Updates and Meeting Minutes:
Winter 11 Term
Jan 27, 2010: New team
- welcome new team members! Also welcome to Rupali and Anupal, two Masters students in electrical engineering =)
- our voltage protection breadboard seems to be having some problems (perhaps loose contact/wire/component or burnt IC). We'll need to look into this.
- we will be focusing on several aspects of the project this term, and hopefully finalize multi-bike enclosure design and begin construction - see the Plan for Winter 11.
- For our newcomers - a great opportunity approaches! The project development team is interested in developing some educational videos for our bike and solar thermal project. This would be a great opportunity for those new to get more working knowledge of the system, and at the same time we'd be able to show future members how it works. Justin also mentions that we would be able to promote it to prospective sponsors for fundraising which is an awesome idea.
Fall 10 Term
Nov 4, 2010: Enclosure2
- we looked at the enclosure dimensions with the prospective enclosure from Tariq, and it seems definitely plausible.
- We looked into the possibility of removing the metal cage of the dump load to save space, and it'll be alright as our enclosure would be closed.
October 21-Nov 2, 2010: Enclosure Discussions
- Hussin has found some bridge rectifiers from Sayal Electronics Cambridge (25A 200V Quick Tab GBPC1502) that we can use as diodes. Each set contains two diodes so we'll need only three for the 6 motors. As they are electrically isolated, we'll be able to attach aluminum brackets as heatsink, or perhaps mount directly to the enclosure should it be metallic material.
- As for the enclosure, we have several options available. Hussin got us into contact with Tariq Naqvi, SYDE lab instructor who happened to have some enclosures available! Its dimensions are smaller than I hoped, but since we would be able to get this for free, I'd like to try to use these. Another option would be the industrial level Hammond Manufacturing enclosures which is what they typically use in the industry. If we do choose to go with these, we can see if we can approach the company for a sponsorship (They're approximately $300). We'll also need to figure out the exact size we want before this happens.
- Great news! Hussein has managed to score some freebies from McPhail's Cycles for an expensive looking ($400?!) bike stand! They were apparently going to throw it out as the fluid mechanics in the load resistor was broken, but this works out great for us as the mounting spot for the motor is already available! We'll be putting up some advertisements for them on our enclosure and website for their contributions =)
October 14, 2010: Design Decisions
- The diodes issue - Kurtis has found some 16A blocking diodes from an ebay seller rated for 800V. However no breakdown voltages nor forward voltage were given.
- Hussin has suggested that he'll look into the facilities in the ECE department to see if he can get access to any enclosures or diodes that we can use. This would be great!
- Enclosure Design - We've revised the original design of the enclosure. With a limitation on wire lengths and turning radius of the wires, we may be able to run with more flexibility with a enclosure like below.
UPDATE: The ebay seller has replied to Kurtis, and unfortunately he does not have more information then what's provided. I find this hard to believe... I was expecting there would be some specifications on the part for such important specs in design
October 7, 2010: New Team! Aiming high!
- We've assembled a new team with the departure of our previous grad students. They've done so much to bring the project to the current state, and now it's up to us to complete the system.
- Our team is aiming to have the system in a functional state by the end of this term. Very ambitious and more than my original plans, but we're going to try!
- Goals this term:
- functional electrical system with enclosure
- Clean up single bike prototype system box - swap capacitors and tidy leads to make it safer
- rig yellow bike stand with new support cups and motor mount
Spring 10 Term
August 16, 2010: Detailed Project Status
July 27, 2010: Project Status
- Blocking diodes for the multi-bike system need to be specified, along with a module for mounting them and connecting wires to them.
- Diode specs: 15A to 20A current capacity, forward voltage VF as low as possible (VF * Current = wasted power), reverse breakdown voltage > 20V (to prevent current from back flowing from cap which can be up to 15V). Heat sink is an asset.
