Template:SEARC

Project Overview

This is a joint project between:

Project created and supervised by:

  • SEARC's lead researcher Adegboyega Babasola
  • Dr. Joshua Pearce, adjunct professor of Queens University

Research Period:

  • June 2011 - Ongoing

Objective

To design a charging cart for a 3D printer that is completely mobile, and runs solely on renewable energy.


Fig. 1-RepRap Logo

RepRap Background

For the project, a RepRap Mendel running on gen6 electronics was chosen.

The RepRap is a low-cost 3D printer, designed by Dr. Adrian Bowyer. It runs on open-source software. And is self-replicating.

More information on the RepRap can be found on the RepRap at:
RepRap.org/wiki

Designing the Power Circuit

Power Considerations

Fig. 2-Power Circuit
Fig. 3-Component board
Fig. 4-Battery configuration
Fig. 5-Cart at OCE Discovery 12
Fig. 6-Cart at SES 2012


Two 220W solar panels were donated by Queens University for the project, therefor the power circuit was designed around them.

PV power modelling software was used to possibly reduce the number of panels needed to only one. But that was not a viable solution for the power objectives.

2 DC power supplies are required:

  • 12V
  • 14-24V

Max power consumption

  • 50 - 60 Watts (RepRap)
  • 60 - 70 Watts (Computer)

Days of Autonomy Required = 5 days @ 7 hours of operation per day

Power Circuit


See Figure 2 for power circuit wiring diagram. Figure 3 & 4 are the component board and the battery layout.

  • 2 x Schüco 220W Polycrystalline Solar Panels (Model: MPE 220 PS 09)
  • Fusetek 4-Pole Combiner Box
  • MorningStar ProStar 30A Charge Controller (Model: ps-30)
  • 2 x 20A Fuses for Over Current Protection
  • Powerbright 400W PSW DC/AC Inverter (Model: ML400-24)
  • 4 x Power Deep Cycle 120AH Batteries (Model: TC-12150C)
  • 2 x Single Circuit On/Off Battery Switches (added april 10th, 2012)

Designing the Mobile Cart


For the cart to be functional, many things had to be factored in. It had to be:

  • Sturdy enough to hold the weight of the batteries and panels, approx. 620lb.
  • Narrow enough to navigate through doorways.
  • Able to move over uneven or rocky surfaces.
  • Mobile enough for one or two people to move it.

The cart was built with 3/4" plywood for the table top and shelf, 4"x4" cedar for the legs, and 2"x4"s for reinforcement. Pnuematic castors were chosen for the wheels. Originally two swivel wheels and two static wheels were used on the cart. Although they did work, it was decided, that switching the static wheels for two more swivel wheels would greatly improve mobility, and it did.

The real challenge of designing the cart was how to incorporate the panels onto it. When deciding how to mount the panels, many things were taken into consideration, the panels must be:

  • Mounted in such a way as to fit through doorways.
  • Able to adjust to different inclines for different situations, including 180̊ for southern locations.
  • Shielded from damage during transport.
  • Adjustable by one or two people.
  • Attached solidly enough to avoid bending and damaging while adjusting.

The finished cart can be seen in Figures 5 & 6.
To attach the panels, one of the panels was fitted with 3/8" steel flat bar on the inside of the frame for reinforcement (see Figure 7,) to prevent the frame from twisting and possibly shattering the glass while adjusting. Then they were riveted together with piano hinge, so the PV of the panels were facing each other. A beam of unistrut was fit inside the steel reinforced panel, and held in place with four brackets. Four hinges connect the unistrut and panels to the body of the cart.
The top panel (the reinforced one connected to the cart) has two square steel tubes attatched to the bottom corner of it(see Figure 8.) At the other end of each steel tube is a thick 4" bolt (see Figure 9.) There are three holes at the base of either side of the cart that the bolts easily slide into (see Figure 10.) The holes were drilled out to hold the panels at 0°, 20°, or 30°. There are two legs attatched by "L" brackets to the underneath of the other panel's frame (see Figure 11.) The legs were constructed of three pieces of slotted angle bar so they could be adjusted to different heights for the different angle settings. They automatically drop down when the panels are unfolded.


Figures 6-10 demonstrate how the panels open and close.



Updates & Plans for Improvement

Cart Leg Shading

With the current front leg design, unless the cart is constantly rotated to stay inline with the sun, there will always be shading on the bottom panel from one of the legs. This can be alleviated by using telescopic legs. With telescopic legs, they can remain collapsed when the panels are set to a lower angle, to avoid overhang.

  • Update (May 28, 2012) - Three equal 13.5" lengths of slotted angle bar were used in lieu of telescopic legs. The shading problem has been fixed.

Wind Shield

When printing outside while the cart is charging, wind can cause premature cooling of the filament coming out of the extruder head. This can be fixed by building either a premanent transparent barrier surrounding 3 sides of the printer, or a removable 3 wall barrier that can put in place when printing outdoors.

Recycler Extruder

Build Your Own Mobile Solar Cart

Supply List

Item Model Quanity

& Size

Schüco 220W PV Panels MPE 220 PS 09 2
MorningStar 30A Charge Controller PS-30 1
Powerbright Inverter ML400-24 1
Power 120AH Batteries TC-12150C 4
Fusetek 4-Pole Combiner Box 1
Blue Sea Systems Battery Switch 6006 2
20A Fuses 2
8" Pneumatic Locking Swivel Casters 2
8" Pneumatic Swivel Casters 2
3/4" Plywood 4'x8'
4"x4" Lumber 12'
2"x4" Lumber 34'
Piano hinge 64"
Heavy duty 3" hinges 4
3/8"x 1 1/4" Steel flat bar 20'
Rivets 32
Galvinized steel slotted angle bar 7'
Steel 1" square tube 7'
1 5/8" x 7/8" Unistrut P3300T 64"
3 1/2" x 3 1/2" Steel L Brackets 8
1 1/2" x 3 1/2" Steel L Brackets 2
4" 3/4" Bolts 2
3/8" x 3/4" bolts 40
3/8" x 2 1/2" bolts 6
5/16" x 2 1/2" Self tapping hex head screws 16
#10 3" flat head wood screws 100

Build Instructions

See Also

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