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Has anybody made a computer controlled Herbie overflow?

1K views 10 replies 5 participants last post by  GraphicGr8s 
#1 ·
I have a Herbie style overflow on my aquarium. It works pretty awesome, but I have to adjust it every few days.

This seems like something pretty simple to automate. Measure the water level in the overflow and use that to drive a motor to turn the gate valve. The only tricky part seems to be the mechanics to interface a motor to the gate valve.

1) Is this something people are interested in?

2) Has anybody done this before?
 
#8 ·
A solenoid opens up when electricity is applied to it, otherwise it is closed. So in a power outage or power failure they will close which would almost be beneficial. If you put a valve in line with these you can manually control water flow as well. If you put solenoids in parallel to each other you can decrease and increase water flow easily with a computer control. It would require some programming and may be costly but I am fairly certain it can be done.

Your method would most likely be cheaper but you're relying on something mechanical which can be fairly harder to control. How much do you adjust the valve to get the flow you need? And what happened if the motor f's up and continues turning without stop and breaks the valve? Those are issues I see with this. Solenoids in my opinion would be your best bet, though there are issues here as well.. power failure to solenoids and not pump catastrophe. Either way a computer controlled system has its difficulties and problems. Manual may be simpler but requires more monitoring. I feel like I'm rambling here

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#9 ·
A solenoid isn't going to have enough control granularity to tune a Herbie overflow. I find that I have to get my gate within a pretty small window for my Herbie overflow to be silent.

As you said a solenoid is opened or closed, which doesn't give me much granularity. That leaves me a few options.
1) Open and close the solenoid often. That's going to be noisy and I doubt it would work very well. I'm not even sure solenoids are meant to be used like that.
2) Add some complexity to the electronics so that the solenoid can be partial opened. This seems a lot more difficult to me than turning a gate valve with a stepper motor.

Your method would most likely be cheaper but you're relying on something mechanical which can be fairly harder to control. How much do you adjust the valve to get the flow you need?
I was thinking of using a PID control loop for controlling the stepper motor. The PID loop would optimize for a specific height of water in the overflow. Considering that the Herbie operates silently as long as the water is within 1" range means that the PID loop doesn't even need to be tuned very well since it doesn't have to be super accurate.

And what happened if the motor f's up and continues turning without stop and breaks the valve?
I can set a maximum current on the stepper motor driver that will prevent the motor from having enough torque to break the valve if it turns beyond the range. In the case that the valve is turned all the way, the motor will start torquing up and start consuming drastically more current. This drastic increase in current will blow a resettable fuse causing the controller to be turn off.
 
#11 ·
A solenoid isn't going to have enough control granularity to tune a Herbie overflow. I find that I have to get my gate within a pretty small window for my Herbie overflow to be silent.

As you said a solenoid is opened or closed, which doesn't give me much granularity. That leaves me a few options.
1) Open and close the solenoid often. That's going to be noisy and I doubt it would work very well. I'm not even sure solenoids are meant to be used like that.
2) Add some complexity to the electronics so that the solenoid can be partial opened. This seems a lot more difficult to me than turning a gate valve with a stepper motor.



I was thinking of using a PID control loop for controlling the stepper motor. The PID loop would optimize for a specific height of water in the overflow. Considering that the Herbie operates silently as long as the water is within 1" range means that the PID loop doesn't even need to be tuned very well since it doesn't have to be super accurate.



I can set a maximum current on the stepper motor driver that will prevent the motor from having enough torque to break the valve if it turns beyond the range. In the case that the valve is turned all the way, the motor will start torquing up and start consuming drastically more current. This drastic increase in current will blow a resettable fuse causing the controller to be turn off.
Actually solenoids were used in exactly that way to adjust fuel flow on carbs. You could regulate flow by determining how long a solenoid remains of or on in a set length of time.Dwell.

As I see it not only do you need to control a valve but you also need a flow sensor in addition to monitoring water height to work efficiently.
Sounds like a Rube Goldberg idea though.
 
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