Castle - Make A Special Edition Monster - Page 8 - RC-Monster Forums

marzac2 · 06.13.2008, 06:43 PM

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

suicideneil · 09:18 PM

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

) 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....

bdebde · 06.14.2008, 03:38 PM

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.

lutach · 06.14.2008, 09:54 PM

A question for the engineers out there

. 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.

06.15.2008, 01:06 AM

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).

lutach · 06.15.2008, 10:00 AM

Quote:

Originally Posted by Five-oh-joe

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.

GriffinRU · 06.15.2008, 12:27 PM

Quote:

Originally Posted by lutach

A question for the engineers out there

. 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.

Very nice post, Five-oh-joe

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.

lutach · 06.15.2008, 12:41 PM

Quote:

Originally Posted by GriffinRU

Very nice post, Five-oh-joe

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.

GriffinRU · 06.15.2008, 01:16 PM

Quote:

Originally Posted by lutach

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.

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.

02:01 AM

Quote:

Originally Posted by GriffinRU

Very nice post, Five-oh-joe

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.

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?

suicideneil · 06.15.2008, 01:13 PM

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.

GriffinRU · 06.15.2008, 01:20 PM

Quote:

Originally Posted by suicideneil

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.

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