Tch, tch! Not good for the bearings.I ran this with the pump dry.
@ronv
The LF150 PTC limiter in your post 523 looks a promising candidate. Rotor lock (11A) would trip it in ~ 2 sec according to the spec. Not clear how long it would take to reset itself?
From what I've read they reset in a few seconds if the fault is removed. There is some "leakage current" in the tripped mode (milliamps) that keep it tripped. So it would reset in between each pump cycle. Certainly seems like the simpelist solution.
Need to check the safe operating area of the slow start FET to see how long it would stand up to the high power disapation (14v X 5 amps) is a lot of watts.
Yes, we'd need to look into that.Need to check the safe operating area of the slow start FET to see how long it would stand up to the high power disapation (14v X 5 amps) is a lot of watts.
Yes, I was. I've drafted a design for a voltage-controlled reg so that 18V would be the normal output but it could be programmmed to go lower for the low-speed 'feed-time' mode if required.Are you considering using a switching regulator to drop from 24 V nominal?
I wouldn't class that as 'absolutely need', but it would be handy for Joe to have if it's a straightforward mod and you have the time (and Joe isn't concerned about voiding the warranty!).A modification to turn the OEM controller into a variable 3A power supply for testing purposes?
If you take the BLDC explanation that I linked to and simplify it down to a 2-pole stator and a 2-pole rotor does that make sense? The Hall sensor only has to provide an on/off output to drive one transistor base/gate.It still bothers me, that the commutation doesn't make any sense.
If you take the BLDC explanation that I linked to and simplify it down to a 2-pole stator and a 2-pole rotor does that make sense? The Hall sensor only has to provide an on/off output to drive one transistor base/gate.
So one can stay on indefinately? If so, does that explain the solder blob? That would work.
Dyson has developed gone to 104,000rpm brushless DC technology to combine efficiency and manufacturability in its latest handheld vacuum cleaner.
"Because it is two pole, it is very simple, and when you make it run at high speed, you can make it incredibly small," Dyson's Andy Clothier told Electronics Weekly. "It is 84% efficient, which is high at this small size. At this voltage and power level, to get a brushed motor this efficient is very difficult. Our old motor was 40% efficient."
Overall the motor, dubbed DDM (Dyson digital motor) V2, is 55.8mm in diameter and weighs 139g.
Notoriously tricky to start predictably, the motor uses asymmetric poles. "You have to have enough saliency on the poles to make it start in the right direction," said Clothier.
With brushless motors, there is a choice: sensored or sensorless - incorporate a magnetic sensor have tell the electronics when to switch coil polarity, or use a more powerful processor and sense rotor position from back-EMF.
"The way we designed it was to integrate the electronics into the motor. It is the least expensive way of doing it," said Clothier. "The PCB is in exactly the right place to carry a Hall sensor."
Control comes from a simple 8-bit Microchip microcontroller, not one that has special motor control peripherals, said Clothier: "We used our own motor control technology. To get the absolute best, we make sure the motor produces constant power regardless of speed and the battery voltage."
The power control is largely open loop - determined from detailed knowledge of the motor and impeller dynamics, combined with motor speed derived from the Hall sensor. Up to 3,300 adjustment per second are made.
The battery is either six or four lithium ion cells depending on the vacuum cleaner model: DC31 (pictured) or DC30 respectively.
Up to 10A at 20V, and up to 13A when the battery voltage drops, is switched into the motor by an H-bridge of mosfets.
To get current to change direction fast enough with such a low supply voltage requires low-inductance windings - in this case twin coils wound in parallel.
The whole motor, and its mechanical and air environment, was modelled extensively.
"That is where most of the work went in: we developed our own simulation tools to model the whole motor including its electronics," said Clothier. "We also used some commercial finite element software for spot checks and detailed work, but 90% was designed by our own software."
Modelling, for example, showed the sintered neodymium permanent magnet rotor was small enough not need a carbon fibre sleeve to stop it flying apart at full speed.
"This is the kind of thing that looks simple and needs a lot of work," Mathew Childe told Electronics Weekly. "We modelled the motor dynamics and made sure it was stable against vibration right up through its acceleration range, checked the acoustic noise and checked the resonances."
The team also built prototypes that were tested using accelerometers and laser displacement instruments, then fed-back the results. "All the way through, you learn to improve and adapt the modelling process," said Childe.
