Thursday, September 16, 2010

Electroluminescent Strips

Electroluminescent strips are available in all shapes and sizes. They can even be cut to whatever shape is required as long as the end terminals are left unscathed. These strips find use as backlight for watches and other devices having LCDs. High voltage AC signal is required to turn on an EL Display and special drivers are available to achieve this. Typical AC voltages applied to the EL display are 50V to 250 VPK-PK, with a frequency of 50Hz to 1KHz. The current consumption depends on the area of the display - a display having an area of a few (< 5) square inches would draw somewhere around few tens of (< 100) microamperes.
So the job of the driver is to essentially draw a few tens of milliamperes at 3.3/5.0 volts DC and convert it to around 100Vp-p AC at a few hundred hertz and supplying a few tens of microamperes of current.








Information Regarding ELs:

Inside Electret Microphone




Electret Microphones come in all kind of sizes. Let us look inside three of these:


Type 1






Type 2






Type 3





Few useful links explaining the construstion and use of Electret Microphones:
These Microphones are available in Mumbai, India from Visha Electronics Corporation

Breakout Boards

So what do you do if you want to assemble a prototype of a project based on an IC which is only available in Surface Mount Package like one of these?


You make use of an appropriate Breakout Board (BoB). Lets look at some of these:


Quad Flat Package (QFP)| upto 64 Pins | 0.8mm Pitch




Quad Flat Package (QFP)| upto 160 Pins | 0.5mm Pitch





Quad Flat Package (QFP)| upto 160 Pins | 0.65mm Pitch





Shrink Small Outline Package (SSOP)| upto 40 Pins | 0.65mm Pitch




Small Outlined Integrated Circuit (SOIC)| upto 28 Pins | 1.27mm Pitch





All the above breakout boards are available in Mumbai, India from Visha Electronics Corporation

Make sure that before you solder your IC to the breakout board, you do remove the extra tinning from the tracks using a soldering iron and copper desoldering braid as shown in the photo below. Use of soldering paste while doing this is recommended. This will flatten the tracks and the you would be able to easily and accurately position the SMD IC before soldering it.


Eagle design files of a few other breakout boards are also available here.
Please note that breakout boards are not recommended for use with ICs which deal with high frequency signals (i.e. those above a few megahertz)

Wednesday, September 15, 2010

Inside a Ceramic Filter

Here are how the insides of a 460 kHz Ceramic Filter look like:






Ceramic Filters (3 pin devices) are not to be confused with Ceramic Resonators (2 pin devices).

Some more info on these from around the internet:

Inside a Ceramic Resonator

Here are how the insides of a 455 kHz Ceramic Resonator look like:






Ceramic Resonators (2 pin devices) are not to be confused with Ceramic Filters (3 pin devices).
455kHz is used as the Intermediate Frequency in AM Radio Receivers.
Some more info on these from around the internet:

Inside a Power Resistor

What do the insides of a power resistor look like?

Here are photos of 2.2 ohms/5 watt wire wound ceramic resistors. The outer shell is made of ceramic (which is a good conductor of heat but a bad conductor of electricity).



In Mumbai, India, such resistors can be bought from Visha Electronics Corporation



References: