critique my schematic, please

This is to control lights on my reef tank. Along with this, there will be two more LEDs to be controlled independently, they will each have a dedicated pot. So, the complete arrangement will have 3 (pot, relay) 4(LDD, LED, fan) 1 (RTC, 12V wart, 5V wart, arduino, power supply)

I didn't write this from the ground up-I used a previous project as a guide and modified it. I 'think' it's right, but am not sure. If someone knowledgeable could let me know if I have the hardware part of my project right, I'd appreciate it.

I am hoping the RTC/arduino can allow me to turn the 3 lights on and off at different times.

RTC.pdf (531 KB)

no current limiting resistors on pin 8

no transistor on relay on pin 11
power sourced from arduino to relay

I do like the Arduino, can you let me know that model that does not need to be connected to power ?
[ op's. the device labeled a wart is, evidently a power supply for 5v, my bad ]

hey, everyone is a critic !

You asked, you get!

Why are you connecting the wiper for the pot to a digital input?

Separate the mains ground from the low voltage ground. They have different purposes.

Weedpharma

hey, everyone is a critic !

You asked, you get!

Yes and yes, HA!

dave-in-nj:
no current limiting resistors on pin 8

no transistor on relay on pin 11
power sourced from arduino to relay

I do like the Arduino, can you let me know that model that does not need to be connected to power ?

Absolutely am NOT saying it shouldn't have them, but on a similar build for an algae scrubber, pin 8 to the LDD and pin 11 to relay are hooked up as shown. Maybe I got lucky.
What resistor value would work for pin 8?
Would 2N3904 or 2N3906 be good for pin 11?
OK, I think I've got you about power to arduino-I should connect 5V at the barrel jack, then arduino VCC to relay VCC?

weedpharma:
Why are you connecting the wiper for the pot to a digital input?

Separate the mains ground from the low voltage ground. They have different purposes.

Weedpharma

The pot is for dimming the LEDs. I have it hooked up like that on my algae scrubber and it does work. On the scrubber, I used a 10K pot. I drew a 25K pot because that's the closest to 10 I have. It's the 25 turn type.

Put the wall warts ground and main power supply ground together, then ground everything else separately. And then connect them both to ground?

Thanks you guys, I appreciate the responses.

Absolutely am NOT saying it shouldn't have them, but on a similar build for an algae scrubber, pin 8 to the LDD and pin 11 to relay are hooked up as shown. Maybe I got lucky.
What resistor value would work for pin 8?

the LDD-1500 takes your PWM and converts it to PWM. the input would appear to be dead ended onto an FET or some such. the data sheet does not talk about current. that said, it is typical to use a 220 ohm on LEDS on the output of digital pins. if using a 220 ohm does not alter the operation, that it wold offer a limit to current in case of a short. that is a SWAG, btw.

Would 2N3904 or 2N3906 be good for pin 11?

yes, but it does require use of a resistor on the pin to the base. not sure of your relay. best to post a link to your relay. it may have an opto and then you need something on the order of 330 to 500 ohms. if the relay is just a relay, then you also need to add a diode to protect your input from the spike of back EMF when the relay changes state.

OK, I think I've got you about power to arduino-I should connect 5V at the barrel jack, then arduino VCC to relay VCC?

nope,. you did not mention which arduino, but as soon as you said barrel jack, that means UNO, Mega or one of the larger boards. the barrel jack requires 7 to 10~ish voltage, not 5.
the relay needs power and will spike the power supply, since your 5v is powering the relay coil and powering the Arduino, you need to address that with caps. also not shown.
but, you are correct, the 5v goes to Vcc, 'wart' thru me, thought it was a consumption device, not a power supply. kinda expected power supplies to be labeled power supply......

The pot is for dimming the LEDs. I have it hooked up like that on my algae scrubber and it does work. On the scrubber, I used a 10K pot. I drew a 25K pot because that's the closest to 10 I have. It's the 25 turn type.

you sure this feeds pin D-6 and not A6 ?

==============
upon further review.... the RTC should not be connected to the power (-) rail.
it should be connected to the ground of the Arduino, which should not be connected to the (-) of the power rail.

in my earlier post, I commented on the simple way the Arduino runs with no power input.. once I figured that wart means power supply in some language (other than English) I realized that THAT device generates power all on it's own without any source. THAT is the device I am looking for !

I reconfigured the grounding scheme and added a resistor between LDD dim and Arduino pin 8. I left 5V to Arduino VCC to power that device.

Really good catch on the pot wiper, thanks! I relabeled it A1.

I didn’t do anything to pin 11 to relay because I’m not sure where each leg of the transistor should go.

I also renamed the 5V wart and 12V wart power supplies. I’m just used to calling those ugly little things wall warts. Sorry for the confusion.

Here’s my relay, I’ll only be using three of them. The relay coil will be powered by 12V as will the fans.

http://www.ebay.com/itm/231429969189?_trksid=p2057872.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT

That link seems disabled, but the relay has a 12V coil optocoupler.

RTC.pdf (581 KB)

You've been reading Make Magazine, haven't you? Your schematics use only blocks for symbols and are difficult to follow.

Please review the links in my signature about drawing schematics.

I never heard of make magazine. I just made a diagram to show my hookup plan. Sorry you find it difficult to follow.

cut that ( - ) power supply line above the fans. that way, the Arduino ground wraps around and conects both the fans and the RTC

Like that? That has the Arduino, relay, RTC and fans grounded together, but doesn’t that line still need to be grounded?

Edit; Should the 25K pot be grounded on the same line as the Arduino, relay, RTC and fans?

Should the negative output from the main power supply that feeds the LDD be connected to the mains ground like the 5V and 12V power supplies are?

RTC.pdf (575 KB)

No, you should not connect your circuit to the Earth wire in the wall plugs. If you have a metal case on your project and mains voltage coming into it, then you should connect the Earth wire to the case, as close as practical to the cable entry.

If you only have 12V and 5V coming in from plugpack power supplies, then you should have no connection to Earth anywhere.

I had not planned to use a metal case, but I can if it helps.

I went ahead and connected the 25K pot ground wire to the fan, RTC, relay and Arduino ground.

IDK, somehow it looks better like that.

Should I connect the negative lines from the 5V and 12V supplies to the same ground as the Arduino, etc., or leave them connected to the mains ground?

Should the negative wire feeding LDD be grounded?

RTC.pdf (582 KB)

  1. Don’t connect any part of your circuit to mains ground.

  2. Everything that’s intended to interact needs to be connected to the same ground. For example, your 12V fans don’t need to interact with any other part of the circuit, so you can just join them straight back to the negative terminal on the 12V supply and it doesn’t participate in the circuit ground.

  3. Learn to use ground symbols in your schematic. It saves a lot of confusing lines all over the place. Almost every single component needs to connect to the circuit ground so you don’t need to draw that line everywhere.

  4. Where do the LD1500s get their ground from? I should think that power supply negative should be connected to the Arduino ground.

The 5v supply does not appear to have any connection to the Arduino. It is however connected to mains ground.

Weedpharma

Three changes. Four if you count the use of the circuit ground symbol. That did clean things up-thanks.

The negative side of the main power supply for the LDDs is now connected to the circuit ground.

The negative side of the fans is now connected to the 12V power supply.

The negative side of the 5V power supply is now connected to the circuit ground.

5V runs straight up and connects to Arduino at VCC.

Thanks guys. Does this look like a properly grounded circuit?

RTC.pdf (600 KB)

OK, so be offended and ignore my advice.

No offense taken. If I were to write more schematics I'd see about getting one of those programs. Anyway, I hope my schematic is now reasonably easy to follow.

An arrow pointing sideways is not a ground symbol.

I also don't understand what you've done with the LED power supply.

Glad to hear it. Text only is a dry medium...

None of those are programs. I do 99% of my programs with a pencil and paper, too. Did you look at the links? A clear schematic helps you see where you might be doing something wrong.

Hey, at least you aren't using Fritzing... snork.

MorganS:
4. Where do the LD1500s get their ground from? I should think that power supply negative should be connected to the Arduino ground.

MorganS:
I also don't understand what you've done with the LED power supply.

The only thing I did to the LED power supply is connect the negative side to the circuit ground, which connects it to the Arduino ground. Maybe I misunderstood your directions. Also, all circuit ground symbols now point down.