USB Powered soldering iron - Page 1
Forum section: electronics / general

author: cowana
author_rank: Frequent Contributor
timestamp: April 07, 2014, 06:31:59 pm
content: I was browsing everyone's favourite auction site earlier, and came across a soldering iron designed to run off a USB port.The tip (if you can call it that) looks terrible, the temperature regulation is no doubt non existent, the idea is pointless... but I can't help but wonder if it would even get hot enough to melt solder (ignoring any components or traces for a moment).USB allows up to 2.5W, two ports may allow for 5W best case - which sounds very low to heat up that much exposed metal. They also show it with a 9v battery adaptor - I'd be very surprised if they could get close to 5W out of a standard PP3 battery, although the voltage drop probably means they're safe without having to design it for dual 5v/9v use...I think it's the worst soldering iron I've come across - can anyone beat it?Andy

author: tjb1
author_rank: Regular Contributor
timestamp: April 07, 2014, 06:35:05 pm
content: There is a review of one of these on Youtube,Frozen Electronicsis who did it I believe. If I remember correctly, he broke it before he was able to record how it works by reversing polarity.Edit: Nope, it was Connor as seen below this post.

author: Jarrod Roberson
author_rank: Regular Contributor
timestamp: April 07, 2014, 06:52:08 pm
content: I have seen hot glue guns hacked to use RC Li-Po batteries for repairs to airplanes "in the field", I am sure they don't last long but it looks like a cool hack.I can't imagine a 9V or USB power source being effective for soldering the thermal recovery time has to be measured in minutes!

author: Nerull
author_rank: Frequent Contributor
timestamp: April 07, 2014, 09:21:32 pm
content: LiPo packs can source a pretty massive amount of current for their size. A 2200mAh 30C pack has a max constant current rating of 66 Amps - 732.6 watts for a 3S pack - though it won't be lasting very long at that draw. At a more reasonable wattage, it would last quite a while.USB is 500mA.

author: Matje
author_rank: Regular Contributor
timestamp: April 07, 2014, 10:43:02 pm
content: Quote from: cowana on April 07, 2014, 06:31:59 pmHmm, the Battery Charging Specification for USB seems to allow for 7.5W (well, theoretically 25W) from a single port. Still would suck.But just you wait. Them standards people are working on USB 3.1 being able to deliver 100W (at 20V).So we will no doubt see entire soldering stations powered from USB. Actually everything connected to a computer will be powered over USB. Pity the power supplies will be the size of a small house and weigh nearly as much.And people will complain that these contraptions do drain their laptop accumulators within minutes... ;-)

author: amyk
author_rank: Super Contributor
timestamp: April 08, 2014, 01:49:58 pm
content: It's definitely not going to work for most electronics but 2.5W concentrated in a tiny area will produce enough heat to melt solder. You could probably manage to solder 0201 or 01005 SMD parts on equally tiny traces with an appropriately sized 2.5W heater.As for a 9V battery, no.

author: richard.cs
author_rank: Super Contributor
timestamp: April 08, 2014, 02:30:04 pm
content: Most desktop PCs current limit with polyfuses on a group of ports, so I can believe a 2amp / 10W soldering iron would "work" on many (but far from all) PCs. Might be ok for small work - I have a 12V 10W iron somewhere that's usable.

author: wraper
author_rank: Unknown
timestamp: April 08, 2014, 07:20:07 pm
content: Quote from: amyk on April 08, 2014, 01:49:58 pmI highly doubt that as such parts are usually soldered on multilayer PCBs with multiple beefy ground planes such as in mobile phones.

author: David Hess
author_rank: Super Contributor
timestamp: April 08, 2014, 10:15:39 pm
content: Quote from: Nerull on April 07, 2014, 09:21:32 pmHardly anything that powerful is needed. Iso-Tip has been making cordless soldering irons for decades. They are not powerful enough to work with a heavy ground plane but plated through holes are not impossible.QuoteMy quick and dirty calculation based on the Iso-Tip cordless soldering irons comes up with about 2.5 watts so 5 volts at 500 milliamps from USB might be enough. I could be off by a factor of at least 2 though. I would have to dig mine out of storage and test it to make a better estimate.

author: Jarrod Roberson
author_rank: Regular Contributor
timestamp: April 09, 2014, 03:45:17 pm
content: Here is a soldering iron powered by LiPo batteries.

author: David Hess
author_rank: Super Contributor
timestamp: April 09, 2014, 04:38:46 pm
content: Quote from: mojo-chan on April 09, 2014, 03:27:48 pmThe old Iso-Tip cordless soldering irons just use a pair of NiCd C or sub-C cells rated at about a 1C discharge rate.How does high efficiency work with a resistive heater in a soldering iron tip? If Hakko gets better than 100% efficiency which is typical, then they are really onto something.

author: NiHaoMike
author_rank: Super Contributor
timestamp: April 09, 2014, 08:00:35 pm
content: I once had a ColdHeat soldering iron. It actually works great for small connections, but the ceramic tips break after a few uses.

author: amyk
author_rank: Super Contributor
timestamp: April 09, 2014, 08:51:18 pm
content: Quote from: David Hess on April 09, 2014, 04:38:46 pmResistive heaters do have 100% efficiency, but what I think he means is that they've reduced the heat losses so there's less heat wasted (i.e. traveling backwards toward the handle) and more spent towards heating the tip. A little bit of power can be enough to heat something beyond the melting point of solder -- e.g. the filament in those <1W incandescent lamps can glow white-hot. It's then only a matter of how much power is needed to maintain soldering temperatures on a PCB.Also, using the adjective "cool" to describe a soldering iron is a little amusing.