Hi John, This part you bought, the Panasonic EVQ-WTEF2515B reminds me of common ALPS encoders often used in car radios etc. The choice of part is interesting because it has 15 pulses per 360 degrees which happens to be 360/15=24 degrees per step. That might work out to a step size of 24kHz per detent which fits nicely as a base multiple of sound-card bandwidths used in SDR software. So one step is 24 kHz and one revolution is 360 kHz.
Beware though, often these cheap coarse encoders are prone to failure with heavy use. But perhaps it is ok with SDR if you choose to do most of your tuning on the PC and only occasionally use the shaft encoder for larger jumps. A search for this part number on Google reveals a DigiKey part number P80675-ND at $8 USD per qty.-1, but no stock. Looks like it is a discontinued part. To sammple this simple A-B output quadrature encoder, you will need a routine that over-samples. Some incremental quadrature encoders have a Z output that is non-coherent with quadrature A and B outputs, therefore removing the need for an oversampling signal and opening the possibility for hardware only absolute direction plus relative pulse position output decoding using only the likes of XORs and flip-flops. I provide a link to an example of just such an encoder below. Here's a brief but decent page on quadrature decoding in-general: www.fpga4fun.com/QuadratureDecoder.html Follow this link for an example of an A+B+Z output high quality high-resolution (up to 3600 PPR) 32mm incremental encoder with square wave output. These cost around $70 USD each. CUI Inc. P/N MES20. There's a timing diagram showing the Z output on the down-loadable data-sheet. www.cui.com/adtemplate.asp?invky=455913 One has to remember that the quadrature incremental encoder is the basis of the PC mouse. There are trivially priced chips out there (in 1000,s qty.) that decode a couple of ball-driven saw-wheels with two optical detectors per wheel and then ouput direction and position pulses serially via the likes of a PS2 interface. But dealing with PS2 and often mouse protocols is perhaps a hassle with a micro-controller. But if it can be done, then you might be able to salvage an old PS2 mouse and use the decoder inside. A better way... Here's a couple of quadrature decoder chips (LS7183/4) that are good for micro-controller interfacing. USDigital distributes these US-Made chips for around $3 USD each in unit quantity. www.usdigital.com/products/ls7183-ls7184/ The manufacturer of these decoder chips is LSI Computer Systems of Melville N.Y. (LSI/CSI) www.lsicsi.com/ There are lots of other quadrature decoder chips available from LSI/CSI. Various interface types too, like parallel bus, SPI/Microwire etc. Check here: www.lsicsi.com/encoders.htm Good luck and be sure to update us with your results. Best 73's, David WB4ONA --- In [email protected], "John H. Fisher" <[EMAIL PROTECTED]> wrote: > > Hi David, I am trying out a new encoder which I bought at Electronic > Goldmine for $1 ea on sale until 5/1/08: > > <http://www.goldmine-elec-products.com/prodinfo.asp?number=G16267> > > (Incidentally I bought my 16x2 LCD displays there for $2 ea, too) > > I am in the process of wiring it in even as we speak. I won't know how > well it works until I actually write the software. My ohmmeter tests > were a little strange, so I am anxious to see if the $1 encoder works. I > will have to pole the inputs because the interrupt is either high to low > or low to high but not both. Although I have toyed with the idea of > reversing the interrupt in the interrupt and never missing a lick. > However I can't guarantee this encoder will work until I actually get it > running in the next day or so. I bought 15 of these encoders which they > say cost $6 originally. It also has a pushbutton if you push in on the > shaft. I'm going to use that to select the digit we want to adjust. I > hope to underscore or invert or blink the current digit and roll to the > next digit if the shaft/knob is pushed in. Of course this is all > vaporware until I get it working :-) > > drmail377 wrote: > > > > John, What shaft encoder are you using? David > > > -- > Regards, > John > > ========================================================= > email: [EMAIL PROTECTED] > photos: http://www.flickr.com/photos/k5jhf/sets/ > videos: http://www.youtube.com/profile?user=k5jhf > files: http://briefcase.yahoo.com/[EMAIL PROTECTED] > web page: http://www.geocities.com/[EMAIL PROTECTED] > call sign: K5JHF > ========================================================= >
