8 Channel Relay Board - Proofreading

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. :slight_smile:

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.

How do you say it's poorly drawn?

retrolefty:

[quote author=Papa G link=topic=160464.msg1201554#msg1201554 date=1365991113]
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. :slight_smile:

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.
[/quote]

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

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

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

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

If so, you will use a circuit like http://www.ebay.com/itm/8-Channel-DC-5V-Relay-Module-for-Arduino-PIC-ARM-DSP-AVR-MSP430-TTL-Logic-/271188081780?pt=LH_DefaultDomain_0&hash=item3f2411bc74&autorefresh=true.

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.

codlink:
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

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).

retrolefty:
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.

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).

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

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.

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.

Relay Board Simple.brd (176 KB)

Relay Board Simple.sch (989 KB)

What is Vcc connected to?
What do IN1-IN5 connect to?

CrossRoads:
What is Vcc connected to?

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

What do IN1-IN5 connect to?

IN1-8 are Arduino inputs to activate the optos.

From the marking on the relays, they appear to have 5V coils also.
Maybe 5V on both sides.

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

Thanks Crossroads. +1

Did some more testing and you're right. After I hooked it up the right way it worked.. But now I have a problem with relays 4, 6, 7, and 8. They do nothing. Going to check my soldering tomorrow.

I do have some revisions for the board to make it easier to assemble though, but really only cosmetic..

Thanks to everyone