Re: [time-nuts] 50:50 duty from a PRS10
Dave M wrote: Hello, I have a PRS10 rubidium which gives a 1pps output. The output is a 10 us positive pulse. I need to convert that to a 50:50 duty cycle pulse. Still 1pps. I'm hoping for a simple circuit rather than having to use a pic. I don't mind a bit of propagation delay, but I need to preserve the low jitter on the rising edge, and hopefully also the falling edge. Any ideas out there Regards Steve The simplest way that I can think of is to feed both inputs of an XOR gate with your 1pps signal to double it to 2pps, then feed the XOR output into a flipflop to get back to 1pps with 50% duty cycle. You might have to delay the 1pps into one of the XOR inputs with a small RC to reliably trigger the flipflop. Use 74HC or AC gates and the jitter should be tolerable. Cheers, David dgminala at mediacombb dot net All that will achieve is generating a pulse about 10us wide of indeterminate polarity. Bruce ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] 50:50 duty from a PRS10
I was wondering how one would even use a PIC. You can make a 10MHz to 1PPS divider using a tiny 8-pin PIC. I have extras here. Send me email off-line if you want one. Cost is $2. /tvb ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] 50:50 duty from a PRS10
On 07/22/2011 05:38 AM, Dave M wrote: Hello, I have a PRS10 rubidium which gives a 1pps output. The output is a 10 us positive pulse. I need to convert that to a 50:50 duty cycle pulse. Still 1pps. I'm hoping for a simple circuit rather than having to use a pic. I don't mind a bit of propagation delay, but I need to preserve the low jitter on the rising edge, and hopefully also the falling edge. Any ideas out there Regards Steve The simplest way that I can think of is to feed both inputs of an XOR gate with your 1pps signal to double it to 2pps, then feed the XOR output into a flipflop to get back to 1pps with 50% duty cycle. You might have to delay the 1pps into one of the XOR inputs with a small RC to reliably trigger the flipflop. Use 74HC or AC gates and the jitter should be tolerable. The rise and fall transitions which trigger the XOR gate will cause the XOR output to occur at those times and not with a 500 ms spread as you wish them to be. You really need some form of memory that recalls that we have a high period for 500 ms rather than the 10 us. The method (and inherent precision) will vary, but there is no alternative to this memory. Dividers from the 10 MHz ensures it is a synchronous timed transition. If the fall transition isn't critical, the 555 solution or similar will do. Cheers, Magnus ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] 50:50 duty from a PRS10
Hello, I have a PRS10 rubidium which gives a 1pps output. The output is a 10 us positive pulse. I need to convert that to a 50:50 duty cycle pulse. Still 1pps. I'm hoping for a simple circuit rather than having to use a pic. I don't mind a bit of propagation delay, but I need to preserve the low jitter on the rising edge, and hopefully also the falling edge. Any ideas out there Regards Steve Feed the PPS into both inputs of a 74HC164 clock with 10MHz to clock, ~CLR grounded. Take outputs C and H into J-K Flip-Flop (74HC112) also clocked with 10MHz - I think that will do it. See the schematic of my Frequency Divider http://perdrix.co.uk/FrequencyDivider/Frequency%20Divider%202%20Schematic.pdf where I take the RCO output from an AC163 and use this to derive 1MHz 50% duty cycle. The full write up is here: http://perdrix.co.uk/FrequencyDivider/index.html Regards, David Partridge -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Magnus Danielson Sent: 22 July 2011 10:02 To: time-nuts@febo.com Subject: Re: [time-nuts] 50:50 duty from a PRS10 On 07/22/2011 05:38 AM, Dave M wrote: Hello, I have a PRS10 rubidium which gives a 1pps output. The output is a 10 us positive pulse. I need to convert that to a 50:50 duty cycle pulse. Still 1pps. I'm hoping for a simple circuit rather than having to use a pic. I don't mind a bit of propagation delay, but I need to preserve the low jitter on the rising edge, and hopefully also the falling edge. Any ideas out there Regards Steve The simplest way that I can think of is to feed both inputs of an XOR gate with your 1pps signal to double it to 2pps, then feed the XOR output into a flipflop to get back to 1pps with 50% duty cycle. You might have to delay the 1pps into one of the XOR inputs with a small RC to reliably trigger the flipflop. Use 74HC or AC gates and the jitter should be tolerable. The rise and fall transitions which trigger the XOR gate will cause the XOR output to occur at those times and not with a 500 ms spread as you wish them to be. You really need some form of memory that recalls that we have a high period for 500 ms rather than the 10 us. The method (and inherent precision) will vary, but there is no alternative to this memory. Dividers from the 10 MHz ensures it is a synchronous timed transition. If the fall transition isn't critical, the 555 solution or similar will do. Cheers, Magnus ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