- Mounting module: Depends on diode package. Digikey sells a number of TO-220 package diodes that meet our requirements. To connect the diode to cables, we will need to design a PCB module for each diode. It can be very simple: two screw type connectors (surface mounted or otherwise; if you take the front panel off our C60 charge controller you will see the type that we need) that are each connected to a different terminal of the diode through the PCB. The wire coming from the motor connects to one connector and the wire going to the combiner connects to the other connector. PCB link: http://www.ece.uwaterloo.ca/~pcboard/
- Do a search for "power diodes" - these are modules with their own connectors and everything and designed for power applications. They might be insanely expensive and have high VFs but we wouldn't need to deal with making PCB. See this example: http://www.infineon.com/cms/en/product/channel.html?channel=db3a3043243b5f170124d974602e740c
- Mounting for electrical components
- Board is being designed to minimize cable lengths. An AutoCAD will be provided at the end of this term. Basically, it will be a flat board where the combiner, capacitor, breaker box and inverter are on one side while the charge controller and dump load (the two heat sources) are on the other side. The dumpload is to be mounted on 2 inches thick sheetrock (a type of drywall), with the dumpload itself standing off the sheetrock be another inch (see dumpload instructions). Certain junctions will need to be provided by a terminal block unless we want to put two wires into one connector. Terminal block will need to be specified.
- Yellow bike stand modifications: motor to be mounted on a metal plate, which is conneected to the stand's built-in hinge (there are holes on the hinge for this already). This plate is then tensioned to the stand just like the existing stand that STEP entirely manufactured. The cup for holding onto the bike needs to be re-manufactured with a longer rod so the stand will actually clamp onto a bike (distance between the two cups is currently too wide; stand was designed to work with the included quick release that replaces the rear axle of a bike).
- One of the two farad capacitors does not work; it acts like there is no capacitance. Confirm whether the other two farad capacitor works or not.
- Mechanical bike smoothie maker idea should be investigated.
Winter 10 Term
Mar 30, 2010: Bike #2! + Safety Feature Improvements
- Some major progress today - After discovering that one bike has a hard time keeping up with ~50W for any extended period of time, we're putting on bike #2. With 2F capacitors on the way (brand new ones this time so hopefully more durable), we will be using the 58F cap for now. The original screws of the capacitor terminals have been swapped out with longer ones to allow for more terminal connections (currently with nuts as spacers - not the best setup but works for now). FYI, original screws taped onto the inside of the box that held the capacitor and inverter.
- The second motor has been updated with the large hard plastic terminals to prevent insertion pole mismatch.
- To discharge the capacitor, we've added a bypass switch for the dump load that allows the dump load to directly feed off of the cap. This allows the light bulb to drain the capacitor. Interestingly enough, this setup causes the light bulb to dim as the capacitor drains and the voltage decreases - a great visual representation of the discharge status.
- We now have two bikes working with the big capacitor, and it takes about 40 seconds for two riders to charge the cap to 12V working voltage for the inverter. Two riders should be able to comfortably keep up with a load of 75W.
Here's a
safety guideline for the bike generator operation. We can keep it with the box for safety show to distract people's attention away from the rat nest inside the box...
preliminary parts list: needs to be finalized by the end of this week so that we can purchase parts with time for parts arrival before end of term.
Mar 19, 2010: Wire Ampacity/Power Loss Calculations
Wire sizing must follow the electrical code for safety reasons. The chosen size of wire must be able to withstand the current drawn through it without overheating. The ampacity of the wire determines the maximum current level that can safely be drawn through said wire continuously without deterioration. The chosen wire would ideally minimize voltage drop from wire resistance, and hence should be limited in length.
Here's the Drawing for the wiring diagram/wire sizing, devised based on the tables found in the "Canadian Electrical Code Part I - electrical safety code".
Drawing -
VisioDrawing -
PDFUpdate:
http://www.altestore.com/howto/How-to-Size-Wiring-and-Cabling-for-Your-System/a62/ explains that while AC systems found in house wiring must support the ampacity, low voltage DC systems need to also factor in power loss. Our wire selection must fulfill ampacity requirements, fall within tolerable power loss and be also commercially available.
Mar 16, 2010: Electrical System Design
Our research finds that the suggested components fit our needs. You can download all the info, datasheets, owners manual of our chosen components here.
