A slight distraction

I have an interest in alternative vehicles and power, and lately have been working with someone (Steve) who works for a company that I contract too. He introduced me to recumbent bikes. As a result of talking with him and research on the internet I have built my own HPV.

It's a recumbent trike which has been made from 2 donor kids mountain bikes reclaimed from the local waste transfer station. The wheel size is 24".

It is mostly finished now, I need to get new road tyres for it as the existing nobbly off-road tires are severely deteriorated. I also want to fit some lights and other stuff to make it a bit more visible. I am hoping to use it for local trips in the area and work my fitness up to the point where I can ride it to town (it's a 30 minute drive through forest and farmland).

I have not done a lot on the electric bike lately (I did have a sit on it the other day). We are looking at starting to build a house on our property and need to get started on building it before the end of the year, so unfortunately this will stop me from working on the electric bike for the most part, but I am hoping to build the inverter and start writing the software for it before the end of the year. I have purchased a few sample ATxmega processors from Farnell for the inverter.

Progress update

We have now moved up to our property and have sorta settled in. We have setup a small 1kW off grid solar power system with a 1380Ah 12V battery bank. We are heading into summer so at the moment we are generating lots of surplus power. We have usually recharged the battery bank to 100% full before lunch time at the moment.



This is good because the surplus can be used to recharge the bike. Speaking of the bike I have not done too much work on it since the move, however I have been thinking and planning on it. I have got some work with a local induction motor manufacturing firm which is giving me a better insight into the working's of the induction motor. I have seen the regenerative braking effect and am pretty confident that this will be quite easy to add (the motor when driven slower that the motor rotational speed will cause it to turn into a generator that backfeeds DC voltage, perfect)

I was planning on using the Atmel AT90PWM3B processor for the inverter, however now Atmel have released there XMega series of processor, they look very cool. I don't need much incentive to play around with new stuff but these processors are jammed packed full of very nice features like 2million ADC samples per second (12 bit), advanced waveform generator (perfect for motor control), new event bus and DMA to namea few. Farnell have listed the 44pin ATxmega64A4 which I think would be perfect. It is a 3V part so I may have to tweek my current inverter design. They have the 100pin A1 part already in stock at the moment, but the pin spacing is a little too fine for a handmade board and I don't need all the IO. The current design uses the 28pin AT90PWM3B which only just had enough IO with no room for expansion.

Will hopefully now update the blog more often as I expect to be spending a bit of time each week on the bike.

Even busier

Well, we completed the renovation on the house and sold it within 4 days of putting it on the market (we were thinking it would take a few months). So this has put the bike on the back-burner even more so for the short term. We will be moving mid year so once the move is complete and we're settled in then I hope to get back onto the bike.
The move will create some additional problems however with the bike, the place we are moving to has no mains power so recharging will have to be done with leftover power from an off-grid solar power system. Which could work out ok since I like to ride in the summer so that is when we should have left over power.

Busy year so far

This year has been very busy with work and house renovations, unfortunately it's taking time away from the bike project. I have updated the schematic and sourced a better suited IGBT for the drivers and added some on board capacitance after some good feedback(thanks Will). I am just setting up my subversion server and an ftp server here so that I can host the project files a bit easier.
I have setup a workbench and purchased some steel to make up the motor brackets. I am just saving some money for the batteries and components for the motor controller. I have made up a small low power encoder(this is a for another project) which will be able to detect motor direction and speed. It will have 2 encoder counts per revolution.
So the todo list ATM is:
- Purchase battery's and battery charger
- Make motor brackets
- Make battery cradle
- Extend chain by 2 links
- Make and test motor controller(lot of work here, build prototype and write software)

I have now completed the initial schematic for the 3-phase motor controller. I have to update some footprints and then it will be time to start on laying out the PCB. You can download stuff from here

Schematic PDF
gEDA project
gEDA symbols

The schematic is done on gEDA, the PCB will be done on PCB the PCB editor that is part of the gEDA package. The software will be written for avr-gcc. Both gEDA and the c complier are open source projects, and very good at what they do. Currently gEDA only works under Linux, but the compiler will work under windows with wan-avr(Just a side note I am designing and writing all the software for this project on a asus eee 901 with gentoo installed on it, a fantastic piece of hardware).

To get the gEDA project to run you need gEDA suite installed, uncompress the project and uncompress thje symbols. You need to make the gschem point to the schematic symbols directory. To do this you can simply uncompress the symbols tar into your linux home directory and everything should work. Otherwise you could just copy everything in the /lib/schematic directory into the /hardware/mc directory. Otherwise have a look in /hardware/commonrc and update/add the schematic directory to the component directories. One this is done change directory to the /hardware/mc directory and run make edit, this will open gschem. Have a look in /hardware/makefile for a list of other things you can use make to do.

Please if you do know anything about 3-phase motor control I would appreciate any feedback on the design, and I will post updates and corrections as I make them.

Motor controller and batteries

I have got caught up over the holiday doing stuff on the house, but I have been researching and drawing up the schematics for the motor controller on gEDA. The first draft of the schematic is about 80% complete and I have layed out the components, I just need to do some tweeking and adding in component details(resistor and cap specs etc). I hope to have to up within the week for comments/feedback.

I am now looking at getting 18 of the EVH15120. These are a comprimise between price and performance. Since they are designed for EV use they should last a while, they will fit into the frame of the bike, and there not too heavy. The upside is there easy to get and at least half the price of Lithium. The downside will be the weight and the charge time.

I have attached the LED blinkers to the bike and here is a pic.
And the back...
I have bought some workshop equipment that will help me with the fabrication of the batttery case/tray and motor mounting brackets etc. I have got most of the electronic components that I need to build the controller too.

Indicators, Grips and the Motor

I have been getting quite motivated lately to get some work done on the bike. I have just received some led blinkers. I have ordered the 0-5v hall effect twist grip throttle that should be arriving tomorrow. I have done some more research on Mosfets and IGBT's for the motor controller. At the moment I am leaning toward a 600V IGBT. I am switching 360V which is a little on the high side for mosfets, and there are some quite quick IGBT's. I am about to start the schematic for the motor controller.
The good news is that I have finally cracked open my 3kw 3 phase induction motor and had a peak at modifying the wiring to half the voltage I need to drive the motor with. I started by cutting the tape holding the wiring together and numbering each slot. The motor is a 4 pole motor with 36 slots. This gives me 12 slots per phase,and each slot is paired to make 6 coils per phase. There are the 6 wires coming into the motor and 9 wires that jump between coils. After writing all this down I then had to work out what it meant and what I have to cut to take the 6 in-series coils in half to get 2 3 in-series coils and run them in parrallel to get half the voltage. I figured out that each phase has 3 slots next to each other and then the next phase has 3, then the next and so on. This give me 4 sets of 3 slots per phase which is where the 4 pole comes from. So I have found the 3 wires I need to cut to halve the voltage. Yay!!!