Diy Eeg (and Ecg) Circuit

April 3, 2018 | Author: Nicholas Larson | Category: Electroencephalography, Amplifier, Electronic Filter, Resistor, Operational Amplifier
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DIY EEG (and ECG) Circuithttp://www.instructables.com/id/DIY-EEG-and-ECG-Circuit/?ALLSTEPS Contests let's(/contest/) make 12 Steps Community Login (/community/) ( ) Explore (/tag/type-id/) Create (/about/submit.jsp) DIY EEG (and ECG) Circuit by cah6 (/member/cah6/) (/) Download (/id/DIY-EEG-and-ECG-Circuit/?download=pdf) share what you make > (/about/submit.jsp) (/id/DIY-EEG-and-ECG-Circuit/) + Collection Favorite (/) About This Instructable 62,574 views (/files/deriv/FEH/C1XA/H5TU9RMD/FEHC1XAH5TU9RMD.LARGE.gif) Posted: Aug 10, 2012 License: 159 favorites cah6 (/member/cah6/) EEGs are a noninvasive way to look into your brain. While the brain is extremely complex, areas of it can lock into circular firing patterns, resulting in telltale brain waves that one can observe with the right equipment. Intensity of these waves change depending on your internal state. The waves we will be most easily able to distinguish are alpha and beta waves -- alpha waves occur at around 8-12 Hz and when measured from the frontal lobe provide an estimate of how relaxed a person is, while beta waves are around 12-30 Hz and correspond to how much a person is concentrating or how alert they are. The concentration of each wave can also tell more specific things about your thought patterns depending on where you measure them from. For example, alpha concentrations on the left motor cortex increase when you think about moving your right hand. Regardless of where you're taking measurements, looking at the concentrations of waves in real time - a process called biofeedback - can give you much greater control over them. This tutorial is an in-depth guide on how to make your own simple EEG circuit. Along with monitoring brain wave concentration, the final circuit can also be used as an ECG, as a way to see your heartbeat trace. The circuit will use 3 electrodes - 2 to measure a voltage difference across your scalp, and one as a reference to ground. Depending on how many parts you already have, the circuit could only set you back around $10. (/id/EEGFollow 22 (/member /cah6/) Tags: eeg (/tag/type-id/category-technology/keyword-eeg/) circuit (/tag/type-id/category-technology/keywordcircuit/) Related EEG "Coral" headband (/id/EEG-Coral-headband/) by dukode (/member/dukode/) The aim for this project is to be easily available and understood by people of every technology background. For those electronically savvy, I will include up front a finalized schematic so you can jump right into making it yourself. For those that want more guidance, I will include a detailed description / explanation of every section of the circuit, showing you what it does and why you need it. (/id/How- How to hack EEG toys with arduino (/id/How-to-hackEEG-toys-with-arduino/) by frenzy (/member/frenzy/) Brain-Controlled RC Helicopter (/id/BrainControlled-RC-Helicopter/) by puzzlebox (/member /puzzlebox/) Then, I'll move onto the software (Processing based), which is a very important piece in actually interpreting the raw data you receive. So - let's start! (/id/Brain- 1 of 20 9/25/2013 5:29 AM DIY EEG (and ECG) Circuit http://www.instructables.com/id/DIY-EEG-and-ECG-Circuit/?ALLSTEPS Brain-Controlled Wheelchair (/id/Brain-ControlledWheelchair/) by jerkey (/member/jerkey/) + Collection Favorite (/id/BrainMindflex Duel Bluetooth Arduino FIO Hack (/id/Mindflex-Duel-BluetoothArduino-FIO-Hack/) by mbmosher (/member DIY EEG (and ECG) Circuit by cah6 (/member/cah6/) Step Download 1: Parts (/id/DIY-EEG-and-ECG-Circuit/?download=pdf) (/id/DIY-EEG-and-ECG-Circuit/) 12 Steps (/id/MindflexSee More (/tag/type-id/?q=) (/files/deriv/FLZ/T2TP/H3Z3C82W/FLZT2TPH3Z3C82W.LARGE.jpg) I purchased most of my parts from Digikey (http://www.digikey.com/) (and Amazon). Their layout might seem slightly intimidating at first glance, but they seem like the cheapest place to get parts. And they have the USPS first class shipping option ( < $3 for small orders, choose this! It will save you a lot.), meaning you don't have to spend the same amount on parts as shipping, as it is on some websites. Chips: - 1x Instrumentation Amplifier - AD620AN (http://www.digikey.com/product-detail/en/AD620ANZ /AD620ANZ-ND/750967) - This is the most expensive, and most important part. While technically you can make your own instrumentation amplifier from 3 op-amps, I could never get my own to give me good results. Precision cut resistors in this ensure that it'll do its job. - 2x Quad Op-Amp - TL084CN (http://www.digikey.com/product-detail/en/TL084CN/296-1784-5ND/277429) - Any Op-Amp will do. You need 5 single amps, this one just includes 4 in each chip. Capacitors: I would strongly suggest buying a capacitor bundle from ebay or the like, espcecially if you plan on ever doing some other sort of electronic project. One bundle and you're basically set for life. Regardless, whether you buy them in a pack or individually, make sure to include these capacitors : - 1x 10 nF, ceramic - 1x 20 nF, ceramic - 1x 100nF, tantalum - 5x 220nF, tantalum - 1x 1uF, electrolytic - 2x 10uF, electrolytic Resistors: Same as capacitors, I suggest a bundle. This (http://www.amazon.com/Joe-Knows-Electronics-ValueResistor/dp/B003UC4FSS/ref=sr_1_1?s=toys-and-games&ie=UTF8&qid=1340397296&sr=1-1) is a very good one, has all the values you need (minus the potentiometer). The individual values you'll need, though, are: - 1x 1kΩ Potentiometer - via Digikey (http://www.digikey.com/product-detail/en/3362P-1-102LF/3362P102LF-ND/1088411) - very useful to adjust your gain on the fly. - 2x 12Ω - 1x 220Ω - 1x 560Ω - 2x 22kΩ - 1x 47kΩ - 2x 100kΩ - 2x 180kΩ - 1x 220kΩ 2 of 20 9/25/2013 5:29 AM found here (http://www.amazon.Ambu Neuroline Cups seem to be the most cost-effective method. a nice conversion calculator with dB to linear gain/attenuation can be found here (http://www.jpg) battery. Regarding power: the easiest way to power the circuit is with 2 9V batteries. This one (http://www.excluding the ~90x amplification the data receives by going through the instrumentation amplifier.DIY EEG (and ECG) Circuit http://www.com/Elenco-Piece-Pre-formed-Jumper-Wire/dp/B0002H7AIG /ref=sr_1_1?s=toys-and-games&ie=UTF8&qid=1340398467&sr=1-1&keywords=jumper+wire+set) for everything else.aspx?PID=23913). and easy to reorganize/reorder if you end up needing to.A breadboard to wire everything on.amazon.jpg) The attached picture is the final schematic.5mm audio cable (http://www.Wires (http://www. connect the positive lead of one battery to your positive power supply line and its negative lead to GND (ground).1x 1MΩ . . .instructables.com/usa/search/product/neuroline_cup. . That is. I've also included the frequency response of the finished circuit (taken with the NI myDAQ.jpg) (http://cdn. For those not too familiar with dB. Thanks to user jonencar for the link in the comments.amazon. each box is a single op-amp (couldn't find a non-dual op-amp using this schematic program). I like that pack.amazon. a good all-purpose oscilloscope) -. and its negative lead to the negative power supply line. since it's pre-cut and keeps your board tidy.3. After the instrumentation amplifier. . To feed your op-amps -9V to 9V of power. I suggest saving the jumper wires specifically for connecting the various stages of the design.com/e/cad/db. Electrode Supplies: . and one backwards.com/100-Stranded-Wire-Gauge-Black/dp/B0006O94DE/ref=sr_1_1?s=toysand-games&ie=UTF8&qid=1340398643&sr=1-1&keywords=22+gauge+wire) and cut it yourself. This will make it very modular.amazon.ambuusa.2x 9V batteries for power.com/id/DIY-EEG-and-ECG-Circuit/?ALLSTEPS DIY EEG (and ECG) Circuit by cah6 (/member/cah6/) Connectors: Download (/id/DIY-EEG-and-ECG-Circuit/?download=pdf) (/id/DIY-EEG-and-ECG-Circuit/) 12 Steps + Collection Favorite .LARGE.com/Parker-Spectra-Electrode-Gram-Tube/dp/B0002CA8RQ /ref=sr_1_1?ie=UTF8&qid=1340913387&sr=8-1&keywords=spectra+360+electrode+gel) Step 2: Complete Design (/files/deriv/FR5/NQTR/H3QFL7UP/FR5NQTRH3QFL7UP. connect one battery the correct way.LARGE. You can also get plain wire (http://www. connect its positive lead to GND.instructables.LARGE.com/microtivity-400-pointExperiment-Breadboard-Jumper/dp/B004RXKWDQ/ref=sr_1_3?ie=UTF8&qid=1340398203&sr=8-3& keywords=breadboard) is large enough.mogami. 3 of 20 9/25/2013 5:29 AM . With the other (/files/deriv/FTY/HDPF/H6MF2WPG/FTYHDPFH6MF2WPG.electrode gel (http://www.html).com/FUV/VMQ0/H3QEXKLR/FUVVMQ0H3QEXKLR.com/Cables-Unlimited-AUD-1100-06-6-Feet-Stereo /dp/B000SE6IV8/ref=pd_sbs_t_7). and comes with useful jumper wires.2x 270kΩ . take care not to connect wires together unless a black circle is there with the connections . It is possible to make 4 of 20 9/25/2013 5:29 AM .a cross without a dot doesn't indicate a connection. The Common Mode Rejection Ratio (CMRR) is a value given to the amplifier that corresponds to how well it ignores the common offset between inputs. you will eventually connect an electrode from your leg directly to the GND line. and the rest is connected vertically. This will ensure that "0V" is your leg's voltage (unaffected by any head activity).jpg) An instrumentation amplifier takes as its inputs 2 voltages. however. In general.1V and 2. A higher CMRR is better. G. there's a possibility that it's not perfect. if you need it.the breadboard layout looks like a pretty jarbled mess (it gets really hard to avoid that when you try to fit everything on a 30-column board). Follow the actual schematic -. the output is slightly skewed if both input voltages are offset the same by some amount. the blue is the output of the 30 Hz LPF.com/id/DIY-EEG-and-ECG-Circuit/?ALLSTEPS DIY EEG (and ECG) Circuit To "set" GND. and will change the output slightly accordingly. Instrumentation amplifiers. where we will process the data a bit more. and outputs the difference between the two multiplied by some gain. The program also didn't always layer the components correctly. one with notes on it and one without. and that all readings will vary by cah6 (/member/cah6/) from there. Step 3: Stage 1 . we also have to make sure that as our data is going through the circuit. A perfect amplifier would take as inputs 2. To clarify some specific colors used on the breadboard view -. then reduce noise by enough to get a good signal into the computer. with breaks in connections across the middle gap. When looking at the schematic. On real amplifiers.LARGE. Download (/id/DIY-EEG-and-ECG-Circuit/?download=pdf) (/id/DIY-EEG-and-ECG-Circuit/) 12 Steps The biggest design goal for this circuit is to obtain the data. are not perfect. and the white wire is the output of the gain stage. It isn't exactly how I did it. As we will be using our computer's sound card to get the data in. Still.all red wires are power lines. The box at the bottom represents the audio cable going to the sound card. The green wire is the output of the first notch filter.DIY EEG (and ECG) Circuit http://www. things to remember are that in breadboards the power lines (top and bottom rows) are connected horizontally. but should give you a general idea if you haven't worked with breadboards before. and since there's no way to test the "breadboard schematic". A real one is influenced by this common offset. and output 0.Instrumentation Amplifier (/files/deriv/F1O/L5RJ/H3QFJ1G9/F1OL5RJH3QFJ1G9.1V*G. as this is the point where the sound card clips the data off. Use it as a general guideline. and all black are basic interconnections between circuit pieces (most are connections to ground).instructables. As we will be using +-9V through batteries to power the circuit. and will output something closer to what a perfect amplifier would. I do NOT suggest using that picture as a strict guide on how to wire everything. it never peaks above or below this value. the yellow is the output of the 8 Hz HPF.2V. + Collection Favorite I've also included an example of how to lay out the components on a breadboard. we have to cut noise enough that the signal with noise does not spike above or below +1V and -1V. analog.LARGE. you can see that the formula for gain using this chip is G = 1 + 49. I personally couldn't get a good reading with a self-made instrumentation amp. This is a good number to get the data into a not-miniscule range. we'll add a way to adjust gain on the fly a bit later. You should also see on this datasheet that on your actual circuit.com/id/DIY-EEG-and-ECG-Circuit/?ALLSTEPS DIY EEG (and ECG) Circuit your own instrumentation amplifier (usually with 3 op-amps (http://en. your active electrodes (ones that are not the ground electrode) will be connected to pin 2 and 3 (-IN and +IN).2 with a 560 ohm resistor. due to power line interference.com/FB5/LWP9/H3QFM1WR/FB5LWP9H3QFM1WR.jpg) (http://cdn. the gain is changed by altering the value of the resistor between pin 1 and 8.instructables. which equates to a gain of 89.wikipedia.DIY EEG (and ECG) Circuit http://www.LARGE. 