Matthew Venn » projects

dc booster PCB

matthew venn — Mon, 26 Sep 2011 13:51:54 +0000

This aim of this project is to build a small, adjustable DC/DC converter with an input from 1v -> 5v and an output of 5v->12v at up to 1.2A. With a 3v to 9v conversion at 1A it is 85% efficient. Photos taken during the design process are here.

After much searching I found and successfully tested the LM2623 (datasheet here). This great little converter chip does just what I need. The only problem is that it’s tiny! So this project is the one where I finally conquer my SMT fears!

I prototyped the board first with through hole and then with SMT components. The schematic and board are available here.

I used pretty much default component values from the datasheet. The only thing I did different was to add a trimmer for adjusting the output voltage.

All components are specified to 2A. The last numbers in the list below are all farnell part numbers. It works out at £4 each plus vat for 10 kits.

C1 22uF 1759435
C2 100uF 9695672
C3 4.7pF 1650903
RF1 1M trimmer 1174187
RF2 100k 1576183
R3 150k 9335978
D1 schottky diode 1680071
L1 4.7uH 1864113
IC1 LM2623 8207445

You can buy a professionally manufactured circuit board from me here:

SMT tips

SMT is a different technique to through hole, and requires some different tools. The most important things are a magnifying lens of some kind, liquid flux (I use a pen with good results) and solder braid to remove excess solder. Fine tweezers and a fine tipped soldering iron are also very handy.

Before soldering a component, apply flux onto the pads. Then place the component and check alignment. Apply a bit of solder to the tip of your iron and touch it to the pad while holding the component still with the tweezers. The flux helps the solder flow into the gap between the pad and the component’s pin. Now the component is attached, check the alignment and then move on to the other leg(s). This time apply the solder to the join like soldering through hole. Finally, go back and touch up the first pin you soldered. Check everything thoroughly with the lens after soldering. Having to go back to fix things can mean removing other components first!

For the tiny chip, solder it in place as above, and carefully check alignment! Then apply solder to all the pins and don’t worry about bridging. Use some of the fine braid to remove the excess and you should see a beautiful joint after!

Construction

Before starting it is worth scraping the white silkscreen off L1’s pads – this is a mistake I made when making a custom device in Eagle.

Place the components in this order: C3, R3, RF2, C1, IC1 (then test), L1, D1 (stripe on the right), RF1, C2.

After placing IC1, check these connections with a multimeter:

pins 1 & 5 -> ground
2, 6 & 7 -> + out
3 -> bottom pad of C3
4 -> left hand pad of RF1
8 -> D1 (+ out side)

Testing

Check the input resistance is large (above 1M). Then set your PSU to 3v and if you have current limiting set this low, 100mA is fine. Apply the current and you should see about 8.5v on the output. Use a screwdriver to adjust the trimmer and set your desired voltage.

If you get 0v or the supply voltage out then you probably have a bad connection somewhere. I’ve found bad joints on the big cap (C1), and the diode. I’ve also missed a pin a few times on the IC, but if you check the connections as I’ve listed above then this shouldn’t be an issue.

If you get a large negative voltage it will be because C1 isn’t connected properly.

Notes

At very low start up voltages (<1.5v) the board will look like a short circuit because the DC/DC controller shorts the input to charge the inductor. It needs about 2A to start at these low voltages, and then the current will drop to normal.

A beginner SMT artist will take about 30 minutes to build and test – as long as there are no mistakes!

Improvements

Bigger pads for trimmer and C2
Remove silkscreen over L1 pads (actually tdocu layer)
Indication of positive side of D1

polargraph energy monitoring

matthew venn — Mon, 19 Sep 2011 16:43:45 +0000

Understanding energy is difficult, even for engineers – as we can’t see, feel or touch it. Conventional home energy monitors try to address this through representations in numbers, screens or bar charts, but many of us aren’t inspired by this!

The Polargraph Energy Monitor creates a physical record of our energy usage by plotting circles corresponding in size to the energy being used in real time. For the home, the energy is drawn within a picture frame. For public spaces: the Polargraph scales easily to many meters across, ideal to draw on interior and exterior walls.

Exposing energy use in a meaningful way allows us to understand where and when most energy is used, encouraging us to make simple changes to live more energy efficiently.

You can download an explanatory PDF here.

Instructable coming soon…

floppy drawbot!

matthew venn — Wed, 24 Aug 2011 12:05:24 +0000

Make a fun spiral drawing robot out of an old floppy drive and arduino! Here is the instructable.

maze puzzle box

matthew venn — Mon, 21 Mar 2011 09:54:56 +0000

I’ve been working on a new project over the last 5 months, but keeping it quiet so I can surprise people with it… Well I’ve now posted an instructable so the cat’s out of the bag!

