Watts/RPM plotter

[gizmo]

Hiya.

I'm working on a project that might be of interest. Its a power to RPM plotter, based on the little Maximite computer. The "device" will let you connect up an alternator so it can read volts, amps and RPM. You then spin up the alternator with a drill, lathe, engine, whatever, a few times from 0 to 1000rpm, and it will then present you with a graphical plot of the power curve, save the data as a excel file, and let you compare it to previous tests. Normally generating such a bunch of information takes hours, you need to find a power source that can hold the alternator at set RPM's while you write down meter readings, without over charging the test battery or cooking the dump load.

This device can do the whole test in a few seconds, with 1 RPM accuracy. Each RPM reading is averaged, up to 100 readings per RPM, so the more you rev up and down the alternator, or the slower you change the RPM, the more accurate the results.

Its based on the Maximite computer, a little hand size computer kit based on the PIC32 processor running at 80MHz, and runs on 12v. The Maximite connects to a VGA screen ( or composite video ), standard keyboard, and stores its program / data onto a SD card. You can log months of data on a 2Gig card. It uses a version of BASIC very similar to QBasic, with a few added commands. Its just like a little TRS80 PC, but a hell of a lot faster. It also has 20 input/output pins, 10 analogue and 10 digital. These can be used to measure volts, amps, etc. Sampling rate is pretty good, I've had it read over 1000 voltage levels per seconds, and I put together a simple CRO program and its displayed the mains hum! The digital pins can be used to measure frequency ( up to 200kHz ) , period, duration, etc, and act as interupts. The Maximite cost $79AU.

I'm putting a page together on my site about using the Maximite for RE related projects, will post the link once its up and going. I think the Watts to RPM plotter will be handy, especially for testing a new alternator and calculating the best turbine to suit it. I've also got a windmill controller/logger that will graph power to wind speed in the pipeline. Having the VGA screen output mean makes it easier to display lots of data at once.

Link to discussion about the Maximite on my site, including links to the designer and supplier http://www.thebackshed.com/forum/forum_posts.asp?TID=3378&PN=1. I think for its price its a great little bit of gear.

Glenn

[fabricator]

That does look really interesting, but for guys like me who are tech challenged it's all kind of a blur.

[Rover]

I think its really cool, some of us play around with 32bit controllers, glad you found one that meets your needs.

As you have discovered, the fun parts are learning the platform, learning how to wire sensors, sampling rates, and obviously learning some form of language.

A few  of us use parallax propellers (32 bit with 8 cores) , which are nice since you can run the cores in parallel, great for sampling. The PIC seems to be the true winner for use though.

keep posting.. good stuff!

[SparWeb]

Glenn,
That looks like a great kit.  I still use your PicLog, but that would be a step up, you have to admit.
MicroZed and Altronics both seem to be sold out.  Check out the warning:

PLEASE NOTE: We are experiencing a significant number of backorders for this product. Unfortunately we cannot offer any assurances of when stocks will be available. The first and second production runs have all been pre-sold. Further production runs are scheduled for July & August delivery.

I was reading more on Geoff's website.  He mentions that "all you really need" are the parts, the microcontroller, and the break-out board.  Do you know what board that might happen to be?  I've tried to find it on the Microchip website but it's buried in the mass of information.

[gizmo]

You can find the adapter boards here http://futurlec.com/SMD_Adapters.shtml. I think once you price out the parts, its just as easy to buy the complete kit, and its in a nice little box with a front label and stuff.

I think its going to be a popular bit of gear, very easy to use compared to other micro controllers.

Glenn

[SparWeb]

Thanks Gizmo,

I can't solder SMD, but I know a guy who knows a guy...

...And I take it that the board featured in the article, with the USB, switches, ports and SD card port, is a "proprietary" board that only comes fully assembled...  Hence the backlog?

[gizmo]

Yeah I wouldn't be too keen on soldering a 64pin chip the size of my finger nail either Apparently its not that hard to do, but you need a fine tiped iron and bloody good eyes, or a magilight in my case. I should have a go one day.

The Maximite came as a kit, with the Pic chip already soldered into place, you just need to fit the other components. Took me about an hour to put together.

Glenn

[richhagen]

I've been following these types of stories, and have been becoming increasingly jealous of folks like DamonHD who can log and plot the power there system collects.  I would also have a use for a tachometer/power logger for similar reasons as Gizmo, although for the smaller mills I build. 

As a result I finally plunked down a bit of money and bought a little microcontroller training kit, this one is a basic stamp and uses a very easy to use basic programing language.  I've built basic counters and sensors only to date, but it does not take a great leap of imagination to see the great potential of these.  I did realize pretty quickly though that the chips are too expensive to build more than a one off of something for my own use with these controllers.  I am thinking that the maximite would be great for the main data logging on a system like mine, but for the myriad of projects that I forsee, I have begun looking at other PIC chips.  The reason is that if I design a circuit of interest, I can put it on a board and build several with minimal cost for this sort of thing.  It is hard for me to justify the time and effort to design and program these types of projects just to build one of them.  Although the initial development costs might be a bit more, I have been looking at this system:

http://www.mikroe.com/eng/products/view/297/easypic6-development-system/

Which I am hoping would enable me to design and build a variety of simple systems using inexpensive and available pic chips.  I will have to save up a bit of currency for it though as I am not a dozenaire like Ghurd.  Rich

[SparWeb]

The wait time started to get me frustrated     Looking around, there are the Parallax Propellor, the Atmel Mega32, and the Arduino Mega2560 (sister to Atmel?), each of which which are rather complex but offer lots of inputs, the boards are ready-made, and all you have to supply is the surrounding parts.  Programming these is another matter.  I would deduce, from the popularity of the Arduino with school robot projects, that it's easier than the Atmel. 

The mega2560 promises 16 analogue input pins and 54 digital inputs (maybe some of the digital pins are converted to analogue by the software, so 38, your choice).
The analogue is read at 10-bits, so 1024 points on a 5 Volt scale is pretty fine (5mV resolution).  I2C output to a LCD screen, USB port on board already...
60 bucks in Canada...  Can plug in a SD card reader board as an add-on if I want it.  What could go wrong?

If I can't use it for a datalogger, I'll just HAVE TO build a battle robot for my kid.  Aw the duties of parenthood...