Curt Welch

Yeah, I'm aware that tripping is heat. That's why I wrote "not just heat". The other part I was looking at on Digikey specified its trip temperature as over 200C. So not just hot, but very hot! But my thought is that the trip point will...

But the trip cycle _is_ heat. Polymers have non-trivial amounts of creep, which could explain deterioration after (repeated or long-term) tripping. The particles are embedded in the polymer, expansion of the polymer pulls the particles apart...

Thanks for that reference to the actual PTC Ken. I had found something on the internet that pointed to a different brand but otherwise same basic specs. 500 mA hold, and 1A trip point. That sounded like a good rational choice since the...

Fuses generally protect against fire or wiring (or battery) damage caused by hard short circuits. Don't expect semiconductors to be protected adequately by a fuse. Polyfuses have the characteristic that once triggered they have a permanent...

PTC fuses limit current by increasing their resistance. They don't stop the current from flowing like a traditional fuse. Instead the current stabilizes at some high but hopefully not too destructively high amount. How high the steady current...

That is some serious looking hardware! I was dubious that you could be stressing the PTC that much as I have never heard of this PTC issue with Teensy before, but it looks like you are indeed sending Teensy where no Teensy has probably gone...

Sure. First, no, we are not using the SD at all. No card in the slot. The robot where we run the teensy is FULL of heat-producing electronics and motors. The teensy itself is mounted on a PC board that is stuffed with other electronics and...

PJRC manufactured the Teensy up until March '25 and then turned the manufacturing rights over to SparkFun which has manufactured them since. To my knowledge, there were no intentional functional changes when the manufacturing changed hands...

With the new board, I've now added 320 mA of external load on the 3.3, with the board drawing 162 ma with no external load, overclocked at 804 Mhz, and no problems wth the PTC. Total USB load is 487 mA. PTC output is 4.6V so it's dropped some...

I am almost positive that there are no clones of Teeny 4.1 floating around. I have read that PTC fuses can weaken over time if subjected to repeated tripping/resetting cycles or perhaps just fairly severe thermal cycles. That doesn't seem like...

This morning, I pulled a brand-new Teensy 4.1 out of the box and have been testing it. So far, I've seen no PTC fuse issues on the new board. I've only run at 200 mA loads so far but was getting ready to add some external load to the 5V circuit...

Thanks for reporting the above. It's interesting and very useful information.

I did a bit more testing yesterday on a Teensy 4.1 board with the PTC fuse removed. By overclocking the CPU I could force it to draw more current and produce more heat. On a board with the fuse removed, I could overclock all the way to the max...

So many questions. I'll briefly comment on this one. We're trying to better support dynamic CPU frequency changes on Teensy 4.0. This wasn't really feasible on Teensy 3.x, because nearly everything's clock is integer division from the CPU...

A more robust polyfuse that's 0603 might be 0603L075SLYR which has a 750mA hold current at 20C. It has a much lower max resistance after tripping too. https://www.digikey.co.uk/en/products/detail/littelfuse-inc/0603L075SLYR/3661955

We just had to hunt this bug down for work, and I thought I would share what I found. We have a Teensy 4.1 as a controller in our robot that recently started rebooting for no known reason. It would not just reboot once, but keep repeating every...

The F1 PTC fuse I suspect, is this part: https://www.digikey.com/short/5t5fjzj3 Bel Fuse Inc. 0ZCK0050FF2E PTC RESET FUSE 6V 500MA 0805 But as Paul already said two years ago, you have Q1 circled in your picture. I had to hunt this down for...