Help with Water Pump

[KeepItSimpleStupid]

Didn't the Hall device, have pull-ups, so both would be normally ON or really dependent on Vgs. Again, a chicken and egg problem, is Vgs lower than the operating voltage of the hall device?

Is it conceivable that both coils could be on at the same time?

I did load the sim, but don't know what to do with it.

What temperature measurement for the coil did you want me to try to do again? My power supply is limited to 3A or so.
I do have another that's probably capable of 10A 32V, but reconfiguring would be a bear. I just got the manual today. I would have to change a transformer tap. It's set for about 12 V right now.

Here is a website with a suggested model for a DC motor. http://www.ecircuitcenter.com/Circuits/dc_motor_model/DCmotor_model.htm How much of each ingredient, well that's your problem.

 

[KeepItSimpleStupid]

@Joe
While your bored and since you will be working with some potentially dangerous substances (Di-Hydrogen Monoxide), you should read this webpage: https://dhmo.org/ and be familiar with it's MSDS https://dhmo.org/msdsdhmo.html

 

[ronv]

Soft Start

Here is a sim of a pump start. Works out pretty good. Current limit at 6 amps instead of 9 minimum voltage a little over 14 volts which if I recall right is higher than the slow speed on the factory controller. Little over an amp at 19 volts - but I faked the back EMF at 12 volts. No way of knowing.. I used a speed of 3000 RPM.

 

[ronv]

Didn't the Hall device, have pull-ups, so both would be normally ON or really dependent on Vgs. Again, a chicken and egg problem, is Vgs lower than the operating voltage of the hall device?

I think they are gate to source. That is how the hall gets its positive voltage. (only one gate negitive at a time) The FETs a P Channel so the source and gate are both at 24 volts (or off) untill the driver pulls the gate low. See post 604.

Is it conceivable that both coils could be on at the same time?

The hall sensor wouldn't have any Vcc if that happened.

What temperature measurement for the coil did you want me to try to do again? My power supply is limited to 3A or so.

If you could set the power supply to 2.15 volts the coil should draw 1 amp. As it heats up the resistance of the coil will go up (and the current down). If you could check the current after say 2 seconds we could calculate how hot the coil will get with the 6 amps applied and the rotor locked.

Here is a website with a suggested model for a DC motor. http://www.ecircuitcenter.com/Circuits/dc_motor_model/DCmotor_model.htm How much of each ingredient, well that's your problem.

Thats the one I tried to modify so it would actually work inside a circuit, but it was beyond me.

 

[leonardason]

You want to run two pumps per controller using two independent controllers. Pumps on about 30 seconds and pumps off about 5 to 10 seconds. Timing could be done using a 555 timer chip configured to drive the relays used to switch the pump(s) on and off. There is a good number of ways to go about this depending on budget and how fancy you want it to be.

 

[salty joe]

@Joe
While your bored and since you will be working with some potentially dangerous substances (Di-Hydrogen Monoxide), you should read this webpage: https://dhmo.org/ and be familiar with it's MSDS https://dhmo.org/msdsdhmo.html

According to that site, DMHO is used by cults, NAACP, KKK, terrorists, in baby food, all kinds stuff. I saw no connection to electronics. Am I missing something?

 

[alec_t]

Way back I suggested using the same or similar simple switcher that the OEM controller uses

You did indeed, KISS. If Joe's willing and able to salvage bits from the OEM controllers (I presume there's one per pump) that would be the cheapest option. But if not, then those chips are pretty expensive compared to the 1084. If we had a schematic of the OEM controller it might be even simpler just to mod the controller

I think the pump uses a P Fet

Is that usual in BLDC motors? From KISS's post-mortem on the pump I don't think we even know if FETs or BJTs drive the coils.

I once tried to build a motor model but all I did was pull my hair out.

I've now reached that point too (not that I had much hair to pull out in the first place!).

I haven't been able to duplicate the 130 HZ oscillation with a short.

Nor can I with the pump model as per your asc file. Try this:

 

[salty joe]

You did indeed, KISS. If Joe's willing and able to salvage bits from the OEM controllers (I presume there's one per pump) that would be the cheapest option. :

Yes, I have six factory controllers that I think I can salvage parts from.

 

[alec_t]

Before you start gutting them, Joe, let's ask KISS, pretty please, if he could draw a schematic of the OEM controller?

 

[ronv]

Is that usual in BLDC motors? From KISS's post-mortem on the pump I don't think we even know if FETs or BJTs drive the coils

I came to that conclusion based on a similar hall chip to your schematic and the one posted in #604. This was the only combo I could find that would match the board lay out.

