#NowShipping- Micro Adjustable Breadboard Supply V2

Ahh! I am back ! I have been travelling a lot and quenching the inner travel monster in me. According to my calculations largely based on GPS i have done 6444kms in the span of 8 days this month. That an average of 800kms per day. I covered states from Tamil Nadu in the south to Jammu and Kashmir in the north. The travel bug is now on a hangover of sorts ! Quite a while back, i made an adjustable, tiny-form-factor,no space wasting supply as you can see here . I really loved that project and went on to make it a bit better. Since, i wanted to keep that form factor intact. I went on and invested in getting the PCB made professionally. It turned out great! I added the two things to enhance usability :

  1. Ability to measure current on the fly without messing( Ah! Argentina..:/ ) with  whats connected to the supply.
  2. Provided some pads on which you can use a multimeter to set voltage without poking into the breadboard.

Here is the final board and the kit-assembly sequence.

Kit Contents

Kit Contents

A diode on the bottom! Do'nt worry it sticks out and doesnt hinder!

A diode on the bottom! Do’nt worry it sticks out and doesnt hinder!

Pads to measure voltage! The Headers poke into the power rail on the breadboard!

Pads to measure output voltage!
The Headers poke into the power rail on the breadboard!

Supports standard DC jack with polarity protection

Supports standard DC jack with polarity protection

The pink jumper can actually be removed and an ammeter can be connected to measure current!

The pink jumper can actually be removed and an ammeter can be connected to measure current!

The completed board

The completed board

Aligning the regulator with the silkscreen

Aligning the regulator with the silkscreen

Heat Sink

Heat Sink

Heat Sink Compound

Heat Sink Compound

Just in-case anyone is interested ! I am providing a DIY kit around it that is available here. Free Shipping(India Only)Yeah! Only additional tools required are just nippers( micro-shear)/cutters and soldering iron+solder. Cheers, Rohit

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The Small Solution to the BreadBoard Power Problem

We all use breadboards for prototyping. We all use DC Adapters to add power to them. But i used to do this by simply taping the wires to the DC Jack and then use it on the breadboard. This was always loose and clumsy and i always has to find out the polarity as some manufacturers are smart to not ground the outer shell. I even blew an IC this way once, when it was taken for granted. Some manufacturers do keep the outer part (shell) as positive while ‘most’ keep it negative!

Duh!

So, I found out a better way to make breadboards compatible with DC jacks and polarity issues. This is small board with headers that plug into the breadboard. It has a diode to make sure nothing flows reverse and a small 0.1uF cap to provide some rudimentary decoupling.

I quickly designed the board,etched it and filed it to shape.

Board design

Board design

Schematic

Schematic

Before the bath

Before the bath

On the breadboard

On the breadboard

And Tada! I have one little board that has ‘inherited’ two worries ! Two things of the “To-Worry-about” list 😀
This shall end the biggest #issues while using #breadboards #DCJacks and #PolarityCheers!

CoffeeBreak Tutorial #4: Windows Phones on Ubuntu 12.04LTS

 

I have a Nokia Lumia 520 device that fails to enumerate as a USB Storage on my Ubuntu 12.04 LTS desktop. Things are not as plug and play it seems. I have been using the skydrive( *cough* OneDrive ) route to access media for a few weeks until today i sat down to fight the issue Running..

lsusb

shows:

nokia1This means the Linux knows that we have a nokia mobile phone! But it doesnt provide a file access to it.

A little dig shows that ‘modern’ ‘smartphones’ use MTP (Media Transfer Protocol) to transfer data ! Its a modified Picture Transfer Protocol.. Ubuntu 12.04 has no ‘native’ support but Ubuntu 13.04 does have it.

So, 2 options :

  1. Install 13.04 (rather upgrade)
  2. Find a work around

Well it turns out there is a PPA called GVFS (Genome Virtual File system)-MTP( Media Transfer Protocol) that can be installed to help nautilus get the device! This surfaced when some android devs were getting issues working with MTP on Android 4.0+ .(Does anyone care about WP8 anyway? )

The commands/steps are:

  1. sudo add-apt-repository ppa:langdalepl/gvfs-mtp
  2. sudo apt-get update
  3. Run the update manager and install update
  4. Restart
  5. Plug the Lumia
  6. It must show!

