Why isn't there many soldering station that uses a switch-mode converter?

[technix]

Dave already have one of those soldering iron power supplies blowing up on him. That got me thinking: why isn't many soldering stations use switch-mode converters, which can be easily made to work with a wide input voltage and is irrelevant of the input frequency.

One design idea for a switch-mode soldering station is use a laptop power brick as the universal input converter that emits 19.5V 3A. Then use an adjustable buck converter to implement the feedback-controlled heater driver.

[NiHaoMike]

One design idea for a switch-mode soldering station is use a laptop power brick as the universal input converter that emits 19.5V 3A. Then use an adjustable buck converter to implement the feedback-controlled heater driver.

That's what the TS100 did.

[ataradov]

From "reputable" vendors - laziness and legacy. PACE still designs new products with some hardcore obsolete 8051 MCUs in them in PLCC package.

I think there is a reasonably good switcher soldering stations sold on AliExpress. I'll try to find the link.

Ok, it was banggood. Here it is https://www.banggood.com/Mini-V3_0-T12-Digital-Temperature-Controller-Soldering-Station-Soldering-Iron-Tips-T12-K-p-1338117.html

I've seen some good reviews of that station.

And for completeness here are the tips https://www.banggood.com/10pcs-T12-Soldering-Iron-Tips-Set-for-HAKKO-FX951-FX952-p-1191594.html

[Nusa]

Dave is something of a special case. Most of us don't have to worry much about having ~120V hardware lying around to accidentally plug into ~240V power. Especially those of us that live in ~120V areas, as the reverse case isn't very dramatic.

Soldering irons are just an ideal scenario for transformers. Once you've got low voltage AC, all you have to do is connect it to the heater, add triac control and a control system and you're done. The tip heater doesn't care if it gets AC or DC, nor does it require any power conditioning. Plus you get isolation for free with a transformer.

Yes, modern irons will need some DC for the fancy displays and control systems, but a few diodes and caps will give you enough for that purpose. No need to switch to a full-fledged switching supply just for that.

[ataradov]

No need to switch to a full-fledged switching supply just for that.

Size and cost are also factors here. Big transformers are expensive. Actually, if I knew about that $50 Chinese station, I would not have bought Pace ADS-200.

Also, not having that marketing dude write "we are sorry" email may be nice .

[Berni]

I only see it as a good thing. Its always nice to see a big reliable chunk of iron in there. No heavily stressed caps to dry out, no switching noise and when is the last time you had lightning blow up something running from a transformer?

I have seen universal input 110/220V transformer power supplies tho. Some of the old Keithley bench DMMs use it. It actually starts up in 110V mode but has a softstart resistor that limits the current in case it is plugged into 220V. This makes the transformer give a bit of a angry buzz as it saturates, but the current in the primary is limited by the softstart resistor so nothing bad happens to it. A second or so later a circuit realizes its running on 220V and clicks a relay that switches the transformer taps into 220V mode, the angry buzz stops and it continues running in 220V mode. If you plug it into 110V then it just turns on without any buzz or relay click.

[001]

SMPS also have a problem with grounding and leakage
It is not good do get about 80V at iron tip
It can kill components

[Shock]

I'll take an iron transformer any day. The downside is extra cost for decent transformers, everything else is a benefit - weight, esd/operator safety, reliability, longevity.

[technix]

SMPS also have a problem with grounding and leakage
It is not good do get about 80V at iron tip
It can kill components

There are SMPS power bricks that uses three-prong mains connector that has an resistively earthed negative terminal. And that type of power bricks with a rated output of 12V/5A and 20V/3A are pretty much standard products now costing less than a big hunk of iron as used in transformers of that type.

12V/5A ones usually use the standard center-positive barrel jack too for further standardization. 20V/3A ones also mostly uses a common laptop power connector.

[coppercone2]

You could make the circuit intelligent and get a transformer and use the same power system. Like a voltage detect that prevents energy from being used if its not used with the right taps, or even automatic switching. It should have power good and earth ground detect as a lab iron IMO those would be nice features.

I don't want that tip making noise that can harm something like a spectrum analyzer if you have it soldered into the circuit when you are prototyping something like a RF filter and you forget to disconnect the SA and touch it with the iron or something. It needs to be safe for the best microwave equipment and other sensitive devices (assuming you don't have ridiculous earth grounds in your lab).

[coppercone2]

Dave is something of a special case. Most of us don't have to worry much about having ~120V hardware lying around to accidentally plug into ~240V power. Especially those of us that live in ~120V areas, as the reverse case isn't very dramatic.

Soldering irons are just an ideal scenario for transformers. Once you've got low voltage AC, all you have to do is connect it to the heater, add triac control and a control system and you're done. The tip heater doesn't care if it gets AC or DC, nor does it require any power conditioning. Plus you get isolation for free with a transformer.

