Hi Olin, Here are a few comments on how I (and others often use ballast tanks....), I sent it to some-one that asked off list... Basically the way I use the ballast tanks in my sub is to flood the tank until the sub is essentially neutral in terms of buoyancy. Once this has been done actual depth control is performed using the control surfaces on the sub (rear and forward planes). I sense the actual depth by using a pressure sensor. So in terms of the ballast tanks what I need to do is to ensure that the correct amount of water is taken on to give me the neutral state. The easiest(!) way to do this would be to add water (slowly)to the tanks until the correct state is obtained, then measure how much water was in the tank. Then whenever I want to dive I simply command the tank control stuff to take on this exact amount of water. Now because of issues like type of water (and water temp) the amount of water needed to be taken on will vary from day to day. So what I want is a simple setup routine that I can use whenever I sail. Simply put the boat in the water, run the tanks until the tower is just under the surface, then mark the water level and store it in eeprom. Then away we go. Only problem is the measuring how much water bit! Sigh As I think I mentioned in another post there are better tank designs (piston tanks) that make the closed loop stuff much easier. What I was (I'm going off the whole idea!) looking for was a way to used closed loop with my current design! Oh one other bit of information. Simply monitoring the state of the water level outside of the sub does not work very well due to the relatively long time it takes the hull to actually flood and settle (hence adding water very slowly in the section above). But once you know how much to take on you want to do this as quickly a possible.... Andy ----- Original Message ----- From: "Olin Lathrop" To: Sent: Thursday, October 19, 2000 6:44 PM Subject: Re: [EE]: Help water level > > 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. > > So why do you need to know the amount of water in the tank? Isn't this > something the servo controls implicitly in an attempt to maintain the > desired depth? > > > Anyway if anyone is interested the current configuration can be seen at > > http://freespace.virgin.net/andy.shaw/subcomsep2000.htm > > Pretty cool, Andy! So when will this be fully operational torpedoing those > annoying jet skis? > > > ***************************************************************** > Olin Lathrop, embedded systems consultant in Devens Massachusetts > (978) 772-3129, olin@cognivis.com, http://www.cognivis.com > > -- > 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: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics