Subham's Electronics Circuits World: Project

Here are some projects of electronics are available

1. Finger print based security system=

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Personal Safes are revolutionary locking storage cases that open with just the touch of your finger. These products are designed as secure storage for medications, jewelry, weapons, documents, and other valuable or potentially harmful items.These utilize fingerprint recognition technology to allow access to only those whose fingerprints you choose. It contains all the necessary electronics to allow you to store, delete, and verify fingerprints with just the touch of a button. Stored fingerprints are retained even in the event of complete power failure or battery drain.These eliminates the need for keeping track of keys or remembering a combination password, or PIN. It can only be opened when an authorized user is present, since there are no keys or combinations to be copied or stolen, or locks that can be picked.

In this project the fingerprint module from Miaxis Biometrics is used. It can store up to 750 finger prints on its own memory. It can be controlled through its serial port.

The microcontroller AT89S52 interact with the module. You can Add a fingerprint, Delete a fingerprint and Identify the fingerprint.

To add a fingerprint, just show the finger on the module and press the ADD key. Now the microcontroller will send the ADD command to the module and the module will add it into the memory.

To delete the finger follow the same as above.

To identify the finger, press the Identify button and if the finger matches then the Relay is complemented.Also the fingerprint ID is displayed over the LCD display.

For more details about the Fingerprint module, please check the datasheet and you can get it from the datasheets page.

2. Disco running light =

The disco light

Disco Light

Power supply

Processing Section

Pule Section

In side the contenor

After complete

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Disco lights specific circuitry and micro controllers

This is where the disco lights are different to the beat triggered strobe light. Instead of each beat triggering a high voltage xenon flash tube to create a bright white flash, it serves as a cue to a microcontroller to produce the next pattern on a set of coloured halogen lamps. These lamps are rated at 12V, 50W and came in red, yellow, green and blue. I purchased them from Jaycar Electronics, catalogue numbers SL2741-SL2744. I would urge that you also purchase some holders for these bulbs as they get rather hot so the proper ceramic bases are much less likely to cause a fire than any impromptue mounting solution and take it from me, the pins don't solder well and it's a pain to change bulbs if soldered to wires. ;)

But back to the circuit. Figure 3 shows the rest of the circuit for the disco lights. Here, I have chosen to use a PICAXE microcontroller. These are an educational variation of the PIC microcontroller family and whilst they have several major limitations, the only one that is going to be a problem here is the memory capacity. For this reason, I reccomend that you use the PICAXE 18X rather than the 18A that I used here (which has been discontinued but it was the one in stock at my local electronics shop). They are pin compatible. You can of course use any microcontroller and I highly reccommend using one that you're familiar with especially if it can be programmed in C as after a while, BASIC becomes a bit verbose for my liking at least. Details about the PICAXE can be found at www.picaxe.co.uk. You will also need to download the free software and make up a programming cable. They're really easy to use, even if you're new to microcontrollers (but know enough basic electronics to do the rest of the project). If you are experienced in the use PICs or ATMEGAs then you'd be better using those. I personally used a PICAXE so that I could give someone who'd never used a micro before a chance to write the code for me and the patterns were so cool that I continue to use his code. It can be downloaded at the bottom of this page. :)

The pulses from figure two come in on the right of figure 3 at the point marked A. These are then level shifted down from 9 volts to 5 volts by Q1 which also has the effect of inverting them. Thus, the microcontroller should be programmed to respond to a falling edge. S1 is a switch that I provided for manually changing patterns or otherwise interacting with the disco lights. Likewise, LED DS2 is next to this push button. I also placed LED DS1 next to the sensitivity pot from figure 1 on the panel to indicate triggering so that it can be adjusted more easily. Outputs 0 to 3 control the MOSFETs which in turn control the 50 Watt halogen lamps.

MOSFET Selection

I used IRF1405 MOSFETs as I had some spare and they were massively overkill for this application. Yes the 169A drain current rating would probably melt the legs clean off but I originally purchased them due to the low drain resistance of 0.0053 ohms. Remember, the lamps will draw around 4A but could pull a lot more when cold, so I suggest at least a 16A MOSFET to be safe. As they are a little bit inductive, a 30 volt or more MOSFET is preferable, otherwise you will need fast diodes and/or snubbers. When you have some you'd like to use, calculate the loss at 4A continuous. My MOSFETs have a junction to case thermal resistance of 62 degrees per watt which means that for every watt that they dissipate, their junction will be 62 degrees hotter than the ambient air. The air could well be as high as say 35 degrees with those halogens near by so at 1 watt, they would hit 97 degrees and their maximum temperature of 175 degrees C would be hit at (175-35)/62=2.26W. Due to their low on resistance, however, they will dissipate just 4x4x0.0053=0.08W so will barely get warm and won't need a heatsink. For a thermal resistance of 62 degrees, I'd suggest you find a MOSFET of no more than 0.05 ohms as although this is conservative, the resistance of a silicon MOSFET goes up as it gets hot, causing a phenomenon known as thermal runaway where it gets hotter so dissipates more power so gets hotter etc until it is destroyed! Of course you could dissipate a few watts with a decent size heatsink but I'd rather spend that heatsink money on better transistors in the first place!

The big stuff

Figure 4 shows the rest of the circuit. This is the power supply. T1 is a 110V or 230V (depending where you live) to 9V AC transformer. I suggest you use at least a 150VA transformer and limit the number of simultaneously on lamps to 2 in your software as this gives plenty of overhead. I used a 300VA toroidial transformer that I had lying around from an old project so am able to easily run all 4 lamps at once, although the bridge would get extremely hot if I were to do this. Some might find it odd that I use a 9V transformer for 12V bulbs and still others might say that it's because when I rectify and filter the output, I get 12V DC. Neither is entirely true. To get anywhere close to a smooth DC with such high power, low voltage lamps, C1 would need to be almost a farad! It is more a token gesture to smooth out any spikes. So the bulbs are in effect getting a rectified 9V sinewave which is going to mean they are not running at full brightness. I have not noticed any lack of brightness to be honest, they are unpleasant to look at directly and I feel that the extended bulb life is worth it. (They are not designed for being flashed as far as I know). This is, however, one of the main areas where I shall improve on in the disco lights MK2 but that is a long way off. F1 should be a slow blow fuse rated sensibly according to your transformer. E.g. my 300VA transformer at 230V shoul in theory draw up to 1.3A at full load so a 2A fuse makes sense or with only 4 lamps, a 1A may even be ok! At 110V on a 300VA you would want a 3A fuse, etc etc.

Please note, it is not an error, the negative of bridge D2 is not connected! Whilst all circuits here share a common earth through D1 (and the associated rather large ground bounce), D2 supplies the positive rail for the small electronics an C3 is able to smooth this pretty well due to the much smaller power consumption of the circuits compared to that of the lamps. Thus, D1 should be a large bridge and WILL NEED TO BE WELL HEATSINKED! In the photos further down you will see that I used a small CPU heatsink I had lying around. D2 won't need a heatsink and could be constructed using 2 common 1N4001 or 1N4004 diodes. It is fairly obvious that P1 is a mains plug and S1 is a mains rated power switch. U1 ensures that the audio electronics receives a nice clean power supply. Without it, there WILL be false triggering, believe me, I tried without it. R2 and C6 provide a low pass filter for a super quiet power rail for the microphone. U2 provides a 5V rail for the microcontroller.