Paul & Sabrina's cheap DIY 144v motor controller

[MPaulHolmes]

I'm almost done with a power section layout for the SR controller. I'm sending it to Advanced Circuits, since they do stuff with 4 ounce copper now. The plan is to drill holes and mill the sides and top flush of an approximately 10"x1"x2" aluminum block, send it in to be type 3 anodized, and use that as the heat spreader. The company that does it can do 1 to 2 mil thick anodizing, and they say it's 2000-3000V/mil of isolation, and as hard as saphire! The SR control boards should be here either tomorrow or Thursday.

Oh I just did some figurin' about how much energy the aluminum block can absorb. That will give me a loose idea as to how much energy can be dumped into it in short bursts:

Specific Heat Capacity of Aluminum is 900 J/(m*degC). My Aluminum block will have a mass of 0.889 kg. If I consider a change of 30 degC for the aluminum block to be acceptable for short periods of time, the amount of energy the block can absorb is:

900*0.889*30 J = 24000 J.

Now, at 1000amps, if it's wasting 2000 watts of power (oh please don't be that bad!), it will take the heat spreader 12 seconds before the temperature has raised by 30 degC. At that point, the software can throttle back a bit, and allow the energy to slowly seep away.

I'm not sure if my reasoning is right, but it makes sense to me! Please tell me if I'm not understanding something! ya!

[MPaulHolmes]

OK, so I finished the layout, and for 1 pcb from Advanced Circuits, it's *only* like $450 (the 4 ounce copper makes it expensive). In quantities of 100, they are $30 each.

Now to PCBcart.com...

Quantities of 75 are $8 each. Quantites of 1 are like $50 I think. But friggen pcbcart.com takes gerber files, and my stupid free software can only be sent to Advanced Circuits. Holy cow I want to punch something right now. Eagle is $1000 for the layout editor and router thing. Altium is like $30,000 hahaha. If only I was a believer in pirating software! makes me mad! Let me rephrase that... If only my wife was a believer in pirating software! There is a slight chance that I could be tempted to the dark side to avoid paying $800000000 for software, but she would lay the smack down. hahaha. Makes me mad.

I tried the free software in Linux, and as soon as I ran into a point of confusion, I tried to get "help", and the help file explained that their focus was on getting the software working, and not making help files, so I never did figure it out.

I also tried freepcb, which is free routing software, but not free layout software. I'll retry that right now I guess. Where's a fork when you really need it? Right in the eyeball!

I want all the stupid dang pcb layout software out there to burn in the fires of heck and darn-nation. I'm sorry for my language!

[sawickm]

Originally Posted by MPaulHolmes

I want all the stupid dang pcb layout software out there to burn in the fires of heck and darn-nation. I'm sorry for my language!

Hi Paul,

I feel your frustration !!!

Here are some links to PCB Design software:

PCB design tools - Good PCB software links

Kicad - Open source (GPL) software for the creation of electronic schematic diagrams and printed circuit board artwork. Even does 3D assembly ! Never used it but looks cool and some open source parts libraries too.

If you decide to go over to the “darkside” PM me for a list of PCB software that I can set you up with, for personal use only !!!

Can you output any kind of file with the Advanced Circuits software ? print, plot, image, etc… There might be a translator that could output it then to a gerber file. I have reversed engineered PCB’s but it has been awhile since I have done one.

-Mark

[Tweety]

Originally Posted by MPaulHolmes

OK, so I finished the layout, and for 1 pcb from Advanced Circuits, it's *only* like $450 (the 4 ounce copper makes it expensive). In quantities of 100, they are $30 each.

Now to PCBcart.com...

Quantities of 75 are $8 each. Quantites of 1 are like $50 I think. But friggen pcbcart.com takes gerber files, and my stupid free software can only be sent to Advanced Circuits. Holy cow I want to punch something right now. Eagle is $1000 for the layout editor and router thing. Altium is like $30,000 hahaha. If only I was a believer in pirating software! makes me mad! Let me rephrase that... If only my wife was a believer in pirating software! There is a slight chance that I could be tempted to the dark side to avoid paying $800000000 for software, but she would lay the smack down. hahaha. Makes me mad.

