View Full Version : New to the propellor.

07-17-2009, 04:37 AM
http://forums.parallax.com/images/smilies/jumpin.gif New to spin, but I am a biomed tech. and need a simple 1hz (60BPM) inverted V wave to use as a ECG simulator. Can this be done with a Propellor.
I know a little PBASIC, if this is easier to work with. I have a board of education. Am pretty new to all this as I learned Electronics in the Vacume tube age.

07-17-2009, 04:48 AM
If you just need a single waveform almost any MCU could be used with a DAC and a lookup table. The Propeller would be overkill. Simulating the electrical properties of the electrode interface to the human body is the tricky part. The Propeller might be useful if you wanted to simulate the different waveforms you get with the standard electrode placements, but I'd be inclined to use a small PIC or something similar for that, as well.


Amateur radio callsign: G1HSM
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Post Edited (Leon) : 7/16/2009 10:04:31 PM GMT

07-17-2009, 10:29 PM
Yes, a propeller can do this.

As a tech, are you producing anything you create en masse? If not, the Propeller might be overkill where production is concerned, but it's a great tool otherwise! If you go down the road of learning to do stuff with it, you will find it can do a ton of things easily and without a lot of extra hardware.

Where there are cheaper solutions, they don't have anywhere near the utility / dollar performance the Propeller has.

If it were me, I would get the Propeller Education Kit. It's got a lot of great labs, published on line too if you just want to pick up a Prop or two and get after it on your favorite bread board. Then pick up a proto board or two, so that when you get it all done, you can just build out a more stable device and enclose it for use later. A great alternative option is to pick up some of the boards you will find at Gadget Gangster. The kits are a good deal too as the most common stuff is included. Bread board to prove out, then build up a board for ongoing use.

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Post Edited (potatohead) : 7/17/2009 3:35:24 PM GMT

Ken Gracey
07-17-2009, 10:35 PM
@potatohead and Leon: he's already using the BASIC Stamp, so he doesn't care about the unit cost. ARMY hopes to do this with Parallax products. Inverted V-waves are not something I can program. Wondering if there are examples in our PE Kit. I'll check. . .

Ken Gracey
Parallax Inc.

07-17-2009, 10:51 PM
Clearly, this is a perfect application for Propeller and Pulse-Width-Modulated D/A conversion especially if your simulator requires 12 or more connections. You could even play back nominal and abnormal samples on demand. All you need is a high speed connection from your PC and/or an SD card for storage. I don't know how to get the samples, but I bet you do :)


Propalyzer: Propeller PC Logic Analyzer (http://www.brouhaha.com/~sdenson/Propalyzer)
http://forums.parallax.com/showthread.php?p=788230 (http://forums.parallax.com/showthread.php?p=788230)

Andy Lindsay (Parallax)
07-18-2009, 03:31 AM
Platform:·· Propeller Education Kit (http://www.parallax.com/tabid/134/ProductID/415/Default.aspx)· (A.K.A. PE Kit)
More info:·PE Kit Labs, Tools, and Applications (http://forums.parallax.com/showthread.php?p=617192)

Ken Gracey said...
Wondering if there are examples in our PE Kit. I'll check. . .

The PE Kit Labs book does introduce how to use a D/A conversion object for signal synthesis.· Here's an example of a signal transmitted by the Propeller chip and measured by the Parallax USB Oscilloscope.· The code and circuit were created with the information and examples·in the PE Kit Labs book:


The application (Make Waves - Archive...zip (http://forums.parallax.com/attachment.php?attachmentid=62319)) is attached, and here is the top file (Make Waves.spin).··This particular example is just transmitting one channel of D/A with the DualDAC object, which·uses counter modules for duty modulated D/A conversion.··The DAT section is hand digitized samples from the image on this page:


The oscilloscope display is still a little choppy, 200 samples might work a little better than 100.


Since each cog has two counter modules, each instance of·DualDAC can transmit up to two channels of D/A.· For twelve ECG channels, it would take six cogs, which still leaves one for top level stuff and another for other tasks.· A more thrifty use of cogs would involve using one of the PWM objects obex.parallax.com, which Steve mentioned earlier.· Here are links to a couple of objects that could be used for the PWM D/A conversion.



Andy Lindsay

Education Department
Parallax, Inc.

Post Edited (Andy Lindsay (Parallax)) : 7/17/2009 11:16:35 PM GMT