Peter, Which Andy. Andy Shaw gave the original posting for one of his model subs. He and I know each other through the list because I developed the (PIC-based) electronics another guy sells (Skip@rcboats.com), and I think Andy Shaw is one of his regular customers. Alas, I haven't gotten a sub (yet). He is looking for a method of predicting depth based upon water volume, ie, pump so much water in, arrive at (near) given depth. There are several ballasting systems used in model subs. Andy Shaw's uses a sealed air tank which is compressed or expanded (worm drive usually) to vary depth. Other methods include a compressed-air system which blows the tanks, a la US Navy. Toy subs (as compared against "real" models ) use dynamic diving, in which the sub uses wings to fly to a given depth. Often "real" models use more than one method (the only way to stabilize a moving sub, really, is to use the dive planes). Anyway, there is often very little resistance to water entering the ballast tank - it usually has LOTS of holes in the bottom to allow a fast dive. Andy "Peter L. Peres" on 10/18/2000 04:55:57 PM Please respond to pic microcontroller discussion list To: PICLIST@MITVMA.MIT.EDU cc: (bcc: Andrew Kunz/TDI_NOTES) Subject: Re: [EE]: Help water level Andy, you assume that the tank is open to the water and that nothing opposes its movement in and out. This is not the way it works on tiny subs afaik (but maybe you know better ;-). The only ACCURATE way to know the volume of water in the tank is to use a volumetric pump to fill and empty it and count turns. Assuming there are no leaks (hahaha) that will be accurate. But not to 0.3%. If this is some sort of slow research sub then this will be adequate from all points of view, excepting for the pressurized volumetric pump which is a chapter for itself. If you want to go fast, use the navy way, blow air into the tanks to raise, and vent air out the top to go down. And use a valve to close off the water when not changing pressure. Andy, you are into this afaik, what kind of ballast control do you use on model subs ? Peter -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! use mailto:listserv@mitvma.mit.edu?body=SET%20PICList%20DIGEST -- http://www.piclist.com hint: To leave the PICList mailto:piclist-unsubscribe-request@mitvma.mit.edu