Hey ()blivion, hope you made out on that job.
I wish I had, some times the RRoD just isn't fixable though. At this rate I'm basically doing it for charity. Oh well, I got my fingers in to other investments.
I was told that unless these DC pumps have a soft start, they will fail prematurely.
This is just my opinion (Completely biased opinion, I DON'T want to add more to this layout... LOL) But I don't think a soft start is going to be realistically necessary. Despite what you were told and what the manufacture said. This stuff's pretty tough.
Judging from the pictures of the pumps you linked us, these units are
sealed inrunner brushless motors, with the controller installed in the pumps housing. The parts that would be the weakest and most likely to break in such a system under the stress of hard starting would be the internal FET's. But they are probably heatsinked to the case of the pump, making them effectively water cooled. If not then your pumps were not designed very well. Even so, with the FET's positive temperature coefficient, the hotter the internal controllers get, the less current they conduct, causing negative feedback and inherent stability... to a certain degree.
Now... if you REALLY just have to have some form of soft start... for the pumps sake if nothing else... then you *COULD* hook up big capacitors to the gates of the IRF3205 FET's. Then a (larger) resistor up stream of that. The delay will make the FET's switch slow enough to more or less make your soft start circuit, based on the RC time constant and the FET's threshold. (Go ahead and simulate it if you can Alec_t) This would take less parts and less soldering and assembling for a soft start than has been suggested so far. The only draw back is that our boards FET's will have to dissipate a little bit extra power. This is do to operating in linear mode for a longer time than the original circuit would. But that time will be short, not very often, and with such low power compared to the max power of the FET's that there is no worry of destruction at all. At less than 1/10 a second of linear operation time, with a cool down period of ~30 seconds or more where the FET's are either fully on or fully off, they probably will not even get warm. This is what I would at least try if I even cared about soft starting at all, since it's easy to do and takes few parts. I can add this as an option to the layout later if you want.
Speaking of layout... below is a preliminary final draft of the
original pump circuit (post 99, I think). Note that it's not perfect yet, I'm sure there are mistakes in it. So were going to need some more eyes to look at it and find them before you commit to building the real thing. Also note that I used my own personal style on this when routing all the connections. This style may not fit your soldering ability. Don't worry, I do plan on making a more conventional layout eventually when all ideas and suggestions have settled down. Plus you do have two boards and more extra parts should you mess up *THAT* bad. The wire connections to the solder side are all color coded for easier navigation and identification, except the red main 24v line across the top, which is coded blue. Also, the connections/controls to pump 3 and 4 are swapped, a little confusing but it doesn't effect the way it works. *FINALLY*.....!!!TAKE SPECIAL NOTE OF WHICH WAY ALL THE PARTS ARE TURNED!!!. Get a FET, Diode, or the regulator backwards and . . . *POOF*. . . The magic smoke that makes it work gets set free, never to return.
View attachment 61124
IF (WHEN) YOU SEE MISTAKES, PLEASE TELL ME THANKS!
Usually when you build with point to point proto board you don't do a lot of running lines on the solder side of the board. But when I do it I like to make sudo-traces with bare copper wire, solder, and the excess wires that poke through from the parts I am adding. I like to think this makes things more sturdy since you reduce the number of actual wires going every which way, which are loose and can catch things. I also like to think this improves a bunch of other stuff like current, cooling, ground loops, and appearance. The problem with this way of constructing is it involves more soldering and the soldering of longer joints. Both these can cause problems for people that are less experienced at soldering. It's relatively easy IMO though, considering you could be soldering 48-pin TSOP I FLASH chips (My WRT54G). Or surface mount capacitors and resistors slightly larger than grains of salt (DS Light I just fixed). Or you could be reballing BGA Xbox 360 GPU's by hand (Take a guess who's doing this right now...?), All of which is MUCH HARDER than what I'm asking you to try doing, trust me.