5 of 20 9/25/2013 5:29 AM . Download (/id/DIY-EEG-and-ECG-Circuit/?download=pdf) (/id/DIY-EEG-and-ECG-Circuit/) 12 Steps Using an instrumentation amplifier chip.60 Hz Notch Filter (/files/deriv/FNP/SS4W/H3QF1FD0/FNPSS4WH3QF1FD0. + Collection Favorite The datasheet for the AD620AN (our instrumentation amplifier) is here (http://www.org /wiki/Instrumentation_amplifier)). Step 4: Stage 2 .instructables. it will suffer from a low by cah6 (/member/cah6/) CMRR.jpg) The biggest source of noise in our system will be centered at 60 Hz.com/static /imported-files/data_sheets/AD620.pdf). From it. but unless you make it with precision resistors.400 / Rg. If it is not centered at 60Hz. your circuit will still experience this noise. but if our main focus is alpha/beta wave monitoring.LARGE. as at that resistance it can easily vary by a considerable amount.filters that have a severe reduction of gain around 1 particular by cah6 (/member/cah6/) frequency.com/id/DIY-EEG-and-ECG-Circuit/?ALLSTEPS DIY EEG (and ECG) Circuit Even if you use batteries to power your circuit. The trade-off doing this is that we also filter out a lot of gamma/delta wave data (the brain waves that are about 8 Hz and less). 6 of 20 9/25/2013 5:29 AM . We will use one now.DIY EEG (and ECG) Circuit http://www. it can be fairly easily filtered out with a high pass filter (HPF).instructables. You should see a significant reduction in the amplitude of the 60Hz (light grey) frequency band. and one at the very end. this isn't much of a problem. then do so again once the signal has gone through the notch filter. to cut out any more interference we may have picked up. and as this interference is primarily low frequency. + Collection Favorite Step 5: Stage 3 . our final data will also contain voltage from our galvanic skin response across our head. This will obscure the brain data we want. or even a different 12ohm one.7Hz High Pass Filter (/files/deriv/F2T/5L7V/H3QFL7V3/F2T5L7VH3QFL7V3. take a reading (detailed on the last stage) at the end of the instrumentation amplifier. Download (/id/DIY-EEG-and-ECG-Circuit/?download=pdf) (/id/DIY-EEG-and-ECG-Circuit/) 12 Steps The notch filter is most sensitive to changes in the 12 ohm resistor. we will have 2 "notch" filters . try a 10 ohm resistor.jpg) As we are measuring data across the skin. to cut out as much interference as we can before we apply any more gain to our circuit. For this reason. To ensure the notch is centered at 60Hz.LARGE.jpg) (/files/deriv/F9Q/7EO6/H3QFJN23/F9Q7EO6H3QFJN23. As it is a high by cah6 (/member/cah6/) pass filter. while frequencies below will be continually reduced.com/id/DIY-EEG-and-ECG-Circuit/?ALLSTEPS DIY EEG (and ECG) Circuit This filter is a 2-pole HPF with a cutoff frequency of 7. the circuit outputs data that is reduced to about 71% of its original value. The filter having 2 poles means that in the region below the cutoff frequency. while a single pole would only reduce it by a factor of about 7.DIY EEG (and ECG) Circuit http://www. the Download (/id/DIY-EEG-and-ECG-Circuit/?download=pdf) (/id/DIY-EEG-and-ECG-Circuit/) 12 Steps gain falls off much faster than a simpler resistor/capacitor circuit. + Collection Favorite 7 of 20 9/25/2013 5:29 AM . our double pole design reduces data by a factor of about 56 by the time it gets to 1Hz. I've also included the frequency response of this particular section.instructables. frequencies above this cutoff will approach a gain of 1. Along with the circuit design.23Hz.23Hz means that at this frequency. in this circuit.5. More specifically. A cutoff frequency of 7. and decreases from there at a rate such that by 300Hz it has attenuated the data by about a factor of 100.LARGE.instructables. as combined it can contribute a good amount of noise to our data.instructables.jpg) Next up.com/id/DIY-EEG-and-ECG-Circuit/?ALLSTEPS Step 6: Stage 4 . I've included the frequency response of this section here.71 at 31.1 Hz HPF and Gain of 83-455 8 of 20 9/25/2013 5:29 AM . More specifically. we want to filter out data above the frequencies we are interested in. we want to get rid of anything above that.jpg) (http://cdn. Again.DIY EEG (and ECG) Circuit http://www.23Hz. The circuit design is very similar to the high pass filter from stage 3 . as beta wave information stops out at 30Hz.LARGE.31Hz Low Pass Filter DIY EEG (and ECG) Circuit by cah6 (/member/cah6/) Download (/id/DIY-EEG-and-ECG-Circuit/?download=pdf) (/id/DIY-EEG-and-ECG-Circuit/) 12 Steps + Collection Favorite (/files/deriv/F94/TYG6/H3QFJ1IY/F94TYG6H3QFJ1IY.it has a gain of .com/FRO/NM3B/H3QF1F05/FRONM3BH3QF1F05. Step 7: Stage 5 . however. just for some extra attenuation of unwanted noise.148V to 455*89.2*20e-6 = .Another 60Hz Notch Filter (and into the computer!) 