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 !