So, i followed the above link and after a bit of restarting the device finally showed up!

nokia2

But i was not quite able to access it as it failed to mount the device repeatedly. I replugged it a couple of times and went to Terminal and typed natilus and then it got mounted! I was able to access the SD Card and phone memory without issues.

nokia4

The read(copy from device) and write( paste to device) both operations worked!

nokia3But there was no thumbnail preview ! If you want to view an image just copy paste it somewhere outside the device to view it.

Hope this helps the small niche of people who have a WP8 based phone and have an Ubuntu System !

Cheers!

 

 

CoffeeBreak Tutorial #3:The Easy Peasy Stepper Driver/Stepper Motor Test Circuit

 

Stepper motors are quite widely used for CNCs/3D Printers or other Electromechanical hacks like the polar plotter etc. ! There is as always a constant need to run the motor to check whether its aligned properly or not? Does the flex coupling has any issues? Is the driver dead or alive and the best one- whether the current setting is fine to generate enough torque to hold or move the lead screw.

Pestered by the same above questions i wanted to build my own driver/motor tester overnight and it ‘must’ be microcontroller-less since there is no actual use of a controller here! I stumbled open this awesome project that i saw on Hack-A-Day.

It uses an ATiny AVR microcontroller which is (no offence to the author) an over-kill as most modern stepper drivers like the ones from polulu  need just two signal i.e STEP and DIR.

A pulse on step pin will initiate a step to the internal indexer that handles what coil has to be energized based on the sequence and micro-stepping settings, while the DIR is a level signal whose level decides whether the internal indexer of the driver counts up or down!

So, only two inputs i.e Pulsed input for STEP and level input for DIR. This can be achieved using the 555 timer in the astable mode. The Output of 555 i.e pin 3 will go into the step pin and the DIR pin is pulled up using a resistor and it is also connected to ground via switch.

This gets the job done! We can also have a POT to vary the frequency since some motors dont respond to faster pulses due to rotor inertia.The driver i am using is based on DRV8825 from TI. It is slightly wider than the polulu one. (You might call me a TI fan boy 🙂 )

With the designing almost final , I grabbed a piece of perfboard since, i didnt had the time to etch the board.

The circuit is as follows:

final

It has two power inputs 12v, 5v and a common ground, all of which are sourced from an ATX! The circuit itself is pretty simple.

The final build on a 8mm perfboard is shown below.

perfboard1

PERF

I chose to use a SMD 0603 10K resistor between pin 8 and 7 to reduce the space and connected 104 (0.1uF) Ceramic caps as shown. The switch is a 10xx and the capacitor is required at the input of stepper driver to reduce supply dips when it draws current. I have used female headers for the motor since most motors come with a connector that can be easily wired up with a single strand wire. I used the Power Terminal connectors for the main 12V Driver supply as the driver is rated for 2.5A which is too high for the usual jumper cables !

top and bottom
 

TIP: If you are using the non-tinned/less tinned headers that have been lying around in the component box for a while, make sure to rub the connectors using sandpaper to remove corrosion residue on the contacts else it might seem soldered but it wont actually be soldered. Also you may use some extra flux.

Video:

Cheers !

Rohit Gupta

Travelogue: Ahemdabad Che!

 

Gujrati Food.. Umm .If you love gujrati food in which ever part of the country you are and then go and visit Ahmadabad for some reason and eat those “Jalebi, Fafda” or Khandvi, I bet your entire “Gujrati Food here(at your place) is good” notion will be changed and you will abstain from eating Gujju Food anywhere else. It has been Months and i haven’t eaten my favorite Khandvi. Its also so pirated here in Delhi. Well.. Food Piracy !

In this travelogue I will go through my adventurous journey into the food and people of Amdavad (as they say there). We were recently there for MakerFest  and in whatever time we got I and my group consisting Of Ishan and Saral sneaked into the city to explore be it late night (1am-ish) or early morning! What i am going to illustrate was done in bits and pieces , but surprisingly can be done in one full day! So, the below log can be done chronologically but was done in 2 days due to other important tasks 🙂

We were based out of Nehru Nagar. So most delicious shops were located nearby. If you plan to roam around next day, try eating something light in dinner as the next day will be “Heavy” .

