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In this project, you will build transmitter and receiver circuits using an IR LED and a photo-diode. The circuit is based on obstacle detection when a person or thing comes in between the transmitter and receiver. The alarm gets triggered and beeps continuously till the time the circuit is reset.

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Step 40:

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Step 43:

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<p>Can anyone direct me to a good photodiode?</p>
<p>Hi DanieL291,</p><p>thanks for the comment. We are not sure from where you could get a photodiode? you might wanna check out adafruit or spark fun in US. Happy to answer any more queries, if you have any. BTW, we are soon coming up with our Indiegogo campaign: https://www.indiegogo.com/projects/the-coolest-diy-makers-kit-you-will-ever-own/coming_soon</p><p>let us keep talking,<br>-GP</p>
<p>What switch are you using?</p>
<p><a href="/member/DanielL291/" rel="nofollow">DanielL291</a>: Hi, we are using an SDPT relay. </p>
will u plz send this video to me....yazzimiralla@gmail.com my mail id
<p>dear yhip'sanz :we do not have a video. You can download the step by step guide. thanks</p>
Can anyone tell me which type of relay used here.
<p>Hi pankajp, this is an SPDT relay -12 V</p>
<p>The title of this instructable should not contain the word &quot;security&quot;. Detecting and defeating this system is very easy for a minimally serious attacker.</p><p>Security would be achieved if a microcontroller was installed in the transmitter and receiver circuits. The microcontrollers should be synchronized to both run the same pseudo-random number generator algorithm, generating a few numbers per second. When the number generated is above a certain threshold, the transmitter should light up, and the receiver should expect to receive; if that doesn't happen, the alarm should be triggered. When the number generated is below the threshold, the transmitter should not light up, and the receiver should expect to not receive; if that happens, then the alarm should be triggered. Emission/reception or lack thereof should last until a new random number is generated.</p><p>That is a basic idea; some other issues would need to be addressed, for example: Seeding of the random number generator, choosing an appropriate threshold, initial synchronization, corrections and resynchronization to minimize the impact of clock drift in long duty cycles, adjusting for the delay/switching time of the photodiode, and probably more.</p>
<p>Dear Vandalf,</p><p>Thanks for your awesome inputs and ideas. We just designed this project to help people learn 'how an IR and photodiode works'. It is a project, not a product. The idea here was to help people learn not design a perfect system to catch attackers. We really welcome your ideas to work on a micro-controller based project. Why don't you implement your idea and make it happen? We can really make a good project instruction (we engage professional photographers to click each step). BTW, this project is a part of the DIY Makers Learning Kit that we are soon launching on Indiegogo: www.mandlabs.com. Thank you</p>
<p>Thanks for the detailed Instructable including all of the theory and explanation of how/why the circuit operates. </p><p>I do have one random question... </p><p>I realize the answer to this depends on several internal and external variables but overall, if any possible response-time limiting factors were made ideal: Is this circuit's response time fast enough to trigger when an object moving at very high speeds (say, a bullet fired from a rifle) passes through the transmitting line of sight/light? Do you happen to definitively know, or maybe even have some math to calculate/predict response-time limitations, perhaps how long (micro-seconds/nano-seconds) the path of light must be blocked to allow the rise/fall/mechanisms of action to occur? </p><p>Again, thank you for the Instructable and thank you in advance for any additional info/thoughts relating to response time you may be able to provide. </p>
Dear DrummRBoy,<br><br>It is a very good question. Honestly, we didn't think that far with this project. I think this would next level for this project. It will definitely involve some mathematical analysis. We really welcome the opportunity for any maker to work on this. This project is actually a part of our DIY Makers Kit that we are soon launching on Indiegogo. Here is the link: http://mandlabs.com<br><br>Looking forward,<br>Regards<br>
