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Topic: 8 Channel Relay Board - Proofreading (Read 13061 times) previous topic - next topic

Papa G



I see how you got confused. Notice they are biasing the phototransistor to switch faster rather than act more linearly. I don't know what the purpose of the Olimex circuit is. It's an optically coupled OR-gate that resets the processor for whatever reason I don't know. :)


Not quite. It's poorly drawn. Note that each opto collector has a I1, I2, I3, or I4 label. These wire over to digital input pins on the processor chip.


lol, no I mean the schematic posted with reply #26.

codlink

so, my question in reply 26, will it work?
//LiNK

Papa G


so, my question in reply 26, will it work?


Is you intent still to energize the relay with a LOW on INx?


codlink

#34
Apr 15, 2013, 05:02 am Last Edit: Apr 15, 2013, 05:04 am by codlink Reason: 1
To make this easy, I attached just one of my relay circuits.  This schematic, from what I can see, is the same as in the link that Papa posted, except for adding a LED (w/resistor) between GND and +5V.
//LiNK

Papa G


To make this easy, I attached just one of my relay circuits.  This schematic, from what I can see, is the same as in the link that Papa posted, except for adding a LED (w/resistor) between GND and +5V.


No, more like this.

retrolefty



To make this easy, I attached just one of my relay circuits.  This schematic, from what I can see, is the same as in the link that Papa posted, except for adding a LED (w/resistor) between GND and +5V.


No, more like this.


Yes, that is a proper interface from opto to relay switching transistor. I would not bother with having two visual leds performing the same function, I would eliminate the opto input led indicator and adjust it's series resistor to compensate for it's elimination.

Lefty

AlxDroidDev

Instead of using 8 Arduino pins to drive your board, why no use one a single 74HC595 between the arduino and the optocouplers?

This way you'll use only 3 arduino pins, instead of 8, and the complexity added to your design will be minimal (and a 595 is pretty cheap).
Learn to live: Live to learn.
Showing off my work: http://arduino.cc/forum/index.php/topic,126197.0.html

codlink


Yes, that is a proper interface from opto to relay switching transistor. I would not bother with having two visual leds performing the same function, I would eliminate the opto input led indicator and adjust it's series resistor to compensate for it's elimination.

Lefty


Wow, I just noticed the LEDs..  You're right.  I will have to change my design for the relay LED.  I wanted the LED to light when the relay has power (Not switched on).  The LED on the opto would light when the relay switched on.  It's not really a necessity to have either LED, but I like seeing the lights.  Besides, I have hundreds of 1206 LEDs in a variety of colors..

Thanks Retro and Papa.  Just to let you know Papa, I knew how transistors worked, but the symbols stumped me for some reason.  Last night (late), it finally sunk in.  So, +1 to ya both.


Instead of using 8 Arduino pins to drive your board, why no use one a single 74HC595 between the arduino and the optocouplers?

This way you'll use only 3 arduino pins, instead of 8, and the complexity added to your design will be minimal (and a 595 is pretty cheap).


Good idea, have quite a few of those in SMD that I have been wanting to use.
//LiNK

Papa G

Quote
Thanks Retro and Papa.  Just to let you know Papa, I knew how transistors worked, but the symbols stumped me for some reason.  Last night (late), it finally sunk in.  So, +1 to ya both.


Thanks, codlink, I knew you'd get it if you thought about it long enough.

codlink

Well, I finally got around to assembling the relay board and guess what?  It doesn't work..  No LEDs, nothing.  When the 24V is connected I am getting ~21V on the Arduino input pins..

If anyone could take a look at my Eagle files, would appreciate any insight.
//LiNK

CrossRoads

What is Vcc connected to?
What do IN1-IN5 connect to?
Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

codlink


What is Vcc connected to?


Vcc is 24V supply.  Now that I am looking closer, do I have Vcc and +5V backwards?

Quote
What do IN1-IN5 connect to?


IN1-8 are Arduino inputs to activate the optos. 

//LiNK

CrossRoads

From the marking on the relays, they appear to have 5V coils also.
Maybe 5V on both sides.
Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

codlink

I see your point.  It's getting late here so I will try tomorrow doing some more troubleshooting.

Thanks Crossroads.  +1
//LiNK

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