Really? Hmm, I would've thought otherwise. Make the motor large enough and do some electronic trickery to reduce the current X number of seconds after each step coil is energized, or something like that.

Sorry griffinru -- my post was put up while I was still editing it. So you didn't see the final version.

The stall current thing is a 1/X relationship current vrs RPM -- non linear with RPM. So at stall, current is infinite (limited by motor phase resistance -- not much of a limitation.)

Stepping through the rocks would be hard, while smooth rolling would be great. Stepper's are good when you need holding torque, but they are not efficient as you can see. While at mid-to-high RPM you can stall them at unexpected load.

Brian,

Think about a brushless motor as a stepper motor with magnets and a synchronous controller. :)

Yeah, I understand that, but I figured since there are so many more phases to get more samples from, slow running would be smoother. In effect, a hundred-phase BL motor.

In a regular 3-phase BL motor, you have to get so many revs before you can get a good reading on actual rotation, so slow/stall conditions are harder to deal with.

Just throwing ideas out, sometimes it's nice to think outside the norm...

Post #666...
It doesn't matter, you do not like sensors, it is alright.
You have interesting opinion about optics.

I have done some research on stepper type motors for crawling, and the main issue is the resistance of the phases (in effort to prevent ridiculous amp draw) and that the ESC would have to be matched to the motor in terms of PWM so that the coils didn't blow under load.

It would be much simpler to just throw a sensor on an outrunner to bump up the starting torque and zero rpm sync, then switch to sensorless at around 500 to 1000 rpm depending on motor. Some over current protection might be a good idea.

There are 2 phases (sometimes 4, still wired as 2) and just 200/400 slots rotor, think sync as Patrick said. The only feedback is encoder...

I would guess by the layout of the MGM, they have more (or larger package) fets. If my third try on the MMM fails, I would be willing to Frankenstein together my MGM power boards with the MMM brains for a totally bulletproof ESC (sorry Patrick).

GriffinRU: can it be done? (brain transplant)

Not really,
The trick is at fet's drivers not in fets. While they do have nice layout, CC's board is also nice. But there is a small difference which is clear on the board and inside firmware as well. I think if Patrick will do the same, he might get similar performance with current firmware.
But, Frankenstein, in this case would be very complicated.

New MGM's I think have the same fet as CC, if you check old 160Amps ESC had 4 boards now 160Amps has 3 while 224Amps has 4...

I guess I will have to install the MGM in my truck this weekend (just got it back with 3.23 firmware), since it looks like I will have to wait a while on the MMM sent in for replacement. Maybe the new firmware on the MGM will allow me to run reverse without all the quirks (crosses fingers). Castle IS by far better on the software side, I run reverse on the mm's (as well as the MMM for the whole 5 min I got to run it) and never worry about it, until I need it, it just all works like it should. I have had all kinds of wierd things go on with the MGM at one time or another. One nice thing on the MGM is the ability to read out the max temp (internal) and the amps (hint, hint Patrick).

Let me know how your MGM does with the Neu.

Sure thing.

I have the new software and run it with the medusa with none of the reverse quirks that it had running the 600xl. The medusa's being four pole should be quite similar to the neu in behavior I would think.

I've had great success with my MGM controller and the updated firmware. I run a Neu 1512.

Some kind of telemetry feature, even a basic one, would be nice on the MMM- download the info via castle link to your PC or laptop. Temp, current draw, motor rpms would be awesome- even if it had to be a little add-on box or something that plugged into the main PCB, like the fan does or something.

Intelligent Q now:

With regards to the fan issue, can I get a definative answer as to what Castles take is on case-modding the MMM? I would like to do something like BrianG has done and turn the esc into a convertible, but use my own larger (more robust :whistle:) 40mm fan to improve cooling, but I dont want to void my warrenty (modified case can be re-used even if the PCB went poof a bit...).