<p>not words to talk</p>
<p>Hi, ykgreat, Thanks for the comment. We are happy to answer queries. BTW, we are soon coming up with our Indiegogo campaign:<br><br>https://www.indiegogo.com/projects/the-coolest-diy-makers-kit-you-will-ever-own/coming_soon<br><br>let us keep talking,<br>-GP</p>
<p>Good instructable thanks!</p><p>I would suggest not to use the word step in your slides and have those numbered differently than the steps in the article.</p><p>I noticed in both Step 20: &quot;Step No. 12 &gt;&quot; and Step 21: &quot;Step No. 13&gt;&quot; you refer to connecting the positive of the photo diode. </p><p>This should obviously be the negative terminal in Step 20 as you mentioned in other slides.</p><p>Great effort.</p>
Hi Rob,<br><br>Thanks for the comment. Oh, yeah, this creates a bit of confusion. Actually, most of our tutorials have been already prepared. I check the step:<br><br>1. Step no. 12: The photo-diode is reverse biased which means its anode (positive) terminal should be connected to ground. This step is perfectly fine.<br><br>2. Step no. 13: Yes, You got it all right. There is a mistake here. The negative terminal should be connected to the resistor. Great! Many thanks for finding the problem.<br><br>Great feedback!<br><br>BTW, we are soon coming up with our Indiegogo campaign:<br><br>https://www.indiegogo.com/projects/the-coolest-diy-makers-kit-you-will-ever-own/coming_soon<br><br>let us keep talking,<br>-GP
What is the maximum distance the the transmit and recieve be and still function reliably.
Hi Tracker, thanks for the comment. It all depends upon how powerful the IR and photodiodes are. The ordinary range should be b/w 1-2 ft. Happy to answer more queries. BTW, we are soon coming up with our Indiegogo campaign:<br><br>https://www.indiegogo.com/projects/the-coolest-diy-makers-kit-you-will-ever-own/coming_soon<br><br>let us keep talking,<br>-GP
Very good instruction and I have just one suggestion. Place a clamping diode across the relay coil and you will prolong the life of your transistor. Place the diode cathode on pin 2 of the relay and the anode on pin 1. This protects the transistor from the collapsing high voltage field of the relay.
Hi HBSkrimit, Thanks for the comment. Wow, it is a great suggestion. Yes, it is a good practice to use a diode to protect the transistor. Suggestion all taken :) <br><br>BTW, we are soon coming up with our Indiegogo campaign:<br><br>https://www.indiegogo.com/projects/the-coolest-diy-makers-kit-you-will-ever-own/coming_soon<br><br>let us keep talking,<br>-GP
<p>A very well laid out and perfectly detailed explanation that should mean that most everyone can build this circuit pretty easily. It would perhaps be nice to include some circuitry (or maybe an Arduino) to allow us to set the buzzer continues to sound ?without </p>
Thanks Chopperaddict for the comment. We are happy to answer queries. The buzzer in this case beeps once the obstacle is detected. You will need to remove the battery connections to reset the circuit. Yes, the same could be done through Arduino board as well. BTW, we are soon coming up with our Indiegogo campaign:<br><br>https://www.indiegogo.com/projects/the-coolest-diy-makers-kit-you-will-ever-own/coming_soon<br><br>let us keep talking,<br>-GP
<p>the best one111111111111111111111</p>
Thanks Krishna for the comment. We are happy to answer queries. BTW, we are soon coming up with our Indiegogo campaign:<br><br>https://www.indiegogo.com/projects/the-coolest-diy-makers-kit-you-will-ever-own/coming_soon<br><br>let us keep talking,<br>-GP
<p>Best instructional yet!!</p>
Thanks MDGeo for the comment. We are happy to answer queries. BTW, we are soon coming up with our Indiegogo campaign:<br><br>https://www.indiegogo.com/projects/the-coolest-diy-makers-kit-you-will-ever-own/coming_soon<br><br>let us keep talking,<br>-GP
<p>very well explaindd, thnx</p>
Thanks Boesh for the comment. We are happy to answer queries. BTW, we are soon coming up with our Indiegogo campaign:<br><br>https://www.indiegogo.com/projects/the-coolest-diy-makers-kit-you-will-ever-own/coming_soon<br><br>let us keep talking,<br>-GP
<p>THANK YOU VERY MUCH</p>
Thanks for the comment. We are happy to answer queries. BTW, we are soon coming up with our Indiegogo campaign:<br><br>https://www.indiegogo.com/projects/the-coolest-diy-makers-kit-you-will-ever-own/coming_soon<br><br>let us keep talking,<br>-GP

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