9 of 20 9/25/2013 5:29 AM . the resistor and capacitor in parallel provide some extra filtering of high frequencies (Fc = 1/(2*pi*10nF*100kΩ) = 160Hz on a low-pass filter). this 83-455 gain is on top of the 89. The main purpose of this section.LARGE. from about 10 to 30 uV. This op-amp is a non-inverting amplifier (http://en. the gain of this circuit is G = 1 + R12/(R13 + 0) = 1 + 100k/(220 + 0) = 455. Using a middle value of 20 uV. Remember.org /wiki/Operational_amplifier#Non-inverting_amplifier). Alpha wave amplitude varies from person to person. It doesn't have to be maximized such that the amplitude is the highest possible without clipping . this means the ending voltage reading could range from 83*89. you'll increase the error incurred from digitally reading the data into the computer.com/id/DIY-EEG-and-ECG-Circuit/?ALLSTEPS DIY EEG (and ECG) Circuit by cah6 (/member/cah6/) Download (/id/DIY-EEG-and-ECG-Circuit/?download=pdf) (/id/DIY-EEG-and-ECG-Circuit/) 12 Steps + Collection Favorite (/files/deriv/FPG/QOXA/H3QFJ1IX/FPGQOXAH3QFJ1IX.DIY EEG (and ECG) Circuit http://www. as it's a small value and won't contribute much to the gain).jpg) The beginning of this circuit contains a quick HPF of cutoff frequency 1Hz (Fc = 1/(2*pi*R11*C11). turning the wiper changes its resistance linearly between 0 and 1000 ohms.just know that if you make it too small.instructables. Once you've started taking readings. The potentiometer is a variable resistor . lies below this. When it is turned all the way to the right.2x gain from the instrumentation amplifier. voltages don't fluctuate offscreen (over 1V). Step 8: Stage 6 .wikipedia. and so has a gain of G = 1 + R12/(R13+R14).when the input is connected to the first pin and the output to the second. On the other end. adjust the potentiometer such that when you're not moving at all. the gain is G = 1 + R12/(R13 + 1000) = 1 + 100k/(220 + 1k) = 83.81172V. (ignoring the 10nF capacitor. with the 220Ω resistor and potentiometer (pot for short). This means that when the pot is turned all the way to the left.2*20e-6 = . you should connect the end of the cable between the 22k resistor and 220nF capacitor (the yellow alligator clip).instructables. As shown in the picture.5mm male-to-male cable (this is the same size ending as any headphone jack). To get the data into the computer. and you're good to go! 10 of 20 9/25/2013 5:29 AM .jpg) Even with all the previous filtering stages. but that can be ignored through software once the data is loaded into the computer. the first 2 notches are the right and left channels.the same line you connected your GND electrode to (the red alligator clip in the image).LARGE. Connect the other end of the cable into the microphone port of your computer. and the one furthest down is GND. the data will still at this point contain a good amount of 60 Hz noise.com/id/DIY-EEG-and-ECG-Circuit/?ALLSTEPS DIY EEG (and ECG) Circuit by cah6 (/member/cah6/) Download (/id/DIY-EEG-and-ECG-Circuit/?download=pdf) (/id/DIY-EEG-and-ECG-Circuit/) 12 Steps + Collection Favorite (/files/deriv/FUY/EDNA/H3QETR43/FUYEDNAH3QETR43. we will be using a 3.DIY EEG (and ECG) Circuit http://www. On the cable. inserting these into their appropriate place in the circuit. To fix this. I suggest connecting the other end of these alligator clips to jumper wires.LARGE. The final data will still have a small amount of noise. we will process it through another notch filter centered at 60 Hz. identical to the previous one.jpg) (/files/deriv/F22/KAB3/H3ZN4VY6/F22KAB3H3ZN4VY6. and the base of the cable to the GND line of your circuit -. php?act=viewProd& productId=16) are known to be very good ones.gtec. The inion is the point where your skull ends at the back of your head.gtec.PNG). onto the electrode setup and code. these (http://www.com/id/DIY-EEG-and-ECG-Circuit/?ALLSTEPS (/id/DIY-EEG-and-ECG-Circuit/) 12 Steps + Collection Favorite Step 9: Getting electrodes. such that it is above both the nasion and inion. The increase should be even more apparent if you relax and try to clear your mind while your eyes are closed.wikipedia.LARGE. Parts of your head you'll need to know for this are the mastoid (http://en. DIY EEG (and ECG) Circuit by cah6 (/member/cah6/) Download (/id/DIY-EEG-and-ECG-Circuit/?download=pdf) http://www. The nasion is the ridge between your nose and forehead.at/var/plain_site/storage/images/media/images/support /mount_gammacap_nasion_inion/10705-1-eng-GB/mount_gammacap_nasion_inion.which one you choose will depend on a mix of convenience and what you wish to measure. just between your eyebrows.google. Alpha waves are around 8-12 Hz waves.google. and only require 1 electrode on a section of the scalp with hair.png&imgrefurl=http: //www. tie the bandana tight around your head. For this setup. and tape the ground electrode to the skin there. Check this page for updates.com /imgres?imgurl=http://www. we will be primarily measuring alpha waves with this setup. For a trial demonstration. and proper placement (/files/deriv/FH9/V3GW/H5JVXVJC/FH9V3GWH5JVXVJC.gtec.gtec. your electrodes should be roughly in the area of Fp2 and O2. as I'm currently investigating cheaper ways to make your own electrodes.jpg) For the electrodes themselves.wikipedia. As mentioned. whenever you close your eyes there should be a distinct increase in alpha wave concentration. find your left mastoid.png& imgrefurl=http://www. The mastoid is the bone behind your ear: you can easily feel it by rubbing that area. First.com/index. Put one electrode about 1 inch above and 1 inch to the right of your nasion.instructables. and in general increase in amplitude when you are relaxed or in a more meditative state. though. you'll need a bandana and some tape (I used electrical tape.svg) top down view. and inion (http://www. Clear away any hair. are quite large in amplitude. The bandana will be used to secure in place the remaining 2 electrodes.org /wiki/File:Processusmastoideusossistemporalis. but scotch tape or even a band-aid would probably work). 