Ramblin' Dan's Workshop

The Texas heat is killing me in the unconditioned shop. It is keeping me away from experimenting with the Xbee and the Parallax Propeller (computer). The inside temperature in the garage shop has been hovering at 100 degrees while the outdoor has been 105 to 107.

This is NOT for a few days mind you. We have been getting this temperature every single day for over two months steady. Yes, every day.

My new shop fan helps a lot at 80 or 90 degrees but near 100 or over it is just like sitting in a blowtorch. No fun. I tough it out in the morning (on weekends) for a few hours but by 10:00 or 11:00 AM,  it’s breaking over 100 again.

Actually the little control computers don’t mind this kind of heat. They are very low powered so don’t generate much heat on their own. It depends on how much power you pull from them.  I can’t say that about the PC computer that I use to write the application software. I believe it is maxed out with 105 degree ambient air temp trying to cool the processor, hard drive and other PC components. I had one of my CNC computers (another machine) shut down from the heat after running almost four hours. Luckily I had just finished the part I was cutting and was bringing the HB2 back to home position. I don’t do long CNC runs anymore in a hundred degree shop.

I like the newer Propeller processor. With 8 processors or “cogs” it is a “hot” multitasking little controller. That is figuratively hot. Not environmentally hot. I definitely have it earmarked to be the processor on the boat end. I was thinking about it today, and I am going to also use it on the shore terminal.

I don’t think I need its multi cog power on the shore unit but my thinking is to keep the software programming the same “flavor” for the entire project. I can put the BS2 STAMP to other uses.

I have a few ideas how to design the shore transceiver. It will be a small standalone unit. I was originally thinking of using a PC or Net Book as the shore terminal with just an XBee for the communication. The more I thought I decided a control box would be a better interface and not so expensive (to fix) when getting too close to the water, if you catch my drift. A BS2 would be plenty of computer smarts to run things but as I said above, I’m going to opt for another Propeller.

But hey! Who says I can’t play with my options.

With the Propellers at both ends of the communications I can dedicate one or more cogs in each Propeller to just run the XBees at their best transmission rates. Decision made.

If the Texas heat takes a few days off over the holiday weekend, I plan to get a lot more done with testing the com link. Then I can start designing the Propeller proto boards for the real link.

I also discovered there is a new Propeller multicore processor in the works. It will be bigger and hotter that the present Propeller. But hotter will also be the heat it generates. I suspect it will be more useful in applications where enough “shore” power is available and chip temps can be controlled. I think the Parallax Propeller has a great future and will be useful for a long time.

As you can see I have two of the Parallax HB-25 Dc motor controllers now on my workbench. They are rated at 6 to 16 volts (DC) at 25 amps. That should be rugged enough. I figure I only need one for testing but I would like to run twin screws on the demo boat.

The controller is just over 1 ½ inches square and about the same in height. That makes them very small for the power they can handle.  What makes them so high capacity is the attached micro cooling fan under the component board. There is a machined heat sink between the fan and the controller chip. The heat sink is drilled with holes like Swiss cheese.

When I first saw these controllers probably a few years ago, my first thought was these were perfect for electric motor control on a model boat; actually large electric motors on a large model boat. Now I get to test my initial premise.

Electrics and water always has me concerned. It is very possible the boat may be operated in times of light rain. So one of my challenges is how to mount and protect these controllers from moisture. If it was easy, anyone could do it. Other than a complete sinking, it’s a matter of splash control.

Then I just need a hull that is unsinkable (Titanic?)

Trials will of course be run in calm waters but who knows what thrills may lay ahead when confidence and reliability allow the operating envelope to be expanded. Maybe build the first model icebreaker with a balsa wood hull.  Uh… no, that can wait.

I got some time this Labor Day weekend (2011) to get an XBee  interfaced with the Propeller processor. The pictures show the tiny interface board required to change the pin spacing from the XBee to fit the spacing on the Prototype Breadboard. This is some more of the micro soldering I have written about before. That's all this board does is change the pin spacing.

What I can see here is the XBee running in full duplex. That means it can listen and talk at the same time. Just like talking on the telephone. Well, maybe I can't do that but the telephone does it very well.  :)  That's a pretty big deal in the world of communication and has certainly removed some concern from me determining if this system will work fast enough for good control. I think that is not an issue at all now that I can use the Propeller.

Dedicating one of the cogs (processors) in the Propeller to just manage the communications means I can do whatever else necessary with the other cogs and not slow down the two way communications with the shore unit.

It has been a great weekend. The weather in Texas finally broke this morning (Labor Day 2011) as it was 68 degrees on my back porch this morning. The wind had been blowing hard all day before and the night before so I knew something was changing.

At 7:30 AM I sat on the porch in my "got dressed" shorts, sippin' a cup of fresh ground French Roast coffee, munching on my last chocolate walnut brownie, and freezing my a** off! I'm not conditioned to under 70 when it's been 105 to 115 for several months straight. Never the less, it was a great day to work in the shop.

The picture shows the BS2 micro computer in the foreground with an LED, a photo transistor, a piezo speaker (squeaker would describe it better) and a servo motor all hooked up to the I/O pins. That is the Propeller behind it also with some I/O stuff on board. Both systems are capable of communicating both directions on the wireless XBee network.

My theory has been proven to my satisfaction. Now I will begin to design the real world component application so I can test how those components will really work, then do radio range checks before I switch to the prototype boards.

It sure was nice to have a cool day in the shop.