Today, we finally did a range test on the 433MHz Emergency Stop board I made.
The minimum range the project is looking for was 50ft, reliably. The good news? We managed that distance no problem. Better news? The range is so far we're not sure how to appropriately measure it.
Indoor's where you expect reception to be worse. We left the transmitter in our lab and walked away with the receiver to a point in the building we could not receive the signal anymore.
This ended up being about 150 feet, through the doors of our lab (which have been known to be pretty impervious to RF), not even close to line of sight, and while transmitting at the lowest voltage possible.
Next up was an outdoor range test, again plugged in to an outlet at one building the transmitter was left to transmit. The receiver was walked behind buildings and a range of about 200ft was managed, although it could probably go further.
Finally, we did a Line of Sight Test, One person on one side of the parking lot, myself on the other side. With line of sight, we've easily managed 450ft. Just 9 times the required distance for the E-stop. Thats with the 3.0V minimum transmit voltage (works up to 5.2V).
Later this week we will test using a different method. Namely find a dead end road and drive straight down it until we can't receive anymore, and try this with the higher transmit power, also.
I'd bet we can get over 1000ft out of these things if we try.
Ill put up pictures of the schematics and a parts list for those interested in this. ~60$ gets a reliable link up to about 1000ft (Data sheet says you can get 3000ft if you know your RF design...I don't). If your looking for simple switching, this beats the price of Xbees.
Sunday, March 13, 2011
Friday, March 4, 2011
Open Source Linear Algebra Computational Software
This is a post for anyone who has done linear algebra and gets 2-3 pages into a question, and realizes they screwed up a step on page one.
It's happened too often to me to be funny anymore. half an hour wasted because that "-2v1_z" really should have been "2v2_z" and then everything would have come together properly.
If its happened to you before, or you want some software to check your work against. I suggest looking into this "Maxima" Project.
What it is, is very comparable to the symbolics library in matlab. However comes with a lot cheaper license (Free) and does the work in literally a 10th of the time. Its a considerably higher performance implementation to what Matlab currently implements.
Really, really crappy screen shot of Maxima.
I know that this totally sounds just like a plug for them. But compared to what I usually use I was impressed with the amount of features that a program like this has. Apparently it has plotting functions too (not nearly as powerful as Matlab in this respect).
One nice feature is the copy as image and copy as LaTeX functionality. Means you can use Maxima to render an equation quickly without the stupid PDF recompiling that LaTex does. Then Quickly and accurately get the right function into Latex without any of the usual hassles. (Particularly useful for equations that have many elements, sums or integrals in them).
If you're taking a Linear Algebra Course, and want to check your work with this. If you're like me and multiplying a bunch of symbolic rotation matrices together, or your in industry or as a hobbyist looking for a free solution to evaluate some problems. I'd strongly suggest this download as being a big step in the right direction if you don't want to shell out 150$ for a Matlab License.
It's happened too often to me to be funny anymore. half an hour wasted because that "-2v1_z" really should have been "2v2_z" and then everything would have come together properly.
If its happened to you before, or you want some software to check your work against. I suggest looking into this "Maxima" Project.
What it is, is very comparable to the symbolics library in matlab. However comes with a lot cheaper license (Free) and does the work in literally a 10th of the time. Its a considerably higher performance implementation to what Matlab currently implements.
Really, really crappy screen shot of Maxima.
One nice feature is the copy as image and copy as LaTeX functionality. Means you can use Maxima to render an equation quickly without the stupid PDF recompiling that LaTex does. Then Quickly and accurately get the right function into Latex without any of the usual hassles. (Particularly useful for equations that have many elements, sums or integrals in them).
If you're taking a Linear Algebra Course, and want to check your work with this. If you're like me and multiplying a bunch of symbolic rotation matrices together, or your in industry or as a hobbyist looking for a free solution to evaluate some problems. I'd strongly suggest this download as being a big step in the right direction if you don't want to shell out 150$ for a Matlab License.
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