OPTOFAST

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)

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

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

Vcc (In)
Vcc (In)
IN 1
IN 2
IN 3
IN 4
GND (In)
GND (In)

P2 - Output

8-pin, right angle, 0.1" pitch

Vcc (Out)
Vcc (Out)
OUT 1
OUT 2
OUT 3
OUT 4
GND (Out)
GND (Out)

Test Card Measurements

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