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Application: Stormwater autosampler (Global Water WS700) in a location away from any power source
Power: 12V 4Ah battery
Hey guys,
We are having issues with our autosamplers turning on and running a peristaltic pump until the battery is depleted beyond repair. The autosamplers are turning on due to the presence of runoff (as theyre supposed to), however, if the float switch in the bottle is not triggered (due to a lack of water) the sampler pump will continue running until the battery is completed depleted. We have tried low-voltage cutoff switches, however, they draw power from the battery resulting in a dead battery after a few days, which is problematic as we typically set the autosamplers out for multiple weeks without visit. Solar is not applicable as the samplers are located under a thick canopy.
There are accessory plug ins on the autosampler which I am hoping I can connect a timer that will automatically shut off the sampler once X amount of time has passed.
We need a timer, likely analog, that wouldn’t draw any power while on standby and can plug in via aux plugs.
Does anyone have a solution for this problem. I haven’t been able to find anything applicable on the internet as of yet but have thought about trying to rewire an analog timer in the mean time.
Any information or insight is greatly appreciated!
Are you using the optional water sensor? As I understand the device, this will prevent the machine from operating if water is not present. Another way of asking is, do you have a jumper or sensor installed in the water sensor jack?
Best wishes,
APDahlen
BTW, this sounds like the perfect application for a microcontroller in sleep mode. For example, a diabetic’s blood sugar meter is able to run for the better part of a year on a tiny battery. It does this as the microcontroller has entered a battery saving sleep mode.
I’m currently working on a demo project but it will take a few weeks to get it running. The sleep mode isn’t overly difficult, but it does take a good understanding of the microcontroller.
For our application we need the sampler to sample the initial flush, 15mins, 30mins, and 45mins after the initial flush. The water sensor would allow the sampler to turn off, however, if there is another rain event afterwards our collected samples would not represent the initial runoff event.
I will look into the microcontroller! Any updates on the demo project would be greatly appreciated!
Implementing an OFF-delay shut-off circuit would typically require some modification of the water sampler device such as wiring it in series to disconnect the battery or the motor pump wire while using some kind of voltage but would ideally draw very minimal current. I don’t know enough how your unit works or how you’d like to modify it, however click here for some OFF-delay SSRs (solid state relays) to consider depending on your voltage and current ratings. We may locate better options depending how you are looking to modify it.
I have little understanding of the inner workings of the WS700 besides basic functionality. My hope was to simply plug in a timer into the input and output plugins for pump 2. Not exactly sure how it would interact with the power source and peristaltic pump.
I appreciate the efforts you are contributing to this issue! I’ll continue exploring options.
We could think of this in terms of states. At a minimum we would need:
A signal to initially start the timer.
A signal to stop the timer (this could just be elapsed time e.g., shut down after 5 minutes).
A signal to restart the timer (this could be the same signal as used in part 1 e.g., it was raining on Monday, it’s raining again on Friday).
Apologies for not having a direct answer. Sometimes this can feel like walking in the dark. Speaking of darkness, we still don’t know how the WS700 works internally, this only adds to the confusion.
Don’t have time to look in depth but a quick peak shows me that you could connect the pulse output into an arduino that can be programmed to disable the system by disconnecting the power after the measurement cycle is done
Wondering, what is the setting for “Pump sample size”? The manual says:
Note: In the “Full” position, the sampler will shut off the pump after one hour, even if the bottle is not full.
So, if you set it “Full” does the pump go OFF after an hour?
However, that probably does not prevent the pump going ON again, if there is a new trigger event…?