Yes, modern irons will need some DC for the fancy displays and control systems, but a few diodes and caps will give you enough for that purpose. No need to switch to a full-fledged switching supply just for that.

you want to use a quality circuit because its used inside a electronics lab not an out door light dimmer. Don't take shortcuts just because the process control step time constant is long you need to care about your operating environment. Those irons are running very often and if there is a few people in the same room and you shove some kinda bootleg ass power system into it you will have problems or ruined experiments. Some evil charge pump to save a 50 cent LDO or whatever can cost a good product. And  you want it to be reliable and repeatable without weird failure modes because of cheap power systems.

Save that kind of stuff for something like a wood engraver in a wood shop. Or a hot knife tool for plastics work or whatever.

[Zero999]

SMPS also have a problem with grounding and leakage
It is not good do get about 80V at iron tip
It can kill components

There are SMPS power bricks that uses three-prong mains connector that has an resistively earthed negative terminal. And that type of power bricks with a rated output of 12V/5A and 20V/3A are pretty much standard products now costing less than a big hunk of iron as used in transformers of that type.

12V/5A ones usually use the standard center-positive barrel jack too for further standardization. 20V/3A ones also mostly uses a common laptop power connector.

Another solution is to connect the output to earth, via a Y capacitor, which is very common in switched mode power supplies with a non-earthed output.

In my experience most soldering irons have an earthed tip, so it's a non-issue.

I don't know why switched mode power supplies in soldering irons, aren't as common as they are in other pieces of equipment, such as oscilloscopes.

[coppercone2]

yea but if the earth pin gets loose or something its probably going to much worse then a conventional supply because of the high frequencies being used

i kinda want filtered DC there I don't give a shit about the cost

magnetic field

[mikeselectricstuff]

There was a Youtube comment that suggested that AC is preferable for high temp heating as migration within the element was an issue.
I have no idea how plausible that is at soldering temperatures - any metallurgists here ?
 

[coppercone2]

Well I read literature for kilns and they have migration problems at high currents with DC because the fields cause the wires to bend

I actually wonder if it would be annoying and pick up parts. Maybe its a bad idea. The plating is iron.

[technix]

There was a Youtube comment that suggested that AC is preferable for high temp heating as migration within the element was an issue.
I have no idea how plausible that is at soldering temperatures - any metallurgists here ?

Well I read literature for kilns and they have migration problems at high currents with DC because the fields cause the wires to bend

I actually wonder if it would be annoying and pick up parts. Maybe its a bad idea. The plating is iron.

Switch-mode converters can implement H-bridge output, hence still outputting AC power.

I'll take an iron transformer any day. The downside is extra cost for decent transformers, everything else is a benefit - weight, esd/operator safety, reliability, longevity.

Iron transformer and a quality SMPS costs about the same here in China.

[coppercone2]

thats nasty HF emi from the square waves at significant power levels near components coupled by iron.

[Benta]

It's simply nice to have a heavy base that doesn't skitter all over your workbench. That's reason enough for me to prefer an old fashioned transformer.

[coppercone2]

you can add a steel plate to it to weigh it down, or you use a nice steel chassis.

[Zero999]

yea but if the earth pin gets loose or something its probably going to much worse then a conventional supply because of the high frequencies being used

i kinda want filtered DC there I don't give a shit about the cost

magnetic field

I would have thought that a soldering iron with an SMPS would also be DC, but it could be HF AC if they cheaped out and used a halogen lamp style transformer based supply.

There are greater risks associated with a poor earth connection, especially if the PSU chassis is metal. EMC would be the least of my worries.

[perieanuo]

There was a Youtube comment that suggested that AC is preferable for high temp heating as migration within the element was an issue.
I have no idea how plausible that is at soldering temperatures - any metallurgists here ?

In fine, first comment that point why AC is preferred, tip has longer life.


Envoyé de mon iPad en utilisant Tapatalk

[Benta]

you can add a steel plate to it to weigh it down, or you use a nice steel chassis.

Of course you can. But as a transformer is so cheap anyway, why bother? It's just more complication.,

[coppercone2]

well with a transformer it would be nice to have a steel chassis anyway since its low frequency and in a electronics lab next to circuits being prototyped.

[wraper]

SMPS also have a problem with grounding and leakage
It is not good do get about 80V at iron tip
It can kill components

Does not matter. All ESD safe stations have grounded tip.

[coppercone2]

do you consider that joint between the soldering iron tip and the handle to be good as its frequently thermally cycled and hot oxidizing etc?

I would err on caution with it. There is alot of demand placed on that joint.