hamoodyjamal

Hey all, I have to complete a science fair project within 5-6 days and I need help. My project should be quite simple. The idea is this: There will be an LDR in a small box with a transparent window. When the observer covers the transparent window with his finger, a small door will open. And when he removes his finger, the door will close back. Some things I’m not sure about is if the observer leaves his finger on the LDR after the door has fully opened, what will stop the door motor(s)? And how will the door close after the observer removes his finger from the LDR and for the motor(s) to stop when the door has fully shit? Im thinking the could be small switches that when the door fully open/closes, they will be preesed down and disconnect power to the motor, but what will get them to move again if they have no power? This is a simple demonstration of how biometric technology works. I am fully aware 'real' biometric door use much more sophisticated technology to actually scan the fingerprint. My budget is around $35 Any help will be much appreciated. Thanks.

Hi, I have a simple solution for you. However, it does not include a Solar-cell to charge the battery. I have done this 3 times and worked great! All you need are some simple desktop speakers, and a rechargeable battery (or you can use normal batteries). The thing is, most simple desktop speakers (ones used for computers) have a built in transformer to drop the voltage to say 12V (in my case, it was always 9V with my speakers). So, you can hack through the transformer and connect the battery as the power supply, your speakers should work and become portable. They provide some what enough power for background music. About 5W. I used a single 9V rechargeable battery rated 170mAh and it lasted a couple of hours on full charge. However, your speakers may need more/less than 9V (i.e. 6V or 12V ...) you will need to measure the o/p of the transformer. You will, however, get a higher reading than what it is actually. Mine measured 15V when it was actually 9V. I think the 15V is called RMS volts. I don’t know of a specific way to measure the actual voltage, but you can try by playing something and setting the speakers on the loudest. WARNING: YOU WILL BE DEALING WITH 220V SO BE VERY CAREFULL NOT TO TOUCH THE TRANSFORMER INPUT WIRES My point is that you can use a battery to power simple desktop speakers. You may be wondering what I mean by simple, well, speakers that have minimal knobs, i.e. volume and power. This way, you won’t have to go through the trouble of building a circuit then housing it. Hope that helps. ;D

Im baaaack! Wow, that took longet than i expected. Was fun though. I see someone has built this project, or part of it. and is having some trouble. I couldn't quite understand what he/she wrote. Maybe you can shed some light on it? I presume the cuircuit i should build works fine???? you know, the one with the TL072 and NE567. ;D

You can build one your self. Just use a 555 timer set to say 500Hz (the frequency should be between 20Hz to 20KHz - human ear range) to drive a small speaker. Basic really. Yet again, you can always use a buzzer, or a relay (thats right, sounds wierd but true i can tell you if your interested) Later ;D

Thanks Ante. Really!!

Hi Ante, I found a website (using the google cached feature) but its blocked by my ISP, i think its becasue the link has the word H A C K . It doesnt have any hacking guids or anything that i know of, i dont know why they would block it. What i have in mind, is that if you (or someone) could save the page and then post it here. The link is: http://www.hackcanada.com/homegrown/wetware/brainwave/index.html Thanks ;D

Your welcome, Well, common sense would tell you the shorter the range, the cheaper, and sometimes this is the case. It all depends on what circuit you build of buy. You can try one of these circuits http://home.att.net/~wzmicro/avsender.htm http://www.epanorama.net/links/videocircuits.html#transmitter (many here) Video transmission F.A.Q. - http://www.hicam.com.au/art_faq.htm Hope that helps! Let me know how it goes ;D

Hi all, I once came accross a product which helps you... well, its like these glasses with LED's mounted on the lenses and you plug the glasses to the computer (via a cable ofcourse) and then you download these files and open them in a program, which in turn will turn on these Red and Green LED's in a special sequence. this claims to help you relax, get rid of phobia (i think thats how its spelt) and some other cool things. My cousin told me about this thing he bought --> Glasses with LEDs and i presumed thats the brainmachine. Unfortunately, its expensive and wont ask if i can open it. Is I crazy to have such a thought!!!! Therefore, i searched the web for the schematic, but couldnt find one. I know it should be a simple circuit because it connects to the computer via a 3.5mm Jack to RS232 adapter. Does anyone have such a circuit in their archive? Pleeeeeeeease?!?!?!?! Sorry for the poor explanation, but that's all i got. Thank you all!

Hi, Im gonna be out of town for a week or so. Going to my sister, hehe, cant wait ;D I wish i can get on with this headache project and just finish it. Later!

Transmit video --> Possible To the whole Town --> Not so easy. Needs expensive equipment Legal --> You need to buy a liscense. That ofcourse depends on your country.

Hi, I changed the pin numbering accordingly. Is this better? Also, are the "Inverting" and "Non-Inverting" Pins arranged correctly? Tip: Pins 3 and 5 (+) are "Non-Inverting" and Pins 2 and 6 (-) are "Inverting". Thanks ;D

HEHE, silly me. I used the image of the 307 op-amp and just labeled it TL072. Sorry. :-[ I'll see to the project ASAP. Thanks ;D

Hi, Ive seen devices where you can plug in them a USB Flash disk (any) which has MP3 files and then you plug the device in the cars lighter socket (for power) and this device has built in FM transmitter so you can listen to the MP3's on the radio. You can dismantle it and make your own package ;D It wont be cheap either. Not much of a help am I, hehe.

Hi, Is this circuit what i should be building? Also, can you check if the op-amps and the photodiode (especially) are arranged correctly. If they're correct, ill just set my 555 timer to 100KHz. BTW, my sister gave birth yesterday. So i might not get to the project very quickly. HEHE, im an uncle now!!! ;D ;D Thanks ;D

Hi, BTW, why do i need an op-amp in the first place? cant i just connect to the input of the NE567 to a photodiode? or is there not enough power? Also, since the photodiode is a photo volatic cell, will it not give power to the input of the NE567? The above 2 questions sound similar. But im not sure if the second one sounds right. Thanks ;D