Step 5: Preparing the circuit

Since I have no experience in electronics whatsoever, this was the toughest part for me to find out.
Other instructables had no good explaining on this subject.

So for everyone who's new to this electronics stuff and have no idea what they're doing, here is some explaining for the circuit.

1. How many LED's to use?
The average LED needs 3v to work.If you are going to put the LED's in series (like I did) you need to calculate how many LED's you can use with your adapter. The formula you can use is adapter output voltage / LED voltage = Total LED's

So if you use a 12v adapter with the 3v LED's its: 12 / 3 = 4 LED's

You can also put LED's parallel in the circuit. But I'm not getting into this, just so that this instructable stays simple and easy to understand for everyone. Let's just focus now on the LED's in series.
If you want to experience with more LED's, you can always calculate your LED's and resistors here.

2. The real voltage on a adapter.
Before I went building this circuit, I thought it would be useful to measure the real voltage on the adapter. The sticker on the adapter (photo 1) says the output 12v. But once I hooked it up on my multimeter, it shows that the actual output is around the 18v (photo 2).

So that means I can calculate the LED's again: 18 / 3 = 6 LED's.

Since I'm going to make the LED's in series I can use 6 LED's in my circuit. 

3. The 3.5 audio jack plug
Which wire is what? That's what I was asking and trying to find out.
As you can see on photo 3, the plug itself has 3 metal parts, and 3 wires in the black protective layer.
On the photo I explained which wire is what.

Now with this information you can go to the next step, building the circuit.