11 of 20 9/25/2013 5:29 AM .org /wiki/File:21_electrodes_of_International_10-20_system_for_EEG. nasion (http://www. There are many possible electrode placements . and the second the same distance from your inion.com/imgres?imgurl=http://www.discountdisposables. Because one electrode lays on your occipital lobe (the part of your brain used for visual processing).at/Support-Offer/FAQ/Tips&h=389&w=410&sz=32&tbnid=67W64DTMB1JjyM:&tbnh=90& tbnw=95&zoom=1&usg=__CXDcWJ4adYvjxji6RjwkyFJ4Gjg=&docid=sd5hJ1RQxi1DhM&hl=en& sa=X&ei=sCXrT8SYJarY2QXj_LWfAQ&ved=0CGYQ9QEwBg&dur=202).at/Support-Offer/FAQ/Tips&h=389&w=410&sz=32& tbnid=67W64DTMB1JjyM:&tbnh=90&tbnw=95&zoom=1&usg=__CXDcWJ4adYvjxji6RjwkyFJ4Gjg=& docid=sd5hJ1RQxi1DhM&hl=en&sa=X&ei=sCXrT8SYJarY2QXj_LWfAQ&ved=0CGYQ9QEwBg& dur=202).DIY EEG (and ECG) Circuit Now.at/var/plain_site/storage/images/media/images /support/mount_gammacap_nasion_inion/10705-1-eng-GB/mount_gammacap_nasion_inion. Using this (http://en. Next. This is because these waves are the easiest to produce. we will measure alpha waves originating from the occipital lobe. Code available here (http://rapidshare. This program is really just a data acquisition / visualization one. as I did in the code. so that you can see what its meant to do. The most common way to convert signals from the time domain to frequency is with the FFT (Fast Fourier Transform). the program will give you an error and take you to the line where you typed in the former. you can represent very complicated signals (any signal!) as a combination of a number (sometimes an infinite number) of sine waves.pde). 12 of 20 9/25/2013 5:29 AM .com/id/DIY-EEG-and-ECG-Circuit/?ALLSTEPS Step 10: "Processing" the Data DIY EEG (and ECG) Circuit by cah6 (/member/cah6/) Download (/id/DIY-EEG-and-ECG-Circuit/?download=pdf) (/id/DIY-EEG-and-ECG-Circuit/) 12 Steps + Collection Favorite (/files/deriv/FQ4/7TBN/H401UZ2Y/FQ47TBNH401UZ2Y. and one that was half the amplitude the first but at 2 Hz. If you're new to programming. just unzip the download.org.e.if at some point you type in FFTHeight instead of FFTheight. FFT. Don't be afraid to break it. the guys that made processing have some really great basic tutorials here (http://processing. I encourage you to tinker with the program . you stick them into a power outlet). One thing to note is that Processing is case sensitive . From this. in frequency you would see two lines .instructables. I didn't document every single function that I used . since a working version can always be found here. because there is a danger involved if there's a spike in voltage from the wall outlet. as well as exactly what it takes as inputs and produces as outputs. AudioInput. It does exactly what I just described -. and one at 2 Hz with a height of 0. you can fry your computer's sound card. If in time you had a wave that was made by adding one sine wave at 1 Hz. you would see the sine wave we all know and love in the time domain. It doesn't require any installation. Also.one at 1 Hz with a height of 1.it takes as input a section of time domain signal. specifically at the manuals under the tools tab at the top. This data can easily be visualized by displaying each band as a bar with a certain height. If they accidentally touch a high voltage source (i. Data can be represented in many ways. Audio classes won't be found as easily there (minim.LARGE.org. If you have a pure sine wave.5. Regardless.DIY EEG (and ECG) Circuit http://www. To find documentation for those pieces. look here (http://code. open the folder.com/files/4025495621/READ_EEG_cleaner.I encourage you to really play around with it and make something of your own! The next step is an optional one detailing something a little more fun that I made with the type of data acquired in this program. but in the frequency domain would just see one line at f = 1.if you're unsure about what a part of code does. available at http://processing. BE VERY CAREFUL WITH THE PROBES GOING TO THE SOUND CARD. two common ways being in time and frequency. you should look up the function being used at processing. I want to make a few notes and give a general outline of what it does here. and outputs bands corresponding to the concentration of certain ranges of frequencies in that signal. make your own. say oscillating at 1 Hz.compartmental.jpg) CAUTION: I highly suggest doing this on a laptop. a little background on the FFT. Download the sketch (what programs are called in processing). etc).change things. There are a LOT of things you can do with this circuit -. and while there should be enough documentation to understand what's going on in the sketch. Representing information into frequency domain usually amounts to showing data as the combination of a lot of sine waves with various frequencies and amplitudes. etc. First thing to do is to download Processing.net/tools/minim/). The program should be good to go as is. and open it up.org/learning/). and run it. You can use one set of batteries for both circuits. Because the game code incorporates object oriented programming. experienced programmers will likely find it easier to follow along. but the general concept is a simple pong game where you control the paddles with your concentration of alpha waves. except you need two. To monitor more simultaneously. The circuit used for this one is exactly the same. and active electrodes on the right frontal and occipital lobes. You can read most of this in the attached processing code.LARGE. I highly suggest reading this tutorial (http://processing.com/id/DIY-EEG-and-ECG-Circuit/?ALLSTEPS Step 11: Playing Pong With Your EEG DIY EEG (and ECG) Circuit by cah6 (/member/cah6/) Download (/id/DIY-EEG-and-ECG-Circuit/?download=pdf) (/id/DIY-EEG-and-ECG-Circuit/) 12 Steps + Collection Favorite (/files/deriv/FRO/Y9DR/H461X1ZN/FROY9DRH461X1ZN. Rapidly cycling through the channels samples all of them at a rate necessary for good data acquisition. while those that have not worked with object oriented code before may have a harder time.jpg) I also decided to make a quick demo game of something more fun you can do with the EEG circuit. however. Quick video demo of me using it against a wall here (http://www. you need to use a microcontroller such as the Arduino Uno (http://www. The electrode setup is the same as the previous code slice .GND behind left ear. and to open your eyes and focus to make it move down. you can monitor two EEG nodes at once (right and left channels). The easiest way to manage the controls is to close your eyes and relax to make the paddle move up. To get it in via the audio cable. If you fall into the latter category. since you have two players.Using Arduino to get more inputs By using the microphone input to your computer. and the other circuit to the other audio channel (the middle section