This is the making of go:toTrash were we are showing the steps involved in the construction.
This longboard is driven by a BLDC-motor, that is controlled by a VESC (Vedder’s Electronic Speed Control). The throttle and brake is controlled by a wireless Wiimote Nunchuck.
The base of the driveline is a kit by DIY Electric Skateboard (http://diyelectricskateboard.com/product/single-motor-electric-longboard-kit/).
The kit is made for the SK3 motor series and included trucks with motor mount, wheels, pulleys and timing belt.
The motor mount is welded into the truck, the design is really good and the welding job is well done. The drive pulley is the weak point in the drive line, it’s wobbly and hard to calibrate. DIY Electric Skateboard seems to have switched it for a new pulley made out of aluminum now.
The motor is a Turnigy Aerodrive SK3 168kv 2400W Brushless Outrunner Motor (http://hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=38055).
On the board I use 4x3s LiPo 8Ah 30C (http://hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=32214), it gives about 350 Watt hours of energy.
The motor driver is developed by Benjamin Vedder, he have been developing several years now and he have been implementing a lot of nice features into the ESC.
The VESC can drive a brushless motor sensorless, it measures the back-EMF and can track the position very accurate even at low RPM’s. It also has regenerative braking that charges the battery’s while braking.
A nice feature is also the cruise control, it’s PID regulated and very accurate because of the good tracking of the motors position.
I used a nice IP67 rated rubber sealed case for the VESC (http://www.biltema.se/sv/Bygg/El/Fast-installation/Kopplingsdosa-2000021071/).
A big capacitor us coupled together with the VESC, it creates a big inrush current when the battery is plugged in. A big inrush current can create sparks that oxidizes the connectors and make big ripples in the voltage in to the VESC that can cause damages. Vedder made a small PCB that slowly charges the capacitor, it’s based on a charging schematic from the forum Endless Sphere.
The capacitors and the inrush limiter is hosted in the casing as well.
The Nunchuck for Wiimote has a nice grip and several extra buttons to use for extra functions. Nyko does make a wireless version of the Wiimote Nunchuck.
The Nunchuck is communicating with the Wiimote through I2C, so is the wireless receiver for the wireless version of the Nunchuck. The wireless receiver is stripped of its case and hooked in to a I2C bus on the VESC.
Because the Nuncuck is made for gaming it keeps sending the last known command on connection loss, for example so that the gamers gas pedal won’t be affected in game. This is not a good thing when you are driving for real.
Vedder has made a replacement PCB for the Nunchuck chassis that using the NRF24L01+ radio. It’s more safer and have a greater sending distance.
Although I have no longboarding or skateboard experience i found it quite easy to ride the electric longboard. I found it easier to keep my balance on the board while having constant power driving it forward. The ability to brake also makes it easier to get on and off.
It’s a really fun way of transportation, it’s fast and you can carry the longboard every where when don’t driving.
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!
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.
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.
CyckelLjudet is a bicycle equipped with a PA-system, LED-lights and solar panels for taking your party with you.
It’s going to attend at the Westpride Parade in Göteborg 2015-06-14.
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.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.
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.
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).
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!
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.