Member Since: March 12, 2010

Country: Canada


Started tinkering with electronics in the late 60s… 3 degrees and +25 years of engineering later, still tinkering.

Current work is mostly software-defined radio (analogue and digital/DSP), robots, shop gear (Rb 10 MHz ref project), and apps.

  • I suspect your DMM is too slow to see the transient. The sensor does not produce a constant AC voltage proportional to how much it is bent, rather it produces a “spike” (+ve and -ve). If you are using an analogue multimeter, you are in even worse shape. Put it on a scope and you will see the spikes…

  • Welcome interns and co-op students. Each of you will be assigned a work station where you will learn to share space, equipment, tools, and company perks like this multi-purpose, SparkFun-supplied, hackable, Joie de vivre inspiring, rest and recuperation surface. Like most things we share, it is your responsibility to keep it clean… hey, Dave… what’s the deal here?

  • Sadly, the SAM1198-X-X parts above are non-stock at Digikey. You might try making your own from a longer strip. Sure, you may lose a receptacle cutting the strip, but you would get more beefy pins. The SAM1198-50-ND CONN RCPT .100" 50POS SNGL GOLD is the -03 pin length, which I believe is 10 mm and almost exactly the same length as the stackable headers above. The cost difference is not huge…

  • Member #219744 - your question is answered in the datasheet; that’s what they are for ;-)

    Always RTFM

  • Reading this and other comments, I have the following suggestions. 1) have clean, stable power going to the Tx and Rx units. These have gain and mixer stages that will pick up and amplify pretty much everything. Put a scope on the rails and make sure they are steady when the Tx/Rx units are operating. 2) Put a low-pass filter on the Tx output. It doesn’t have to be really steep and can have a passband >= 330 MHz. That will make sure that the harmonics mentioned above don’t interfere with other devices. Of course, a bandpass filter would be better, and is only slightly more complicated. If someone can determine the output impedance of the Tx antenna port, then try to match that. 3) The wavelength of a 315 MHz transmitter is about 95 cm. You should get decent efficiency with a ¼ wavelength = 23.8 cm wire antenna provided it’s isolated from other conductors. Check out ARRL info on antennas for other kinds that may be useful… 4) If you are lucky enough to have a spectrum analyzer, use it to see what’s going on with the Tx. Pay attention to “spurs” outside the desired band and the above-mentioned harmonics. If you only have an oscilloscope, you may still be in luck if it’s digital storage and has an FFT mode. You can single-shot trigger and take a look at the spectrum using the FFT (of course, the scope has to be 350 MHz or better (probably 500 MHz)…

    Have fun,