Paul & Sabrina's cheap DIY 144v motor controller

[MPaulHolmes]

As for metal case or not, here's what people have told me:

Metal case cuts back on EMI to the outside world. Would your cell phone work while driving? What are you doing on the phone while driving? Text that foul temptress later.

Hmm... Also, would the heatsink being attached to the heat spreader be enough to keep it cool inside, even though it would be surrounded by an insulating material like Lexan? I have no idea! Maybe!

Hmm... I know how to go to Home Depot and make a lexan box pretty friggin cheap, so that's always an option. In that case, Mounting "heat sink down" might be better.

[MPaulHolmes]

You are right about that! It's attached to my bank account. I tried to get the paypal credit card, and let's just say I still don't have a paypal credit card. I'm not saying I was denied...

[ev59rag]

You dont have to use paypal credit card.... any credit card will work. I think they use it as another level of security check.

[adamj12b]

Hi Paul,

I thought you might like to actually see the surface mount machines making some boards.

CASE Assembly Solutions, Inc. - Quality Electronics Manufacturing - Facility

A short way down is a flash video of the machines that place 50k parts a minute. The video dose not do the machines justice as it moves faster then the camera can record, the machine was actually slowed down as well to better show it working.

In the video, the machine places all passive components as well as any other parts that come on tape reels. The board is then transfered to the next machine on conveyers to the next machine that places parts like large IC's and processors form trays and tubes. Then it travels down another conveyer to the 9 foot long multi stage reflow oven. When it comes out the other side, there all done.

Then in the other room is one of the coolest machines I think I ever seen. It is basically a giant dishwasher for PCB's. Ever felt a PCB that was kinda sticky or had a white film on it? That is from the resin used in soldering. This giant washer pressure washes the boards and then blow dries them. Sparkly Clean ready for shipment.

-Adam

[MPaulHolmes]

OK Adam, that was awesome, I'm not going to lie. The John Henry of soldering and surface mount placement would be really depressed right now. He would be soldering until his heart burst, and the machine would be sitting in the corner, mocking him. We have got to have a surface mount version.

[MetroMPG]

Brings back memories. I once had a job for a while in a Nortel factory operating a wave solder machine, among other things. Lots of surface mount machines there too. I did a LOT of soldering type work.

[MPaulHolmes]

Darin, you are versatile. Hey! I need something soldered! Hey, I need someone to sail a giant boat! Hey! I need someone to make an electric car for $150.

Oh, I finished etching the mosfet/diode side of either the Joe's or Adrian's controller. hmm... I'm not sure who's it was. The other side is almost no etching with this new layout. Mostly just a huge ground plane. It also has the benefit of making 3 ounce copper have the current carrying capacity of 6 ounce copper. And it's very easy to lay down extra solder or to solder copper wire to the bottom to help with current carrying on thinner copper boards.

Also, all the capacitors are on one side, but I'm ordering larger ones, so the total ripple current rating will be almost identical to 24 of the other capacitors. The same ESR too. In bulk, I think this way will save maybe $10 or $15 too. I would take a picture of the newly finished etch, but the batteries are recharging.

Does anyone have any mu metal sheet or foil laying around? I would like to enclose the control section in mu metal to protect it from radiated EMI. The EMI shouldn't be getting through the cables because there is optical isolation between the power section and the control section. Man, that control section is going to be quiet.... Toooo quiet.... maybe sheet steel will be good enough.

[charlie_fd]

For future board version(s) I will get a price quote from a local shop, since for me shipping costs form Australia to US and then to Europe add up quite a bit. However for this round is best to test identical set-ups in order to minimize board and components influence in the results.

Here's a picture of the nice shiny board I've been using for my DIY fuel injection controller (mega-squirt project v2): mega-pcb.jpg

[MazdaMatt]

We've got one of those machines at my work, but we're not quite so hardcore. I think it is only a few hundred parts per minute and we manually load them and manually take them out to put in the oven. Before the pnp is the solder screen machine, it lines up the board, drops a stensil on it and squeegees liquid solder over the board. That leaves solder perfectly placed on all the tiny SM pads ready for pick'n'place.

I'm glad that you have been reading up on new technology. Lets be honest, you hacked this controller together using some VERY basic hobbiest parts. Going up to a chip with 6 highly configurable PWM lines is a major step towards professionalism, Paul. Good work.

Do you even need to worry about EMI? This thing is pretty low frequency. 16kHz switching and a 3krpm motor? I can't see that interfering with much.

[MPaulHolmes]

Hi Matt! Actually there is noise in the 50 to 100 MHz range from ringing on the edges. There might actually be even higher frequencies but my sad little oscilloscope can't handle it.

Awesome job, Adrian! That looks beautiful!