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Author Topic: opto input quetion  (Read 532 times)
rage3657
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« on: March 02, 2010, 04:22:41 PM »

guys!! am electrical tech and noob sa electronics, have 2 quetions here, found this drawing on olim3x site on their PIC IO board.  http://olimex.com/dev/pdf/PIC/PIC-IO.pdf
 
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1. ano purpose ng 1n4148 connected across opto input leds?
2. sa manual ang sabi ..."Four opto-isolated inputs will allow to detect voltages in range +5-24VDC".  totoo ba to?? up to 24vdc?? with the same resistor value and wattage??

am learning thanks sa mga sasagot.
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« on: March 02, 2010, 04:22:41 PM »

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mArKhAo
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« Reply #1 on: March 02, 2010, 04:28:49 PM »

guys!! am electrical tech and noob sa electronics, have 2 quetions here, found this drawing on olim3x site on their PIC IO board.  http://olimex.com/dev/pdf/PIC/PIC-IO.pdf



1. ano purpose ng 1n4148 connected across opto input leds?



protection....

Quote
2. sa manual ang sabi ..."Four opto-isolated inputs will allow to detect voltages in range +5-24VDC".  totoo ba to?? up to 24vdc?? with the same resistor value and wattage??

am learning thanks sa mga sasagot.

hmmm, baka merong specification sa data sheet...
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rdpzycho
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« Reply #2 on: March 02, 2010, 04:31:49 PM »

1. reverse voltage protection, karamihan ng optoisolator mababa ang inverse voltage na kakayanin. since 'yung user ang magkakabit ng voltage doon sa input, kailangan may additional protection.

2. yup. kailangan lang naman ma-meet 'yung minimum current para mag-on 'yung output transistor.

sinagot na pala ni markhao. Grin
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« Reply #3 on: March 02, 2010, 04:34:29 PM »

ito lang max ratings ng opto nyo...

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rage3657
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« Reply #4 on: March 02, 2010, 04:38:04 PM »

pero kung ipasok jan 24vdc diba masyado malaki un forward current di ba mag iinit un resistor ans magtatagal ba un opto coupler, if am not mistaken kung 24vdc forward current nya would be around 63mA
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piona
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« Reply #5 on: March 02, 2010, 04:41:07 PM »

^ yong R1-R4 na 330 ohms pang 5V input lang na dropping yan recompute nyo sa ibang input voltage.

....o di kaya baka yong Vce ng opto ang ibig nyang sabihin, para saan ba yang apat na opto ?
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rage3657
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« Reply #6 on: March 02, 2010, 04:44:12 PM »

^ yong R1-R4 na 330 ohms pang 5V input lang na dropping yan recompute nyo sa ibang input voltage.

Ahh ok then dapat specify nila yan sa manual ano. wala nmn ako balak gamitin yan nabasa ko lang sa website nila.

thank u sa mga sumagot ha.
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rdpzycho
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« Reply #7 on: March 02, 2010, 04:45:05 PM »

assuming low forward voltage 'yung LED, yup mag-iinit siya. most probably, high forward voltage 'yung LED, dahil 'di nila i-indicate na kaya 'yung 24V kung magiging masyadong mataas ang current.
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