Actually the issue is not the depth of the sub (I already have depth sensors using pressure on the sub), this issue is providing closed loop control over the amount of water in the ballast tank. I'm rapidly coming to the conclusion that this is heading towards one of those "If I wanted to get to X I wouldn't start from here!" sort of conversations. I think that using a different type of ballast tank (probably a piston style one as described by Andy Kunz in an earlier mail and as often used by some of the sub builders in Germany) would be a better way to do this. Shame I've already built the thing (and to be honest it works really well - but I do like to try new things!). Anyway if anyone is interested the current configuration can be seen at http://freespace.virgin.net/andy.shaw/subcomsep2000.htm The bottom four pictures on the page show my sub. Click on the images to get a bigger version. You can see the dive module with ballast system etc. If you look closely you should be able to see the 16C71 which currently controls the thing. More details are at: http://freespace.virgin.net/andy.shaw/microcon.htm Andy ----- Original Message ----- From: "Stouchton" To: Sent: Thursday, October 19, 2000 3:49 PM Subject: Re: [EE]: Help water level > How about this: Looks like what is of concern is not the sub's depth from > the bottom, but its depth from the surface. What about using an upward > firing depth sensor... look for the water air discontinuity. > > When in college we used depth finder transducers to communicate to a > submerged sub to give it commands. When we established a two way link, we > noticed a reflection that aligned with the surface of the pond, and timed > the reflection to judge the subs depth. > > Now if we only had side-scan sonar we could find it again ........ > > -----Original Message----- > From: pic microcontroller discussion list > [mailto:PICLIST@MITVMA.MIT.EDU]On Behalf Of Andrew Kunz > Sent: Wednesday, October 18, 2000 7:18 AM > To: PICLIST@MITVMA.MIT.EDU > Subject: Re: [EE]: Help water level > > > 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 > > -- > http://www.piclist.com hint: PICList Posts must start with ONE topic: > "[PIC]:","[SX]:","[AVR]:" =uP ONLY! "[EE]:","[OT]:" =Other "[BUY]:","[AD]:" =Ads > > > > -- http://www.piclist.com hint: PICList Posts must start with ONE topic: "[PIC]:","[SX]:","[AVR]:" =uP ONLY! "[EE]:","[OT]:" =Other "[BUY]:","[AD]:" =Ads