OptoFast

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Tindie-larges-v2.png

Optocoupler Performance Video Series

OPTOFAST-P668-720px.jpg

Related Product

Tindie-mediums.png This is the OptoSmall card.

This is the OptoSmall card

Features

  • Opto-Isolator card
  • 4-Channels
  • 4N25 Optoisolators
  • Input /Output isolation
  • Transistor driver for Opto LED reduces required drive from 10 mA to under 500 uA
  • Input channels share their own common VCC/Ground
  • Output channels share their own common Vcc/Ground
  • 8-pin header for input
  • 8-pin header for output
  • Configuration Options
    • Speed enhanced
    • Bypass Input transistors
    • Remove Output collector resistors
  • 49x49mm
  • (4) 4-40 mounting holes

Schematic (One channel)

OptoFast-SingleChannelSchematic.PNG

  • U1 represents U1-U4 (channels 1-4)
  • Q1 represents Q1-Q4 (channels 1-4)
  • R1 (BASE) represents R1-R4 (channels 1-4)
  • R5 (DIR) represents R5-R8 (channels 1-4)
  • R9 (VCC) represents R9-R12 (channels 1-4)
  • R13 (FAST) represents R13-R16 (channels 1-4)
  • R17 (COLL) represents R17-R20 (channels 1-4)

Options

  • Refer to schematic for impact of options
  • Install R9-R12 = 330 for all options (VCC)

Do not Bypass Input Transistor - Standard Option

  • Install Q1-Q4
  • R1-R4 = 10K
  • 500 uA input current (@5V drive)
  • Install transistor
  • R5-R8 = Do not populate

Bypass Input Transistor - Special Option

  • Do not install Q1-Q4
  • Do not install R1-R4
  • R5-R8 = 0 Ohms

Open Collector Output - Special Option

  • R17-R20 = 4.7K (1mA of output current)
  • R13-R16 = No not populate

Fast Option - Standard

  • R13-R16 = 47K

Connectors

P1 - Input

8-pin, right angle, 0.1" pitch

  1. Vcc (In)
  2. Vcc (In)
  3. IN 1
  4. IN 2
  5. IN 3
  6. IN 4
  7. GND (In)
  8. GND (In)

P2 - Output

8-pin, right angle, 0.1" pitch

  1. Vcc (Out)
  2. Vcc (Out)
  3. OUT 1
  4. OUT 2
  5. OUT 3
  6. OUT 4
  7. GND (Out)
  8. GND (Out)


Test Card Measurements

OptoFast-TestSetup-720px.jpg

Setup

  • Goal was to determine the performance of the OPTOFAST card
  • 5V operation
  • Same 5V input/output power supply
  • Each of the channels were configured uniquely/individually
  • MHS-5200A - Digital DDS Dual-channel Signal Generator
    • 1 KHz square wave
    • 5V signal level
  • Single channel checked at a time
  • Oscilloscope
    • Rigol DS1054Z
    • 50 MHz
    • Ultra Sigma software used for screen captures

Notes

  • Note that the input buffer transistor inverts the signal
  • Built a card that has four different configurations
  • Options
    • Fast/Slow
    • Direct drive input LED/Transistor Buffered input

Test Results

Channel Fast/Slow TransBuff/Direct Input Rise/Fall Time(uS)
1 Slow Transistor Buffer Fall 28.6
1 Slow Transistor Buffer Rise 1.8
2 Fast Transistor Buffer Fall 6.68
2 Fast Transistor Buffer Rise 3.6
3 Slow Direct Input Fall 1.84
3 Slow Direct Input Rise 27.4
4 Fast Direct Input Fall 4.24
4 Fast Direct Input Rise 5.28

Observations

  • Input Transistor effect
    • Value of the input transistor is that does not require a high drive level input
    • The input transistor has very little effect on speed - a couple hundred nS slower than direct drive
    • The inversion effect of the input transistor moves the "slow" time around
    • Downside of the input transistor is that it has less noise immunity since the transistor turns on at 0.6V vs the internal LED in the optocoupler at 1.5V?
  • Output "fast" circuit
    • Output pullup of 4.7K affects the rise time of the output
    • The fast is faster, but not in some conditions
      • Average of rise/fall is better
      • Transistor buffer instance rise input is slower with the fast output
      • Fast output helps the output rise time

Ch1-Slow-NPNBuffer-InFall

Ch1-Slow-NPNBuffer-InFall.png

Ch1-Slow-NPNBuffer-InRise

Ch1-Slow-NPNBuffer-InRise.png

Ch2-Fast-NPNBuffer-InFall

Ch2-Fast-NPNBuffer-InFall.png

Ch2-Fast-NPNBuffer-InRise

Ch2-Fast-NPNBuffer-InRise.png

Ch3-Slow-Direct-InFall

Ch3-Slow-Direct-InFall.png

Ch3-Slow-Direct-InRise

Ch3-Slow-Direct-InRise.png

Ch4-Fast-Direct-InFall

Ch4-Fast-Direct-InFall.png

Ch4-Fast-Direct-InRise

Ch4-Fast-Direct-InRise.png

Layout

OptoFast-Layout.PNG

Assembly Sheet

OptoFast Assembly Sheet