| Electronics > Projects, Designs, and Technical Stuff |
| Liquid Level Circuit Design |
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| tautech:
--- Quote from: sirklezero on December 10, 2018, 03:59:16 am --- --- Quote from: tautech on December 09, 2018, 07:49:19 pm ---Why optical ? Is the liquid non-conductive ? Old thread: https://www.eevblog.com/forum/beginners/which-sensor-to-use-for-salt-water-level/ --- End quote --- nah, it's just water. I went with the optical ones because, honestly I didn't know any better when I bought them and they looked pretty fancy :-[ At least they work really well. --- End quote --- FYI I attach the file from that thread just in case you missed it: A single XNOR IC, 4 resistors and 2 caps. Toggles between 2 states. |
| rhodges:
I am doing a similar project. I have a 1000 liter "tote" (International Bulk Container) that I will use as a secondary water tank. I thought about mechanical floats and finally decided to use an ultrasonic distance sensor. The HC-SR04 cost $1.25 on ebay. I will drill two holes on the top of the plastic tank for the transmit and receive transducers. Its board will be on top of the tank, held in place by friction. I did not think about an optical sensor, but I would be concerned that water drops might stay on the optical surface and give a faulty signal. Will the Mosfet saturate with TTL input? A CMOS buffer might be a good idea, or use a P Mosfet and a 2N3904 or 2N4401 to pull down the gate. Off topic: If anyone is interested in using the HC-SR04 with an STM8S103, I have put my library and example code on github. Here is the wiki summary: https://github.com/unfrozen/stm8_libs/wiki/lib_ping:-Control-one-to-three-HC-SR04-ultrasonic-rangefinder-devices. |
| Wimberleytech:
--- Quote from: rhodges on December 10, 2018, 02:27:36 pm ---I am doing a similar project. I have a 1000 liter "tote" (International Bulk Container) that I will use as a secondary water tank. --- End quote --- Be sure to post when this project is done!! |
| David Hess:
When I was reading your description, I immediately thought "set-reset flip-flop" but I might have made it with discrete transistors or high voltage CMOS logic so no regulator is required. Where to place the reverse EMF suppression diode depends on the application. In this case with a slow acting solenoid, across the solenoid is the best place. The low voltage drop across the diode makes for a low decay time but that is irrelevant here. A zener diode or resistor in series with the diode could be used to raise the reverse voltage and decrease the decay time. A diode across the transistor would direct the decay current into the positive supply which may or may not be acceptable. Unless you use a really small power MOSFET, heat sinking should not be required. The only real question is power dissipation while turned on which depends on channel resistance which can be absurdly low such that no heat sinking is required. |
| sirklezero:
yeah, my project is for a humidifier to help maintain a consistent'ish relative humidity in my workshop where I build classical guitars. I've got a dehumidifier element to it as well; it gets super dry during the winter here, and super humid in the summer, so the climate management is always a tug of war. |
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