I like to think of it this way; a heatsink on an esc only works with good airflow, and to get good airflow the esc needs to be posistioned like so. Unfortunately, this isnt always possible, so a fan is therefore used to provide artificial airflow, replacing the natural airflow that would be present as the vehicle moves along at speed (certain chassis and shell designs prohibit airflow). I dont believe a fan should be used as a forced-cooling device like a desk fan pointed in your face, that does imply that that the esc runs too hot under normal conditions. Replacing lost or unavailable natural airflow with a small fan is perfectly acceptable in my view. Plus, fans look cool....

What version is yours.

guess I better get busy and get the thing installed.:whip:

So the new version of the firmware is working good then. Is any of you guys with the new firmware experiencing acceleration when braking? what about no braking at all when it doesn't accelerate?

3.22, I bought the controller from another guy on here who had sent it off to MGM to have it updated.

On the 600XL I experienced the issues with acceleration when braking and different reverse quirks, however on the medusa these are nonexistent.

Ok, I guess I won't be selling my 2 MGMs now. I will just send them to MGM and get the 3.23 firmware and after I get them, I'll report back.

I ran mine for a few this morning, seems like a new controller. I will post more results in an appropriate thread this evening after more running. Sorry for the highjack.

A question for the engineers out there :lol:. Would it make sense to have a lot of MOSFET (Lets say a FET driver already was chosen and powerful enough to drive close to 300 FETs) on a controller to make each MOSFET work less to provide the power some of us need? Lets say I have a design for a controller with 240 MOSFET total, 80 per board, would it actually run cooler because there will be less load for each MOSFET? The reason for this is I see a few controllers with less FET that actually run a bit hot, but a controller with the same spec (AMP rating wise) with more FETs will actually run cooler. One example is one of my 30A old Kontronik controller runs cooler then some of the latest 35A controllers.

Well, I would think that the more surface area you have to dissipate a set amount of wattage, the better. More FETs translates into more surface area to handle the same wattage (heat we need to dissipate). But with that said...

The only thing I would be conecerned with is if there would be some sort of inefficiency with driving that many FETs? I mean, each FET is only efficient to a certain point, and what about switching losses? More FETs means more wattage lost due to switching loss no?

Interesting problem posed lutach. I'm going to keep an eye on this thread to see what the general concesus is from Patrick and Artur (and anyone else who's an EE- which I am not).

I've seen some DC/DC converter that was small and packed a lot of FETs. This was in one of the many electronic magazines I receive and the company was claiming they don't require a heat sink. They were saying something about a dense PCB, which in my point of view means a lot of components placed as close as possible. The Tekin R1pro for example, packs a lot of FET in a small package. That's why I'm asking this question with the switching part covered. I would think the more the FETs, the less heat will be generated to make a certain amount of power. I attached a couple of pics that shows some controllers that are proven to be really powerful and here is a link of another one http://www.rc-monster.com/forum/show...6&postcount=16.

Very nice post, Five-oh-joe :great:

More fet's bigger foot print more surface area to dissipate heat, more overall losses...
Fet's driver need to be very nice or need to be on each FET's board, but try to sync them...possible.

Let's do quick theoretical calc, if you can drive fet's as fast as fet can switch (non-real) then 300 fet's you meant total, so 50 fet's per leg/100 fet's per phase. Dynamic losses would be ~10W on fet and ~10W on diode, check attached image. With 3 phases your loss would be ~60W just for switching at 15kHz PWM, that would cook ESC pretty fast without proper heatsinking, by the way can be a nice heater :)

It would be nice to keep dynamic losses matched to pcb heat dissipation capacity.

I am pretty sure, Patrick can add/correct my post if required.

Artur,

What I was getting at is basically looking at the Tekin R1 controllers. They are small and pack a lot of FET for the space so if we were to make them a little bigger and add more FETs, would that make the FETs work less to produce the same power and thus having less or the same amount of heat? I own a Etti 200A controller and I ran it a few times. This controller is only rated for 5S lipos and I ran 5S on it and the controller didn't even get warm. This controller doesn't have a heat sink like most car controllers and I was surprised on how cool it was. My set up at the time only pulled 98A spikes, but I ran my truggy for 7 minutes. The one picture in my previous post shows a 6 power board controller that puts out a lot of AMPs. Something like that would be great for the surface side of the hobby.

