8 Channel Relay Board - Proofreading

So, for example R16 (T16) needs to be pulled high?

[quote author=Papa G link=topic=160464.msg1201545#msg1201545 date=1365990199] The circuit is pretty hard to see for me and I think there is a mistake in it anyway. It looks like the wire shorting out the relay coil shouldn't be there. Notice where the collector of the phototransistor goes and notice that the emitter is not grounded.

Edited: Sorry, that was poorly worded. I meant notice how the collector on the ebay circuit is wired to 5 V and their emitter goes to the base of the driver transistor as opposed to the way your circuit is wired. [/quote]

Ah, I understand now. I attached a schematic of which I was basing mine off of.

Now my first sentence on this post would rectify the situation, pulling (T16 for example) high? Since you can't see (lol), the wire going from the collector to the base of the relay transistor.

avr-io-b-sch.gif|1624x1127

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. :)

[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. :) [/quote]

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. :)

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?

[quote author=Papa G link=topic=160464.msg1201563#msg1201563 date=1365992311]

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

Is you intent still to energize the relay with a LOW on INx? [/quote]

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.

Single Channel Relay.png|1073x311

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.

relay.png|1121x332

[quote author=Papa G link=topic=160464.msg1201601#msg1201601 date=1365997457]

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. [/quote]

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