We woke a early( well 10:30am it was i guess) and reached the famous ‘Juna Sherbazaarwalla‘ for his jalebi fafda combo. Fafda is made out of besan and is usually eaten with green chillis. But imagine if you combine the three. Its an atomic combination, Sweet, salty and spicy -3S ! We saw a local person, on the road sitting on his 80’s Lambeda Scooter and savoring Kadhi also along with 3S’s . So we ordered it too. And it added more ammo to the stuff. Kadhi was a bit sweeter and less salty. We ended up ordering Dhokla too.

Best Jalebi in town
Yum!The best algo is Jalebi in one hand and fafda in another and then dip fafda in kadhi and eat the jalebi first and then fafda. Loop until you drop!

I dont like spices a lot. So, i avoided the chillis. Ishan loved it and posed for it.

Bas kar!

 

I browsed the shop and found some other interesting stuff as well. Jee Lalchaye Raha na jaye
Make that 4

Ji Lalchahe Raha na jaye!

 

They were basically all dhokla’s and Samosa but a bit sweeter and nice. Not to say we tasted them as well. We were fortunate enough to be in Gujrat at the time of Uttaran which is when you can get the famous Undio (Dish) and see Gujrat in its full colors.

Round 3

Next we moved to The Khaman Shop! On the same road as Juna Sharebazaar walla , but a little further. Khaman is similar to Dhokla. But I couldn’t understand whats the difference.

The Khaman Shop

 

The Undio is basically a very spicy but tasty vegetable dish. It contains a lot of oil (I dont know why). But it was very tasty. It had Potatoes,Coriander and lot of other veggies i dont remember. Avoid this is you hate Oil and Chilly.
UndioThen we had the Khaman. It was just Awwwwesome! There was a nice tinge of garlic and sweetness i haven’t noticed anywhere. There is also a female version of Khaman called Khamani. Its a bit more crunchy and Spicy.It has tasty besan bhujia sprinkled over it and served with yellow chutney. Yummy..

Khaman Dhokla

Khaman Dhokla

Khamani

Khamani

PS: Just before you start suspecting me of over-eating. This was eaten by a group of 3 😛

With our input buffer almost full. We couldn’t order full plates of stuff we saw in the shop and were happily obliged by the shop owner who gave us some taste samples!

Taste Samples- Dhokla,Khandvi and Barfi Dhokla

Yellow- Khandvi, White-Green- Dhokla, White-Barfi Dhokla

The shop has almost 20 Different types of Dhoklas. Wow!

Since, our stomachs needed some rest. We needed to sneak out to some place of fun and walk.We headed on to Kankaria Lake. As always, prefer Local BRTS which is quite an efficient way to go around the city. Public Transport is always better.

Kankaria LakeThe lake is a pretty huge one, with a lot of things around it like Toy Train around the circumference, Fish Museum , Eating Stalls,Speed Boating, A Hot Air Balloon Ride,Kids in plastic balls that dont sink ( I dont know what its called 🙂 ) and a ATV track with Polaris quads meant for kids below 12 ( :/ )

Train Ride was pretty good. Good ‘ol Days as kids were revisited. Beware the Train Driver can yell at you if you get off the running train.It doesnt go over 12kmph.So, we did got over at Fish Museum. Hahaha.. DONT TRY THIS!

The Fish Museum  was pretty nice. Its a two floor museum with lots of different fishes on display.I dont eat fishes (Vegetarian) and don’t know many fish names other than Piranha ( Piranha 3D 😛 ) , gold fish ( Childhood stories), Sharks (Jaws) and Turtles. All of them were present there. Happy to meet you in person guys! We also did a little experiment to see if fishes react to Jazz Music. Conclusion: Well Some do, Some Don’t!

After our input buffer almost empty, we though of eating ; Whats better than Vada Pav. We ordered Vada Pav at the local stall on the lake! It was pretty bad. Some famous person has said, ” Chilli is the mask of a bad cook” . The Vada Pav was filled with Chilli. This is a pretty old street food trick when they sell water/drinks by selling spicy food. Busted!

We then had some ice-cream from the “What-we-thought-local” shop called Havmor. But it was some real bang on buck. Totally awesome! There was no Kwality Walls, Cream Bell or Mother Dairy there but Havmor was infact a chain of Ice-Cream Parlors Spread across city.The Raja–Rani flavor ice cream is pretty good, just in case you have trouble choosing.

