making a capacitor from a plastic container

i think you got the wrong transistor! still not to worry i got all sorts here, what size transformer do i need? as for the inductor one i was thinking of using a pencil core for the graphite, maybe inside a straw and wrap the coil around the straw, then for a float i could use a ping pong ball with the pencil led stuck into it ok sounds a bit naff but might be worth a try.
how do i measure inductance? i have a LCR meter but i dont actually know how inductance is measured! actually skip that question thats being lazy i should do a bit of research on that with google! is so easy to just ask stuff without at least trying to find out and i really hate that, ive found if i try and find the answer first i uncover all kinds of useful stuff

Don't be tempted to use expanded polystyrene for the float unless you thoroughly waterproof it with an impervious layer; otherwise your float will absorb water over time .

alec_t said:

Don't be tempted to use expanded polystyrene for the float unless you thoroughly waterproof it with an impervious layer; otherwise your float will absorb water over time .

Click to expand...

i was thinking pingpong ball with pencil lead stuck into it and the other end of pencil lead goes into a drinking straw with a coil wound round the outside of it

https://www.electro-tech-online.com/threads/fuel-gauge.111163/#post-910389
I played with a similar project some time back and ended up using 13 reed switches in a brass tube which avoided having my electrical components in contact with gasoline and I used a home made float with magnets in it for my fuel gauge sender.
In the attached drawing, the inner part of the capacitor could be just about any thing, stainless, aluminium, steel, or some metal that's coated or paint to avoid corrosion.
IMHO, you would want the height of one of the capacitor plates to be as small as possible, yet cover min and max level so the change in level has the highest percentage possible.
The outer plate should be glued to the container wall so it can't warp or flex so the space between plates available to be filled with water remains constant.
The circuit board could be mounted to the outside plate to minimize the influence from the leads.
When I built my capacitive gauge, it worked quite well, so with the addition of a couple of comparator set to turn your pump on and off at the proper levels, you should learn a lot
Oh yea, be sure and follow the link in the first post of the referenced link, http://www.rst-engr.com/kitplanes/ June, July & Aug of 2000

interesting idea!loads to play with!