How to test the optocoupler MOC7811 ??

[Kavitha Seetharaman]

Hii ..

I'm using the optocoupler MOC7811 for my project . But i dont know how to check it whether it's working or not ... Can anyone help me getting its circuit .... Also, please tell me thw working of this optocoupler ....

Thank u
- Kavitha

 

[ericgibbs]

Hii ..

I'm using the optocoupler MOC7811 for my project . But i dont know how to check it whether it's working or not ... Can anyone help me getting its circuit .... Also, please tell me thw working of this optocoupler ....

Thank u
- Kavitha

hi,
Post the circuit of the opto coupler section and we can advise.

 

[SABorn]

It helps if you do some of the leg work and find a datasheet to post so we dont need to spend our time searching for one.

Its a PHOTO INTERRUPTER not a optocoupler isnt it?

Think its got a IR led and a photo transistor.

With the led powered the transistor should be on and with a object placed into the slot to block the IR light the transistor should be off.

On average the led is rated at @ 1.8 volts at 50mA.

a data sheet will give a better idea on actual values.

Pete.

 

[Kavitha Seetharaman]

Actually i'v been searching for its datasheets , but didnt get it .. I searched many sites...

Yes, it has an IR LED and a phototransistor.. But dont know how it works actually ...

 

[SABorn]

Thought i explained above the basic operation

Do this help.

 

[ericgibbs]

Actually i'v been searching for its datasheets , but didnt get it .. I searched many sites...

Yes, it has an IR LED and a phototransistor.. But dont know how it works actually ...

HI,
This is MOC7811 d/s

 

[Kavitha Seetharaman]

Thanks ....
If we give the Vcc=5V to the LED , wat should be the output obtained at the collector ??
Should it be 5V if there is no object placed in between ???

 

[Kavitha Seetharaman]

Can this circuit be used ... ??

What should be the output voltage obtained from this ?
The resistor values are just appropriate values...

 

[ericgibbs]

Thanks ....
If we give the Vcc=5V to the LED , wat should be the output obtained at the collector ??
Should it be 5V if there is no object placed in between ???

hi,
DONT connect the Emitter directly to +5V else you will blow it.

Use a series resistor that will allow current of just under 20mA thru the emitter, assuming a Vfwd for the IR emitter diode of 1.8V thats [5-1.8]/0.02 = 180R

Connect a 2k7 resistor from the detector collector to +5V and the emitter to 0V, you should see a ~ 5v change at the collector when you block the opto path.

EDIT:
that circuit you posted I would use a 2k2 in place of the 1k, the 220R will be ok

 

[Kavitha Seetharaman]

will the output be 5V, if the opto path isnt blocked ??

 

[ericgibbs]

will the output be 5V, if the opto path isnt blocked ??

Hi,
With your circuit is should be +5V when blocked.
Thats because the detector transistor is not conducting

 

[nabilahsk]

can we use ir led and phototransistoe separately in circuit if we doesnt want to use moc7811? and if we check the moc7811 with supply does it will glow?

 

[MikeMl]

If you try to make a photo-interrupter using a discrete IR emitter and a IR photo-transistor, the Current Transfer Ratio will not be as good as a manufactured one like a MOCxxxx You will have to drive the LED very hard to get a few 100uA at the photo-transistor collector, whereas the MOCxxx will have a CTR of like 0.25 (10mA in gets 2.5mA out).

Since the human eye cannot see IR, you will not see any "glow". If you aim an IR LED directly at your eyes, you can damage the retina. DO NOT DO IT!!!

 

[nabilahsk]

tq for the info

i had check the moc but the output is still 5v even i block the moc with a piece of metal......what should i do to make it function? i follow the circuit and the procedure to make i function but he output not coming

 

[MikeMl]

What is the voltage which drives the IR emitter?
What is the resistor in series with the IR emitter?
Are you sure you have connected the IR emitter so that the anode is more positive than the cathode?
Have you inserted a mA meter in series with the IR emitter to see how much current is flowing through it (should be about 20 mA)?

What is the resistor connected to the photo-detector collector?
What voltage is the other end of the resistor tied to?
Is the photo-detector collector voltage more positive than the photo-detector emitter?

Is the IR emitter cathode and the photo-detector emitter tied to ground?

 

[nabilahsk]

how to test moc7811

voltage which drives the IR emitter= 5v
resistor in series with the IR emitter = 360ohm
already connected the IR emmitter but not sure if it is more postive than cathode

Have you inserted a mA meter in series with the IR emitter to see how much current is flowing through it (should be about 20 mA)?
do you mean using a multimeter or what?

resistor connected to the photo-detector collector is 10kohm
voltage is the other end of the resistor tied to is 5v

photo-detector collector voltage more positive than the photo-detector emitter?
this case im not sure...how to know it is more positive ? using a multimeter to?
can u tell me the step

lastly, yes already tied to the ground both the IR emitter cathode and the photo-detector emitter

 

[MikeMl]

Break the circuit, and install the multimeter (in DC mA current-measurement mode) in series with where you measure the current.

Put the multimeter in the DC VOLTs mode, and read the voltage between the red probe + and black probe -. If the meter reads positive, then the red lead is more positive than where the black lead is connected.

Off hand, I'm guessing that someone hooked up the IR emitter without a current-limiting resistor in series with it, and let out the magic smoke...

 

[4pyros]

You can look at the IR LED with a digatal camra or video recorder to see it is working. Generly if it is drawing current it should be working.

 

[nabilahsk]

afraid in default of mocXXXX

using ir photodiode n phototransistor also can right eventhough it is not good as moc7811......if i wanna use it it is not eligible? actually im buying moc7811 online from inidia..there's no moc7811 component in malaysia..my projetc is just about 2 more weeks.....im afraid cause i make a mistake by buying only 1 moc..thats why i ask u if i use it separately it can function too right?