CyckelLjudet & Festmaskinen at Regnbågsparaden West pride Göteborg

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After assembling CyckelLjudet we managed to arrive at Götaplatsen were the parade Regnbågsparaden were supposed to start.

The solar panels worked really great, we had no trouble at all and the LiPo was charged nicely.

We did use an old Sennheiser wireless transmitter to send the audio from the DJ-booth at Festmaskinen to the PA-speakers at CyckelLjudet.
We had some problems with wireless interference, but it hold up well most of the parade. Go 80’s technology!
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CyckelLjudet – Attaching electronics and solar panels

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All pimped out and ready for the west pride parade Regnbågsparaden!

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To be able to drive the amplifier for the speaker we use an UPS. On top of the UPS you can see the solar regulator Solar80.
The solar regulator is charging a 6S 8Ah LiPo battery pack. The solar panels will generate maximum of 600W of power, and the PA-system will draw about 65W of power, so the battery will be more of a buffer.

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After some spec-readings we realized that the Solar80 wouldn’t handle the maximum of 70V that the solar panels could generate, it only supported 48V. So we switched it out for Flexmax 80.
Both the controllers were designed for lead-acid battery’s and not for LiPo battery’s. I was missing a parameter to set the charge voltage, also there was software limitations that you couldn’t go around, like the charging current for example, you could only go as low as 5A.
We’re trying out the solar panels and solar regulator in the sun charging the LiPo. The stop-charing-limit was set to 25.2V which is the voltage of a maximum charged LiPo, but the solar regulator was still inputing voltage well above 25.2V because the solar regulator is designed for lead acid battery’s. We then set the maximum-charging-voltage to 24.8V that seemed to help, the voltage over the battery didn’t reached over 25.2V.

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Cables from the solar panels.

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Amplifier/mixer in place, and so is the LED-bars.

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go:toTrash

Here’s a new project me and my friends are working on, go:toTrash. It’s a radio-controlled trashcan that is supposed to help people throw their trash properly.

Our city, Göteborg Stad, are doing a marketing campaign to prevent littering on the streets. In collaboration with the advertising company Frank & Earnest they gave Chalmers Robotics the challenge to make Göteborgs iconic trashcan movable.

The trashcan weights around 90 kg, so we have to put some strong motors in to make it move.
The plan is to help people throw their trash more easily by driving the trashcan to them. So the driving velocity is going to be quite low, at the most 5km/h.
One evening at the hackerspace Simplex Motion came by to visit us and introduce their cool servo-motor 100A. They asked us to use it and evaluate it.
Simple Motion 100A is a servo with a BLDC and a outrunnermotor inside of it, it runs on 12-24VDC and can deliver 100W (400 peak).  We soon implemented it into our project.
Our teammember Erik Sternå did some calculations on the forces needed to drive the trashcan and came to the conclusion that we needed a gearbox with 1:25 ratio.
We come i touch with OEM Motor that sponsored the project with gearboxes.
Unfortunately we don’t have time to buy an implement a belt-driven wheels, so we have to connect the shaft to the wheel with a shaft-coupling. This makes the driveline quite long, so long that we can’t make the wheel-pairs symmetrical. The shafts are offset by 65mm.
It’s not a optimal placement for the wheels but okey, we can always compensate for it in the software.

DIY Moving Head Spotlight PAR RGB-LED

There’s a small festival up in Uddevalla (Sweden) called Elinorspelen. It’s a non-profit festival with the goal to have fun and spread culture. Unfortunately the festival have a very low budget and can’t afford all the equipment that it needs, and lighting has especially been down-prioritized.

Two friends of mine, and I, decided to do something about it. We got together and started discuss what kind of stage light that would be possible to buy/make.

We all agreed on that moving head spotlights would probably the cheapest alternative that gave the most visual effect.

Research

We started out to search for cheap LED-diodes to make our own spotlight.
But after a day or so we quickly found out that to just build the a LED-array would cost as much as a commercial spotlight. For example this LED PAR 56 black 151 LEDs RGB 16W for 296SEK.
We soon gave up the idea of making our own LED spotlights.

But we found out that all the cheap LED-spotlights had a very wide beam angle, and we wanted a very narrow beam.

Making an RGB spotlight on a tight budget

We got back to the idea of making an spotlight ourselves. Picking out narrow 10-13° viewing angle LED’s from Ledz.com.

As I started to pick parts to the project, the list grew longer and the price were raised by big numbers.

I managed to find really cheap geared stepper motors from eBay for a really cheap price; 28BYJ-48 DC 12V, plus controller, for around 26SEK a piece. After some research it looked like that model i widely used in different DIY- and Arduino-projects.

After a few weeks of picking components forward and back I’ve come closer to a final budget on 450SEK per spotlight, and that excluding some material prices like polycarbonate. I suspect that the final price per unit will end up on 500SEK. That’s at least 3 times cheaper than any commercial light.

You can find the budget for the spotlights here (Google Drive).

