first, @bar why not use the trough hole chips, it’s more easy to mount a heatsink to the multiwatt15 package. @jetrock@bar the L298 can also be used in parallel. linking the H-bridges of one chip to double the output apms
Just make sure you link 1 to 4 and 2 to 3. (See ST’s L298 datasheet)
In a way it would make sense to make some kind of modular design. for this Seperate H-bridges.
Its a shame that there is no “nano-like” version of the Arduino Mega, That would make the electronics less bulky and more flexible. The New Teensy could be an option (although I don’t know the price compared to a Chinese Mega) and there is another 50x50 mm footprint Mega-clone but thatone is still a bit in diaper-class, and could have some growing pains, so not really an option yet.
How much computing power does Maslow need on the arduino? Now with the simplified math due to the linkage wouldnt an Arduino nano, mirco or pro mini be enough to do the trick?
I agree that the through hole chips might be nice. They’re the same price and they do distribute heat better. They turned out to be quite a bit more expensive when we went to have the boards made because then we would have through-hole components on both sides of the board and SMD components on one side which would make it a bit of a custom job.
We’re getting those made right now, but basically it ties the chip on the bottom to the ground plane, and on the top to the heat sink so we should get better heat dissipation.
Are we still seeing issues with this? I know when we were first figuring it all out we were loosing chips left and right because sometimes the sled would run off the top and try to tear itself apart which stalled both motors at once. Now that the software is more stable that kind of thing hasn’t happened in a while.
I second the Teensy as a good option if you are looking for a tiny but awesome processor. Supporting the Teensy project is great, and we’re using a couple of their libraries so I would expect that getting the code to run on a Teensy would be pretty trivial. You might have to move some pins around, but I think there’s enough
My experience with PCB groundplane as a heatsink is that it works fne in a dust free environment, but it also spreads heat to other components (like capacitors) that prefer to be cool. Specially low cost ‘shenzen-dumpstore’ capacitors have a tendency to dry up and fail in warm environments.
Even when using multiple ground layers as heatsink this usually can’t dissipate as much heat as you really would like. add sawdust, and the dissipation becomes worse.
I’m not sure how much cheaper it is to get fully assembled PCB’s with SMD vs trough hole
But maybe if you use 3 Chips and bridge them all, as described in my previous post, so that every axis has one full chip to its disposal. This might just be enough?
How hot are the chips after cutting a full sheet?
I also have been looking at Atmega based boards like FlyDuino, Arducopter, and a few others.
As these have male 3-pinheaders for every in or output instead of the arduino’s female pinheaders, this makes it more easy to strap things together with chinese electronics ‘LEGO’ (without the need to create a PCB to make it somewhat reliable). Though i have no experience with Arduino based RC electronics, and don’t know if these boards are 100% compatible.
I never worked with a Teensy, and the need of installing extra software for it to work with arduino adds another layer of annoyance in case odd stuff happens and you need to figure out what’s causing it.
Apart from that the Teensy looks ideal for this…
I did that, but don’t have a clue how to install firmware on them…
Or how to port (is that the correct term) the firmware to something that runs in Linux.
And then you most likely also want to run a real time kernel???
In a way this would indeed be nice, but then you also need to install an OS ON the machine. More code, more bugs, more point of failure?
It’s a double edged sword, Less electronics, all in one solution. vs Reliability in Simplicity
I tend to bounce back and fwd between those two. But deep down my gut feeling screams, stick with SIMPLICITY.
There are a few ARM boards who have an Arduino on board.
And there are boards like Rasberry, Up-board, Tinkerboard, who have a bunch GPIO pins.
But having a separate Microcontroller for the machine, and a USB to separate the computer from the controller has it’s advantages.
It also would be cool to add a 3d printer ‘RAMPS’ display with SD card to make it run stand alone. Without the need of a PC. Slap proven designs on an SD card and let the machine work on it’s own.
I meant the no OS bare boards. The Blue Pill is just one example, I paid around $2 for some to play around with. You’d need to do some porting and a new controller board retrack
for the precise timing that’s needed, you really don’t want any OS involved. You
can go to a real-time varient of the OS (which is what linuxCNC does), but you
would really be better leaving the stuff that needs precise timing on it’s own
dedicated processor (that’s why the beaglebone series is so great for this sort
of thing, they’ve got a pair of co-processors on the board that are fantastic at
doing the precise timing stuff.
Here goes - I had a heat sink that was falling off all the time. I have a 3D printed solution but it takes hours to print and hours to remove the supports.
I like the idea of the epoxy. I found: http://www.arcticsilver.com/ta.htm
There are two kinds: Silver and Ceramic. I plan to use the Ceramic which has the advantage of being non-conductive (so it won’t short anything out if it gets on the CPU leads). Any tips?
Artic Silver is epoxy plus a thermally conductive filler.
Thermal compounds are intended to fill the tiny gaps between the chip and heatsink. They’re supposed to be used in as thin as possible a layer because none of them conduct as well as a heatsink. Not a case for the bigger the gob the better the job. Although with one of the epoxies you need to find the balance between conducting and sticking; too thin and (like mine) the heatsink falls off.
Real fanatics will lap and polish both the chip and heatsink to make them as flat as possible. Tried it once on a PC cpu, didn’t seem worth the effort. ymmv
I live in Phoenix. We have already had 100+F days. 120F is possible. What are the limits to the controller?
Do I need to just add fan or do I need a coolant type design.
Thanks.
