@Giga It is possible to fit a motor driver within a 56mm circle, but as you can see from the picture it would need smaller transistors and would have less current handling. The layout of the logic board would be a challenge, like I would have to ditch the gate drive dc/dc, some interfaces, and a few other things.
A sleek 60mm tube with integrated electronics would look rad. Maybe we can work on that design next after this one?
I also had a problem with diameters so I designed a liitle piece for assembling different tubes, maybe it could be useful in the case of bigger or smaller motors
Nick
I was thinking about this in regards to the broken lift mast pictures that were posted by @Southernkiwico. If a mast breaks and the electrical cables tear I would want the ESC to be on the board rather than in the motor pod. If the ESC is in the motor pod you would risk both losing it if the mast and wires get separated from the board and also you would short between the + and - , through the water, which would cause the batteries to catch fire.
I agree that the risk of all of this happening is small but if it does happen the damage could be catastrophic. Just another point to think about.
Thanks.
Hovav.
Wouldnt you have an inline fuse to stop this happening? or individual battery fuses on a 18650 battery?
I’ve been thinking about how to package the electronics. I hope this concept is able to be integrated into a wide variety of designs, and that someone will find it useful.
The ESC enclosure has two parts: the logic and first switch board are housed by a can with a rear face seal and screw holes to mount to the motor adapter/prop guard mount. Additional switch boards stack up and face seal against the mast clamp/nose cone face. The can seals around a motor adapter.
The switch board heat sinks and electronics housing would be supplied with the ESC. The motor adapter and mast clamp would need to be made specifically for the motor and mast in the application. This is my design, which adapts to an APS 80100. Both components can be done a bunch of different ways, this is how I happened to do it.
Here is the thruster broken apart so the wiring connections can be made and ESC programmed.
Inside view of the motor adapter.
Nose/mast clamp separated from the electronics
Here are 3D models:
Tested a single board today to overtemp cutoff. 100A to a single switching board with no cooling takes about 10 seconds before the overtemp cutoff kicks in. The important part is that the overtemp is effective.
The switching boards are stackable, so that means current capability is as high as the number of switching boards. Each board can do 75A continuous, peaking to 100A for 10 seconds or so. The design is based on the VESC6, so it makes sense that the performance of 1 switch board is similar.
I would like to do a beta test, if anyone is interested. This would be a limited number of production modules for technical/power users (that’s everyone on this forum), with the goal of finding any deeper bugs before mass production. This is also an opportunity to test the switching boards to their limits in water and see if my ratings are too conservative. The price for this run would be 300 USD for the logic board and first switch module, and 125 USD for additional switch modules. price will get cheaper if I can get ~10-20 people on board
Specs (it’s basically a VESC6):
I can’t afford to make them if no one wants to buy them, so please send me a message if you want to buy one at this price, and I will get them on order (after I order its 6-8 weeks for delivery). Once they get here I will set up a web-store where you can pay for them, and hopefully receive them shortly.
Nick
I like the idea of sealing the ESC in an aluminum can. I think in order to imporve, this can may be filled with high dielectric constant oil so the cooling will be more effective. As it is now, I am affraid that the contact between the heat generating components ( FETs ? ) and the cooling media (Aluminum can wall and sea water ) will make the cooling less effective.
Thank you for sharing this !!
Hovav.
Very nice job on designing those boards!
For me personally 425$ is a bit too pricey and I would also fear to loose or destroy motor + ESC in a single ground contact, or - more likely - have water ingress as result of a crash and fry this expensive ESC.
Good point. I got about .6K/W to the outside with .25" thick aluminum backing. I guess that could be a little high? It’s still a 3D model so its simple enough to add more aluminum for better conductivity. Could also cross drill the heat sink part. That would keep things ice cold.
Sorry Benjo, low volume pcb manufacturing is unreasonably expensive. I don’t have enough money to make these boards either. 
If I can get more people on board, the price comes down by a lot. All I can do is ask around to try and find help. Perhaps you have a rich friend who is into watersports?
I hope you get the support you need to get these in to production. Development of direct drive 80100 motors has been quite interesting on this forum and your work with the electronics is quite impressive to me. Mainly because its well beyond my understanding. Great work and contribution to the forum. I hope it works out.
I understand that.
I assume you are not only having the PCB produced but also have them assembled? Maybe it would make sense to solder 1-3 units yourself and sell them at cost to reputable members of the community that can test them. I would assume the raw parts price including PCB somewhere in the ~150$ area for logic + one switch module? That would be more reasonable for a blind buy. I hope this doesn’t sound disrespectful or something, I just want this to work out 
Hi @nickw1881,
I would consider buying, what is the limit to the number of switch boards you can use before you overheat the FET drivers? Impressive design!
@benjo the boards I am using now were done with a batch prototyping service and assembled on a saturday by me. 5 logic and 5 switch boards bare (pcbcart.com): $200. Materials to assemble two logic and two switch boards: $600. Amazingly, it is cheaper to have boards fab and assembled in china than it is to buy just the materials in America. Also the thermal performance of a proper spec board will be too good for me to lead free solder with an iron and a heat gun. I could barely make the crap spec prototypes with tin/lead.
@Antonbit @hovav Here is my heat math:
Concept pictures:
Possible options to improve thermal performance is
#1, thicken the aluminum
#2 cross drill the sides of the heat sink with 3mm/.125" holes. That would turn it into a “water block”, but with no need to pump the water. It’s a little more complicated manufacturing (3rd milling operation) but it sure would keep things cool.
@jakebarnhill1 I am confident it will work fine with 3 switches. I don’t know what new problems there might be with 4 or 5- could be just fine. Gate drivers are way overbuilt. The power connections in and out, and current sense circuits will hit their power limits before the gate drivers and gate drive power supply have a problem.
Nick
It’s been a long time since I did the undergrad course in heat transfer so I am a bit rusty but I get your point. bottom line you think there is good enough heat dissipation ? As I said before, I think you are doing an awesome job here !
I would like to offer some help. I was thinking - do you know this company : www.nano-di.com ?
They are a PCB rapid prototyping 3d type printer and I am a good friend of the CEO. Please take a look at their site and if they can produce the PCB, I will ask them to do it hopefully for free or if not I will ask them for a quote. I guess you will have to send me the GRBL files for that.
Please let me know.
Thanks
Hovav.
Ok, interesting. I was under the impression that you can build a VESC 6 by ordering all parts from mouser and soldering it yourself for around 100$ + connectors. What makes it that expensive for you? I know you have a special design, but component wise it is still a VESC 6.
Isnt it a bit early for a public beta? I would really advice to do some more testing before selling.
Also, how is the current sharing between the switching boards? There is no way that the current sharing is equal since the board further away from the control logic sees higher resistance than the one that is closer to the connections.
It looks like the gate drivers are on the control board, how did you size the gate resistors and accept a range of fets in parallel? This is normally very challenging in switching power electronics design (you will either be switching slower than needed or overloading the gate driver).
How is the temperature monitored for the different switching boards? Do you detect max temperature for all boards? Or just the case temperature?
These are just a few of the major thing that jump to mind. Don’t take my comments to harsh but from my opinion it is to early to sell.
@JTAG great points. I need help testing in real world conditions. I would never ship boards that I have not bench tested to advertised spec. I have already tested my prototype to the limits of my ability. I cant test it any harder by myself. To your points:
Power sharing: this design cannot possibly share power perfectly, as you noticed. But it doesnt need to. Part of this is rating the boards conservatively. 100A peak 75A continuous is well below the 300A rating on each fet. Even if they do not share perfectly, no single fet can exceed its ratings.
4A gate drivers with 4.7uF bootstraps. The 12V gate drive power comes from a 1A dc/dc. Theoretical max peak drive currents are <=1A with chosen gate resistors. The driver circuit is in no danger with 3 switch stacks. I dont recommend using 4 or 5 switch stacks, though its probably safe with diminishing returns.
Gate balancing: gate resistors are per-fet, which you can see on many esc from kde, castle, hobbywing, etc. Some fets are going to switch slower than others. Its not about everything being perfect, its about everything staying within its ratings.
Temp monitoring is only on the closest board. The vesc software allows 1 fet temp input.
@everyone I think I have an idea. A large portion of the $425 was to cnc the round, underwater aluminum in-thruster heat sink parts. What if this isnt strictly for underwater use?
If I shipped without the aluminum, people could do their own heat sinks in the board like they do now. We are all DIYers here. If people can make a whole efoil, they can make a heat sink or water block by cross drilling a piece of 3/8" (10mm) aluminum.
I could get 10 logic and 20 switch boards for $100 each. If I sell near cost (this was always the plan), that puts the price at about the same as commercial escs: $200 for a 75A and $300 for a 150A 14S esc. As mentioned previously, those ratings are continuous and conservative. If I can get the price down cheaper for the beta I will do it.
This would let people test in their existing rigs, without risky thruster mods and undersea electronics. I can handle the $800 cost of the stacking pins. Does this seem more reasonable?
Edit for clarification: It’s going to take months to actually get everything here and built and bench tested. I am trying to establish whether or not this is something I should do, or if just leave it alone and get high. We are talking serious money (to me). If 5-10 people say “yes we like it” here’s the game plan:
@nickw1881 this is sick, the ESC is the only thing I’m affraid of in this project because it ain’t cheap and it ain’t durable most of the time. But you’re gently developing one especially for us, how can we not be stocked? As I don’t want to burn 300$, this a great alternative, please keep it up!
