13-08-2012, 03:11 PM
foot power generation
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PIEZOELECTRIC SENSOR
One type of piezoelectric is a crystalline material made up of unit cells (defining its physical properties) that lack a center of symmetry, while charges are oriented symmetrically, making the material electrically neutral Mechanical stress disrupts the symmetry of the charges, producing a voltage across the faces
Voltage across material is described in format of “xy-mode” x axis is the axis along which voltage is produced, and y axis is the axis being stressed
The strike of the heel against the ground can be modeled as a force impulse that causes the sudden deceleration of the foot. The effect of the shoe sole (especially the cushiony sole of a sport shoe) is to widen this impulse as it does work compressing the sole. When the sole springs back, it does not exert as much force in return as was imparted to it by the foot, and the loss is converted into waste energy manifesting itself as heat. With a piezoelectric device, some of this waste energy can be turned into electricity.
DESCRIPTION
The LM3421/23 are versatile high voltage N-channel MosFET controllers for LED drivers They can be easily configured in buck, boost, buck-boost and SEPIC topologies. This flexibility, along with an input voltage rating of 75V, makes the LM3421/23 ideal for illuminating LEDs in a large family of applications. Adjustable high-side current sense voltage allows for tight regulation of the LED current with the highest efficiency possible. The LM3421/23 uses Predictive Off-time (PRO) control, which is a combination of peak current-mode control and a predictive off-timer. This method of control eases the design of loop compensation while providing inherent input voltage feed-forward compensation. The LM3421/23 devices include a high-voltage startup regulator that operates over a wide input range of 4.5V to 75V. The internal PWM controller is designed for adjustable switching frequencies of up to 2.0 MHz, thus enabling compact solutions. Additional features include "zero current" shutdown, analog dimming, PWM dimming, over-voltage protection, under- voltage lock-out, cycle-by-cycle current limit, and thermal shutdown. The LM3423 also includes an LED output status flag, a fault flag, a programmable fault timer, and a logic input to select the polarity of the dimming output driver. The LM3421Q1/23Q1 are AEC-Q100 grade 1 qualified andLM3421Q0/23Q0 are AEC-Q100 grade 0 qualified.
PCB FABRICATION TECHNIQE
You need to generate a positive (copper black) UV translucent artwork film. You will never get a good artwork, so it is important to get the best possible quality at this stage. The most important thing is to get a clear sharp image with a very solid opaque black. Now a day, artwork is drawn using either a dedicated PCB CAD program or a suitable drawing/graphics package. It is absolutely essential that your PCB software prints holes in the middle of pads, which will act as center marks when drilling.
It is virtually impossible to accurately hand-drill boards without these holes. If you're looking to buy PCB software at any cost level and want to do hand-pro typing of boards before production, check that this facility is available. If you're using a general-purpose CAD or graphics package, define pads as either a grouped object containing a black-filled circle with a smaller concentric white-filled circle on top of it, or as an unfilled circle with a thick black line (i.e. a black ring). When defining pad and line shapes, the minimum size recommended for vi as (through-linking holes) for reliable results is 50 mil, assuming 0.8mm drill size 1 mil=(1/1000)th of an inch. You can go smaller with smaller drill sizes, but through -linking will be harder. 65Mil round or square pads for normal components and DIL ICs, with 0.8mm hole, will allow a 12.5 mil, down to 10 mil if you really need to. Centre-to-centre spacing of 12.5 mil tracks should be 25 mil-slightly less may be possible if your printer can manage it. Take care to preserve the correct diagonal track-track spacing on mitered corners; grid is 25 mil and track width 12.5 mil.
Developing
Do not use sodium hydroxide for developing photo resist laminates. It is a completely and utterly dreadful stuff for developing PCB's. Apart from its causticity, it is very sensitive to both temperature and concentration, and made-up solution doesn't last long. When it's too weak it doesn't develop at all, and when too strong it strips all the resist off. It is almost impossible to get reliable and consistent results, especially when making PCB's in an environment with large temperature variations. A much better developer is a silicate-based product that comes as a liquid concentrate. You can leave the board in it for several times the normal developing time without noticeable degradation. This also means that it is not temperature critical no risk of stripping at warmer temperatures. Made-up solution also has a very long shelf-life and lasts until it's used up. You can make the solution up really strong for very fast developing.