Automated NSW maker build

Hawkdl2

Hawkdl2

Mad Scientist
The objective is to develop the last component of my "fully automated reef tank" - an automated NSW maker. Discussion of this project started a few weeks ago in this thread: http://www.reefcentral.com/forums/showthread.php?t=1788103

Since then, after a lot of good advice in the earlier thread, I picked up a linear actuator and a few other components to build one version of a salt distribution device. I am also working on a completely different approach (with an auger) and will post progress on that after the parts arrive and I find time to play around with them.

This is a bench mock up to get the mechanical, structural and electrical issues worked out. The actuator is 12V bi-directional (it pulls and pushes), and works really well.

I replaced the stock tin blast gate slider with a longer one I made out of aluminum. The cast aluminum blast gate body is screwed to the ABS mount/salt chute. The ABS mount/chute goes through the plywood base and will lead to my NSW holding tank. You can see I've made a hole in the gate smaller than the blast gate body to limit the flow of salt - I will adjust the size after I get to testing the salt flow rates.

Blast gate closed:
actuatoropen.jpg


Blast gate open:
actuatorclosed.jpg



As built, everything works very smoothly. It takes a bit over a second to open or close the gate.

I am a bit lost as to how to wire up the two 12V leads so I can alternate polarity to reverse the motor. I believe this is done with two relays (I have one at the moment), but some help from one of our resident electrical experts would be very appreciated.
 
The safe way is to use a double pole double throw relay (DPDT). And a single pole single throw,(SPST), or another DPDT if it's more convenient.

Hook the motor to the COMMON terminals of your first DPDT relay. Then hook leads to the other four terminals this same DPDT relay in a crossed pattern.

Next you supply your power to each of the crossed leads. Immediately the motor will run in a direction. The direction you have it wired with this directional relay, when the directional relay does not have its coil energized.

If you energize the coil the motor will instantly reverse.

So there are your two directions.

But to actually turn the motor on and off you need another relay - the second one.

This one you put in the power leads leading to the directional relay. When the coil is energized on the supply relay it feeds power to the directional relay. Depending on the directional relay's coil being energized or not controls the resulting direction.

So you end up with two switches. Energize the supply relay coil and the motor runs. Additionally energize the directional relay coil and the motor reverses.
 
Lets see if I can explain (not where I can draw a schematic for you). We will ignore what controls the logic for now (what kcress is trying to describe)

Take a DPDT relay...

Lets name the PINS

COMMON_1
NC_1
NO_1

COMMON_2
NC_2
NO_2

COMMON_1 and COMMON_2 are wired to the power source

Relay PINS NO_1 and NC_2 are tied together AND to one wire of the motor.
Relay PINS NO_2 and NC_1 are tied toegehr AND to the other wire of the motor.

The motor runs in one direction when the relay coil is energized and the other direction when the relay coil IS NOT energized.

You start and stop the motor by removing the power feeding the common pins.
 
Here's the wiring diagram from a booklet that came along with the door actuators I bought. I think this still requires a rocker switch so I don't think it will work for this application. Is this similar to what you're describing?

boshrelaywiringppt.jpg
 
That diagram shows automative (a.k.a. BOSCH) relays. They are only SPDT (Single Pole, Double Throw). The circuit is not what you are looking for, it does not do the polarity reversing, the purpose of the relays is to allow higher current 12V to switch the lock based on the alarms low current lock driver output.

Standard automative relay contacts:

85 and 86 are the relay COIL.

30 is COMMON
87 is NC
87a is NO


You could wire two of these together (by running their coils in parallel) to derive a DPDT relay. I would however, just buy a DPDT relay at Radio Shack and leave the bosch relay for the car :)

Hope that makes sense.
 
...An incredibly interesting thread, that is, the very limited amount of it that I understand. :spin2:

Can't wait for the finished product!
 
OK, I'm back from a business trip and picked up some relays from the Shack today. Based on kcrerss and BeanAnimal's tips, and some research, I came up with this circuit. If I understand it all, I am replacing the second, SPST, relay with my controllable Apex outlet. Actually, both wall warts will be on controllable Apex outlets, though only the 12V coil energizer power supply is shown as such.

Does this look correct?
actuatorrelay.jpg
 
Ok, I labeled the terminals incorrectly - at least for the Radio Shack relay I have. I don't think it changes the circuit, but this is how it should look. A1 and A2 are NO and B1 and B2 are NC.

actuatorrealy2.jpg



BeanAnimal, if you're out there, you have the POWER SOURCE wired to the common terminals. kcress has the MOTOR wired to them. Did you mean MOTOR? from my research, it does appear they should be wired to the motor.
 
It can be made to work either way... Draw them both out to get a better understanding. Use the schematic symbols for a relay, not the graphical :)

Not trying to be evasive, just tyring to help you understand how it works :)
 
A progress update. The hopper funnel finally came is as did my Neptune EB8 outlet block. I just threw this together and slapped a couple coats of poly on to see if it will work, but the wiring is complete and everything is ready to mount on a wall somewhere to hook up to the controller.

I've been working on the programming and I think I have the logic sorted out. I hope to test it in the next couple of days.

nswmakerhopper.jpg
 
Very interesting build.

How do you plan to keep the salt from caking/compressing/absorbing moisture to ensure an exact flow rate?
 
-awesome build , subsribed :) !

-One thing you got to keep in mind / under control is the humidity , salt is very hygroscopic , therefore it want to suck water out of the air to get it.
This froms bigger chunks and layers that could faul your saltcontainer bin or gatevalve making it hard to close the valve or even blocking it.
-You have to make your bin air tight and keep the gate valve and bin as far as possible away from any water or humid/condensing air/water.

greetingzz tntneon :)
 
I would look into adding an auger or mixer of sorts to the hopper, we use an automated hopper with auger to dose potassium permanganate when we treat lakes/streams with rotenone for fisheries management and they are very very accurate. Great now i'm looking at my work equipment in tank terms....
 
I have several ideas to address caking. I have a Kitchenaid blender I plan to try turning into a stirrer and I'm going to try bagged CaCl as a desiccant.

My first objective is to see if I can control the salt feed reproducibly enough to get close, but to a bit over the target SG, then a conductivity probe to adjust the SG bu topping off with RODI. For me the real challenge is the sensitivity and accuracy of the conductivity probe. If I can time the gate accurately enough, I may be able to get to the target SG without adjustment. We'll see.
 
-It`s a good idea to dose your salt a little bit over NSW , then fine tuning it by adding additional osmosis water :thumbsup: .
Gonna work much better than tuning it only with the salt.
Are you planning to make an continuesly salt water maker or one that does it in batches ?
And how big would these batches be?

greetingzz tntneon :)
 
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