Nor can I with the pump model as per your asc file. Try this:

When I tried it it looked ok. - attached

 

[KeepItSimpleStupid]

@Joe
It's plain water.
https://en.wikipedia.org/wiki/Dihydrogen_monoxide_hoax

 

[alec_t]

@ronv
I see you've shifted the Schottky anode connection from ground to FET drain. That makes a big difference .
I also found that dropping V1 from 24 to 22 stopped the oscillation (presumably the 1084 is just within its SOA then). N.b. the actual pump motor has no visible Schottkys. Can't explain how the internal FETs ever survived.....simulation shows > 1kV spikes without them!

 

[()blivion]

N.b. the actual pump motor has no visible Schottkys. Can't explain how the internal FETs ever survived.....simulation shows > 1kV spikes without them!

Some FET's have inbuilt Schottky diodes for just this reason. The FDP7030BLS/FDB7030BLS for example. Also, a lot have in built zeners on the gate to prevent damage from static.

 

[ronv]

@ronv

I also found that dropping V1 from 24 to 22 stopped the oscillation (presumably the 1084 is just within its SOA then).

Yes, I think so. That's why I added the .5 ohm before the regulator, but in real life the pump circuits won't try to run until 2 or 3 volts anyway. I am wondering if 6 amps for the current limit is to much. What do you think. (see below)

N.b. the actual pump motor has no visible Schottkys. Can't explain how the internal FETs ever survived.....simulation shows > 1kV spikes without them!

I was thinking they just let the FET go into avalance mode. That would clamp the "kick" to less than 40 volts. That was why I added the zener across the P FET simulaton since Spice doesn't model avalanch. If that is what they do instad of a special FET like B is talking about it is one more reason to hold the start up current low.

Here is a real low budget thought. How about going back to the FET swotch and add 2.5 ohms as the sense resistor? Not sure how big it would need to be to surviive 230 watts for 2 seconds.

Forget that idea.. Only 5X the rated wattage for 5 seconds.

 

[KeepItSimpleStupid]

Coil test in Air:
2.15 V, 0.96A indefinite. No significant temperature rise or current change. Not surprising, you have to be over 2.5A anyway.

 

[ronv]

Hmm, I'm suprised. That's a couple of watts. I would have expected it to at least get warm. But I guess thats a good thing as far as the coil being able to withstand 6 amps.
Could you try it at 4.3 volts?

 

[KeepItSimpleStupid]

I may have to try this again tomorrow and possibly with a better ammeter. I used the internal ammeter in the supply. So, consider these results preliminary: 73.8 F 1.86 A (might be wrong), 4.3 V; 4 min later 103 F 1.79 Amps

The motor laminations and coils probably weigh at least 1 lb. It overloads my 200 g scale. The other scale is MIA at the moment.

 

[ronv]

Here is a link to a calculator. It puts it at 132F. Maybe some inside coils are hotter than others.
I'm thinking the coils are open to the water. Is that right? Big heatsink.

**broken link removed**

 

[salty joe]

Before you start gutting them, Joe, let's ask KISS, pretty please, if he could draw a schematic of the OEM controller?

Is that doable, KISS? If that's asking too much, I understand completely. I could take a stab at tracing the components along with a picture of the factory controller.

 

[KeepItSimpleStupid]

We really don't have to do ALL of the controller. Most of it will be taken from the datasheet of the switching regulator. The power supplies are the most important.

I can tell you this:
1) I removed the OEM PCB today
2) I can't read some of the part numbers
3) The OEM PCB has a conformal coating on the trace side
4) It is a single-sided board
5) There is a C16 470 uf 25 V cap across the motor terminals.
6) It is fed by a 68 uH, 0.37 ohm DCR inductor (didn't even check the frequency) [Output ripple filter]
7) Probably the resistors near F1 and the resistors near T2 AND T3 (Can't read the numbers) set the three output voltages.
8) There is probably a 1000 uF cap on the output, so that would account for the sluggishness.
9) There is all of 26 or so components to worry about and 8 are in the datasheet. Critically, there are about 6.

That LC filter will do some current limiting too.

There is this for sharing schematics **broken link removed** and of, course there is LTSPICE.

I do have so Ketchup work do do a home though.

You do nice pics. A front, rear and pic from front lighted from the back would be useful. I'd do the front and back outside for the best lighting. You can play games with the flash indoors, if you put a piece of paper in front of it to diffuse it.