It was now time to leave this pleasant lake and move to some godly place. ISKCON Temple was the place. There is a bus stand outside Kankaria Lake and you can get direct bus to ISKCON Temple. We passed over the Sabarmati Lake front and captured this beautiful sunset.

WP_20140106_034

It took us quite a while to reach there. People were happy to help us when we wanted. Good People always smiling! We reached ISKCON Temple near the time of arti and as always the ISKCON Temple Arti is pretty hair raising! We paid our tribute to Lord Krishna and stayed there for a while. Bliss!

Then after the ARTI was over, we had the prasad and went outside, collected our shoes and ate chinese samosas. This is a pretty standard ‘delicacy’ in any Indian Marriage. Its basically a Indianized Fried Wonton and is served with Momo Sauce. Still better than that Vada Pav!

The Question was now what? Go to the BaseCamp or Go somewhere else? Obviously Go somewhere else, But where? We were suggested by a person to do visit the “Drive-In Cinema” . Its probably there in two Indian cities Mumbai and Ahemdabad. So, why not! Bus Route is way out of question suggested Here Drive. We took the Auto to “Drive In Cinema”. It basically a place where you can Drive into a large ground with your car and watch the movie out of the car itself. The Screen was huuuuuggggeee ! Dhoom-3 was being played. We joined in. Its a great experience but even if you dont have a car, there is a small auditorium built near the projection room that can accommodate you!
Drive in Cinema

 

There were small poles with built in speaker and Amps too, because if they had a central amp, then those long wires load the central amp a lot.

We enjoyed the movie and had “Dabeli” during the interval. It was way better than that Vada Pao and Standard Pop Corn. Its a type of Vada Pao only but a bit different.I guess they dont use Besan in the tikki/vada they have inside it. Prefer a butter Dabeli if you have an option.Below is the picture captured when the butter was smoked.

Dabeli

It was a bit spicy, but the chutney neutralized some of it. But the time the movie was over. We were hungry! Damm Hungry. We took an auto to Nehru Circle. It was 10pm so night charges apply! We asked the auto person to drop us off the circle as well. We found another good shop!

It served the best Vada Pao and Khasta Samosa Ever!

The Best Vada Pao in Town

The shop owner was a pretty nice lad. He was from Rajasthan and was very much patriotic about Gujrat and kept on repeating “Aap humare Gujrat mein aaye ho“. When asked about NaMo his words were sweeter than the Jalebi we had in the morning.

We ate Vada Pao and Samosa! The Vada Pao ( i am a fan boy of ) was a bit different than the one i had in Dadar,Mumbai near Siddhivinyak which is rather advertorial to be the best in Mumbai. It was spicy but good but this one was the best! 10/10 . When asked about the secret, he said he has a special chutney which uses Khumani (I guess). If you love Vada Pao go here! Its near Nehru Circle and opens till late!
Vada Pao

Samosa

 

The samosa was also good. But it was the chutney that had all the magic!

Next we moved to a Pizza Shop-Real Paparika. Unlike Dominoes or Pizza Hut in Delhi, Amdavad has a lot of there joints which are essentially home-grown Italian Food Chains. Since we were half full, so we ordered the 4 pizza Combo! Surprisingly they have an unlimited food combo for 129 INR.
Late Night Pizza

Well the pizza was good. But not surprising.It was comparable in quality to Dominoes and far well prepared but was pretty basic! Next we moved to the local soda parlor to have some late night soda! The soda shop had a chach flavored soda that was worth trying.

Soda

 

As we drank the soda , we could see city getting ready for Uttarayan. Kite thread ( Manja) was being glazed with glass and various different kites were being made.Too bad we wont be in the city on the day! But there is always a next time.
Manja

Sada Haq Aithe Rakh Patang

 

As we were walking towards our apartment, we thought about various things, the people’s love for the city, NaMo, Food and It was never a bad time for some late night ice cream. Ice Cream anyone?
Havmor Ice Cream

 

Cheers,

આવ્જો (āvjo)

Rohit

 

Edit: There is a bit more to Ahemadabad – The Sabarmati Ashram, Vintage Car Museum, Science City and Delux Gujrati Thali ! Maybe next time ! 😀

CoffeeBreak Tutorial #2 : Adding USB charging to an old Android Tablet

I am a sad owner of a BSNL PentaTab. It is a horrible tablet with a very glitchy hardware/software. Although, enough of the rant..It just gets the job done. I recently had an issue when the tablet stopped charging from its DC jack a week after its official warranty ended ( This always happens 😐 ). The tablet does have a USB-OTG and a Mini-USB for data, but does’nt support any charging via the USB interface. I fail to understand this.

