On the main board, there needs to be mods for the two diodes and the caps need upgrading. The snubber looks missing too.
The main board needs the provisions of either variable voltage outputs or two fixed values. If you want to implement a lower voltage for feeding. We may be able to do this with two trimmers. Basically a high value fixed resistor with a trimmer to ground and another transistor switched trimmer in parallel to the other trimmer with or without a series resistor.
It would be nice if a NOT FEED signal was on the daughter card, even if in pass through mode. A small FET could also be used for a FEED signal. The ULN2003 o.c. relay driver chips is one of my favorites because with the inputs open, the output is off, a high is on and a low is off. I've never played with DIGITAL TRANSISTORS. As usual SMT, e.g.
https://www.electro-tech-online.com/custompdfs/2012/06/DTC114EET1-DPDF.pdf Probably would not use them. The only requirement for this signal, is that when unconnected, the motor runs at normal speed. The idea is, if the signal is not connected, the system is in NON-FEED mode.
This daughter card didn't have a PTC thermister, a pump LED, or alarm LED. A power lLED would already be provided. There are three unused LED's on the board. I could look at those circuits a little closer.
The daughtercard doesn't seem all that bad. It may be possible to use a SIP header on one of the existing IC's to mount the board with or without cutting all of the traces. You could also route the signals through one of the DIP locations too.
The DIP construction technique is still viable too where you cut all of the traces from the DIP pattern, insert a socket and then wire the gate to that. Take the other DIP socket and out as many components as you can on it. The transistors needed could use some other pads.
It still offers the idea of building one, doing the testing and then having daughter boards made. Afterall, there are 6 and possibly a spare. I'd ALMOST be inclined of going this route.
@Joe See page 17 (wire wrap wire) of this catalog: **broken link removed** I'll see if I can send you a few feet of the colors I have.
Loctite Takpak
http://www.stanleysupplyservices.com/product-detail.aspx?pn=121-315 can be used to secure wire to the PC board.
A reminder, is that the OEM controller will accept a DC input. The polarity doesn't matter. You will lose another 1.2V or so from the available output.
Personally, I'm still worried about the pump. The Melexis IC really looks like a perfect fit for the Hall device. If so, the application data looks wrong with respect to 24V operation with higher current. I also believe that once you put a MOSFET outside of the IC itself, you then need to provide spike protection outside. Absolute maximums are their for a reason and so 18V offers some comfort when operating at 12 V. Absolute maximums is not a given. ie. Some devices could say survive 30 V, but some may not be able to survive 18.1V.
The "controller" is simple and on the first iteration, protecting the possible fragile motor makes the most sense. The "kill" will likely be from a spike that destroys one of the MOSFETS.
Operating the pumps at the lowest possible voltage can only help. Rotor lock might be difficult to achieve in a highly sloshing tank unless stuff gets gunked up. Regular cleaning will be part of maintenance anyway.
The "POSSIBILITY" of redesigning the electronic commutation has to be considered. The motor driver, as designed, should prevent catastrophic damage to the motor coils. There is no reason to SACRIFICE a pump to make those changes. The cost of a modified motor will mostly be in time and will be messy.
My guess is that there are no other real options. The Tunzie is a closed system which also may not be suitable and WAY TO EXPENSIVE, so even with painstakingly removing epoxy and repotting, the cost would still be OK.
Once you say that your going to make 6 or 7 PC boards, it starts to make more sense to have it include the power supply too. The hard to source parts (inductors) can be pulled from the board.
So, a desoldering tool is in the cards. Everyone starts out with one of these:
http://www.digikey.com/product-detail/en/DP-140/K500-ND/610377 Radio Shack used to carry them. An extra tip is useful. And solder braid which is available in different sizes:
http://www.digikey.com/product-detail/en/80-2-5/80-2-5-ND/306981 It's basically braided wire that has flux on it. When you heat the wire over top of solder, the solder wicks into the braid. When using the vacuum soldering tool, there are times that you need to heat the connection, add MORE solder and then suck it out.
This has definitely been a really interesting thread and I also want to thank everyone for their contributions.
. It's getting that we need a satnav to find our way round this thread to cobble together all the contributions.