[time-nuts] 50:50 duty from a PRS10
Hello, I have a PRS10 rubidium which gives a 1pps output. The output is a 10 us positive pulse. I need to convert that to a 50:50 duty cycle pulse. Still 1pps. I'm hoping for a simple circuit rather than having to use a pic. I don't mind a bit of propagation delay, but I need to preserve the low jitter on the rising edge, and hopefully also the falling edge. Any ideas out there Regards Steve ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] 50:50 duty from a PRS10
How close to 50% duty cycle do you need. is 0.50 good enough or do you need 0.5 ? If all you need is 15% accuracy a 555 timer set up to make a 0.5 second pulse would work but if you need better, then maybe a phase lock loop with a much higher than 1Hz oscillator and then you divide that down to 2Hz and the 2Hz triggers a flip flop. On Thu, Jul 21, 2011 at 10:14 AM, ExpertEngineer expertengin...@btinternet.com wrote: Hello, I have a PRS10 rubidium which gives a 1pps output. The output is a 10 us positive pulse. I need to convert that to a 50:50 duty cycle pulse. Still 1pps. I'm hoping for a simple circuit rather than having to use a pic. Chris Albertson Redondo Beach, California ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] 50:50 duty from a PRS10
On 07/21/2011 07:48 PM, Chris Albertson wrote: How close to 50% duty cycle do you need. is 0.50 good enough or do you need 0.5 ? If all you need is 15% accuracy a 555 timer set up to make a 0.5 second pulse would work but if you need better, then maybe a phase lock loop with a much higher than 1Hz oscillator and then you divide that down to 2Hz and the 2Hz triggers a flip flop. Take the 10 MHz and divide down to PPS rate, synchronise with the PPS if it is important. Otherwise you can go mid-ways to only divide down a little, then use that to synchronise the output of the 555 and then synchronise it in a second DFF with the 10 MHz. There are many ways to hold state, a capacitor is one such way. Cheers, Magnus ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] 50:50 duty from a PRS10
Chris wrote: How close to 50% duty cycle do you need. is 0.50 good enough or do you need 0.5 ? If all you need is 15% accuracy a 555 timer set up to make a 0.5 second pulse would work but if you need better, then maybe a phase lock loop with a much higher than 1Hz oscillator and then you divide that down to 2Hz and the 2Hz triggers a flip flop. The PRS-10 already has a 10 MHz output locked to the 1 pps. Just count the 10 MHz. Best regards, Charles ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] 50:50 duty from a PRS10
The PRS-10 already has a 10 MHz output locked to the 1 pps. Just count the 10 MHz. I was working only with the information in the post that said only a PPS was available. I was wondering how one would even use a PIC. But if you have 10MHz then divide that down to 2Hz with decade counters. But using the PIC means a smaller chip count -- Chris Albertson Redondo Beach, California ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] 50:50 duty from a PRS10
Hello, I have a PRS10 rubidium which gives a 1pps output. The output is a 10 us positive pulse. I need to convert that to a 50:50 duty cycle pulse. Still 1pps. I'm hoping for a simple circuit rather than having to use a pic. I don't mind a bit of propagation delay, but I need to preserve the low jitter on the rising edge, and hopefully also the falling edge. Any ideas out there Regards Steve The simplest way that I can think of is to feed both inputs of an XOR gate with your 1pps signal to double it to 2pps, then feed the XOR output into a flipflop to get back to 1pps with 50% duty cycle. You might have to delay the 1pps into one of the XOR inputs with a small RC to reliably trigger the flipflop. Use 74HC or AC gates and the jitter should be tolerable. Cheers, David dgminala at mediacombb dot net ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
