![USB Soldering Iron](https://www.experimental-engineering.co.uk/wp-content/uploads/2016/05/20160504_152437-300x169.jpg)
Here’s a novel little gadget, a USB powered soldering iron. The heating tip on these is very small & might be useful for very small SMD work. Bigger joints not so much, as it’s only rated at 8W. (Still breaks the USB standard of 2.5W from a single port).
These irons aren’t actually too bad to use, as long as the limitations in power are respected. Since nearly everything has a USB power port these days, it could make for a handy emergency soldering iron.
![Heater Socket](https://www.experimental-engineering.co.uk/wp-content/uploads/2016/05/20160504_152658-300x169.jpg)
The heater & soldering bit are a single unit, not designed to be replaced separately. (I’ve not managed to find replacement elements, but at £3 for the entire iron, it would be pretty pointless).
Above is the socket where the heater plugs in, safely isolating the plastic body from any stray heat.
![DC Input Jack](https://www.experimental-engineering.co.uk/wp-content/uploads/2016/05/20160504_152707-300x169.jpg)
The DC input is a 3.5mm audio jack, a non-standard USB to 3.5mm jack cable is supplied. Such non-standard cables have the potential to damage equipment that isn’t expecting to see 5v on an audio input if it’s used incorrectly.
![Touch Sensor & LED](https://www.experimental-engineering.co.uk/wp-content/uploads/2016/05/20160504_152653-300x169.jpg)
There isn’t actually a switch on this unit for power management, but a clever arrangement of a touch button & vibration switch. The vertical spring in the photo above makes contact with a steel ball bearing pressed into the plastic housing, forming the touch contact.
![MOSFET](https://www.experimental-engineering.co.uk/wp-content/uploads/2016/05/20160504_152646-300x169.jpg)
The large MOSFET here is switching the main heater current, the silver cylinder in front is the vibration switch, connected in parallel with the touch button.
![PCB](https://www.experimental-engineering.co.uk/wp-content/uploads/2016/05/20160504_152634-300x169.jpg)
The main controller is very simple. It’s a 555 timer configured in monostable mode. Below is a schematic showing the basic circuit.
![555 Monostable](https://www.experimental-engineering.co.uk/wp-content/uploads/2016/05/Monostable-Multivibrator-using-555-Timer-Circuit-Diagram-300x261.jpg)
Big Clive also did a teardown & review of this iron. Head over to YouTube to watch.