Paul & Sabrina's cheap DIY 144v motor controller

[jackbauer]

hey Dave that brings me back. hand drawn pcbs! i used a program called easypc. still use an old version. very nice and easy to get to grips with.

what bout this:
PCBCAD40 pcb CAD printed circuit board design software - eBay (item 250588545020 end time Mar-10-10 03:47:30 PST)

unless your going designing multilayer boards for a fembot or some crazy dsp system then a $1000 piece of software is a waste imo. for half that you could probably give the schamatic to a contractor and get a board designed and built!

[dave koller]

Originally Posted by dcb

Oh I hope not

OK OK Tomorrow I will show you some wire wrap LOL -- it is home ....

[MPaulHolmes]

1000amp current sensor results!

OK part number CENTRON CSA-1V

Now, the centron was soldered to a single sided pcb. For a measurement range of 0-1016amp, the bottom of the pcb needs to be 0.75" away (actually 0.754") from the bus bar. That's 12 bare fiberglass boards (pcbs without the copper). Higher temperatures make the current read slightly less than it actually is.

There are more numbers, but we are going to Montesano! My old town! (they now call it "Monte sa yes to drugs". It's a depressed logging town. hahaha. Well it used to be. I don't know how it is now.

I also ordered a part (that's on a 25 week back order) that should be able to be much closer to the bus bar.

[dcb]

lol, fembot I don't know if Sabrina would approve.

[drbobwoolery]

Anodizing aluminum for insulation requires PURE aluminum. This is particularly true of thin layers with parts bolted to them. Alloys produce unpredictable coatings both softer and more conductive than desired. Go over those MOSFET tabs with a whetstone to chamfer the edges and corners. You are probably better off with through holes, insulating sleeves, machine bolts and nuts than tapping holes and expecting the anodizing to insulate the threads. Last go-round on anodizing for insulation was microvolt level EEG signals.
Talk to your anodizing shop BEfore fabricating the parts. ask me how I know

[CamLight]

Originally Posted by jyanof

Yah, the fan/heatsink seems to work well. I had thought about using heat pipes for an IGBT based power section. But, this is a whole other discussion

As for mosfet heat generation, it depends (mathematically at least) which term - resistive or switching - dominates the heat generation. The formula for switching losses is linear with respect to current, whereas the resistive losses are proportional to current squared as you mentioned. In our case, with the 20 ohm gate resistors in the controller and the really low Rds_on characteristic of the mosfet, the switching term greatly dominates the heat generation of the mosfet. Thus, the heat generation appears to be roughly linear with current (as calculated).

Good points, I agree.

[CamLight]

Originally Posted by drbobwoolery

Anodizing aluminum for insulation requires PURE aluminum. This is particularly true of thin layers with parts bolted to them. Alloys produce unpredictable coatings both softer and more conductive than desired. Go over those MOSFET tabs with a whetstone to chamfer the edges and corners. You are probably better off with through holes, insulating sleeves, machine bolts and nuts than tapping holes and expecting the anodizing to insulate the threads. Last go-round on anodizing for insulation was microvolt level EEG signals.
Talk to your anodizing shop BEfore fabricating the parts. ask me how I know

Good tips for increasing the contact area for a FET.

And good points about the threads! I was assuming that only the flat surfaces would need insulating and that the MOSFETs would be larger-cased version, like TO-247 and TO-264, where the screw (or clamp) never touches anything electrically hot. I agree, counting on the anodizing to hold up to the extreme forces on localized parts of the threads is not a good idea.

Talking to whomever is plating your parts is a very good idea!

I've had very good luck with Type III coating of 6061-T6 alloy with spring-clamped down TO-264 MOSFETs...but YMMV. I spec'd 0.5mil penetration and 0.5mil surface. I only had a few microamps of leakage at over 100VDC applied between a sanded bare spot and an anodized spot on the heat sink.

[CamLight]

Originally Posted by adamj12b

I love Eagle!! Ive been trying to get Paul to use it for months now!! he tried it once, then went to PCB Artist....Darn you Paul!! I knew it would come back to bite you!!. LOL

One thing that I have trouble with that Paul and I were talking about yesterday was how to create a massive pad for a bus bar??

When I draw a Polygon in the pad layer, and hit ratsnest to redraw the planes I have drawn, the planes apply the .1" isolation to the big pad....And since you cant name polygons in the pad layer.....i have no idea how to fix it. lol

Would you use like the Restrict or Keepout layers to keep solder mask from be applied to the areas of the bus bars??

This is the only problem I have had so far... Maybe one of you know??

-Adam

Adam, I'm not sure if this answers your question, but...
You can assign a polygon to the same signal as your pad (which can now be small) by changing the polygon's Name to the same as the pad's signal name. Then you can set Thermals to match what you need. This allows you to create a pad of any shape and size and have it handled properly for the air wires.

I use a Polygon or Rectangle on the tStop and/or bStop layers to keep the mask away from the parts of the power/GND planes I want to make into bus bars. I prefer using a Polygon, but you can use a Rectangle if you know the size won't change.

[adamj12b]

Originally Posted by CamLight

Adam, I'm not sure if this answers your question, but...
You can assign a polygon to the same signal as your pad (which can now be small) by changing the polygon's Name to the same as the pad's signal name. Then you can set Thermals to match what you need. This allows you to create a pad of any shape and size and have it handled properly for the air wires.

I use a Polygon or Rectangle on the tStop and/or bStop layers to keep the mask away from the parts of the power/GND planes I want to make into bus bars. I prefer using a Polygon, but you can use a Rectangle if you know the size won't change.

Awesome!! tStop and bStop!! Thats what I needed to know. I already have the planes connected to the pads where needed, but I could not for the life of me figure out how to keep the solder mask away from the polygon outline I drew of the bus bar. Ill just change that polygon to the tStop layer and that should solve my problem!! I can finally order my boards!!!

-Adam

[squiggles]

Originally Posted by dave koller

LOL Eagle would do fine for the "PRO"..

Gone are the days of wire-wrap.

Laying out boards - by hand - with exact-o knife and rolls of black paper tape in various tape widths.

Squinting at the light table - haha auto routing - yep, you WERE the auto router!

little pads and IC layouts - stuck on by hand... Netlists?????

Did some 14" X 14" controls yep with TTL then CMOS - 30-40 chips on the board - traces between pins -- "pro" days were much different then...

Yeh, and how about memory boards with dozens of parallel tracks connecting all the memory chips, back in the days when leading edge technology was 2k*8 static ram!! Those tracks drove your eyes nuts!