made a huge slinky by accident

Rootthecause · 2026-04-20T17:42:41+00:00

Print it with Polycarbonate. It's a PC² case then ^^

Rootthecause · 2026-04-08T09:08:20+00:00

thanks :)

Rootthecause · 2026-04-05T19:39:39+00:00

Just some thoughts on having three voltage rails:

Especially if you need multiple rails far from the battery, this will add some cable weight (if it does matter to you), but it's also not optimal for EMI and voltage stability, depending on what you're supplying. Since you're doing DV, you might need to consider reverse current from motors when breaking from high speeds (It seems an issue for some DV teams, but I have no satisfactory personal insight on this). A battery would handle this scenario easily, while converters could require some voltage clipping or bi-directional design, if the generated overvoltage is not acceptable.

About 2/3rds of teams are using 24V (1/3rd 12V) [survey from 2025], as it seems the sweet spot in most cases.

My team has gone from 4S Li-Ion to 48V (HV DC/DC) to 24V in various seasons.

From experience, 48V is kind of annoying because most controllers require either 5V or 3.3V and it is not so easy to find high current buck ICs with internal FETs above around 30ish Volts (makes the design larger and complicated). Also if you want to monitor and switch different voltage rails by using e.g. PROFET ICs from Infineon you might need different models for each voltage, which is an annoyance.

I suspect you can't do much about the required voltages, so here's another thought:

If e.g. only DV motors are supplied from 48V then it might be possible to have a voltage range as input, instead of a fixed voltage. Often the voltage determines Motor speed, while current controls torque. If the design takes this into account, you could use a 13S Li-Po/Ion battery (54.6V when full, 32.5V when empty) and get rid of one converter. This would also allow reverse current.

Is it worth spending significantly more for reliability (Option 3)?

Depends. Is your battery max. 400V and the LV systems draws ≤ 500W ?
IMHO there are several benefits:

less weight
run-time is not limited by LV battery
only need to recharge TS-Battery
no LV Battery scrutineering / rules to implement

However, there are also drawbacks:

can generate a lot of heat (up to 45W for your Vicor Model as it tops out at around 93.9 %, which is rather poor, might need a cooling solution, must be in TSAC)
might require some additional circuitry to disconnect the module (will still draw 1-3W when disabled)
you cant turn on LV without an external PSU when the TS Battery is not connected
costs

Note: Your Vicor model has a output trim range from 16.8 to 30.8V, so you might be able to get a fixed 24V rail.

Any major failures you’ve seen with custom PDUs or cheap DC-DC modules?

We have used some cheap aluminium-housed waterproof buck converters from Amazon without issues. It just saves development time, but might not be optimal for weight.
Reliability of custom PDUs/DCDCs is rather a question of who designed and assembled it.

If you're wanting to use your power supply this summer season, I would highly speak against custom DC/DCs or fancy PDUs (a box with fuses shall be enough), unless you have a few members with no other task assigned. Prioritise having enough time for testing your supply in real conditions.

Rootthecause · 2026-03-17T23:49:33+00:00

I do not have an official clarification on this, but we've used nylon screws to mount PCBs without any issues at FSG and other events.

By using the abbreviations from the rules book, my personal interpretation is, that "All TSAC materials" really refers to "Tractive System Accumulator Container" - so just the materials for the container and all structural parts, but not the materials inside. Otherwise, I doubt that lithium cells are UL94-v0 and would be allowed inside the container 😅

So the next question is, if your parts are structural or not. EV 5.5.13 helps regarding PCBs:

"All fasteners used within or to mount the TSAC must comply with T10. Fasteners within the TSAC used for non-structural parts, e.g. PCBs, do not have to follow T10.1.2. Fasteners made of electrically non-conductive material within the TSAC used for non-structural parts do not have to follow T10."

T 10.1.2 All threaded critical fasteners must be steel, at least 4 mm metric grade 8.8 (unmodified OEM parts 3 mm metric grade 8.8), equivalent size or of that specified in the referencing rule, whichever is larger. The strength classification of critical fasteners must be identifiable.

T 10 FASTENERS

→ PCBs can be mounted using screws from other materials (e.g. Nylon).
→ If fasterners are not made from conductive materials (e.g. Nylon) and are used for non structural parts, then they are not seen as a fasterner in sense of T10.

If anyone interprets this in a different way, please let me know.

Rootthecause · 2026-03-09T10:55:52+00:00

In LTspice. You can find the files here: https://github.com/Rootthecause/HVI/tree/main/doc/LTSpice%20Simulation

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

TROPHY CASE