Hi,
I am looking for advice on the attached design for an Arduino ebb and flood hydroponics tray. I tested the motors for the water pump and fan for current draw and labeled the image. Based on that I selected a wall wart to use in the relay shield to power the pump and fan that's rated above the max current of both running under load.
Based on threads I've found here and read, my questions are:
1 - Do I need to use capacitors on the motors, or is isolation via the optocoupled relays good enough? One of them will be underwater.
2 - Is this even a good idea? I don't see many people using the barrel jack to power the Arduino. I'd rather not use more than one outlet for the Arduino, fan and pump - I am already using a second one for the grow lights on a wall timer.
I appreciate any advice, and thanks!
Well you haven't given much information to go on, like what components you're talking about or what pins anything is connected to. But with any luck that will be o.k. provided there is really nothing connected to the Arduino other than the relay board.
Steve
You need to know the stall/start current for the pump, which is typically 5-10 X the lightly loaded running current.
Choose wall wart supply 2X that rating, and that should easily handle the rest of the load, without resetting the Arduino every time the pump starts.
Otherwise use a separate 5V phone charger with the Arduino, plugged into the same AC outlet.
slipstick:
with any luck that will be o.k. provided there is really nothing connected to the Arduino other than the relay board.
Well there is going to be an LCD 1602 and a rotary encoder, to set the flood and fan schedule. I plan to make the lcd stay off until the encoder wakes it up, and turn it off after 5 minutes with no input.
jremington:
You need to know the stall/start current for the pump, which is typically 5-10 X the lightly loaded running current.
Ah my apologies, the 800 mA is the maximum draw I measured from off to loaded - I ripped it out of a desktop fountain someone gave me years ago and to my utter shock it can pump water high enough to make it useful for this project. It's just a little toy motor that runs at ~95 mA while it's actually pumping water.
I'm using storage totes to hold the plants 6 inches above the top of a bigger storage tote reservoir. The pump will flood the top layer every few hours for about five minutes then turn off so the water drains. The fan will pull fresh air through the roots before the next pump cycle. The encoder and LCD will be used to adjust all the timing values. The whole thing is no bigger than 2 feet long and 18 inches wide.
I appreciate your advice very much - plenty of experience programming but almost none when it comes to circuitry, interference and smoothing peaks. Searching these forums has been enlightening.