There are alot of fets on those escs, but it isnt anywhere near 300- I would assume there is there is some nice graph somewhere that would show the maximum number of fets you could use (of any size/voltage/current rating) before they did more harm than good...

I agree with using more fets though to lower temps/work load- makes perfect sense.

Luciano,
From 50 fet's (300 total) to 8 fet's (48 total, Tekin R1PRO) your dynamic losses falling from ~20W to 3.2W, pcb can absorb that. Conduction loss at 100Amps @25C with 8 fet's ~2W -> as you can see great combo.
Dynamic losses are small with less fet's and becoming dominant with more, so balance should be found in-between on design stage. Where entire ESC been layout and verified step-by-step, you just cannot add fet's boards without penalty.

I can add graph later # fet's vs dynamic vs conduction losses, but it is strongly driver dependant and load as well...

Lets assume you have a quad power board R1, would that make less then the 3.2W of dynamic loss? The controller will have more FETs and each one would be working less to make the same amount of power that a single or double power board controller would be. Another example which is completely off topic would be in car audio. I had a 4 woofer set up in my car and it was loud (Load enough to have neighbors complain that things were falling from their furniture's :lol:), but then I went up 4 more for a total of 8 woofer wired for the same load to the same amp and it was blistering loud. Each woofer was getting less power from the amp, but they were putting out higher db at the same time. The design that I have in mind (Artur I will send you 2 examples via e-mail) will be a total of 240 small FETs with a datasheet rating of 10A each and they come in 30V and 60V. Each power board will have 80 FETs so 40 in the H-Bridge you mentioned in another post. I'm just throwing out ideas basically to see a rock solid controller that is better then a Schulze 40.160, but a tad smaller for around the same price.

Artur,

I sent you the e-mail with the 2 photos. Let me (us) know what you think of those controllers.

We will continue next week-end, need to go.
Dynamic loss is fixed with fet, each fet has a capacitance in the gate (value dependant on temp, load...) to charge and discharge this capacitor requires energy, so more fet's more energy.
Conduction loss would be related to Rdon and more fet's lower value, so good thing, but as you can see you need to keep balance...

I will check e-mail later, and let you know.

Keep in mind TO-220's and D-Pak's are huge packages and can easily absorb ~1W without heatsink, but they are not as fast as smaller, tuned fet's.

Your Amp has a pretty sized heatsink, right :)

Heat sink issues will be no problem as the design I have in mind will allow for a very good heat sink to be used without sacrificing size (Compared to much larger ESCs). Look at this article in Power Electronics Technology http://powerelectronics.com/thermal_...osfet_cooling/. The LFPAKs that I have been mentioning are being compared to the other package found on controllers such as the Schulze 40.160, Actronic 120, Jeti SPIN170-300 and the ones I'm having made. This article is saying things like, "This fact also opens the possibility of further reducing the pc board space occupied by the power MOSFETs by using physically smaller devices and placing those devices closer together. To investigate this possibility, another simulation was carried out where each pair of D2PAK MOSFETs in the H-bridge circuit was replaced with three LFPAK devices.

The LFPAK package is much smaller than the D2PAK, occupying the same pc board footprint as the familiar SO-8 package. However, unlike the SO-8, the LFPAK is a true power package that incorporates a bottom metal contact, which provides an effective heat path out of the device. There is an additional thermal pathway between the top of the device silicon and ambient through the top part of the encapsulation.

Although the LFPAK solution increases the total number of power packages used, the total board area occupied by this solution is significantly less than for the D2PAK case because the LFPAK package is much smaller than the D2PAK." and "In the last few years, there have been significant advances in the packaging of MOSFETs, including the introduction of the power SO-8 package. Bottom-side cooling can now be used successfully to transfer heat through the pc board, even when smaller power packages like the LFPAK are used in place of the D2PAK. The package on-resistance and inductances for these smaller package types are also significantly lower. The total losses in a system caused by these sources are therefore reduced significantly, even with the additional devices needed when using the smaller package types in place of larger MOSFETS.

