Here’s a hairdryer that got to the end of it’s useful life. As you can see they are really pretty simple. Basically all you’ve got is a heating element (behind the front grille) and a fan to blow air around it. Of course there’s always an on/off power switch.
This one has a couple of extras that are pretty common:
1. A safety cutout in case the fan packs up and the dryer gets too hot. (It’s the silver thing on top of the black heating element housing.)
2. Half power setting – you can’t see it in this photo but there are actually two switches side by side. The first switch turns the dryer on but power is routed through a diode at the back of the switch. This makes the dryer run at half power. When the second switch is turned on the diode is bypassed, allowing the hairdryer to run at full power.
This type of hairdryer uses a tangential fan – that’s a type of fan that blows air sideways. Many hairdryers use conventional fans that look like propellor blades. These blow air along the axis of rotation, like a plane propellor.
admin Tech autopsies autopsy, dryer, hair
Oops, I dropped my hard drive!
Well to be truthful it had packed up so it wasn’t much of a loss. And it was only a 1Gb drive in the first place. As you can see below once the lid is off all the major mechanical components are exposed. You may have seen elsewhere that a hair or even a particle of smoke is enough to make a hard drive head crash fatally into the disc – so don’t try this at home. Unless your drive has taken a dive too of course.
The disc platter is very rigid. It’s made of aluminium with a magnetic coating and it is spun round at 7200 or 5400 RPM by a motor underneath. The head is a tiny ferromagnetic device that is aerodynamically designed so that it flies above the disk in the air-flow generated by the disk’s rotation. The head generates a magnetic field when current is passed through it so data can be recorded onto the disk. The clever bit is that it also generates a current when a changing magnetic field is passed across it which means that the same head can also be used to read data from the disk.
The drive is controlled by electronic circuitry on a PCB (printed circuit board). The PCB is on the bottom of the drive.
The control circuit moves the actuator arm to position the head over the correct part of the disk. The electronics can tell by reading the formatting information where the invisible magnetic tracks start and stop.
admin Tech autopsies autopsy, drive, hard, HD, tech
Here’s another in our line of technology autopsies – a GSM cellphone. This one came from a car boot sale but had no subscriber identity module (SIM) card so it wouldn’t work. The SIM card slotted into the back of the case, between the battery and the main printed circuit board (PCB).
As you can see this phone has separate loudspeaker and piezo sounders. The piezo sounder is used for the ring tone. It consists a small crystal which makes a noise when it has a voltage applied ot it. They are very efficient (ie loud!) but are only good for simple tones so can’t be used for reproducing speech.
Having a separate loudspeaker also means less chance of getting deafened if the phone rings as you put it to your ear!
The liquid crystal display needs virtually no power so is ideal in a battery-powered device like a phone. They are also pretty cheap to make which is popular with manufacturers!
The microphone consists a tiny electret which is the voltage equivalent of a magnet. It has a tiny voltage across it at all times which varies with the changes in air pressure that we know of as sound.
The main part of the phone, the audio and digital processing circuitry and the radio frequency circuits are on the PCB, which has components on both sides. Here’s what the underneath of the PCB looks like:
admin Tech autopsies autopsy, cellphone, mobile