High rotational speed put means the impeller can be small, but means it is subjected to high forces. "Most people would use aluminium," said Childe. "Through simulation we designed out as much stress as possible and so we can make the impeller out of carbon fibre-reinforced polymer."
A plastic impeller and steel shaft means welding is out of the question. "Everything in the vacuum cleaner is dependent on bonding," said Childe. "We have had an engineer working for two years on adhesives for the product."
The motor has been dubbed DDM (Dyson digital motor) V2.
What was effectively DDM V1 was actually dubbed X020 and is the switched reluctance designed used in the company's Airblade hand dryer
Thanks, every nickle counts. Efficiency has been a major theme for me with this entire project. If it is an easy fix, I'm all for it. BTW, the idle pair of pumps in the tide simulation "flick" or give a little spin every minute or so to keep fish from sleeping next to pump.@alec, @Joe
Are you considering using a switching regulator to drop from 24 V nominal? This thing will run 24/7/365, so there may be an incentive to go green. Say 6 V drop at 3A or 18 W conservatively. At $0.10 USD /KWH that's $15.78 USD per year per operating pump that isn't doing anything but wasting money. Agreed, the analysis isn't perfect, assumes 1 pump 24/7/365. From what I remember in the thread that effectively means two pumps at 24/7/365 for one of the controllers. The power supplies may be 85% efficient. e.g. the OEM switching regulator and the supply Joe bought to run these pumps. But then, the amount may not be too much in the grand scheme of things.
The reg reguires 1.2 V differential and Joe specified the max output of 24 VDC which I don't beleve for a 24 VDC supply. Joe, could you measure the min and max output again?
Tch, tch! Not good for the bearings..
Hmm. With the pump in air it will accelerate faster than in water. For designing current protection we'd better assume that the start-up time is ~ 1 sec in water if running from, say, 18V (which is what I reckon the long-term average for the OEM controller is). From KISS's analysis, and without knowing the power-handling characteristics of the transistors in the pump, I'd be wary of running the pump 24/7 from 24V. At 18V the pump output should be ~ 10klph (cf 15klph at OEM peak).
Will that be enough?
In that case we could probably get away with using both at their minimum setting. A further 0.6V or so would be lost by using a series power diode (for PS protection against back-emf, as KISS suggested).I have 2 PSs. I was going to run the tide with one and the wave with the other. The min/max for one is 19.1V-24.1V. The other is 20V-30V.
Is that the real layout of the board in post #571?Maybe...... except that I can't make that driver circuit fit the pcb layout in Joe's pics. The resistors would be in the wrong place.
As far as I can tell from Joe's pic (post #411). I'm guessing the transistor terminals but I think the tracks are right. KISS might be able to confirm?Is that the real layout of the board in post #571?
Perhaps. Dual-element N- and S-sensitive Hall ICs do exist it seems, e.g. the Micronas HAL740. That's a 4-legged beast, and its outputs are open drain, so it doesn't tally with what I've assumed in the circuit.Though considering how simple and "budget driven" the design looks, I would assume the Hall sensor to be simpler and more main stream than what you have.
alec said:A further 0.6V or so would be lost by using a series power diode (for PS protection against back-emf, as KISS suggested).
alec said:but I think the tracks are right. KISS might be able to confirm?
ob() said:KISS figured it would work. He was saying something about body diodes being backwards from normal or something too..... IDK, he can explain what he meant by that when he gets on.
alec said:KISS, can you check if the Hall IC in the pump could have had 4 legs? I see a detached wire on the right of the second of Joe's pics (post #411) which perhaps could have gone to the IC?
alac said:KISS, can you check if the Hall IC in the pump could have had 4 legs? I see a detached wire on the right of the second of Joe's pics (post #411) which perhaps could have gone to the IC?
We've already got reverse-biased Schottkys from drain to V+ and from drain to ground (V-). Not enough?The diode just gets connected reverse biased to the power supply
I was just wondering if the Hall IC package had a stubby tab (as per the HAL740) opposite the 3 leads and perhaps that stray wire had become detached from it during the pump dismantling; though the photo doesn't show any obvious tab-like bit nearest the camera. For the HAL740 the tab is the ground connection.No question, 3 pads, so 3 leads?
I'm told custom chips are pretty cheap from China.Maybe RESUN has some friends in the IC business?
alec said:We've already got reverse-biased Schottkys from drain to V+ and from drain to ground (V-). Not enough?
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