I tried the free software in Linux, and as soon as I ran into a point of confusion, I tried to get "help", and the help file explained that their focus was on getting the software working, and not making help files, so I never did figure it out.

I also tried freepcb, which is free routing software, but not free layout software. I'll retry that right now I guess. Where's a fork when you really need it? Right in the eyeball!

I want all the stupid dang pcb layout software out there to burn in the fires of heck and darn-nation. I'm sorry for my language!

Well if you need help with Eagle, let me know... I'm kind of used to it...

[mrbigh]

Originally Posted by bennelson

Visit EV T-shirts to get one.

We'll also get a link to it on Paul's web page at:
Welcome to PaulandSabrinasEVstuff.com

-Ben

PS: the "Value" T-Shirt is only $10. Maybe we could include t-shirts as part of the kit!?!

I received my shirts yesterday!!!
.
.
Now I'm feeling connected

[jyanof]

Originally Posted by MPaulHolmes

Oh I just did some figurin' about how much energy the aluminum block can absorb. That will give me a loose idea as to how much energy can be dumped into it in short bursts:

Specific Heat Capacity of Aluminum is 900 J/(m*degC). My Aluminum block will have a mass of 0.889 kg. If I consider a change of 30 degC for the aluminum block to be acceptable for short periods of time, the amount of energy the block can absorb is:

900*0.889*30 J = 24000 J.

Now, at 1000amps, if it's wasting 2000 watts of power (oh please don't be that bad!), it will take the heat spreader 12 seconds before the temperature has raised by 30 degC. At that point, the software can throttle back a bit, and allow the energy to slowly seep away.

I'm not sure if my reasoning is right, but it makes sense to me! Please tell me if I'm not understanding something! ya!

Sounds like a good estimate. It's a little conservative since you're not considering the heat transfer of the cooling system (fins or water cooling or whatever) that is taking heat out of the heat spreader. Also, if the turn on/off times are less, switching losses could be a lot less. So, that 2000W could be a lot lower. Of course, you're also not considering all the thermal resistances of the mosfet to the heat spreader and it's effect dynamically on the junction temperature. It should be lower with the anodizing scheme than the thermal pad. Very interesting...

[jyanof]

Originally Posted by MPaulHolmes

Testing started!

Results so far:
With 0.5" separating bus bar and current sensor, 166 amps actual through the bus bar caused the voltage to change from 2.469v to 2.900v on the current sensor. For this current sensor, if the output voltage is 4.6v, then that indicates the "maximum current". So in my case, on the first attempt, my current sensor has a range of -808 to 808 amps.

I think I'll give it a bit more space, and see what happens. Not bad for a first space guess though!

Sweet, that's a pretty slick little sensor. Does it matter what's in the "space"? Does it have to be air? Could a block of wood or plastic be machined to the proper thickness and everything glued together? just trying to think of easy assembly methods...

[MPaulHolmes]

It just has to be a material for which a magnetic field can pass through it. So, plastic, fiberglass, wood, anything! Maybe not a big piece of iron though.

[ElectricZX2]

Hard anodizing the heat spreader seems like a great idea for electrical isolation. The only thing I would worry about would be the degradation of thermal conductivity. I get what you're saying about the layer being very thin Camlight, but it might be nice to have some numbers. Type III anodizing is used in industry to provide a thermal barrier in addition to an electrical barrier in some applications (which makes sense since thermal and electrical conductivity are generally directly correlated in metals). For example, part of the reason pistons in ICE engines are hard anodized is to reduce the thermal conductivity of the piston and therefore mitigate thermal expansion allowing for tighter tolerances....

[MPaulHolmes]

Hey! The control boards came today for the SR controller!
Back of control board:


Front of control board:


There are a couple details that I'm going to redo next time, but nothing serious so far.

Don't worry! It's lead free solder they used for the plating.