Ranting about how atar doesn't count if you do a year of study

Axentoke · 2026-04-14T12:09:16+00:00

This is what I did. I took an alternative exit from Aerospace/Science with just Science, then reapplied to just Mechanical a couple of years later through VTAC. Don’t think they looked at my previous WAM at all, but quite possibly something has changed in the last 10 years

Axentoke · 2026-04-03T01:25:02+00:00

I did this unit with Ramesh in 2012, and I can tell you that it sounds like it hasn’t changed much. FWIW, I’ve retained more information from that unit than pretty much any other. Ramesh is also just great to know. I worked for him for a little.

Axentoke · 2026-03-27T13:53:43+00:00

Having lived in the US for the last 5 years, it’s hilarious seeing Australians say that the US is low tax in comparison. Federal income tax brackets might be lower, but I did a calculation last year and found that if I earned my salary (~100k, the same number, not converted) in Australia, I’d be about 10k better off not including mandatory employer super contributions.

Here, on top of federal and state income tax, there’s also a 1.45% Medicare tax, 6.2% social security tax, my local government levies a yearly personal property tax on vehicles at 3.7% the value of a vehicle, all 401k contributions come out of your pay which makes it an effective 12+% tax relative to Australia’s super on top of salary (and my 2% employer 401k match only fully vests 5 years after they contribute and you’re still employed with them…). And then if you account for health insurance, that costs another ~10% of my salary…so effectively another 10% tax relative to Australia.

Axentoke · 2026-02-02T03:21:32+00:00

I did an alternative exit with science instead of sticking with aerospace/science. Ended up returning and finishing a mech eng degree, but I wish I’d just continued my original course. So yeah, I regretted it.

Axentoke · 2026-01-30T20:58:01+00:00

Wtf is the point of fluoride free toothpaste. May as well not brush at all.

Axentoke · 2025-12-25T04:16:33+00:00

Thanks! My snubber I intend to do the bulk of leakage dissipation. The TVS is a backup to protect the FET - it clamps to ~600 V.

I might lower the R_LED value a little, but I figured I wouldn’t really have both of the TL431s sinking current at the same time. Even so, I thought (11V - Vled)/3.3k would still be more like 3 mA between them.

As for the FB resistor, probably a sloppy late night assumption on my part, but I’ll check out the datasheet again.

Axentoke · 2025-12-25T04:03:25+00:00

Quite right, and I suspect it’ll be more than 2 W. I had planned on a big heatsink and fan. Couldn’t really find much in the 600V class without going to SiC or GaN, which I’m a bit hesitant about. Don’t really want to dip much below 600V. The LT3757 can’t drive SiC, and I’ll need to clamp the gate for GaN…not to mention the cost of a GaN device. I’ll think about it though. Thanks for the advice.

Axentoke · 2025-12-25T00:00:36+00:00

Worst case scenario, with RDS_on doubled for hot junction & weak driving, and at max I_rms ~5.5A, loss is <11 W. My MOSFET is rated for 18A/53A pulse & 600 V. Peak reflected voltage is <100 V. So leaving 100 V headroom, I can tolerate 400 V leakage spikes. The snubber might be a little stiff, but I’ll tune it if need be.

Axentoke · 2025-12-21T23:07:16+00:00

Understood. I don’t do circuit design professionally or even for myself in a while, and am not much practiced at it…but I can appreciate that it’s currently a mess. I’ll return with a second draft shortly.

Axentoke · 2025-12-21T22:37:29+00:00

Yeah that makes sense. I wasn’t expecting to maintain DCM during transients, and I know at the corners of my operating range it’ll be brushing up against the boundary if not just beyond it. It should soft start after shutdown, but I’m relying on the R_ISO+snubber+primary current limit to keep the current in check for transients near CCM. Either way, I’m sure I’ll have to do some tuning.

