WHAT chip are you using that has the nice divide by 10 outputs please? I have been wiring 74ls XXXs for years what a pain. Tired of the soldering. Thanks Paul
On Thu, Dec 9, 2010 at 7:47 AM, Bob Camp <[email protected]> wrote: > Hi > > Another simple approach: > > Run a PIC off of it's internal R/C clock > Divide to both 60 Hz with a divider that will do M, M-N, M+N where N is > 1,2,3,4,5 and covers the expected tolerance of the clock > Divide the 60 Hz to 1 Hz > Compare the 1 Hz to a pps output > Based on the 1 Hz being early / late, update N for the next second. > > It actually takes less time to code it than to explain it like this. > > If the built in clock is good to ~ 0.1 % on a second to second basis, your > clock will be far more accurate than the eye can detect. > > Lots of ways to do it. > > Bob > > > On Dec 9, 2010, at 3:47 AM, francesco messineo wrote: > > > Hello, > > > > On Thu, Dec 9, 2010 at 5:13 AM, Michael Poulos <[email protected]> > wrote: > >> Recently I bought a Efratom Ru frequency standard from eBay and a > frequency > >> divider chip that makes 1MHZ,100KHZ,25KHZ,10KHZ,100HZ and a 1HZ output. > >> Today I thought of a way to make a nice 60HZ so you can use a > mains-powered > >> clock for the display (using amplifier and transformer wired > "backwards"). > >> But, now you'll need 60HZ. A European has it easy with 50HZ as you use a > >> BASIC Stamp or Arduino to divide the 100HZ output. But for 60HZ I came > up > >> with a solution: > >> > >> You set up the Arduino to take the 10KHZ from the divider chip and > program > >> it to count off 83 pulses to flip an output. But wait! Unless you add a > >> "leap count" every 3 flips of the output, it'll run fast. Assume at the > >> start the Arduino output starts high then turns low: > >> > >> (83+83+84+83+83+84)*20 = 10,000 pulses = one second > >> H__L__H__L__H__L > >> > >> Every output cycle and a half the voltage swing is a little over 1 > percent > >> longer because of the leap count. This means that the distortion adds a > >> slight inaccuracy, not enough to upset New Year's revelers. But if you > want > >> a better 60HZ, try using the 100KHZ: > >> > >> (833+833+834+833+833+834)*20 = one second > >> > >> You see where this is going with leap counts. The ultimate of course is > one > >> really good Arduino and (after a hex inverter to amplify it) take the > >> straight 10MHZ and apply this leap count technique: > >> > >> (83333+83333+83334+83333+83333+83334)*20 = one really accurately made > 60HZ = > >> one nice second, just the thing for a Nixie clock. :) > >> > >> Now, what is a good hex inverter to take the 10 million HZ of my > rubidiom > >> movement to feed a frequency divider chip (and later Arduino)? It needs > to > >> take the .5 of a volt sinewaIe and squarewave it and in a normal 14 pin > DIP > >> (breadboardable) package. > > > > > > if you are not afraid of a little microcontroller programming, why not > > use a software DDS approach like this: > > > > > > http://www.myplace.nu/avr/minidds/index.htm > > > > it can output a nice sine wave at 60 Hz (or whatever) from say a 10 > > MHz clock really easily and the frequency is also easily tunable in > > software. > > > > I built several similar low frequency (audio range) software DDS using > > AVR and other microcontrollers. > > I usually add a one or two stage active low pass filter after the R/2R > > network. I also used to build the R/2R network out of selected 1% 10K > > resistors, final resistor match is usually good to 0.1% tolerance, but > > in some boards I just put 5% parts. > > Software is basicly an adder and you use the highest byte as a pointer > > to the ram or rom waveform samples, once you understand how it works, > > it's really easy to adapt to your needs. Usually the waveform you > > obtain has a DC offset, but that's easily solved too. > > > > Hope it helps. > > > > Frank IZ8DWF > > > > _______________________________________________ > > time-nuts mailing list -- [email protected] > > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > > and follow the instructions there. > > > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
