990
PWM power supply (szmer.info)
submitted 2 months ago by Ludrol@szmer.info to c/microblogmemes@lemmy.world
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Source: https://lemmy.world/comment/15569796

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[-] brucethemoose@lemmy.world 206 points 2 months ago* (last edited 2 months ago)

Shoudn't it be 25%?

Current is not controlled here, resistance (aka the soldering iron) and voltage are.

Power = Voltage ^ 2 / Resistance. Double the voltage, that quadruples the power. So you only want to plug in 25% of the time to get the equivalent power of 120V.

But it might not melt at double power? Maybe the extra heat helps, I can't find a resistance/temperature curve for a soldering iron...

Source: EE dropout.

[-] homesweethomeMrL@lemmy.world 119 points 2 months ago

nnnNNEEEEEEERRRRRRRRRd!

[-] ch00f@lemmy.world 48 points 2 months ago

Right you are. Oops.

[-] uneatable@lemmy.world 17 points 2 months ago

Ok. I was acountless on lemmy for a long time, your comment made me finally register. Thanks!

So, yeah, with double the voltage you get 4x the power. But you you put 4 times the power at 50% of the time, you get only 2x the power. And the other half of the time, you get 0 power. On the average you get the same power output.

[-] ch00f@lemmy.world 22 points 2 months ago

You double counted there.

You said 4x power 50% of the time and then said “the other half of the time.”

So you’re calculating 50% of 50% which is 25% duty cycle.

[-] uneatable@lemmy.world 15 points 2 months ago

Oh no, I didn't. Should I draw a graph? Pop out some equations?

Let's say P is the nominal power. When I said "The other half" I meant when the solder iron is not plugged. So:

50% of the time at 4xP 50% of the time at 0...

Oh shizzzz, you're right!

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[-] brucethemoose@lemmy.world 7 points 2 months ago

Also, welcome to Lemmy!

[-] uneatable@lemmy.world 5 points 2 months ago

thanks!

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[-] Cenotaph@mander.xyz 16 points 2 months ago

I sure hope someone will be fired for this obvious blunder

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[-] EmoDuck@sh.itjust.works 76 points 2 months ago

There are gas powered soldering irons that are essentially lighters with metal around the flame. Real life savers

[-] zaphod@sopuli.xyz 67 points 2 months ago

There are also battery powered soldering irons.

[-] BastingChemina@slrpnk.net 40 points 2 months ago* (last edited 2 months ago)

I like the pinecil, usb-c powered soldering iron with temperature control. If you are not doing anything intensive any fast smartphone charger will power it.

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[-] jpreston2005@lemmy.world 59 points 2 months ago

It's only stupid if it doesn't work

[-] Xatolos@reddthat.com 53 points 2 months ago

Should have just left it in, and been able to get the soldering done twice as fast.

[-] betterdeadthanreddit@lemmy.world 19 points 2 months ago

New manufacturing hack unlocked: Install 240v outlets at workstations and fire half of the workforce. Golden parachute and douchey, hand-wavey TED Talk, please!

[-] affenlehrer@feddit.org 4 points 2 months ago* (last edited 2 months ago)

Elon knows more about manufacturing than any other person on earth, he said

[-] oldfart@lemm.ee 26 points 2 months ago

Finally, an usecase for USB irons!

[-] Bronzie@sh.itjust.works 6 points 2 months ago* (last edited 2 months ago)

I just got one, and it’s so practical with a PD battery bank. Can now solder inside or outside on my car/bike with zero hazzle

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[-] tfowinder@lemmy.ml 23 points 2 months ago

Don't they have switches?

[-] farcaster@lemmy.world 25 points 2 months ago

Sounds like a cheap portable soldering iron, which just heats up to some roughly usable temperature whenever it's plugged in.

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[-] Godort@lemm.ee 6 points 2 months ago* (last edited 2 months ago)

Ive seen some really cheap irons that have zero controls, you plug them in and they operate at max power. Basically a wood burning pencil, really.

An engineer that has a project to show off at a trade show will have will have both a power switch and a temperature control on their soldering iron.

[-] cynar@lemmy.world 11 points 2 months ago

I'm an engineer that's been in that sort of situation. If it's planned, you have the tools. Unfortunately, sometimes these things happen and it's not planned. At that point it's taken what you can get. A cheap fire stick will still do the job better than no fire stick.

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[-] affenlehrer@feddit.org 21 points 2 months ago

I've had a similar experience as a child. I live in Germany and found this voltage switch on a hair dryer. My thoughts were like: Switching it to less couldn't possibly hurt, could it? Well it could. It was super efficient though but only for a few seconds before it self destructed.

[-] Fermion@feddit.nl 20 points 2 months ago

They need a 1/4 duty cycle.

[-] Kaput@lemmy.world 16 points 2 months ago

Person Wait Modulation.

[-] observantTrapezium@lemmy.ca 13 points 2 months ago

I had the opposite problem, I brought a soldering iron from Europe to Canada, and despite using a step up transformer, it just couldn't get hot enough to melt the solder!

[-] lauha@lemmy.one 24 points 2 months ago

You should have used 200% duty cycle

[-] RisingSwell@lemmy.dbzer0.com 12 points 2 months ago

Why plug and unplug? Doesn't the wall outlet have a switch?

[-] Azzu@lemm.ee 40 points 2 months ago

I have actually never met a wall outlet with a switch.

[-] RisingSwell@lemmy.dbzer0.com 14 points 2 months ago

Really? Where are you for that? I don't have a wall outlet without a switch, and I've never seen one because why would it just be live all the time?

I'm in Australia for reference.

[-] Tenniswaffles 34 points 2 months ago

We're the exception, most places don't have switches on their outlets.

[-] nik9000@programming.dev 14 points 2 months ago

Looks like it's mostly a UK, Australia, and New Zealand thing.

[-] crmsnbleyd@sopuli.xyz 4 points 2 months ago

India as well!

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[-] Azzu@lemm.ee 13 points 2 months ago* (last edited 2 months ago)

Germany. It's just live all the time, because why wouldn't it? If you plug something in, you want it to work. If you don't want it to work, you either plug it out (which works just as well as a switch, with the same convenience), OR you use the switch at the appliance because why would you try to reach the hypothetical switch at the wall outlet if the wall outlet is behind a drawer, under a table, or whatever inconvenient place? I use my remote control to turn the TV on or off, I don't physically walk to the wall power outlet.

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[-] Johanno@feddit.org 8 points 2 months ago

Afaik it is a safety thing that is handled differently in different countries.

Uk and their colonised countries have this. The reason is that the fuses are in each plug. But no (or almost no) fuses in the power grid of the house. In Europe most countries have a single GFCI and several fuses for power grid sectors in a single place in the house where the power comes in.

I assume the switches on the power outlets are for turning off a switch because there is no GFCI in the house.

[-] jeeva@lemmy.world 5 points 2 months ago

I think in the UK at least this view might be a little outdated - every house I've ever lived in has had GFCI sectors across the house, or had to be updated to have it when work was done.

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[-] TomMasz@lemmy.world 11 points 2 months ago

Reminds me of the time when I helped install some 120 VAC ceiling fans and the electrician* wired them to the 220 VAC line. They spun like a helicopter trying to take off.

*Worked for the local electric utility, we trusted him, foolishly.

[-] RangerJosey@lemmy.ml 9 points 2 months ago

Hey. If it works, it works.

Any port in a storm right?

[-] cm0002@lemmy.world 7 points 2 months ago

So we've officially gone meta around here lol, we did it Lemmy!

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this post was submitted on 15 Mar 2025
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