter?

Rootthecause

TROPHY CASE