08m divide by 60

[papaof2]

grid monitor

Very cool.

I've never seen anything like that for the Ontario or North American grid.

John.

There's some information about a "smart appliance" project in the US Pacific Northwest here http://gridwise.pnl.gov/ and some software you can download to monitor the grid in that area (screensaver and a stand-alone program) http://gridwise.pnl.gov/technologies/transactive_controls.stm

The screen saver has several windows displaying various pieces of information. Most people wil be interested the instantaneous frequency (updated every second). An engineer may find the other windows (waterfall, etc) of more interest.

John

 

[MPep]

My EM-408 GPS unit does .001 seconds resolution.

What is the accuracy - who knows? Some delay inside the unit itself, definitely a delay to send it out in the $GPGGA sentence at 4800baud and definitely a delay while a PICAXE processes it and loads it into a RTC chip.

I'd guess (suppose I could work it out) at no more 1/10th (maybe even worse) accuracy by the time it's done all that

0.001 second resolution is fine and all, but you are looking at the NMEA data out, which does vary somewhat.
I was talking about 1PPS output, literally a pulse of (usually presettable) length that coincides with the Caesium clocks in the GPS satellites. The start of the pulse can be 100ns out from the start, but the main thing to remember is that it is repeatable (as much as it can be!). This means that for project time keeping, this is plenty accurate enough.

MPep.

 

[boriz]

I realised another reason why I’m not entirely comfortable with the diode position in your first diagram. It’s been niggling me since I first saw it, but took a while to surface.

When D1 is reverse biased, on the negative half-cycles, the base of the transistor goes very high impedance. It’s essentially floating. Making it, and any connected PCB tracks susceptible to EM noise, such as the bursts you get when operating a nearby light switch etc.