I took it to the local service person, So that it can be handled “professionally” . That guy took some money and got the job done. But it failed again after a few days.In India, they dont give you any guarantee till when the repair would last. So, there was no point taking it back to him.

WP_20140315_10_16_36_Pro

So, I planned to open it myself. I was surprised to see the board inside. It was hardly populated. :O

WP_20140315_003There were so many reflow-able spots.Maybe they use the same board for all their products. The empty spots “might” just be for SIM Module,Bluetooth or GPS (# Hidden Gold)

I felt heart-broken when i saw the bad soldering on the board. It was probably done by some untrained professional. This makes the board susceptible to shorts. Bad Manufacturer.

Bad soldering by manufacturer inside the tablet

Another thing that surprised me was that the onboard storage of 8GB meant there is an 8GB SD card inside. I wished to see some flash chips like the one on beagleboard. huh!

8GB SD Card So, this is what the manufacturer meant by onboard storage.

The AIM was to make the USB mini-B charge the tablet, hence by-passing the DC-Jack.

This turned out to be very easy. The grounds of the DC jack and USB Connectors were shorted due to the presence of a ground plane of the PCB. Next i took a small single stranded wire and soldered it shorting the positives of the DC Jack and +VUSB.
Adding #USB #Charging #Capability to an #Android #Tablet #Hack

And Boo Yeah! It can now be charged by any USB charger >1A.
Yeah! It #Works . So now it gets charged via USB too. #Juggad

Update: (13th April ’14)

I did a complete resoldering of the bad joints i saw earlier. The speaker was making insane click and screen too. The wires had gone lose.

Here is the final picture. I desoldered all joints and reduced wire length. The GND pad was a bit hard for my soldering Iron as it needed a bit more power. Then i cleaned the joints and laid out wires a bit more systematically!

Cleaning up some joints inside the tablet.

Shazam of Materials- Building the DIY Spectroscopy Kit from PublicLab

I recently got a DIY Spectroscopy Kit from PublicLab . I thought it would be nice to share my Build Log and subsequent spectroscoping most of the accessible light sources.I really loved when we used to work with the “Pro” versions of these in Physics 101 Labs.. I really never thought i could get one at home unless i built this.. This spectroscope is amazingly accurate as one of the tubelights i “probed” had almost identical manufacturers spectrum.. Wow

The kit came in a nice cardboard box and had everything you need to make your own spectroscope. It has:

  1. HD Webcam
  2. Flexible Cable for USB
  3. 45 degree cut wooden piece for fixing the cam.
  4. Good Quality Foam Tape
  5. A Water proof aluminium Conduit box
  6. A stencil/plan for the dark box
  7. DVD as a diffraction grating
  8. A very nice instruction manual
  9. Lots of Fun

The mystery box

Kit contents

Kit contents

Cutting the plans 
Box plans

Cutting the plansAssembling the Box

Make sure the inked/printed part stays outside. We dont want any reflections inside our dark room. Add the Foam Tape to secure the joints and add a piece of foam tape on the spot where its written “Bottom” . We will peel off the other end when we assemble all the components in the conduit.

Foam tape on bootom boxSplit Open the DVD

A DVD is a combination of two parts(actually many but we are concerned about two) . A Diffraction Grating is the heart of this device. We use the one made by a commonly available DVD. The reason is : (Source:Wikipedia)

“Ordinary pressed CD and DVD media are every-day examples of diffraction gratings and can be used to demonstrate the effect by reflecting sunlight off them onto a white wall. This is a side effect of their manufacture, as one surface of a CD has many small pits in the plastic, arranged in a spiral; that surface has a thin layer of metal applied to make the pits more visible. The structure of a DVD is optically similar, although it may have more than one pitted surface, and all pitted surfaces are inside the disc.”

So, take a small blade (in case you dont have big sharp nails) and try to apply force on the disk from the circular edge i.e the thin part and you will soon be able to separate both ends. Discard the shiny part and “cautiously” handle the second part. (No fingerprints)

Split open DVD

You can see this (Warning:PDF) for more on the calculations and preparation of grating part!