Head over to the instructable for all the details! Oh, and while you’re there, please vote for me so I win the laser cutter!

The science of Snow

matthew venn — Mon, 01 Nov 2010 15:52:53 +0000

The “science of snow” is an interactive exhibit that starts by illustrating how snowflakes form and ends with a unique snowflake postcard to take away.

By controlling environmental conditions, you grow a unique snowflake; its shape is a visual history of the journey from cloud to ground.

The exhibit has been shown at many galleries including The Crypt (London) Motorcycle showroom and Lakota (Bristol).

More photos of the build process and the final product including example snow flakes. Source code is here.

I would like to thank Janko Gravner, David Griffeath and Clifford A. Reiter for their research in the field. Their work was used extensively to build this computer model. Lou Smith for his interest and work building the physical installation. Rachel Carless for help with the funding application. David Murray-Rust for computer help and advice. The open source community for providing all the excellent free software with which this exhibit was built.

Comments by the public:

We came for our christmas party had such great fun , made xmas cards and snow flakes. Thank you
Loved it all, but especially the snowflake machine and advent calendar.
I loved the snow flake guys work Thanks.
Personally thought the snowflake was the best ! Thank you for an interesting afternoon.
We particularly enjoyed the installation by Matthew Venn where we produced our own digital snow flake.
Loved the snow flake machine.
I made my own snowflake to take home great idea.
I made the opening night and it was absolutely mind blowing, came back again to play on the snow flake machine.

laser cutter on its way!

matthew venn — Tue, 20 Apr 2010 07:16:41 +0000

my first slice of home laser cutting action! Here is the x and y axis ready to be installed. The motors and controllers are done, the laser is on its way – watch this space!

virtual graffiti instructable / howto

matthew venn — Sat, 19 Dec 2009 05:32:48 +0000

I’ve finished the first version of the virtual graffiti system, which is now fully published (including all code) on the instructables website.

We ran a demo at the blue hut youth club on Thursday where it was very well received!

virtual graffiti

matthew venn — Mon, 23 Nov 2009 09:20:14 +0000

A follow up to my latest post on using processing + linux for virtual graffiti, here is a video of it in action! The code is here: wiimote_sensor_calibration.tar.

linux ubuntu 8.10 + processing + wiimote + wrj4P5 = virtual graffiti!

matthew venn — Sat, 21 Nov 2009 06:32:41 +0000

Inspired by the various wiimote graffiti offerings, but finding no source or instructions (did I not look hard enough?) I decided to do it myself. Here is the first step: getting processing working with the wiimote infrared camera to detect an infrared LED.

After installing processing, I found some instructions on the forum, but I still had some problems. Here is what I had to do:

install processing
install bluez libraries: sudo apt-get install bluez-utils libbluetooth-dev
create ./processing/libraries/Loc and ./processing/libraries/wrj4P5
download bluecove-2.1.0.jar and bluecove-gpl-2.1.0.jar and put into ./processing/libraries/wrj4P5/library/
download wiiremoteJ v1.6, and put the .jar into ./processing/libraries/wrj4P5/library/
download wrj4P5.jar (I used alpha-11) and put into ./processing/libraries/wrj4P5/library/
download wrj4P5.zip and unzip into ./processing/libraries/wrj4P5/lll/
download Loc.jar (I used beta-5) and put into ./processing/libraries/Loc/library/
download Loc.zip and unzip into ./processing/libraries/Loc/lll/

Then I used code inspired from Classiclll to get the buttons and sensor bar working. This code just draws a circle where the 1st infra red source is found by the wiimote:

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import lll.wrj4P5.*;
import lll.Loc.*;
Wrj4P5 wii;

void setup() {
size(300,300,P2D);
wii=new Wrj4P5(this);
wii.connect();
}

void draw() {
background( 0 );
fill( 255 );

Loc p=wii.rimokon.irLights[0];
if (p.x>-1) {
ellipse( (1 - p.x)*width, (1.-p.y)*height, 10, 10);
}

}

Thanks to the bluecove team, the bluez team, processing crew, Classiclll and all open source massive!

portable looping station!

matthew venn — Tue, 11 Aug 2009 22:26:36 +0000

This is my portable looping station, put together for a busking trip to Paris. Everything packs up nice onto the trolley (speaker/power) and a rucksack (laptop and controller).

It’s pretty heavy and will be difficult up and down stairs, but the plus side is that it will last for about 4 hours and it’s nice and loud with a good bass response.