Help with Water Pump

[alec_t]

Nice pics, KISS. Looks like a bit of Dremelling would free up pin 5 for shut-down control, and the top half of the components could be used more or less as is for 2-speed supply (don't think Joe will need 3-speed?). Is the casing for the controller high enough to leave room for a small daughter board with current-sense and trip components?

 

[KeepItSimpleStupid]

I think there is a fair amount of room. The LEDS are on large stndoffs and a 1" tall heatsink has to clear the cover, so you probably have 1 inch of head room.

Most of your circuitry, think could be placed on a DIP header and the one IC can occupy one of the IC spaces.

There is one diode that needs accommodating and I haven't looked at that. The motor diode can easily be mounted on end.

I think your design lacked the two diodes and the snubber that you had in one of your other iterations.

One drawback, it does make the design big instead of compact and there may be SIX of these.

So, not sure if the case is viable for six, but it surely gives you a ready made switcher and it looks like your "glue" will fit.

I just hope Joe understands the concept.

I didn't look at the potentiometer values, but even they are a POSSIBILITY" for speed 1 and speed 2 and so is a 10 turn trimmer.

 

[salty joe]

,Nice pics, KISS.

+1. Thanks KISS.

(don't think Joe will need 3-speed?).

I don't need three speed. If we could make these pumps obey your tidal schematic from post 367, that would be outstanding.

One drawback, it does make the design big instead of compact and there may be SIX of these.

If this thing ends up being bulky, that is no big deal.

I just hope Joe understands the concept.

I'd be a liar if I said I understand most of what you guys talk about. But what this sounds like to me is taking a part of the factory controller and adding some magic to it and ending up with a big controller that works.

 

[()blivion]

For a second I didn't understand that PCB and was thinking that it was some how intended to be run off line!!!!

I was cringing with disgust at the blatant safety violations. Then I realized that the transformer is low voltage AC and needs farther processing. Then it didn't seem so bad.

 

[KeepItSimpleStupid]

Don't you see the InvisaPAK-64 mini-webserver IC? It's the one embedded between the layers of the board or the MEMS module that moves the potentiometers that runs on Cosmic Rays? It definitely runs online.

Now, go find me an LM2576 Spice model.

 

[()blivion]

LOL @KISS. You should be PUNished for your word play.

Now, go find me an LM2576 Spice model.

It's about a billion years to old for SPICE modeling according to **broken link removed**.

OK, maybe an exaggeration, but there *IS* modeling software in that link... If you.. you know... have a MS-DOS 3.3 or later machine handy

 

[ronv]

some sims

I took a look at a start up with the motor modeled as an inductor with back emf.
The only thing I noticed was the first pulse is kind of slow because the motor FET is not turned on hard. The good news is the current is still low and it is only the first pulse. By the next one the voltage is high enough to turn the FET on better.
The other thing to keep in mind is that the start will be much slower than what Joe measured with the high current 24 volt supply or with the slow start from the first controller.
I added the small filter and measured the ripple current in the caps. It looks like the 1000 ufd. would need to be a 105C low ESR type, the 100Ufd. is coasting. Not sure what type is in there. Maybe I can tell from the picture.
I removed the clamp diodes and didn't see any glitches but that assumes the pump works the way I think it does. For 50 cents might as well have them.

 

[KeepItSimpleStupid]

@ronv

Since you basically have the schematic, here are the component values from the OEM supply.
The manufacturer of the caps is SHK and they are 105 C rated.

RAW DC supply: Full wave bridge 8A at 800 V (24 VAC 35 VA incoming)
RAW DC filter: 2 x 1000 uf @ 50 V in parallel
Converter cap & inductor: 1000 uf @ 25V and a 134 uH with a DCR of 0.047 ohms
Output filter: 470uF @ 25V and a 68 uH inductor with a DC resistance of 0.34 ohms


I have a hunch: The hall sensor is rated for 18V and the system operates briefly 10-15 sec or so (memory here) at 22.5 V. Ratings are never spot on. So, I'm guessing that at 12V we would have good reliability, from 12-18 V OK reliability and from 18 to 24 V marginal reliability.

