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Author Topic: opto isolator ?  (Read 2611 times)
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omidsht
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« on: March 16, 2008, 04:04:47 16:04 »

hi i need a circuit with opto isolator to isolate a square signal which is between 5 and -5 with freq of 250khz .
if you can give me an opto isolator which works in 250khz or any circuit using optp isolator , i would be so thanks full .

omid
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Kabron
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« Reply #1 on: March 16, 2008, 05:49:42 17:49 »

6N137
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tutatix
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« Reply #2 on: March 18, 2008, 03:06:57 15:06 »

An easy way to protect a I/O pin:
011 - Optoacoplador para aislar una Entrada o una Salida
http://www.ucontrol.com.ar/Articulos/E-S/e-s.htm#11

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tuvoj
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« Reply #3 on: March 19, 2008, 08:38:27 08:38 »

Hi,

Try to stay away from optos that use IR band components--the shorter the wavelength the better, for hi freq response...

Cheers-Tuvo
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omidsht
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« Reply #4 on: March 20, 2008, 12:11:07 12:11 »

Hi,

Try to stay away from optos that use IR band components--the shorter the wavelength the better, for hi freq response...

Cheers-Tuvo
so what to use instaed ?
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mayler
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Roger that!


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« Reply #5 on: March 21, 2008, 03:49:58 03:49 »

The 4n25 optocoupler works good in theory  in this frequency.

EDIT:
http://www.vishay.com/docs/83725/4n25.pdf
The typical rise time and fall time are 2 µs -> 4 µs = 250 khz (limit). I thought was 1µs of tr and tf, because i worked with a model with 1µs of tr and tf, but wasn't 4n25. My mistake, sorry.
« Last Edit: March 23, 2008, 10:27:38 22:27 by mayler » Logged

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picavr
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« Reply #6 on: March 23, 2008, 07:22:02 19:22 »

the 4n25 cant work with 250khz
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quadro
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« Reply #7 on: March 23, 2008, 07:47:32 19:47 »

4N25 is too slow for 250 KHz since it has rise time max 10 microseconds and fall time up to 10 microseconds. That gives you just 50 KHz.
You could use H11Ax. Switching time for this family is 3 microseconds which gives you range up to 333 KHz.
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huanfai
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« Reply #8 on: March 23, 2008, 09:17:41 21:17 »

you can try some high speed schimitt trigger optocoupler....usually they have higher than 500khz BW... Grin
If you dont have negative voltage supply. Then you will need a 5v to -5v inverter...dont expect the circuit will give you a high current output (if you want a cheap one...), it only can give you 70~120mA.... Tongue
if you use microcontroller then you can use pwm,2 diode and 2 capacitor to generate negative voltage.....even lower power......25mA max ><__><
optocoupler: H11L series...."economy choose"Tongue
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samir
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« Reply #9 on: March 24, 2008, 06:01:58 06:01 »

hi i need a circuit with opto isolator to isolate a square signal which is between 5 and -5 with freq of 250khz .
if you can give me an opto isolator which works in 250khz or any circuit using optp isolator , i would be so thanks full .

omid

hi i need a circuit with opto isolator to isolate a square signal which is between 5 and -5 with freq of 250khz .
if you can give me an opto isolator which works in 250khz or any circuit using optp isolator , i would be so thanks full .

omid


It is better option
http://focus.ti.com/docs/prod/folders/print/iso722.html

    * 4000-V(peak) Isolation
          o UL 1577, IEC 60747-5-2 (VDE 0884, Rev. 2) IEC 61010-1
          o 50 kV/µs Transient Immunity Typical
    * Signaling Rate 0 Mbps to 150 Mbps
          o Low-Propagation Delay
          o Low-Pulse Skew (Pulse-Width Distortion)
    * Low-Power Sleep Mode
    * High-Electromagnetic Immunity
    * Low-Input Current Requirement
    * Failsafe Output
    * Drop-In Replacement for Most Opto and Magnetic Isolators
    * APPLICATIONS
          o Industrial Fieldbus
                + Modbus
                + Profibus
                + DeviceNet™ Data Buses
                + Smart Distributed Systems (SDS™)
          o Computer Peripheral Interface
          o Servo Control Interface
          o Data Acquisition

And good thing about this is that you can get free sample
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carlao
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« Reply #10 on: April 07, 2008, 05:01:12 05:01 »

The 4N25 or TIL111 do not work good over 5kHz. At least in my case, to switch mosfets, did not work.
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samir
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« Reply #11 on: April 07, 2008, 05:49:48 05:49 »

The 4N25 or TIL111 do not work good over 5kHz. At least in my case, to switch mosfets, did not work.
to switch mosfet use optocoupler having push-pulloutput .for example TLP250,PC929,
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charnyutk
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« Reply #12 on: April 09, 2008, 05:40:19 05:40 »

you should try H11L1 or TLP250,it's fast enough.
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tuvoj
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« Reply #13 on: April 20, 2008, 03:57:40 03:57 »

We use the Vishay 6N137 (they also have 2-channel versions in the same footprint) They are very fast -- rise and fall times are in the ~25ns region...

Cheers!-Tuvo
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baltaji555
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« Reply #14 on: April 20, 2008, 06:08:39 06:08 »

you can use etheir 6n135 or 6n136 which has a bandwidth of 2MHz or simply use a transformer since you have a symitrical signal with no dc.
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