of the audio cable). This chip will take as input a number of EEG channels and a number from 0-7.pde). you need a multiplexer chip such as the MAX4051.amazon. so they should share the same ground.com/watch?v=Kyh-13Kxflc). Arduino and Processing code for 3+ inputs is coming soon. 13 of 20 9/25/2013 5:29 AM .instructables. so you can observe 6 channels at once without any extra circuitry.com/Arduino-Rev-3-Uno-R3/dp/B006H06TVG/ref=sr_1_1?ie=UTF8& qid=1344621931&sr=8-1&keywords=arduino+uno) to get the data into your computer.youtube. If you want to observe more. and output only the channel corresponding to the number. The Uno has 6 analog inputs. The associated code is much neater than the data-reading one. Code available here (http://rapidshare.com/files/2686115236/TWO_PLAYER_PONG.DIY EEG (and ECG) Circuit http://www.org/learning/objects/) to get familiar with the basics. Step 12: Going Further . connect one of the circuits the usual way (outlined in the previous steps). They're really. alpha and low gamma are toast. . 2:04 AM Reply (CBET3JKHLJUZS2C) What is 220n cap for? Is it a part of the notch filter or is it used to remove DC offset? (/member /Mvtnns/) navidstuv (/member/navidstuv/) says: please help me. obliterating it. Even with professional EEG systems.. With a Mac. you don't need the 7 Hz HPF.instructables. and will give much better results than a second notch filter.LARGE. My 100nF and 220nF tantalum capacitors looked nothing like in your breadboard. To prevent this. Can I replace the tantalum capacitors with electrolytic/ceramic? Would this have any /rlabina/) I want to make an ECG using your instructable. A good USB audio input adapter will go down to 5 Hz and get around this problem. computer mike inputs all seem to have their own high pass filters. or Kudos. and especially homemade ones. don't see how to upvote but this comment (/member deserves! /mjb123/) mjb123 (/member/mjb123/) in reply to chipstein Sep 15. The electrodes. can produce large unbalanced half-cell potentials--i.com/id/DIY-EEG-and-ECG-Circuit/?&sort=ACTIVE& limit=40&offset=40#DISCUSS) Reply (CDQQJ1OHLSGSPKZ) rlabina (/member/rlabina/) says: Sep 21. 14 of 20 9/25/2013 5:29 AM . and 9-volt batteries. a DC offset of only 84 mV will pin the output against the positive or negative rail. a gain of 89.. With the AD620. 2013. ranging from around 5 Hz for Macs (when they have one) up to 20-40Hz for PCs. With most PCs. which requires some sort of skin prep and conductive /chipstein/) electrolyte. 1 1.. or +1. Thank you very much. the first stage gain is usually set much lower. 2:21 PM (/member place them. 2013. 2013.i realy need your help. really small (see image) and I have no idea how to effect? I would really appreciate it if you can answer my questions. act like batteries--and generate DC offsets of hundreds of millivolts. 9:53 AM Reply (C8WHKUYHLJUXR4L) Mvtnns (/member/Mvtnns/) says: Sep 15. Unfortunately. 3. the most important component of a good recording is good (/member contact between the electrodes and the skin. 8:59 PM Reply (CXT3XPPHJGDLAKN) This is an excellent description of EEG frequencies and all the components of the circuit. I hope you won't mind suggestions from somebody who does EEG for a living.jpg) chipstein (/member/chipstein/) says: Jul 24. 2.e.DIY EEG (and ECG) Circuit http://www.com/id/DIY-EEG-and-ECG-Circuit/?ALLSTEPS DIY EEG (and ECG) Circuit by cah6 (/member/cah6/) Download (/id/DIY-EEG-and-ECG-Circuit/?download=pdf) (/id/DIY-EEG-and-ECG-Circuit/) 12 Steps + Collection Favorite Post Comment 1-40 of 61 Next » (http://www. (/files/deriv/FYS/8VJM/HLSGSPKY /FYS8VJMHLSGSPKY.Chip Like. 2013.. These are available at the same places you can buy the electrodes..instructables. 9:31 PM Reply (C65UWRJHJKC10EP) ClaireSophie (/member/ClaireSophie/) says: Jul 19. I would like to use this EEG for a project where I need to distinguish two different signals.but it has error (/member ('framebuffer objects are Download (/id/DIY-EEG-and-ECG-Circuit/?download=pdf) (/id/DIY-EEG-and-ECG-Circuit/) /navidstuv/) not supported by this harware(or driver)') i dont know what my problem is? is it because of my hardware??? 12 Steps + Collection Favorite polkijain (/member/polkijain/) says: Please help me out to build a robot with it! 5 (/member /polkijain/) Jul 27. What do you mean by sign for left and right? Reply (CRWPSUGHJFSZSYT) polkijain (/member/polkijain/) says: can I use metallic coins for electrodes 5 (/member /polkijain/) Jul 17. 8:34 AM Reply (CXIX9ITHJAHSDCA) (/member /ClaireSophie/) Hey.instructables.DIY EEG (and ECG) Circuit http://www. 2013. 5:01 AM Reply (CTYNW1LHJ602ZJM) cah6 (/member/cah6/) (author) in reply to polkijain Jul 22..:) Thank you in advance! cah6 (/member/cah6/) (author) in reply to ClaireSophie Jul 22. 12:31 PM What exactly do you need? The basic mechanics behind this is 1 that it's taking the difference (/member /cah6/) between the two input signals. 1:28 PM It depends on how you read it. 2013. this might not be the best. as it only measures the relative difference. 2013. 2:12 PM Thanks for your project.it 1 doesn't perform at a certain rate. so it doesn't need to be that high. 12:58 PM What is the sampling rate you get with this EEG? Reply (CZGQ5FIHIPIM1UD) cah6 (/member/cah6/) (author) in reply to generalissimosuvorov Reply (CXO423IHIYWSB7R) Jul 10. 2013. if you wanted to independently read two signals. I believe I just used a sampling rate of 240: we're only interested in frequencies up to about 30 Hz. Reply (CKIZHWYHJFSZSYD) (/member /generalissimosuvorov/) generalissimosuvorov (/member/generalissimosuvorov/) says: Jul 8. 2013. 2013. In (/member /cah6/) my code. The circuit itself is completely analog -. 2013. 15 of 20 9/25/2013 5:29 AM . 12:28 PM It'd probably be too noisy to actually read.com/id/DIY-EEG-and-ECG-Circuit/?ALLSTEPS DIY EEG (and ECG) Circuit Reply (CEHBKBAHKJRZI4V) Aug 20. but the 1 quality of standard electrodes is (/member /cah6/) usually worth it.I downloaded your by cah6 (/member/cah6/) code. You can try. 2013. So. Is it possible this with this circuit? I need a sign for going left and one for right. I'm not really sure why the filter on the instructable worked for me but is giving so many other people problems (and doesn't help that I can't find the source). Reply (C1WJ327HI3TX1QU) Rodolfoelfeo (/member/Rodolfoelfeo/) says: Jun 4. Please reply soon. but the one in that link looks promising. 3:07 PM woow (/member /Rodolfoelfeo/) Reply (C0JZJCGHHJE22ZX) jpeepers18 (/member/jpeepers18/) says: May 15.com/id/DIY-EEG-and-ECG-Circuit/?ALLSTEPS Reply (C1XTNNNHGH723IR) (/id/DIY-EEG-and-ECG-Circuit/) 12 Steps + Collection Favorite 1 (/member /cah6/) cah6 (/member/cah6/) (author) in reply to stanna Jun 20.php shineonyoucrazydiamond (/member/shineonyoucrazydiamond/) says: Reply (CZA66LVHFSH5B9B) May 3. We would like to adapt it to filter out 50 Hz.com /info/circuits/opamp_notch_filter /opamp_notch_filter. 2013.doma (/member/nie. 2013. We've built the circuit according to your instructions.instructables. 2013. 10:15 AM I don't have a ton of time to mess around with stuff right now. 6:52 AM Reply (CU6UGF6HG85CCTF) (/member /nie. Reply (C77N9WRHI3TX1RH) njay3 (/member/njay3/) says: Jun 20.doma/) says: May 4. http://www. Instead it is just attenuating everything below 15 Hz. but you 1 should try the notch filter posted a (/member /cah6/) couple comments down (http://www. 2013. I'm just a little confused about the electrodes. but it is not even filtering out 60 Hz at the (/member moment. 4:02 PM Reply (CTIBY3XHGH6RLL6) (/member /jpeepers18/) What is the case size for the capacitors? Or what are the model numbers for the capacitors used in this design? nie. 10:17 AM I'm not: GND is connected to your body. Let me know how it goes or if you need more help. cah6 (/member/cah6/) (author) in reply to njay3 Jun 20. 7:28 AM Reply (CPZPQ7FHI3TRKH3) Hey. Could you please update this tutorial /njay3/) with notch filters that work and can be easily changed between 50 and 60 Hz. 4:27 PM Great instructable. 12:56 AM have a question. whyCircuit are you using -9 V on(/member/cah6/) the ground pin DIY EEG i(and ECG) by cah6 Download /stanna/) (/id/DIY-EEG-and-ECG-Circuit/?download=pdf) (/member http://www.php). Does the "ground" (/member electrode (the one that connects to your /shineonyoucrazydiamond/) mastoid or reference area on your body) serve as the ground line for the whole circuit? Is the circuit then connected to physical ground at all? Thanks! cah6 (/member/cah6/) (author) in reply to shineonyoucrazydiamond 16 of 20 9/25/2013 5:29 AM . +-9V are the supply pins.radio-electronics.doma/) better filter for power supply broom you can find here. as we only have about a week to finish working on this Thank you. but we can't get the notch filter stages to work at all.DIY EEG (and ECG) Circuit stanna (/member/stanna/) says: May 14. 2013. 2013. 2013.radio-electronics.com/info/circuits/opamp_notch_filter/opamp_notch_filter. 2013. 5:07 PM Yes. 11:13 PM Reply (CH32Y42HEI4FGL7) jonencar (/member/jonencar/) says: Thanks for this sweet DIY! :) Mar 20. we should be able to get extended use. that's ground for the by cah6 (/member/cah6/) whole circuit. 2013. This is mainly for purposes of sterilization. 1 The notch filter I used and listed (/member /cah6/) here isn't a very conventional one. for our purposes. So.ambuusa. /thuiberts/) Could it be that following this schematic does not make a notch filter because I used a regular 220nF capacitor instead of a tantalum one? What I get now seems to be more like a high pass filter cah6 (/member/cah6/) (author) in reply to thuiberts Apr 21.DIY EEG (and ECG) Circuit http://www. 12 Steps + Collection Favorite thuiberts (/member/thuiberts/) says: Mar 21. but can't find it again. document it more. did some searching around for a more cost-effective option and found these: /jonencar/) Ambu Neuroline Cup $7. 2013. but it works for me in both testing and actual use. :) Can pick them up directly from Ambu (http://www. just letting you know! (/member /jchen23/) Noticed that one.kingmedical. 2013. dbhaumik (/member/dbhaumik/) says: 17 of 20 9/25/2013 5:29 AM . 11:12 PM Reply (CJ2XBEOHEI4FGL3) (/member For the electrodes.com/id/DIY-EEG-and-ECG-Circuit/?ALLSTEPS DIY EEG (and ECG) Circuit Reply (CNRG74JHFPTJDUA) May 3. 2013.com) in the US. and fix any issues regarding it.instructables. Picked these up for my first attempt at the EEG circuit and should be giving them a try in the next few days. 2013. however. 1 since these Download (/id/DIY-EEG-and-ECG-Circuit/?download=pdf) (/id/DIY-EEG-and-ECG-Circuit/) (/member signals you're /cah6/) measuring are really only useful in relation to your head's overall ground state. In a couple weeks when I have the time I'm going to revisit this section of the circuit. Reply (CQVWPN4HFSH4PT3) jchen23 (/member/jchen23/) says: Mar 7. 2:57 AM Reply (CW42UCAHEI4BONW) (/member with a not so very steep slope at around 60 Hz. and intended to be disposed of after each use in medical environments.50 for a pack of 10! They are "Single patient use". Will post how it goes. on the guide u list to have 3. 1:07 PM The type of capacitor in that respect shouldn't really matter.com/) is a good option for Canadian DIY. too :) (/member /jonencar/) jonencar (/member/jonencar/) in reply to jchen23 Mar 20. I grabbed the design from some random website as it seemed to be the simplest circuit for the function. 2013. 6:25 PM Reply (C8T0VN7HDYZC0YV) just noticed you also use only 1 10nf capacitor. King Medical (http://www. the batteries are +-9V relative to that spot on your body. . 1:38 AM Reply (C28P3XEHCV8NKED) i did the whole thing and connected it to my laptop. 2013.. (/member I think what I'll do is ignore the amplifier and use the components to make another set of ~ 30 Hz Low Pass filters.. Have you considered doing any more with the device. 2013. 2013.... 11:32 AM Reply (CWAZJIWHBNXV6PW) That's fair enough. 9:57 PM Reply (C8AS472HAQ2ZN5L) (/member /sidharrth/) what do mean by this power line interference??How can u have a power line interferance from a battery source(DC)??would u pls explain about it?? sidharrth (/member/sidharrth/) says: Jan 13. correct? sidharrth (/member/sidharrth/) says: Feb 9. 18 of 20 9/25/2013 5:29 AM .. 2013. 