please clarify the SX-manual's resonator info...

tommy

Hello to all.

· it's time for me to coordinate two separate SX-28's, and I guess it's about time I learned about Parallax's·resonators...· This first·use will be a simple one·- a virtual 555 chip to send a coded 38 KHz infrared beam from one unit to the other...· the units are solidly mounted, twelve feet apart·on my windows (they open my blinds) and I wish to make one a master and the other a slave.·· The resonators will also force the two stepper motors to operate at identical speeds...

· I've picked 4 MHz, as my not-so-critical timing in all my current projects·is based on that, and I can read a TV-remote, and operate my motors·just fine with the·algorithims I've already written at 4 MHz.· Faster is not better for the time being...· in fact, faster creates problems.

· ---> So I will purchase two dozen CST4.00G0H6 resonators (with the internal capacitors) - but then my sources conflict:

++ my version 1.1 (paperback) manual says I need a 100K parallel and a 470Ω series resistor...
++ a pdf version on my computer says I just need a 1Meg parallel resistor.
++ my SX-tech board has room for a resonator, but I see no resistors in the circutry...

·which combination is correct ?
·

---

·...and I will have to pop them in and out during programming and de-bugging, right ? ? ? --- are little 3-hole holders made just for them, or can I just cut down some collet-style sockets ?

thanks.
tommy

P.S.· just how stabile are they ? --- can I use that 4,000,000 figure to make a virtual clock ? ?· (I'm not going to - but is that possible ? ?)





Post Edited (tommy) : 5/10/2007 5:33:42 AM GMT

Bean

In my opinion, the 1 Meg resistor is what you want (if you want to use any at all). The resistor is just insurance that the resonator will startup.

You don't need to remove the resonator for programming, but you do for debugging.

Looking at the datasheet for the Parallax 4MHz resonator, it looks like they are +/- 0.5% and +/- 0.2% over temperature. So total stability would be +/- 0.7% ( 10 minutes per day, not good enough for a clock). For a clock go with a crystal (they are probably 50 or 100 PPM, 100PPM = 0.01% or 8.6 seconds per day).

Bean.

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·

tommy

originator's reply...
· thank you Bean...·· so I gather that the parallel resistor in not too critical - I will use a 1Meg as you suggest - and that no series resistor is required.·· It's a shame that the manuals were all different.
·· None of my simple communications between units is highly speed-critical, but standardizing the speed between units puts another 'tool' at my disposal should the need arise for more complexity.

·I already use a DS1302 as a clock so that the blinds won't open until the sun passes by, at noon-time... and the thirty bytes of free memory that come with·the clock·make it valuable even if I were to not keep the time...

· I shall now re-draw my 'avatar' - that picture / icon on the left under our names (what a strange word - "an embodiment, a representation, coming down to Earth...") - to include the resonator.

thanks.·· tommy