Hello All,
At the moment, I am putting a few probes into a water reservoir manually to check water quality.
I am wondering if anyone has a solution or an example to use an arduino to lower a platform with probes into a water reservoir. The platform will be able to stop when probes are in the water to take readings. Once completed, the platform will raise/return to the original height?
Anyone with experience using solenoid / motors / actuator? Which one will be the easiest to execute?
Interesting project, could you go over why you need the probes to stay out of the water when not performing measurements? I understand they can rely on catalysts in some cases and their lifespan can be extended by keeping them out of the water, is this the case in your project?
As for moving the platform in and out of the water, I’d say the go would be to keep it mechanically simple with a DC motor and a limit switch to detect when the platform, and maybe some sensor on the platform that can figure out whether it has hit the water yet.
What sort of distances are we talking between the top of the reservoir and the waterline?
Hello James,
Trying to prolong the lifespan of the probes really. At the same time, the waterline when pump on/off is about 10cm and the probes would be fully submerged in the water. The pump is on a timer and only taking reading whilst the pump is on.
Having a auto lift would be handy, saving me constantly needing to adjust the probes.
My current thought is fixed the probes position on the platform. Using a water sensor, stop lowering when hit water. Taking readings. Using another water sensor above the probes, 0 < height < 10 cm. When pump stops, water raising, hit the second water sensor. Start lifting to original position.
Just unsure what is the best platform / mechanism to be used in a vertical setting. Something similar to a camera slider but in vertical setting.
Something as simple as a pulley should do, just make sure that the enclosure that you have everything is appropriately rated(if it’s outdoors look for something waterproof)!
From what I understand of the higher part of the forum the limit switch is nothing more than a mechanism to detect when the platform has touched the water. I would research the sensors you are already using, I expect with some sensors if measurements are taken out of water you will get an obviously impossible measurement. If this is the case then no extra hardware would be required to detect the water.
I’m not qualified to answer this question but I would suggest exploring the possibility of gearing, if you use a very low gear ratio the platform would not only allow the use of a relatively small/cheap motor but will make the platform move quite slowly which I expect is a good thing in this situation.
A limit switch is typically a mechanical or optical switch mounted on the rail adjacent to the platform so that it is triggered when the platform is at a certain point. It is used to provide a zero point for the movement mechanism, and to prevent the mechanism from accidentally moving the platform beyond the end of its travel. So the startup routine is to move the platform a short distance away from the limit switch (so it cannot be in the triggered state), then back towards the switch until it is triggered. That position then becomes the zero position, from which all other movement can be calculated. In your case movement is away from the limit switch until either the water sensor is triggered or the distance moved indicates that the sensor is not going to trigger and movement should stop before the platform hits the bottom. If the movement mechanism does not support accurate positioning you might need another limit switch near the bottom.tor prevent overshoot.
Thought of sharing an update. A bit rough atm.
Modified an old dvd rom. Motor shield to drive to the dc motor.
A probe to check if submerged in water - then stopped lowering.
A water moisture probe to check if water rising. Yes - start lifting.
Hi Tien
Sorry I missed this thread over the last few weeks and just noticed the old subject of Limit Switches has come up again.
I think Jeff105671 is not quite correct with his thinking on a “Limit Switch”. What he has described is essentially “End Stop” sensors which is all well and good as far as stopping any motion and /or supplying a reference point by electronic control means. But what if the electronic control circuitry fails and fails in such a manner the driving motor keeps going.
Limit Switches as the name implies limits movement absolutely beyond that point, usually just beyond any “end stop” sensors, and should be completely divorced from any control circuitry. Usually they are mechanical switches (SPDT) mounted just beyond any end stop sensors and remove power completely from any drive motor. They are usually designed and marketed as “limit switches” and are either lever or roller operated (sometimes both) depending on mechanical requirements.
During the last few months I have posted a circuit and description a couple of times of a system I have successfully used many times to suit a brushed DC motor. If you can’t find it let us know here and I will put it up again.
Cheers Bob
This sort of thing should be completely separated from any electronic driver circuits.
It is POLARITY SENSITIVE as it provides a braking diode to stop the motor dead and prevent damage due to over run. Also “steering” diodes to allow reversing the motor off the switch which at this point is open removing voltage from the motor.
Diodes should be 20A rated. Usually found in dual 10A packages either common cathode or common anode. Just join the 2 in parallel.
Don’t forget. If using this circuit BE CAREFUL of polarity.
Cheers Bob