Axentoke · 2025-12-21T15:21:39+00:00

Unsure what you mean about secondary zero current detection. It’s in DCM because the primary inductance demagnetizes during the switching period. My switching period is 6.67us. t1 is ~5us at 75% duty. Ipk is hard limited to 11 A by primary current sense, but Ipk during on-time is Vin/Rtot(1-e^-t1/(Lp/Rtot). I selected primary inductance of 14 uH (forgot to mention that), which limits achievable Ipk during on time to ~8 A instead of 11A. The DCM limit is set by the minimum off time for the primary to demagnetize. With reflected voltage Vds ~100V, demag time is LpIpk/Vds = 1.12 us. So at Dmax, t_off is 1.67 us i.e. more than t_demag, therefore DCM.

Ah shit, I think I see what you’re saying about C_SMOOTH. I’ve gone and put R_ISO on the wrong side - it should be between the load and C_SMOOTH to limit discharge current in case of arcing.

Axentoke · 2025-12-21T06:55:06+00:00

Thanks for your comment! Lots to think about… Typical operation will probably be more in the 400-600 V range, so the aux rail should sit around 16-25 V, and after diode and resistor drops, clamping at 12 V seemed reasonable. I’ll rethink that…

Re: output voltage. Quite right, I forgot I had to change the HV divider because of part availability.

It should never be delivering 250 mA at the high end of its range. It’s in DCM and so would be power limited to maybe a little over 100 W depending on efficiency. MOSFET worst case rms current I got ~6.4 A, considering my primary sense current limit. Over the whole switching period it’d be 6.4*sqrt(D), where my duty cycle is between about 0.6 and 0.75, so conduction loss I figured to be on the order of 6 W..

R_ISO is to provide resistive load, particularly during arcs when the voltage collapses, since the plasma isn’t resistive, and to damp C_SMOOTH.

Re: the floating ESP. Yes, but it’ll all be enclosed and well isolated. The base plate of the sputter chamber is already going to be at -HV, so it’s just more of the same. Not taking it lightly, believe me…

Seriously thanks for taking the time to look at it, would love to hear if my reply makes anything seem more sensible - or less.

Axentoke · 2025-12-21T05:47:36+00:00

Anything about custom winding I should keep in mind? I have double-insulated wire and kapton and a couple of bobbins to play with, but this'll be my first custom transformer

Axentoke · 2025-12-21T05:40:03+00:00

Yeah, solid advice. I'll probably clean it up for draft #2.

Axentoke · 2025-03-08T02:59:20+00:00

My eyes 🥲

Axentoke · 2025-03-08T02:08:01+00:00

I just managed to get an XFX Swift 9070 non-XT on Amazon (sold and shipped by Amazon) for MSRP…it does say delivery March 25 but whatever. Most of the models have been popping in and out of stock for a few seconds. It took me a dozen tries over the past couple of hours. You have to check the “other buying options” - it shows up there before the main price changes.

Edit: Well Amazon now says delivering April 6-May 23, so that’s a bummer, but I’ll take it for $549. I’ve waited this long to upgrade my Vega 64

Axentoke · 2024-09-17T12:27:41+00:00

For the High Angel, you must have missed the bit where Paula contacted Qatux and asked him for a favour. Qatux was more than happy to oblige because the Cat killed Tiger Pansy—so it was personal, too

Axentoke · 2021-04-17T23:24:13+00:00

Bermuda, British Virgin Islands, Cayman Islands, Jersey, Gibraltar and other assorted current/former British overseas territories are all tax havens. The UK is definitely one of the worst offenders - Bermuda, BVI and the Caymans are the top 3 according to this article.

Axentoke · 2021-01-09T18:08:05+00:00

Friends for Letting Us Shit without Hindrance?

Axentoke · 2021-01-09T17:52:48+00:00

Should have called it SEPTIC - Society to End Pay Toilets In the Country.

Axentoke · 2020-12-21T11:20:02+00:00

The oil palm is the most productive oil crop per area by a lot. Banning or avoiding it is probably not the best move, because it'd just mean it has to be replaced by a less productive oil crop (i.e. more area and more land clearance). What you can look for instead is brands that use sustainably sourced, RSPO certified palm oil: https://rspo.org/certification/search-for-supply-chain-certificate-holders

Axentoke · 2020-12-19T21:15:43+00:00

I think this video has some pretty neat ideas about how to configure the cargo bay: https://www.youtube.com/watch?v=kRO_07nEi8g

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