The datasheet fr this part (US891) **broken link removed**

states this:

"These features are combined with the Melexis
patented no-VDD design to fit the IC in a small 4-
pin VK package."

If that's true, then this company may be the only company making the No Vdd hall sensor.

It would also seem that the figure for the other IC with No Vdd that had a suggested P-Mosfet high current option that you should include the diode protection for the FETs when you don;t use the internal ones.

Therefore, I'm going to suggest based on the power supply pump polarity was inconclusive and the no Vdd patent

1) The Melexis US79 3 pin part is a good fit.
2) The +12, +24 V figure may have been misinterpreted.
a) 24V is too large of a voltage
b) The 18 VDC spec of the US79 may have been ignored because of the figure.
3) The last figure in the US79 datashhet needs to include diode protection when external FETS are used.
4) 12 VDC operation would not necessarily be reliable.

 

[alec_t]

I think your design lacked the two diodes and the snubber that you had in one of your other iterations.

Probably. I usually forget something . It's getting that we need a satnav to find our way round this thread to cobble together all the contributions.

So, not sure if the case is viable for six

One switcher per pump, hence one mini daughter board / header per case if we go the modded OEM controller route?

 

[KeepItSimpleStupid]

One switcher per pump, hence one mini daughter board / header per case if we go the modded OEM controller route?

6 pumps x 8 cm x 15 cm is a lot of real estate. Then add wave and tide controller boards.

 

[alec_t]

6 pumps x 8 cm x 15 cm is a lot of real estate.

I thought you were all in favour of a modular system, KISS . Modules would occupy more space than a combi system. The real estate is something Joe already has.
The wave and tide controller boards (could be combined) shouldn't take up much space.

 

[4pyros]

I think this may be more like the hall IC in the pump motors.
**broken link removed**
In witch case it should have all the protection built in.

 

[KeepItSimpleStupid]

Yes, I really think it is, but there issues:

1. The figure on the last page shows an application using P-channel MOSFETS to increase the current which all makes perfect sense, BUT, it shows a +24 and +12 higher current application. The resistors are close. If the IC has an absolute maximum Vdd of 18 V, then 22.5 VDC (The max of the OEM controller) should be too high for an operating voltage, right?

2. Wouldn't adding P-channel MOSFETS DEFEAT the internal overvoltage protection?

I'm saying that the datasheet could be wrong:
1. It's not suitable for 24 V operation (last figure +12, +24)
(The rest of the datasheet says 18V max)
2. MOSFET protection should be external when using external MOSFETS.

 

[KeepItSimpleStupid]

OEM High voltage power.

The attached file is from the LM2576 datasheet PDF page 20.

1. The input would consist of a 240:24 VAC, 35 VA xformer, feeding a 3 A fuse, feeding a KBU808 8A 800 V bridge rectifier. That becomes the Unregulated DC input.

Make the following component changes from the PDF page:

Cin 100 uf ----> 2 x 1000 uf @ 50 V SHK electrolytic caps in parallel.
D1--------------> Likely the same IN5822
L1 150 uH -----> 134 uH with a DCR of 47 mill-ohms
Cout 2000 uf ---> 100 uf @ 50 V
L2 25 uH--------> 68 uH with a DCR of 34 millohms
C1 100 uf ------> 470 uf @ 25V
R2 50 K pot-----> 22,000 1/4 W 1% MF resistor
R1 1.21K -------> 3K 1/4 W 1% resistor (note 1)

Additional part: A metalized polyester bypass cap from pin #1 to pin #3 is on the OEM controller.

The regulator is the non HV part which has a 40 VDC maximum input instead of 55 VDC.

Note 1: Additionally the collectors of T1 and T2 are independently connected to a 5200 ohm 1/4 W 1% resistor and a 2200 ohm 1/4W 1% resistor. The emitter connects to ground. Don;t know what transistor (T1 or T2) selects what resistor. The free end of the 5200 and the 2200 are connected together and connect to the junction of R1&R2 in the attached page.
If you remove T1 and T2, the output voltage would be 10.25V and would not change. If the 2200 resistor was selected by T1 or T2, then the output voltage would be 22.5 V. If the 5210 ohm resistor was selected then the output would be 18.72.