Now cut a sector of this disk and inspect it for fingerprints. Out of curiosity i applied some alcohol on the part with the intention to clean it but rendered it useless. So DONT use alcohol.

DVD diffraction grating

Next , cut a small portion from the farther end of the disk as tracks are more linear there.

Camera Time

The camera is a very beautiful circuit. Be careful with the USB cable provided its not that flexible as it looks.
The camera

Next mount the grating with the circular portion facing the camera. You also need to focus the camera by moving/unscrewing the upper black portion to about 9inches.

I advise aligning it a bit angled and not straight as shown.
Grating on the camera

Prepare the Mount

Now grab the piece of wood and stick foam tape on it as shown. Also use some tape on the sides for securing the wire for the USB camera.
Preparing the stand for camera

Now stick the camera unit on it and carefully stick the wire to the foam tape on the side. Be careful with the wire.

Assemble

Open the conduit box and stick the black box we made earlier by peeling off the tape..
Opening the Case

I suggest adding the extra foam tape to hold the box firmly in place.

Adding extra tape helps in securing the black box better

Now add the camera and slide the USB cable out. Carefully stick the wooden piece with the Foam Tape on its bottom to the conduit floor inside the region of the black flap.
Imaging slit
Now you need a Cable Tie to hold the wire in place and reduce the tension on the wire. A tape will do the job too, less aesthetically though.
Completed
Now screw the cover of the conduit back making sure you dont press on the webcam and start searching for a CFL (We have LEDs now 😛 )

Focus Shift

One thing that troubled me and i would suggest the designers of the kit is that the regulator on the camera heats up a lot and it worries me a lot.Also the USB cable is a bit small.I had to buy a extension cable to enhance the reach.

Calibrating

A CFL is needed to calibrate the build. Basically the wavelengths of certain peeks are known and using these we can calibrate the equipment ( Calibration to know standard- Instrumentation 101) .

So, go to spectralworkbench . Make an a/c so that you can save the data.Next go to begin capture and follow the instruction on screen. Point your scope to a CFL lamp and you will see a live feed on the webpage. Try rotating the scope till you get a bright sample and then move the yellow bar to the spot. Make sure you get green first and then red on your spectra when moving Left to right (ProTip) . If not you can click on flip button. When set click the “begin capturing” button.. and you can see all the stuff being done. When you are happy with a stable spectra click save and fill the form.

You will then be guided back to the site to calibrate. Once the spectra is saved you need to click the calibrate button and click as the dialog says (Be sure you are logged in or “Something went wrong” pops up).

After calibration you can see the wavelengths on the x-axis.

Here are some of my spectra:

blue

A blue LED from a STRIP

bulb

100W Phillips bulb. Extremely high IR content beyond 700nm

Bulbs are considered enormously inefficient as they emit large amount of energy they consume as IR which is not visible to human eye. Only a part of it is actually useful light. But camera’s do see IR . Check by seeing your remote’s Led thru your phone camera?
I always needed a proof of it ever since they taught this to me in 8th grade!
Here it is.

cyan

No wonder it contains Blue and Green

osram

The classic 6500k spectrum from my 40W OSRAM Tube Light

purple

Purple=Blue+Red

red

The pure RED Light from a LED

The spectrum peaks at 625nm. Using Plank’s equation, E=Hv
We have E=1.984V ! Wow.. The value of vf according to the datasheet is 2.1V Typical and 1.8V actual. That’s pretty close!

sunlight

Sunlight

You can see how vividly its true! The tubelight has a more peaky spectrum but the peaks are more or less aligned to the peaks/flats of the sunlight spectrum.

You also notice that sunlight has IR and UV content as well but tubelight doesnt!
Thats why people use sunscreen to protect them from UV!

The best thing about this web based UI is that it is crowd sourced so, If you click on Find similar you might get the same bulb brand or maybe material that somebody had tested. like i found a person/sample with almost same spectrum as i had. If he had given a much descriptive account of his bulb it would have been a lot useful

compIf you want to play around with Spectroscope without attaching it to webcam and just observe it with your eyes there is one by IUCAA here .

Check out the instructable here!

Cheers,

Rohit