You could couple a potentiometer to the drive somehow and translate angular position into resistance. Even if you put a series resistor between the wiper and a D.C. source and connected one leg to the D.C. return, you could select the series resistor so that the full voltage drop across it would be equal to the max input of an eight bit ADC (ADC0808 or similar) the ADC output could then be input to a PIC and the software could be developed for an antenna tuning routine, or whatever you require. ----- Original Message ----- From: "Dale Botkin" To: Sent: Tuesday, October 01, 2002 4:25 PM Subject: Re: Antenna Controller > On Tue, 1 Oct 2002, Alex wrote: > > > I would like to build an improved controller for an amateur radio antenna > > that I use. > > It has a large variable capacitor that is motor driven. > > Have you disconnected the motor from the cap to see how much force it > takes to move the cap? I'm thinking you might be able to replace the > motor with a suitably sized R/C servo, and drive that from the PIC. I > don't know if you could get close enough positioning that way, but it may > be worth the try. Anyway, you could just replace the control box with the > PIC and still keep the same button arrangement. I can almost see the QST > article coming now! 8-) > > > The two things that change are capacitance and angular rotation. I suppose > > angular rotation would be easiest to store,but would mean adding something > > to the shaft that could be counted. The rotation is about 80 degrees and has > > switches that indicate the end of travel. > > If you do want to use the existing motor, see if you could adapt something > simple to the shaft. I'm thinking the optical guts from a mouse might > work, that will give you a slotted wheel you may be able to drill out and > secure to the motor shaft, then use an optical encoder to watch the holes > go by. Again, not having seen the loop -- is it MFJ or AEA? -- I don't > know if the motor has a small enough shaft, or if there's enough exposed > to give you the half inch or so you'd need to get at. > > Another idea would be to keep the same drive arrangement, but use a > stepper morot for the drive instead of a DC motor. Steps from the limit > switch could easily be determined and stored. > > > One last question. I have been using assembler and the Epic programmer, but > > would Basic or C make my life easier especially with bigger projects. I have > > some programming experience with both. > > I know it made my life a lot easier. I learned PIC assembler, having done > a lot of assembly programming in the past, but never did get really > comfortable with it. I got a few projects done, but since I switched to C > it's been a lot better for me. To each his own, some people are dyed in > the wool ASM devotees. I'm right, of course, and so are they! 8-) > > Dale > > -- > http://www.piclist.com hint: The PICList is archived three different > ways. See http://www.piclist.com/#archives for details. > > -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.