The greatest advantage when switching from D2PAK to LFPAK is the resulting reduction of board space occupied by the MOSFETs, since pc board top copper is not needed to radiate heat. The smaller MOSFETs can be placed closer together, and the previously occupied board space is made available for other components." The components that I have in mind though are much smaller measuring 3mm Length x 2mm Width X 0.8mm height. If this works, it should make a very powerful controller.

Thanks Artur!

Lutach- sounds like you got some serious stuff planned. I haven't read through all of your posts yet, so I'm a bit behind. It's nice to have consumer ideas thrown into the mix though!

So what's the difference between the SO8 FETs and the DPAKs? I'm guessing DPAKs have a metal type housing whereas SO8s are still that resin/plastic?

I've found that LFPAKs are inferior to the SO8-FL package (flat lead, leadless SO-8 -- or PowerPAK SO-8 depending on who makes it) because they still have wire bonds on the source leads, where the SO8-FL has copper clips. The SO8-FL package also dissipates heat much better than the LFPAK, which is kind of a half SO-8, half DPAK package.

The DPAK doesn't take as large a die as either the LFPAK or the SO8-FL, and it has about 2 milliohms of package resistance -- making it not very well suited for 30V applications.

Will the LFPAK work better in a higher voltage controller? I do own a controller that uses 30V LFPAK MOSFETs, rated for 6S lipos and it works pretty well. It didn't get hot at all for the 5 minutes I used it. I was impressed by that as the heat sink on it looks really crappy. If you made a HV car controller that looks like the HV and SHV controllers using the LFPAK MOSFETs would that work? I like the way the HV controller looks and I have my HV110 that I still need to send in if you need a guinea pig. I know the LFPAK have some 75V MOSFET and that could even make a possible 16S controller.

Now for my other question I posted before.

Being able to drive all the MOSFETs (keep this in mind), would a controller with 240 MOSFETs total or 80 per phase, but 40 in the H bridge config. work less to make the same amount of power as one with less MOSFETs?

Now, this controller don't need to be all that small. Something that is smaller then the Schulze 40.160 will do :lol:. I know more FETs and other components will add to the cost, but that's only if parts are being bought from Digi Key, Mouser and any other catalog distributors so lets keep that on the side for now. I'm just trying to get a rock solid controller. I even went as far as contacting and sending 1500 MOSFETs to a company in China to make me a 15S car controller and they never did one so you know the problems they are facing. All they make is Airplane and Helicopter controllers. I know they are using the Atmel's ATMEGA8L-16AU MCU and some car controllers that I have uses the same MCU. My guess is they are still having trouble with the software.

If they are using the Atmel part, they are likely using either stolen Jeti software, or stolen Schultze software. Both companies had their software compromised and copied in China. Both companies have tried unsuccessfully to stop imports of controllers with their stolen software. (I can't imagine how much money it would take to go after these companies... they setup shop and only do business out of Hong Kong where they are shielded by the Chinese government.)

So it's unlikely that they have any resources to modify the software for RC car use.

It's funny, most of the controller coming out of China identify themselves as a Jeti-18 (regardless of the type/size of the controller) when connected to Jeti's field programmer. Several others ID themselves as Schultze. I've yet to see a Chinese or Taiwanese controller that has decent software that was not stolen from another company.

That sucks. So did Jeti and Schulze forgot the protect their software :lol:? This company promised me they were going to do it and now it is basically tha, a promise. I might just get the controllers done with what ever software they have and use them is a car with mechanical brakes :lol:.

No, they didn't forget to protect their software. The ATMega software protection can be compromised.

Good thing the quality of Jeti and Schulze are top notch compared to the Chinese version.