Can i use it for android phones to plug it in mobile and let it beat
Hello there,<br>Its an awesome project. But i would like to add something to the circuit if you guys dont mind. :)<br>The thing is for this circuit you have to give an input to it via 3.5mm jack.<br>But using my mod you can use this circuit to make a portable beat sensing light box. Place it on a table when music is being played and the box will response to beats on its own without connecting any cables.<br><br>Hope it helps.<br><br>Regards :)
<p>Could you use an lm358 instead of an lm386. the 358 seems to also work with sound but i dont want to blow that opamp</p>
<p>Hi, just wondering what orientation the LM386 LowAudioAmp and TIP31c Transistor are in? Thanks.</p>
<p>Hi AnikB, what is the 10 mu F item, is it a 10 ohm resistor because I can see someone has referenced a 120 ohm resistor. What do I need please?</p>
<p>Hi AnikB, interesting adding. Do you think it could work using a piezo element, say a piezo disc, instead of the speaker? </p>
A piezo would work definitely. But to my thinking , it would pick up more of the treble of the song rather than the bass pump you would be looking for.<br><br>I think , If you attach the piezo with a both side tape on a wooden frame , it would work better :)
<p>Thank you AnikB.</p>
<p>Thanks for the original instructable, and thanks AnikB for this adaptation. Exactly what I was looking for.</p>
<p>What kind of capacitor should I use? can you take a photo of your circuit for me please :D thankss</p>
<p>sir......what u suggested was exactly what i was looking for......can i have some assistance from you?</p>
Yes , ofcourse :) always happy to help in circuits :)
<p>awesome :) is there a easier way i can communicate with u? btw i want to use <a href="http://www.parallax.com/product/29132" rel="nofollow">Parallax Sound Impact Sensor</a> as the sound ssensor...can that be used?</p>
<p>the thing is , if you use the sound impact sensor , it will obviously work better in detecting the sound. but the output of that module is either 0 or 5volts. But think for the case if there is a continuous signal of sound. then the module will activate for the 1st time when it excites. </p><p>it can be used for the strobe effects. connect the signal output of the module to one side of the transistor. and it should work :) <br><br>and one more thing.<br>the module is a bit costly in india its about 500 rs <br>but lm386 costs 10 rs :P so in cost effective way, i would suggest the 386 ... :)</p>
<p>i got the lm3866 :) so let me get this straight...what is the speaker for....doesnt the lm386 pick up sounds or no? :/</p>
<p>any speaker can act as a microphone.<br>the circuit which i have given for lm386 is a very basic circuit for making it amplify a received signal.<br>here the speaker is acting as an input mic which will pickup the audio which will then be amplified by 386 and then sent to the transistor to act as a activator. i hope it helps :) </p>
<p>ahhhhh i understand i see i see....let me show a list of all the things i have </p><p>-386</p><p>-4 multicolour led lights</p><p>-TIP31c</p><p>-some 120 ohm resistors...</p><p>what else do i need to have everything i need....just a small speaker now?</p>
<p>i also have a 9v battery and its connector and the sand paper and a casing to put it in</p>
<p>i guess then you are totally ready to begin the project :)</p><p>The small speaker can be gathered from broken head phones if you are worried about it :)</p><p>Happy building :)</p>
I got the lights on but they wont blink when I plug in my ipod. What did I do wrong?
how to increase led brightness at low volumes
i made it <br>but how to increase led brightness at low volumes<br>please<br>i need help!
i made it leds do blink but brightness is very low ??
<p>Can you make this mechanism but with this light insted?<br><a href="http://www.kjell.com/se/sortiment/el-verktyg/belysning/led-lister-led-tejp/flexibel-led-tejp/vellight-led-list-150-rgb-5-m-p64148" rel="nofollow">http://www.kjell.com/se/sortiment/el-verktyg/belys...</a> </p>
or add a Mic too
you've lost your left audio feed. splice your power rebuild second set of Leds. remember your audio has varying voltage. your color changing Leds change color under different voltage. maybe alternate them. hell you could have fun. add 1 white led that shines outside the enclosure to a small powered speaker with a photovoltaic cell. wireless speaker and light fun lol
<p>Very cool and simple! However, I would recommend the use of some protection on the audio input. Leaving it unlimited could lead to damage to your sound source as the transistor can be thought of as being made up of two diodes. One diode is between the base and emitter pins and has an on voltage of 1.8V according to the datasheet. If the input voltage exceeds 1.8V, then the current could rise rapidly, leading to damage to the audio output of your device. The base current required to turn on the LEDs increases proportionally as LED brightness increases. Not knowing the output capacity of the audio device adds some risk as well. I also recommend a limiting resistor for the LEDs. Ideally, a preamp circuit would provide both protection and limiting properties.</p>
<p>Do you need the ground to the tip 31c for it to work right.</p>
<p>TylerV11, if you look on step six, you will see that the 3rd pin is grounded. The &quot;body&quot; (or heat sink part with the big hole) does not need to be grounded.</p>
Really interesting i am going to make it but i was wondering if there is a way to filter frequencies i have searched that a lot and everything i found needed arduino. So if anyone knows a different way please respond (also include a circuit if possible)
<blockquote>It will be preferable to put a resistor in series with the led string to limit it`s current.(LED`s current grew exponentially to any overvoltage). also it might be helpful to put a resistor at the base of the transistor for the same reason(preventing overload of audio input caused by higher voltages on BE junction diode of the transistor).</blockquote>
<p>Did anyone notice there are NO current limiting resistors in the base of transistor or for the leds?</p><p>A good way to shorten the life of both...</p>
<p>You're absolutely right, missing current limiting resistor for the leds and missing base resistor for the transistor isn't a recommended practice.</p><p>I understand that the creator of this project wanted to make it as simple as possible, thus keeping the parts count to a very minimal value, but the suggested approach demonstrates a lack of concern for the parts specifications.</p><p>BTW, when reading 18V with your DMM, you have to keep in mind that this is a &quot;mo load&quot; value. The voltage will decrease as the load will increase, to a point where you will get a reading of 12V when there will be sufficient load. So for your calculations, do not take for granted that you have 18V available for your circuit. Just for the sake of it, try to feed your circuit with a constant signal and measure your current and voltage. You'll see a substantial difference.</p>
<p>We used to make color organs (45 years ago - my first build was about 40 yrs ago).<br>There were 3 colors. Each color responded to the signal strength within a certain frequency band.<br><br>My friend's older brother hooked up the lights on their Christmas tree to a microphone so that the colored lights responded when you talk to the tree.</p>
<p>I like how simple is the circuit but how good is the result. After seeing this, I want to make one myself but maybe filtering the audio so I get Low, Mid and High frequencies excitating three different strings of leds.<br><br>And here is a tip that might or might not work. To frost the plastic, instead of sanding it, you could try rubbing some acetone (i.e. nail polish remover) on it. It does frost some plastics such as Bic pens' barrel (which I think is polystyrene). I did frost mine at chemistry lab.</p>
<p>I must say: This is the simplest circuit on Instructables! Anyone can do it! also, I like the Youtube Music link, BONUS! So, if I were giving stars you get 8 out of 5!!! </p>
<p>By far the most time consuming and costly part of this project is constructing the box. A ferrero rocher box should work but can be prone to cracking when drilled. Heat up an old drill bit or even use your soldering iron (with an old tip) and burn the holes out.</p>
<p>Awesome project and I'll be building this soon, but I do have one point to make about LED's and power supplies. He is using a 12v .2amp power supply. This is low amps and yes will power this, but a good rule of thumb for LED power is 12v 1amp = power 50 led's. The voltage has little to do with how many led's you can plug in. Every 20 milliamps can power an LED, so 200ma could power 10 led's not just 4. The lower the voltage the dimmer the light, so a 9v battery will work on 12v leds but it won't be as bright. They do sell 3v, 5v, 9v, &amp; 12v LEDs </p>
<p>Only thing I didn't understand how it is possible to hear and use the Music LED Light Box from the same sound source for example computer. How is it done?</p>
<p>Use a headphone y adapter. Splits the connection jack from the music sourse to use two headphones.</p>
<p>I used a splitter </p>
is it a normal tip31 transistor or works a tip31A or tip31B or a tip31C to? or works it only with a normal tip31 transistor?
<p>What kind of tip31 transistor should I choose? Is it tip31c? </p>
<p>How would i do this project with RGB leds?</p><p>Any help would be apprappreciated.</p>
<p>guys I could not find tip 31 ...but i bought tip41.. Can I use it like normal ...or I have to get tip 32?</p>
<p>any NPN transistor will do... Its main purpose is to act like a switch.</p>
i have same question as @sahul hameeds. can tip41c transistor be used in place of tip31????

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