1 KHz stable oscillator with little time drift ic - Page 1
Forum section: electronics / projects

author: ChrisGreece52
author_rank: Frequent Contributor
timestamp: November 12, 2016, 04:26:16 pm
content: Hello i need to make an 1kHz oscillator using a crystal. but i saw some active crystal oscillator ICs that oscillate by themselves but none of those i found outputs a stable 1Khz sine wave... i also found some ICs that give out 1Khz to 20 or 30 Mhz but i am not sure about their time drift...Anyway thank you i made this so i know if this is possible or if i have to go with the standard way using schmitt inverters and capacitors...

author: Andy Watson
author_rank: Super Contributor
timestamp: November 12, 2016, 04:35:46 pm
content: I would use a micro-controller - probably a PIC 10/12xxxx - one that takes an external crystal and programme it to produce the desired frequencies.

author: ChrisGreece52
author_rank: Frequent Contributor
timestamp: November 12, 2016, 04:37:19 pm
content: I only need a stable 1Khz wave and of course dont want to use a 555 because the stability on the ic hits rock bottom for clock keeping.

author: Andy Watson
author_rank: Super Contributor
timestamp: November 12, 2016, 04:41:27 pm
content: A PIC12F675 has the same number of pins as a 555 - just add crystal and a few caps. Other PICs and ATmels are available - I just use the example of a PIC12F675 because I happen to have one sitting on the bench at the moment.

author: ChrisGreece52
author_rank: Frequent Contributor
timestamp: November 12, 2016, 04:43:28 pm
content: Thank you i wont lose anything with just some experimenting and researching on PIC MCUs ... but i can not stress enough how stable and how little time drift i need it to have since the 1Khz clock will be used to count milliseconds ; in a clock.

author: RandallMcRee
author_rank: Frequent Contributor
timestamp: November 12, 2016, 05:10:37 pm
content: If you look into applications of the CD4060 you will see many circuits that can accomplish what the previous poster suggests. Even adding a low-pass filter the complexity should be two packages (but lots of passives).But if this is a learning experience, keep reading...Jim Williams has published some high stability sine-wave oscillator circuits, seehttp://cds.linear.com/docs/en/application-note/an12fa.pdfAN-43 (google it) also has some sine-wave crystal circuits.also from TIhttp://www.ti.com/lit/an/snoa665c/snoa665c.pdfAnyway, these give you some background about this.

author: DimitriP
author_rank: Super Contributor
timestamp: November 12, 2016, 05:51:01 pm
content: Quote from: ChrisGreece52 on November 12, 2016, 04:43:28 pmMilliseconds are easyStart with a 10Mhz OXCO or TCXO depending or what you can get your hands on, divide it down to 1Khz and you are halfway* there.*Once you have stability and precision out of the way, then you'll want it to be accurate, so then you'll start a GPSDO thread

author: tszaboo
author_rank: Super Contributor
timestamp: November 12, 2016, 06:18:31 pm
content: Quote from: ChrisGreece52 on November 12, 2016, 04:26:16 pmSo please, make up your mind, because oscillators (unless opamp oscilaltor) will not create sine wave for you. Also crystals will not create sine wave. What do you want to do.http://xyproblem.info

author: Zero999
author_rank: Super Contributor
timestamp: November 12, 2016, 06:26:33 pm
content: Quote from: RandallMcRee on November 12, 2016, 05:10:37 pmI agree. The 4060 with an 8.192MHz crystal will do.Note that the original CD4060 is not specified toreliablywork above 5MHz.http://media.digikey.com/pdf/Data%20Sheets/Fairchild%20PDFs/CD4060BC.pdfUse the HEF4060, which is specified to work up to 10MHz at supply voltages greater than 10V.http://www.nxp.com/documents/data_sheet/HEF4060B.pdfIf you need it to work at under 6V then use the 74HC4060, which will work down to 3V.http://www.onsemi.com/pub_link/Collateral/MC74HC4060A-D.PDFIf you need a sine wave, then add a low pass filter and amplifier to convert the square wave to a sine.

author: blackdog
author_rank: Frequent Contributor
timestamp: November 12, 2016, 11:37:17 pm
content: Hi,Look @ this site from Roman Black, he uses a Pic toe generate a 1Khz sine.I use his schematic/software with en TXO and en 24db/Otc low pass filter.The RomanBlack sine generator is use as a stable reference as a injector for a low noise low distortion Wien Bridge.http://www.romanblack.com/onesec/Sine1kHz.htmThis is a part of the schematic of a 1Khz Reference generator i build...http://www.bramcam.nl/Diversen/1KHz-Stabel-Low-Distortion-SineWave.pngI hope this helps, kind regarts,Blackdog

author: Jay_Diddy_B
author_rank: Super Contributor
timestamp: November 13, 2016, 01:08:38 am
content: Hi,+1 for the circuit shown by blackdog. There are many variations that you can do with a circuit like this. You can use logic to divided the frequency from an OCXO or TCXO to 1 kHz and then filter with a 1kHz bandpass filter to get the required spectral purity.It is pretty unusual to require high frequency stability and spectral purity. Normally one or the other is required.Have a look at this:http://www.linear.com/solutions/5968This is an injection locked Wien Bridge oscillator.Regards,Jay_Diddy_B

author: ChrisGreece52
author_rank: Frequent Contributor
timestamp: November 15, 2016, 12:37:15 pm
content: Quote from: DimitriP on November 12, 2016, 05:51:01 pmbut i cannot start with 10Mhz i dont know how also this will introduce parasitic capacitance because the final project will be made on a prefboard not a proper PCB (proper PCB comes later)

author: ChrisGreece52
author_rank: Frequent Contributor
timestamp: November 15, 2016, 12:38:56 pm
content: Quote from: NANDBlog on November 12, 2016, 06:18:31 pmI stand corrected on this one i do NOT need a sine wave because the project i am working on is based on logic ICs so sine waves will become square at the end.

author: ChrisGreece52
author_rank: Frequent Contributor
timestamp: November 15, 2016, 12:42:33 pm
content: Quote from: blackdog on November 12, 2016, 11:37:17 pmAs i said it is not critical to have a sine wave but this method could be used as square wave oscillator right ?

author: Kalvin
author_rank: Super Contributor
timestamp: November 15, 2016, 01:18:47 pm
content: Although the OP doesn't require the sine-wave any more, other readers may find this nice application note useful: "Digitally Controlled Sine-Wave Generator" using a precision oscillator, an MCU and an 8th-order switched capacitor elliptic filter:https://www.maximintegrated.com/en/design/reference-design-center/ref-circuits/2081.html

author: Bryan
author_rank: Frequent Contributor
timestamp: November 15, 2016, 10:30:31 pm
content: Use the PicDiv and divide down a good quality 10Mhz OCXO. use PD15, can divide down to 1Khz with Arm and Sync.http://www.leapsecond.com/pic/picdiv.htm