Hello John,
Usually there is a load (burden) resistor. The voltage drop is then fed via a high impedance to an ADC or whatever active stage follows. The high impedance being there just in case that burden resistor gives up the ghost.
-- Regards, Joerg http://www.analogconsultants.com
Hello Yuriy,
Sorry, mea culpa. I meant to write active rectifier. If you really need linearity down to zero one can use an inverted transistor as a rectifier.
-- Regards, Joerg http://www.analogconsultants.com
If the "burden" resistor is after the rectifier you don't need "active" rectification.
...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC\'s and Discrete Systems | manus |
| Phoenix, Arizona Voice:(480)460-2350 | |
| E-mail Address at Website Fax:(480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |
I love to cook with wine. Sometimes I even put it in the food.
If you study....
The effective burden resistance can be made quite low, yet get 5V FS performance.
If you take 5V as "burden", linearity will be bad.
...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC\'s and Discrete Systems | manus |
| Phoenix, Arizona Voice:(480)460-2350 | |
| E-mail Address at Website Fax:(480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |
I love to cook with wine. Sometimes I even put it in the food.
Google does wonders. :)
Jameco P/N 627591 Mfg TRIAD MAGNETICS Mfg # CSE187L RoHS? No In Stock Yes
10+ 1.81 it will be $36.20 per 20 pcs. Who can beat that?-- WBR, Yuriy. "Resistance is futile"
Ok so these or the Avemco (or whatever they were).
Now, the past 6 or 7 exchanges have been interesting and I somewhat follow, but am not sure where it leaves me. The gurus are starting to talk among themselves (not a problem) but I am not sure what settled upon consensus is and what I shoudl do with the information :)
I still understand that we are talking about active vc passive rectification and/or filtration. The fact that you guys have narrowed this down to two CTs and 2 basic topologies is certainly good news.
With regards to "my" need for a sampling rate for the data logging. 1 sec intervals would be fine. The software has a LOT to do otherwise and I certainly don't want to spend CPU time to update the curernt measurements if I don't need to. If the ony way to get reasonably accurate readings is to sample the rectifier output at higher speeds and average the data, then it will HAVE to be a uC that does this work nonstop and then passes the data to the PC only when asked.
My need is mostly to keep a gui updated with somewhat realtime information as to the status of my connected devices. I will be able to set alarms in my software to trigger on abnormal trends. The actual data logging to disk will be only several times an hour and when the current draw exceeds a preset alarm. Long story short, I need to be able to see how well the pumps and heaters are operating. As the pumps build calcium deposits due to the heat, they begin to draw more current. The current draw is a good indication of the pumps health. I figured If I was going to monitor 10 pumps, I might as well monitor the heaters, ballasts and fans.
This has been a very intersting learning experience so far, and I have not even let the smoke out of anything yet!
%00to 1 ratio is quite practical for up to 30 amps (60 mA out). With a 60 ohm half watt burden, that gives 3.6 volts RMS. I would want to either use a Schottky bridge with something like a 50 ohm burden or a silicon bridge with about a 39 ohm burden. Even though the output does not take up the full 5 volt A/D range, it allows for a bit of surge current without producing a ridiculous voltage.
Very nice, if 30 amps load current is large enough.
If you intend to take a data point every second or so, you need to average the signal over that amount of time (a 1 second or more time constant) to get a representative value with each of those samples.
The largest loads will be
1) dual 150W magnetic MH ballast, so figure 450W draw during operation and somewhat more than that due to the inrush when It powers on. 2) All of the pumps are less than 200W motors, and no more than 2 will be on any given monitored outlet. 3) 500 watt heaters, 1 per monitored outlet.So most of the stuff will be well less than 10A during operation, inrush is a different story.
Hello Jim,
True. But it adds a bit of risk in that the rectifier might croak. Probably not a huge risk if the diodes are nice and big. The inverted transistor wouldn't be a very "active" rectifier except that it needs a wee current into the base.
One issue to keep in mind with the "burden after diodes" approach is harmonics. Might need little ceramics across the diodes so no hum is modulated onto your favorite AM talk radio station :-)
BTW, did you get that power-on detect installed for the kitchen TV? An installation in our house is only considered "done" when the wife has approved...
-- Regards, Joerg http://www.analogconsultants.com
Come on, Joerg! You're picking at straws. Add zeners if you must ;-)
Who needs it?
Just like happens from your power supplies in the lab ?:-)
Yes. But she-who-must-be-obeyed doesn't like the fan noise. So I'll make a form-fitting shroud and use muffin fans.
Right now I'm sawing out pieces of ABS to make a wall-holder/charger for the VTech ;-)
...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC\'s and Discrete Systems | manus |
| Phoenix, Arizona Voice:(480)460-2350 | |
| E-mail Address at Website Fax:(480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |
I love to cook with wine. Sometimes I even put it in the food.
Muffin fans, are you crazy? You aren't in the latte swilling North East! You should use Biscuit fans like any good Southern boy. ;-)
-- Service to my country? Been there, Done that, and I\'ve got my DD214 to prove it. Member of DAV #85. Michael A. Terrell Central Florida
Hello Jim,
I've seen the aftermath of a failed burden, on an RF board. It was not a pretty sight. AFAIR even the fire alarm had gone off. And yeah, it was after I was told "Joerg, you are too paranoid about that, it'll never happen".
Might be a few cents less ;-)
From the cheap computer age supplies, yes. The old Russky linear bench supplies are very quiet.
If you could get a skinny squirrel-cage fan in there those can be very quiet. Then whip up a VF supply and ask her "Can you hear it now?"
Aw, c'mon. Didn't you do wood working once? How about a nice polished teak wood Thompson-Design base.
-- Regards, Joerg http://www.analogconsultants.com
I haven't bought a fan since all there were was muffin fans.
Right now I'm just using an 8" household fan.
How quiet is a biscuit fan?
...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC\'s and Discrete Systems | manus |
| Phoenix, Arizona Voice:(480)460-2350 | |
| E-mail Address at Website Fax:(480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |
I love to cook with wine. Sometimes I even put it in the food.
The ones I've used were very quiet. It's a slightly different style of fan, but it has its uses.
is the original source of these types.
-- Service to my country? Been there, Done that, and I\'ve got my DD214 to prove it. Member of DAV #85. Michael A. Terrell Central Florida
Hello Michael,
Isn't that a really flat squirrel cage fan? Now I don't know how "Southern" squirrels would be :-)
-- Regards, Joerg http://www.analogconsultants.com
Its biscuits that are a southern thing. Squirrels are all over the place, including some newsgroups. (But they pretend to be bears and stuffed donkeys when online)
-- Service to my country? Been there, Done that, and I\'ve got my DD214 to prove it. Member of DAV #85. Michael A. Terrell Central Florida
In message , dated Thu, 14 Sep 2006, Jim Thompson writes
Very noisy, if you snatch his biscuit away.
-- OOO - Own Opinions Only. Try
In message , dated Thu,
14 Sep 2006, Joerg writes
Sciurus roadkillensis. Very flat.
-- OOO - Own Opinions Only. Try
I forgot. To Brits and Aussies, biscuits are cookies ;-)
To me, a biscuit is what you pour sausage gravy over ;-)
...Jim Thompson
-- | James E.Thompson, P.E. | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona Voice:(480)460-2350 | | | E-mail Address at Website Fax:(480)460-2142 | Brass Rat | |
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