OPTOFAST

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2017-01-28T19 42 37.589Z-OPTOFAST-P668-720px-act.jpg

OPTOFAST - 4 Channel Optocoupler Card

See our other Optocoupler cards

  • OPTOFAST-2 - Speed improved 4 channel optocoupler card - Suggested replacement for this card
  • OPTOSMALL - Four channel optocoupler card
  • OPTOOUT8-I2C - Eight channel optocoupler card - I2C interface
  • OPTOUSB - Optically coupled USB to FTDI interface
  • OPTOFASTBI - Two Optos in Two Directions

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-2-Schematic-TransIn.PNG

  • U1 represents U1-U4 (channels 1-4)
  • Q1 represents Q1-Q4 (channels 1-4)
  • R1 (VCC) represents R1,R4,R7,R10 (channels 1-4)
  • R2 (DIR) represents R2,R5,R8,R11 (channels 1-4)
  • R3 (BASE) represents R3,R6,R8,R12 (channels 1-4)
  • R13 (FAST) represents R13-R16 (channels 1-4)
  • R17 (COLL) represents R17-R20 (channels 1-4)

Input Options

  • Refer to schematic for impact of options

Use Input Transistor - Standard Option

  • Common VCC in option
  • Install transistor Q1
  • R1 = 150
    • LED current is 3.5V/150 Ohms = 23 mA
    • CTR = .20, 4.7 mA
  • R2 = Do not populate
  • R3 = 10K
    • Base drive ~ (Vin - 0.7V)/R3
    • At 5V drive this is 4.3V/R3
      • Using R3=10K at 5V this is 0.43mA Ib
      • HFE (MMBT3904) = 100 min
      • That is potentially 43 mA (in the switching range of the transistor)
        • Collector resistor and LED voltage drop are current limiter
    • At 3.3V drive this is (3.3-0.7)/10K = .26mA Ib
      • HFE = 100 min
      • That is 26 mA (in the switching range of the transistor)
  • H1 do not short

Direct Drive - Special Option

OPTOFAST-2-Schematic-Direct.PNG

  • Do not install Q1
  • Do not install R1
  • R2 = 150
    • Input current = LED current = 3.5V/150 Ohms = 23 mA
  • Do not install R3
  • Do not install Q1
  • Short H1

Output Options

Standard Output

  • R17 = 1.2K
    • 5V/1.2K = 4.1mA of output transistor B-E current
    • Leaves 4.7-4.1 mA = 600 uA of output low current

Open Collector Output - Special Option

  • Do not install R17

Fast Option - Standard

  • R13 = 20K (empirically determined from the scope eye)

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

Ch1-Slow-NPNBuffer-InFall

  • 28.6uS

Ch1-Slow-NPNBuffer-InFall.png

Ch1-Slow-NPNBuffer-InRise

  • 1.8uS

Ch1-Slow-NPNBuffer-InRise.png

Ch2-Fast-NPNBuffer-InFall

  • 6.68uS

Ch2-Fast-NPNBuffer-InFall.png

Ch2-Fast-NPNBuffer-InRise

  • 3.6uS

Ch2-Fast-NPNBuffer-InRise.png

Ch3-Slow-Direct-InFall

  • 1.84uS

Ch3-Slow-Direct-InFall.png

Ch3-Slow-Direct-InRise

  • 27.4uS

Ch3-Slow-Direct-InRise.png

Ch4-Fast-Direct-InFall

Ch4-Fast-Direct-InFall.png]

Ch4-Fast-Direct-InRise

Ch4-Fast-Direct-InRise.png

Layout

2017-01-28T19 34 38.489Z-OptoFast-Layout-720px.png