Electronics

I’ve just a basic idea of what components the electrical design needs. Some micro-controller based up on the STM32 series should work well.
Some mosfets to drive the LED’s.
The LED’s should be connected in series to 12V, and have the same pinout as the popular LED-strips that are so widely available now. This should make the testing very easy.

Designing the chassis and mechanics

The designing process were making its way alongside with the budget, a design-change could radically change the budget.

I had a pretty basic idea how I wanted the final product to look like.


A LED-array soldered on to a PCB, the PCB should be mounted directly on an axis that were attached in a U-shaped arm.
The PCB would make the LED-array really lightweight and it should not be a problem for the geared stepper motor to move it.

I also thought of having the cabling layed inside the axis, so why not make the axis into a tube instead of a solid rod?

Moving the U-arm

But how would the U-arm move? I knew that a central shaft would be the focus in this problem. It should be able to move a pretty heavy weight, PCB + Stepper motor + alot of polycarbonate.

I also think that the moving head spotlight should be able to be mounted in several ways; placed on a flat surface shouldn’t be a problem. But be able to hang upside in a ceiling, or hanging from the side of a wall, that’s tough.
The center-axis mus be able to take on forces from many directions.
One thing was for sure, we needed alot of bearings.

With the bearings a shape took form, centered around the axis.

4 bearings are used on the center axis. 2 axial bearings to make it spin easy upside down and standing. And 2 bearings up and down to make the center-axis stiff and prevent it from leaning.

And around the bearings, the framework took place.

Somewhere here the pieces started to place them selves in the big puzzle, it was much easier to design now.

Around the framework we needed a casing to hold out dirt and to keep it pretty.
It’s hard to make a nice chassis by yourself, so  I started to look around for a cheap case designed for another purpose.

I found this cheap water bawl for dogs for around 17SEK. It’s about 200mm in diameter and should house the mechanics and the framework nicely.

Designing in CAD

It’s one thing to have you design in your head and on paper, but it’s hard to grasp if it will fit or not. It’s here CAD-design comes into the picture.
I started to draw the different parts needed. As I draw the parts I could easily adjust lengths of parts to fit each other. Make puzzle-slots for the different pieces in the U-arm.

I try to make an easy design that could easily be milled out in our CNC-machine. The most parts are made so they could be cut out in X-Y-axis. I’m also trying to make as long and narrow pieces as possible, because long pieces are easier to fit narrowly on to a big polycarbonate-sheet.

The last part of the CAD-design was to put it all together, attach bearings to the shaft, build the U-arm.

The first design is now complete. We’ll have to make several adjustments to the design in iterative steps.

But for now, I’m thinking it’s starting to look good!

Sewing backpack straps


This is our new backpack straps for Festmaskinen


We took measurements of backpacks used for hiking and researched how to place the weight on our bodies. We want as much of the weight place on the waist, and less on the shoulders.
I modified the measurements from the hiking backpack a little bigger to handle more weight.


For the stuffing in the strap I used a pretty unusual material, floor mop, it’s soft and still pretty stiff.


For the outer fabric I used an old Ikea-sofa-cover, good strong fabric.


To make the waist-strap more sturdy I cut out some cardboard.


I sew 10 layers of mop-fabric together and placed it inside the waist-strap.


Over the years I’ve collected a lot of nylon straps from old backpacks and bags, I finally found a use for them.
I sew the nylon strap on to the waist belt.


For the shoulder straps I used the same method as the waist-belt, except the cardboard.


I sew a zipper on to the shoulder strap. The use of this zipper is to place cables from the speaker backpack to the DJ-booth and back.


I also sew a cushion for the lower back.

Hot bending the polycarbonate-sheet for speaker backpack



Here we have placed our hotbending machine on the joint that is to be bent.


We used aluminum-foil and paper to isolate material that we didn’t wanted bent.


The corners seems to match!


Vilse removed some plastic left from the CNC.


We used our laser-cutted acrylic angeles to bend the polycarbonate-sheet in to the right angle.


We placed this böp to let the joint cool down


15 seconds left of our 4:25 timer, the heating of the polycarbonate is almost ready.


We used straps to hold the last bend


The last bend is a round corner, the radius is 200mm. We knew it would be very hard to bend it.
We heated like 100mm of the polycarbonate with both hot air gun and the heat bending machine. We heated the area for at least 20 minutes, it wouldn’t bend.


At last the polycarbonate was bending, but it turned out ugly as hell. A lot of bubbles and ugly artifacts, at least this side won’t be that visible.

Our heating machine turned out to be far more superior to the hot air gun.
Lesson learned, never make round curves in polycarbonate!


This is what the backpack will look like. The 12kg weight of the polycarbonate didn’t feel heavy at all. I think the weight will be ok.


To hold the corners of our speakerbox, we use a two-component poly-urethane glue (3M Scotch-Weld Urethane Adhesive DP-610). We got a test-sample from KA Olsson and it worked really great. It’s quite expensive, but we got it a little bit cheaper thanks to KA Olsson.
We used straps to tighten the polycarbonate around the corners. We also applied tape at the edges to stop the glue from seep out.