![]() ![]() ![]() This is classed as a ‘rare earth’ (although it’s isn’t actually any rarer than, say, copper) and makes very strong magnets. I believe the magnets in hard drives are made of neodymium. The fitting obscuring the back end of the arm wasn’t – in this model of drive anyway – screwed in place, it was just slotted on some pins and just needed prising off. The connector could be poked out from the other side, once it two fixing screws had been removed. Later on, connections will have to made to some very, very tiny points on the arm, and it’s going to be a lot easier to trace these points back to the connector, so its important not to damage the plastic cable. This would have poked through a gap in the case to connect to the circuit board on the other side. The picture shows the disk or disks, one on top of the other, like a stack of pancakes – except there are gaps between them, and the arm is actually several arms, one for each disk the arm itself with the delicate heads on the end which read the data from the disks, and with its other end moving between two magnets (not visible at the moment) and finally a flexible plastic multi-way ‘cable’ which joins the arm – and some small circuitry on the arm – to a connector. I was then able to take the lid right off and expose the inner workings – of which there aren’t actually that many. I scraped away the label until I found it and took it out. This almost freed it, but it was only after still experiencing considerable difficulty in getting it completely open that I realised there must be another screw somewhere in the middle, under the label. Having taken these out, it seemed that the top was glued in place as well as screwed, so I went round with the large screwdriver, prying it open. Turning it over, you can clearly see in the first picture the 6 screws round the edge of the ‘lid’ which needed removing. I first removed the circuit board, and put that aside. If you’re going to do the same, you may find a few differences in the details – type and positioning of screws, differently shaped fittings, and so forth, but the principles should be the same. I also needed a large flat-bladed screwdriver, which I used two or three times. The tools required for the job were a small screwdriver set, from which I mostly used a Torx or ‘star’, which I think was size 8, and a very small Philips or crosshead for a couple of screws inside: I’m sorry the PCB side is rather blurry, but I was less interested in that than what was inside. This the 3.5″ hard drive I took apart as my first experiment: You may need to set this to a higher or lower value depending on the type and size of the piezo you have used for your project.Note that in the following post I’m describing taking a hard drive apart in order to reuse some of the parts, but have no intention of putting it back together, or making it work again as a hard drive! The threshold value in the code was set for the piezo disc I used when building the project. Every time the Arduino detects a knock or squeeze, the LED will light up and then gently fade back down to off. You can now knock the sensor or squeeze it between yourįingers. If (sensorValue >= threshold) // Make sure value doesĪfter you have uploaded your code, the LED will flash quickly twice to show you that the program has started. SensorValue = analogRead(piezoPin) // Read the value from Flash the LED twice to show the program has startedĭigitalWrite(ledPin, HIGH) delay(150) digitalWrite(ledPin, PinMode(ledPin, OUTPUT) // Set the ledPin to an OUTPUT Int sensorValue = 0 // A variable to store the value read fromįloat ledValue = 0 // The brightness of the LED Int threshold = 120 // The sensor value to reach before ![]() ![]() Int piezoPin = 5 // Piezo on Analog Pin 5 Code Arduino Piezo Knock Sensor : int ledPin = 9 // LED on Digital Pin 9 ![]()
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