A reversed biased diode is needed from the OUTPUT VOLTAGE (DC jack) (Junction of C1 & L2) to ground. The band of the diode goes to +.

Another diode is needed from Pin #1 of the regulator to the junction of (C1 & L2) The band would be connected to pin #1 of the regulator.


Cout and C1 needs the voltage upgraded to 50 VDC and capacitors with a high ripple current should be used. i.e. capacitors appropriate for switchers

There is a 5V regulator on the board, I need to look at that more carefully. I can tell you it's driven by a 1K series resistor (Raw AC/DC input) and a bridge consisting of 4 X 1N4007 diodes.

 

[salty joe]

The response and help on this project are way, way beyond anything I could have hoped for.
Thank you Alec, Thank you KISS, Thank you Ronv, Thank you ()blivion, Thank you 4pyros. Your generousity and expertise are mind boggling. Who knows, maybe one day I'll get an opportunity to do a favor for you.

 

[alec_t]

Here's one possible add-on as a daughter-board for the OEM controller board
View attachment 65167
The real estate is only a 2" square of strip-board (possibly less; I made no attempt to tidy this up)
View attachment 65168
Mods to the OEM board involve 2 track cuts and 5 drilled holes (shown in yellow), plus unsoldering of the base resistors of T2 and T3.
View attachment 65169

Circuit explanation
U1a-c/D2/R7/R8/Trimmer/C2 form a gated oscillator defining the overcurrent trip time (settable with the trimmer) and the interval between successive trips.
If the control input (pin 1 of U1) is high, current >3A (as sensed by Rsense connected on the high-side of the pump supply) causes Q1 to turn on and pull pin 8 of U1 high thus gating-on the oscillator.
R3/R6/D1 bias C2 to a voltage just below the lower Schmitt threshold of gate U1a, so that the first trip time isn't much greater than successive trip times (which it would be if the cap voltage had to start from 0).
When a trip occurs pin 2 of U1 is pulled low. If either pin 1 or pin 2 is low pin 3 goes high to turn off the LM2576.

Edit: This circuit could be used with little alteration to drive a power FET instead of the OEM controller, if Joe would prefer not to hack the OEM boards (and to save space).

 

[ronv]

Looks good.

Only one thing bothers me now. That is if the pump will reliably start at 10 or 11 volts. Hopefully this isn't the cause of the controller reliabilty problem.

 

[KeepItSimpleStupid]

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.

 

[ronv]

On the main board, there needs to be mods for the two diodes and the caps need upgrading. The snubber looks missing too.

As I mentioned earlier, there should be no need to update the caps or add clamp diodes.

Here is the low esr 105c cap spec..

http://www.mouser.com/catalog/specsheets/EEU-FR Data Sheet.pdf

Here is a write up on avalance mode for the FETs:

http://www.irf.com/technical-info/appnotes/an-1005.pdf

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.

I agree on the hall. I suspect there is a 24 volt one somewhere that we have not discovered. I don't think they would try to run them outside the maximum spec.

When the low side fet was in there (which it is'nt any more) protection was required, but not now. The motor current recirculates in the motor FET.

This has definitely been a really interesting thread and I also want to thank everyone for their contributions.

I'll second that, but I'm still betting we can get the number of posts over 1000.

Second subject:
After looking at the IC soec. and some specs on pumps and fans I am still concerned over the low start voltage. I keep thinking it should be current not voltage that counts but everything talks about voltage. It would sure be nice if we could test one to see how close the design is to the limit. At least with this circuit it won't just sit there cooking, it just won't start.


http://www.ti.com/lit/ds/symlink/lm1577.pdf

**broken link removed**

We could be down to as little as 8 volts where these guys spec. 14 as a minimum.

Somethig to think about.

 

[KeepItSimpleStupid]

@Joe
I sent you a surprise envelope today. There was one part that I really wanted to enclose, but I could not find one. I also sent you a weird male and female header. They can be cut. They might be too high, but they illustrate what can be done. Picture mounting putting one or two female headers where an IC is and then the male header facing down from the bottom of the daughter card. There are some lengths of wire wrap wire (insulated and uninsulated) and some odds and ends.