3 ms·

I want to build a 60.0000 Hz source at 110V, only needs to be 5VA, so I can use a synchroscope to watch the grid frequency wobble around. I wasn't sure where to

I want to build a 60.0000 Hz source at 110V, only needs to be 5VA, so I can use a synchroscope to watch the grid frequency wobble around. I wasn't sure where to start so this will be very helpful. I'll still need some kind of an amplifier or transformer to get the voltage up from an IC at 5V to 110V. Also not sure if the synchroscope will work on square waves or if I have to generate sine waves

pjc50 6y ago
5VA is still quite a lot. If you're outputting that through a transformer you'll be needing to put about an amp in. And for maximum transformer efficiency you'll want to make it sinusodial. There are easier ways to watch grid frequency.
- generatorguy 6y ago
  I was thinking of mounting this old synchroscope like a clock, except of course it doesn't tell time just how much faster or slower the grid frequency is to 60 Hz. What easier ways do you suggest for kind of a grid frequency display other than a multi-meter in Hz mode?
  - whatshisface 6y ago
    For one thing, it is a lot easier to get the wall socket voltage and current down than it is to get the signal generator up to wall socket level.
  - pjc50 6y ago
    So, synchroscopes are phase detectors, and only work when you're fairly close to the correct phase. They don't actually report frequency per se. People have built mains frequency counters: https://fowkc.wordpress.com/2013/12/10/mains-frequency-display/ https://fowkc.wordpress.com/2013/12/10/mains-frequency-displ... (via https://hackaday.com/2013/12/12/mains-frequency-display/ https://hackaday.com/2013/12/12/mains-frequency-display/ ) The core problem is getting an accurate enough reference. That project uses an RTC IC; you might want to try building something that uses a PLL on a GPS pulse-per-second output. The second problem is cleanly spotting where the zero-crossing is. You can take a mains feed from a current transformer or a regular transformer and low-pass filter it appropriately. It is then easy enough to use an op-amp to spot the zero-crossing.
    - generatorguy 6y ago
      Thanks for the links. Indeed if the synchroscope needle is turning clockwise I know the grid frequency is greater than 60 and if counter clockwise then less than 60 and exactly 60 no movement of the needle at all. To me there is something about watching the inertia of the entire system change and it controlling itself to stop frequency excursions and then AGC or other human interventions to restore the balance. Thanks for the ideas and links.
dfox 6y ago
One variant how to do that involves something like UCC3750 (ie. telco ringer waveform generator), another is just using sufficiently high powered audio power amplifier.

pjc50 6y ago

5VA is still quite a lot. If you're outputting that through a transformer you'll be needing to put about an amp in. And for maximum transformer efficiency you'll want to make it sinusodial. There are easier ways to watch grid frequency.

generatorguy 6y ago
I was thinking of mounting this old synchroscope like a clock, except of course it doesn't tell time just how much faster or slower the grid frequency is to 60 Hz. What easier ways do you suggest for kind of a grid frequency display other than a multi-meter in Hz mode?
- whatshisface 6y ago
  For one thing, it is a lot easier to get the wall socket voltage and current down than it is to get the signal generator up to wall socket level.
- pjc50 6y ago
  So, synchroscopes are phase detectors, and only work when you're fairly close to the correct phase. They don't actually report frequency per se. People have built mains frequency counters: https://fowkc.wordpress.com/2013/12/10/mains-frequency-display/ https://fowkc.wordpress.com/2013/12/10/mains-frequency-displ... (via https://hackaday.com/2013/12/12/mains-frequency-display/ https://hackaday.com/2013/12/12/mains-frequency-display/ ) The core problem is getting an accurate enough reference. That project uses an RTC IC; you might want to try building something that uses a PLL on a GPS pulse-per-second output. The second problem is cleanly spotting where the zero-crossing is. You can take a mains feed from a current transformer or a regular transformer and low-pass filter it appropriately. It is then easy enough to use an op-amp to spot the zero-crossing.
  - generatorguy 6y ago
    Thanks for the links. Indeed if the synchroscope needle is turning clockwise I know the grid frequency is greater than 60 and if counter clockwise then less than 60 and exactly 60 no movement of the needle at all. To me there is something about watching the inertia of the entire system change and it controlling itself to stop frequency excursions and then AGC or other human interventions to restore the balance. Thanks for the ideas and links.

dfox 6y ago

One variant how to do that involves something like UCC3750 (ie. telco ringer waveform generator), another is just using sufficiently high powered audio power amplifier.