While the original plan was to have a 10-12 bike system, we've hit a electrical design limit where commercially available products support up to 60A before escalating to expensive products starting at 125A. Therefore we've chosen a 6 bike system with the option for expansion via the use of a 12 input combiner box as opposed to 6 input. Should we find that 6 bikes cannot saturate the system with enough amperage that's anywhere close to the 60A limit, we can add more bikes in for more power output.
We had a little mishap during our event @ Sustainable Energy Fair @ UofT where are Tupperware system gave up and refused to work. Failure point likely to have been overheating from stress, which may have been from the dump load unable to keep up with the inverter not on.
Our 1F cap has been replaced with our 58F cap temporarily. We tested the new system and it works.
There are large differences in the new system with the large 58F capacitor:
1) takes 3, 4 minutes or 58 times longer than before to charge cap until inverter will deliver power
2) system behaviour has changed:
a) longer to charge
b) easier to maintain voltage below threshold (due to longer timeframe with voltage increase)
c) more vigilance required in our volunteers monitoring voltages
d) dump load stays way longer than before (58 times longer, so take that as a minute). Light bulb means
stop pedaling this instance!
Here's the schematic (
pdf,
visio) of the new 6-bike electrical system, revised with Brent's input:
Mar 10, 2010: Enclosure Design
The enclosure was very roughly estimated to be 2'x2'x3'.
Here are some questions to think about when designing the enclosure:
What materials would be used?
How would you secure the components?
How would you access the box?
How do we ventilate the box?
How will we ground the box and how do we tie the negative terminals of the components inside together?
note: electrical code states that systems below 50VDC are not required to have a true earth ground. However, it is best we design a ground feature so protect the more sensitive electronics that we would plug into the inverter, such as laptops.
- just an idea - would a large server chassis be suitable? It has ventilation, metal for grounding, structural stability, slide panel for access? the problem is fitting in the components and finding a large enough chassis.
The mechanical team has decided that given the availability of our budget and the safety required for the stands, plus the exorbitant costs of purchasing just the bike support cups, we have opted to purchase bike stands and add modifications to connect the motor.
Feb 2, 2010: Current System Diagram
Here's a schematic of the current system we have (the one sitting in the Tupperware):
Suggestions:
- Power Monitoring - How far would you need to bike to charge a battery
- Charge Controller - Need to know if it will work with a capacitor? (@ 20V, 15V)
- Experiment: Question - What happens if two motors are connected to charge control, one motor spinning and no diode in place to prevent backflow
- Brian brings up an excellent point of us needing an enclosure or housing unit for all of our electrical gear, because we cant just throw it into Tupperware this time! Once we finalize the dimensions of our components, we'll need the mechanical help to design and build one, or at least a prototype we can use for now.
Jan 2010: Component List
The more we talk about this new electronics system, the more we're realizing that it's something we should make sure we do right. By designing it like a typical off-grid renewable energy project, we can take advantage of off-the-shelf products, while ensuring that everything is safe and compliant to code. It would also serve as a useful tool for demonstrating a typical renewable energy system. As such, we will be looking at purchasing some new components. These products are fairly representative of the bits and pieces we're looking to buy, but we should do some shopping around and a bit of design work to make sure they're alright:
- Xantrex: C60 charge/load control
- should be able to use this as our dump-load control
- Square D: Q024L70RB load centre and QO260 60 amp double pole breaker
- circuit breaker and disconnect for safety
- Midnite Solar: MNPV6 Combiner Box
- safely combine the output from all bike generators (or solar panels) to a single line
- AEE HL-100 air heater diversion load
- serve as a dump load for excess power (essentially a large resistor)
short term goal - let's get some data sheets and specifications, pricing and put together a system design that will serve our needs. Requirements:
1) Connect up to 10 power sources (mix of bikes, solar panel, etc.)
2) Safely protect the capacitor which can only go up to 15V
3) Prevent any generators that aren't producing enough power from being driven by the other ones (i.e. blocking diode like on the current bike)
4) Safely handle the amounts of current and power that are going through the system
Some questions to be answered:
1) Does the charge/load controller handle all the overvoltage protection and switching on of the diversion load?
2) Do the circuit breaks and combiner box support our requirements?
3) Is the diversion load power dissipation enough for our power levels?
