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Author Topic: linear opto-isolation to an ac voltmetter  (Read 6535 times)
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picavr
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« on: April 20, 2008, 10:00:20 22:00 »

i ned a help  about a isolation without a transformmer (with a simple opto isolator) like 4n25 4n35 or pc817 (not hpcl serie ,i can t found it)
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ipek
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« Reply #1 on: April 21, 2008, 12:07:54 12:07 »

http://rapidshare.com/files/109201071/classic-opto.rar.html

 collected two ac power comps... projects maybe idea
stantard general purpose opto couplers make it...
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nkgavali
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« Reply #2 on: April 21, 2008, 01:07:13 13:07 »

One answer could be use V-F converter  and F-V converter and put the PC817 isolation between that.

Nandu
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Walkura
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« Reply #3 on: May 09, 2008, 08:46:34 20:46 »

Today i found it .
Already for some time i was looking for the same thing you describe .
Optical isolation of a analog value for measuring purposes .
Today i bumped into this Cheesy
http://focus.ti.com/lit/ds/symlink/iso124.pdf

Have a look at this .
For me its like custom maid for what i need .

Have a nice eve Walkura
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vovchik02
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« Reply #4 on: May 14, 2008, 06:29:30 06:29 »

I'm use HCPL-7800 good result for tiristor DC sircuit and for AC machine.
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volodja10
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« Reply #5 on: May 14, 2008, 10:50:32 10:50 »

Hi!
There is example of analog optoisolator below. It's the fragment of my working project. +/- 10V - input,
+/- 10V - output. ~20KHz - bandwidth, but can be extended more.

http://rapidshare.com/files/114788938/AnalogIsolator.pdf

volodja

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an007
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« Reply #6 on: May 14, 2008, 11:02:56 23:02 »

see the following document from agilent:
http://www.skyhic.com/media/other/HCNR200_201.pdf

hope this helps,
an007

PS you can replace (with good result) the expensive dual optocouplers using two simila optocouples with LED diode in series. (for better match, you can find also 2 in the same package like TLP504A)
« Last Edit: May 14, 2008, 11:12:59 23:12 by an007 » Logged
beque
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« Reply #7 on: May 16, 2008, 05:57:31 17:57 »

The Iso124 is not Optocoupler but Capacitor Isolation (1pf) and generates noise due to internal oscilator for switching caps.

Use IL300 from Vishay (is quite cheap)

http://www.vishay.com/docs/83708/appn50.pdf

http://www.vishay.com/docs/83710/appn54.pdf

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Walkura
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« Reply #8 on: May 18, 2008, 01:27:18 13:27 »

I will have a look at the IL300 option .
For me noise isnt much of a concern (afterall my measurement concerns upto 45 volts & 200 or 300 Amperes .)
But the ISO124 is quite expensive ,before i came to this i tried voltage to frequency & vice versa but i wasnt satisfied with it .
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sohel
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« Reply #9 on: May 18, 2008, 03:22:11 15:22 »

i ned a help  about a isolation without a transformmer (with a simple opto isolator) like 4n25 4n35 or pc817 (not hpcl serie ,i can t found it)


I would like to say why brother goto expensive parts, as ur requerment is simple. read  unregulated adc for 100 times and get it with avareg value and convert it bcd , then show on seven segment or lcd, another way frequency to voltage , u must read avareg value bcause for stable value.

i have use this procedure for sinewave inverter and squerwave inverter.  sorry for hard english
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Walkura
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« Reply #10 on: May 20, 2008, 06:56:44 18:56 »

Well i need to measure and regulate upto 45 Volts @ upto 300 Amperes .
Electrical contacts between powwerside and logical side are highly unwanted .
(read as i fear a little Chernobyl inside my computers Cheesy)
A few $ is a little price for safety of the testing equipment .

But do not worry about your english Sohel ,you are good understandable for me its not my native language either .

Have a nice eve .
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picavr
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« Reply #11 on: May 22, 2008, 08:47:50 20:47 »


I would like to say why brother goto expensive parts, as ur requerment is simple. read  unregulated adc for 100 times and get it with avareg value and convert it bcd , then show on seven segment or lcd, another way frequency to voltage , u must read avareg value bcause for stable value.

i have use this procedure for sinewave inverter and squerwave inverter.  sorry for hard english


i need this methode because i need a value for six 06 sourse in 220v,and may pcb is limited in space, with an MCU and LCD and 05 relay 2RT and 03 power relay  (40A 12V) and 04 switsher ,
i use asix little transformer (9v 0.5VA )on the pcb but this methode is not robust .
the alternative methode is to use 04 optocoupler with an op-amp for each source but the number total of optocoupler is 24 optocoupler ,i think modifuyng this solution but the linearity is not stable.
think for all
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beque
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« Reply #12 on: May 27, 2008, 09:31:49 21:31 »

This Thesis contains what you want:

http://rapidshare.com/files/118097735/Power_Electronic_Building_Blocks_-_Thesis.pdf.html
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picavr
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« Reply #13 on: May 29, 2008, 11:26:32 11:26 »

is like this,very good doc,i can t said think you,1000 thinks
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bobyper
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« Reply #14 on: June 01, 2008, 08:38:27 08:38 »

Another good current sensors from http://www.allegromicro.com/en/Products/Categories/Sensors/currentsensor.asp
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picavr
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« Reply #15 on: June 03, 2008, 10:44:08 22:44 »

we need the solution with op amp or classical ic,this solution is very good but the problem is the the disponibility of the component
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Walkura
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« Reply #16 on: June 04, 2008, 10:11:58 10:11 »

Last week i made this simulation .
Maybe its of any use for you .
It works just as well with IL300 as that HCPL .

Have a nice day Walkura
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beque
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« Reply #17 on: June 04, 2008, 08:22:27 20:22 »

Walkura

Please, could you send that file in pdf ?
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picavr
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« Reply #18 on: June 05, 2008, 10:34:35 10:34 »

Walkura

Please, could you send that file in pdf ?


if you have proteuse you can open it
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Walkura
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« Reply #19 on: June 05, 2008, 03:40:37 15:40 »

I dont have the adobe software other then reader ,but i made a screenshot .
When i have some time later i will try this same setup with 2 CNY17's .
This morning i did a few quick sims it still needed some work but it seemed promising .
(just replace the hcpl with CNY17 diodes parallel 1 transistor to secundary side 1 to feedback)
More budgetclass you wont find (unless you make your own opto with ducktape and the headlight of your bicycle Tongue )
If i get it  good i'll post the sim here .

Have a nice day Walkura
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picavr
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« Reply #20 on: June 05, 2008, 06:52:30 18:52 »

if there is a simple solution with a simpl optocoupler like 4n25 or pc817 with a fiew component,it will be more best .
i know there is a solution with a HCPL or equivalent,but i need a more simple with a standart components.
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beque
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« Reply #21 on: June 05, 2008, 09:38:53 21:38 »

Try these below...
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picavr
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« Reply #22 on: June 07, 2008, 11:16:14 11:16 »

 i need a circuit that no VCC in input  ,just a (0-220V )main voltage or (0-380v) and in the output circuit can containing a vcc an gnd and output,
the circuit needed is for measuring a six source 220v an with a minimum satandart component.
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radhaeda
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« Reply #23 on: June 07, 2008, 06:00:36 18:00 »

I have used IL300 in applications and its functioning is very good. Low cost, reliable and linear too.
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picavr
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« Reply #24 on: June 08, 2008, 08:24:00 20:24 »

but i can t found the IL300,is there an equivalent composition with 2n25 or pc817
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