2013. or hum.will it affect the /sidharrth/) circuit operation?? 2. is introduced from sources around you that use the mains power supply and will not be due to the battery. which is what the gel does on the passive electrodes... As far as I 1 can tell. 9:55 PM Reply (C5XNE1SHAQ2ZN5J) what i want to know all is about how u derive the values of capacitor and resistors??For eg : in notch filter we used a resistor of 12 ohm and 270k ohm. 2013.whats the new value of resistors and capacitors? Plz help...How u get those values??What was the (/member design?? /sidharrth/) Benny Boy (/member/Benny+Boy/) says: Jan 11. I'm using the Biomedical Toolkit of LabVIEW to write my program.so. 2013.com/id/DIY-EEG-and-ECG-Circuit/?ALLSTEPS Feb 20. for example controlling things? Benny Boy (/member/Benny+Boy/) says: Jan 10...instructables. 10:34 AM Reply (C1M5NEZHAQ3C40K) (/member /Benny+Boy/) Nice one. The power line frequency over here is 50 hz.But im not getting the waveforms in processing.. they just help make a (/member /cah6/) secure connection. i replaced those tantalum capacitors with electrolytic ones of the same value . 7:51 AM Reply (CLW1NPSHD8Z1E6D) DIY EEG (and ECG) Circuit by cah6 (/member/cah6/) (/member Download (/id/DIY-EEG-and-ECG-Circuit/?download=pdf) /dbhaumik/) Will this work with active electrodes? (/id/DIY-EEG-and-ECG-Circuit/) 12 Steps + Collection Favorite cah6 (/member/cah6/) (author) in reply to dbhaumik Mar 4. (/member 1. (0b67c2f5) !!! Its urgent Benny Boy (/member/Benny+Boy/) says: Jan 20.DIY EEG (and ECG) Circuit http://www. Reply (CJ0D80DHDOW40PW) jchen23 (/member/jchen23/) says: Mar 1.org. I should have it all sorted over this weekend. 2013. Thanks for your help. The frequency relates to the number of times a second that that the AC /Benny+Boy/) 50 Hz / 60 Hz interference. The interference can be picked up at various stages current changes direction. but yes they should. 7:02 AM Reply (CE6QWVUHCB8HDJS) (/member /apinto5/) i'm unable to download the code Please help !!! ERROR: Download permission denied by uploader... sidharrth (/member/sidharrth/) says: Jan 13. 2013. 2:37 AM Reply (CB1MWGIHAQ2ZWVZ) (/member throughout the circuit. 11:08 AM Reply (CSRD0QAHDOW6GEX) (/member /jchen23/) if i'm doing ECG. 8:21 PM I haven't used active electrodes at all. would everything on this tutorial be the same? I'm also using arduino but i just figured I switch the soundcard with the arduino. apinto5 (/member/apinto5/) says: Jan 25. 2013. I've put the design into multisim and the response is very different from what you've shown in LabVIEW... it looks like you had a myDAQ available to you but instead you used the sound card of your PC to acquire the signals. I applied 1 another 60 Hz notch filter and LPF (/member /cah6/) just to get rid of any residual noise that may have passed through..instructables... (/member /cah6/) knowing where they are in the diagram. It's a long shot but I was wondering whether you came across any similar issues with your circuit that may help me resolve this problem? 1-40 of 61 Next » (http://www. I am seeing attenuation of all frequencies below 84 Hz and above 2 kHz. Besides that.. 10:20 AM Reply (CP4NAPXHAQ315AT) (/member help me out with a few questions that I have. This really is an amazing project. 3:01 PM I didn't do a whole lot more processing in the program. 2013. /Benny+Boy/) Hey cah6. 6:15 PM What exactly do you mean? Are you having problems finding capacitors / 1 resistors with the appropriate value. Was there a particular reason for this? I am trying to use the myDAQ analogue input channels of the myDAQ to acquire a differential signal from the circuit. including the 50 Hz Notch filters. I see some changes when messing around with the electrodes but am waiting on the electrode gel to take proper readings. I'm not having much luck with the 60 Hz notch filters. once I got the time signal in I just took the FFT of it and displayed that to see the various frequency bands.bt am getting wrong somewhere.pls do /sidharrth/) reply.i need the whole design of the capacitors and resistors used in your circuit..com/id/DIY-EEG-and-ECG-Circuit/?ALLSTEPS Did you have to do much processing of data in your program? I'm applying more filtering in DIY EEG (and ECG) Circuit by cah6 (/member/cah6/) LabVIEW.awaiting ur response soon.....com/id/DIY-EEG-and-ECG-Circuit/?&sort=ACTIVE& limit=40&offset=40#DISCUSS) 19 of 20 9/25/2013 5:29 AM .. Download (/id/DIY-EEG-and-ECG-Circuit/?download=pdf) (/id/DIY-EEG-and-ECG-Circuit/) 12 Steps + Collection Favorite What sort of environment did you take your readings in? Do you have any screen shots of the sort of readings you got from your system? Thanks for your quick response to my other queries.. 2013.. Secondly.DIY EEG (and ECG) Circuit /Benny+Boy/) http://www. etc? Reply (C2X8KBEHAQ2ZJ3U) Benny Boy (/member/Benny+Boy/) says: Jan 6. mostly just because Processing had a built in function for that through the minim library. 2013..But now i need ur help very much!!!! Actually i was trying to design the capacitors and resistors for the past few day..Pls (/member do help me. Much appreciated. I'm designing a similar EEG system based on your circuit.. So far I've made good progress but I am stuck on a few problems and was hoping you could Firstly. 2013.. cah6 (/member/cah6/) (author) in reply to sidharrth Jan 9. 8:51 AM Reply (CWAWD24HBFFJGEH) Thanx cah6 for this wonderful project.. On step 10 there's a picture of the time data (after the quick digital filtering) that I got in.... Instead of the 60 Hz frequency cut off.instructables. with the FFT beneath it. I'll let you know the outcome of the alternative implementation! cah6 (/member/cah6/) (author) in reply to Benny Boy Jan 10. Reply (C04QZ0EHAQ2ZK07) sidharrth (/member/sidharrth/) says: Jan 5. com /app/instructables /id586765571) Visit Our Store » (http://store.autodesk. All rights reserved (http://usa.com/instructables) Resources For Teachers (/teachers/) Artists in Residence (/group/air/) Forums (/community/) Answers (/tag/type-question/?sort=RECENT) Mobile Download our new apps for iOS and android! 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