Level indicator

[nhengineer]

As Marv said, about any float that isn't eaten by oil will work fine.

I think Delrin will float on oil. I have lots of that. I'll check out the density and compatibility with fuel oil.

I have lots of different magnets that would work fine.

This magnet to be attached to the float, right?

You would want something on the bottom of the tube to keep the float from falling off the end if the level got too low and also so the float won't drop below the last reed switch.

Agreed.

The reed switches would be normal open switches. One switch at 1/2 full and another at 1/4 full. The one at 1/4 full would be the bottom of the plastic or copper tube and would stay lit until the tank is filled.

Lit? Wouldn't the bottom reed switch be NO until the floating magnet was near it?

The circuit would be a simple 3 wire 2 AA batteries would operate it just fine.

Why 3-wire?

So, all you would need are 2 reed switches, 2 LEDs, the float and magnets and a tube and some wire.

Why 2 LED's. Would I only need one (red) to tell me when I'm at or below ¼ tank or would the other one (green) be to tell me that the device was operating properly?

I was thinking 3/8" tube would be ideal and the float would not have to be a large diameter. Do you have a lathe or drill press?

Drill press.

You could easily make a float out of anything floaty.

[Sleykin]

As Marv said, about any float that isn't eaten by oil will work fine.

I think Delrin will float on oil. I have lots of that. I'll check out the density and compatibility with fuel oil.

I have lots of different magnets that would work fine.

This magnet to be attached to the float, right?

You would want something on the bottom of the tube to keep the float from falling off the end if the level got too low and also so the float won't drop below the last reed switch.

Agreed.

The reed switches would be normal open switches. One switch at 1/2 full and another at 1/4 full. The one at 1/4 full would be the bottom of the plastic or copper tube and would stay lit until the tank is filled.

Lit? Wouldn't the bottom reed switch be NO until the floating magnet was near it?

The circuit would be a simple 3 wire 2 AA batteries would operate it just fine.

Why 3-wire?

So, all you would need are 2 reed switches, 2 LEDs, the float and magnets and a tube and some wire.

Why 2 LED's. Would I only need one (red) to tell me when I'm at or below ¼ tank or would the other one (green) be to tell me that the device was operating properly?

I was thinking 3/8" tube would be ideal and the float would not have to be a large diameter. Do you have a lathe or drill press?

Drill press.

You could easily make a float out of anything floaty.

Delrin sounds perfect as long as it flots and survives in oil.

You might want more than one magnet attached to the float, a bit of experimenting with the reed switches and a magnet will let you know how close the magnet needs to be and how powerful a magnet you need.

Yes. You could just use one reed switch and one LED to tell you when it was at or below 1/4 full. In your original post you wanted to know you were not above half a tank. The second reed switch would be mounted in the tube at half tank with a barrier to keep it from going higher. The second LED would light above 1/2 and stay lit until you were below 1/2 tank. Between 1/2 and 1/4 tank, no LED's would be lit. Below 1/4 tank the 1/4 full LED would stay lit. If you have a thermostat near where you want to mount the LED's, you could use that to power your tank monitor with just a diode and capacitor and a current limit resistor. The three wires would be one common and one for each switch/LED combination. I can post a circuit if you like....and I can figure out how to post a picture LOL

With a drill press, I would use a hole saw to make my float. Just bore it out to an easy sliding fit on the tube you use, but it won't go over the cap on the end of the tube. Put a small hose clamp around the tube to constrain the float to the 1/2 tank level

[suther51]

A float suggestion, a carburetor float from a small air cooled motor, doughnut shaped and ready made for fuel.

[mklotz]

I can't help wondering if construction would be simplified by moving the switching outside the tank...

Mount the float to a simple rod. Make a fitting for the hole on the top of the tank to act as a guide for the rod. As the float moves, the rod will move up and down outside the tank.

With such an arrangement, small clamp-on actuators on the rod could be made to operate ordinary micro switches held on a frame sitting next to the moving rod.

Such an accessible arrangement would make setting, adjusting and maintaining the switching arrangement easy. In addition, the visible rod and actuators would provide a visual, analog indication of the fluid level.

Just a thought.

[Sleykin]

I can't help wondering if construction would be simplified by moving the switching outside the tank...

Mount the float to a simple rod. Make a fitting for the hole on the top of the tank to act as a guide for the rod. As the float moves, the rod will move up and down outside the tank.

With such an arrangement, small clamp-on actuators on the rod could be made to operate ordinary micro switches held on a frame sitting next to the moving rod.

Such an accessible arrangement would make setting, adjusting and maintaining the switching arrangement easy. In addition, the visible rod and actuators would provide a visual, analog indication of the fluid level.

Just a thought.

I thought about putting the switches outside too. Problem is when the tank is full you will have 3 feet or so of rod sticking out the top unless you go to a lever arrangement to let the float move the rod a shorter distance.

[Frank S]

Aside from everything else another very simple solution would be to purchase a fuel tank sender they are adjustable to a large range of motion if he wanted it to show when 1/4 full as the lowest just adjust it to bottom out at 1/4 tank and if he wanted it to show the upper limit at 1/2 tank adjust it to that position A tiny wall wart could provide the power for the sender and gauge a led could be incorporated as well such as a 2 color green /red No need to invent some adriuno (Spelling) program or fabricate an elaborate magnetic reluctor coil set up or even a floating stick as I described.

[Ronald Lambier]

Check out the following.

Building a Capacitive Liquid Sensor: 8 Steps (with Pictures)

Though it was designed originally for a vehicle fuel tank, it will work for your application.

[garage nut]

That is using an Arduino Micro controller, you can add a WiFi shield and send the reading directly to your phone. I love them. Built a little speed indicator for my lathe with one.

[Saltfever]

Well, a lot of nice electronic solutions so I’ll go down a different path.

All this is based on the assumption the weight of the tank is being held by something not sinking into the mud and the tank is not too far away from where you can mount the tattletale gage.

In simplest terms, the idea is to mount a “load cell” under the tank and run a tube to your observation point. You do not have to carry the weight of the entire tank. One corner or one end is all that is needed. As volume changes weight is affected accordingly. Of course, the gage would have to be calibrated. A dot of nail polish at the two positions should work. “Load cell” could be an old brake cylinder, hydraulic jack, air bag; you get the idea . . . :-)