Fall 09 Term
Dec 2, 2009: Control Circuit
We've finally got a second controls circuit put together for the dump load. It was a bit tricky to figure out the resistors, so in the end Peter put together a simple program in C++ to calculate the appropriate values, based on a couple assumed resistors taken from the controls circuit found on page 16 of the
"Energy Experience Kit" from the Fallsbrook Centre. The figure shown below is a version adapted for our system. In this schematic, the main capacitor is the DC BUS coming from the bike generators. This circuit will cause the 12 V DC relay to turn on at some upper voltage limit, and remain on until the voltage drops below some lower limit. In this way, we can activate a bank of DC bulbs as a "dump load" to help dissipate power if the capacitor bank gets too full. An excellent explanation of how this circuit achieves this can be found in the
kit (conceptual) and in this
document (with math).
The calculations performed by Peter and the resulting values are described
here, and his source code
here. A C++ compiler will need to be used to run the code. In the circuit we put together, the relay activates at an upper voltage of 14 V, and remains on until the voltage gets to below 11.2 V. In the end, it is likely that we will end up tweaking some of these values slightly, either through the potentiometer Rv (to adjust the upper voltage limit) or the variable resistor Rh (to adjust the amount of hysteresis).
Oct 23, 2009: On our way to multiple generators!
If you're buying materials for STEP, we've got an account with WEEF we can use. Just ask one of the old guys to set you up.
We now have TWO working bike generators, and as soon as someone lathes us up a new pulley for the third, we'll be up to THREE! If you're not comfortable/trained in using the tools in the machine shop, just let the old guys know and we'll be happy to give some lessons. Scott is a whiz in the machine shop. Nandan's a welding guru. Both Peter and I can swing a hammer like there's no tomorrow. The student machine shop is located in E3, near the fluids labs.
We've got the electronic components to handle up to 7 or 8 generators working simultaneously! Let's get building
Tasks:
- machine new pulley for third stand (out of steel, so it won't wear out this time)
- build more generating stands
- Using either Scott's existing design, or one of your own. Welded steel? Reclaimed bike frame bits?
- must know how to measure
Oct 1, 2009: Beefing up the power distribution system
- We have now received a brand spankin' new inverter generously donated to us by Xantrex
- Xantrex ProWatt SW
- 1000 W
- true sine wave power (grid quality!)
- accepts 10.5 - 15.5 V(DC) ... over 16 V may damage
- We've also purchased a larger capacity capacitor bank, to handle the larger and crazier load of multiple bikes
Spring 09 Term
May 26, 2009: DC Motors arrived
- Our new shipment of motors has arrived! We've now got three brand-spanking new (or possibly used) 250 Watt, 24 Volt DC motors. Hooray!
May 11, 2009: Stage 1 Prototype Complete:
We have now completed our stage 1 prototype, and are well on our way to completing a fully reproducible design. To date, we have successfully produced about 90 Watts of grid-quality power, though for a fairly short time ... it's much harder work than we originally thought. =P
We are finally ready to start getting out in the public and turning some heads! By the end of the semester, we plan to have three fully functional generators, and will be able to power devices up to about 250 Watts.
We should also be able to use our working design to secure some more funding, both through WEEF and through various fundraising activities.
Past Updates:
We have some initial funding from WEEF ($250), and have the potential to get some more, once a more detailed design is produced (exact motor, materials, etc. are known)
We now need to:
- Determine the reasonable expected power output for an average person (not working tooooo hard)
- go to CIF to use stationary bikes
- Based on the determined output for an average person (power, RPM), select components for initial prototype (DC motor/generator, regulator?, inverter?)
- Brent has a 300 W inverter at home which we should be able to use
- Victor mentioned that he has an old electric scooter, which we may be able to pull a usable DC motor from
- Andrew will ask his friend whos dad owns an electric bike company for spare motors
- Design bike stand/frame to hold bike in place while being pedaled
- Nandan can weld
- building work can be done in mechanical student workshop
- should be relatively portable
- design mechanism to transfer rotation of rear wheel to generator
- must match required rpm input of generator/motor
- must not slip
- must be adjustable to fit different sized bikes (27 inch racing, 26 inch mountain, 24 inch children's)
- once designs are set, build prototype and test the hell out of it
