Transferring data over induced coupling

[Bruce]

But 0402?

Stuff just wouldn't fit otherwise, and we needed the free space for the 418MHz UHF & 125kHz RFID parts. There's a UHF antenna for the Linx RF transmitter on the back of the board just behind the Primeport logo.

These RF parts need x amount of clearance from board components, so we had to go with 0402 to squeeze everything into a keyfob enclosure on a board 1/3 the size of a credit card. The CR2032 battery holder & UHF antenna sucked-up 50% of the
board space.

The board photo looks big, but it's definitely not.

We do all SMD placement under a lab microscope, and beyond the initial prototype, we do all soldering with a RoHS comlpiant reflow oven, and lead-free solderpaste screened boards.

We use the Gold-Flow GF-B-HT reflow oven and a zoom stereo trinocular microscope mounted on a boom stand for SMD placement. Photos attached.

RF design is a whole new world, and if it's not spot-on, you ain't getting that FCC stamp of approval. So you allow for whatever clearance is needed for the RF stuff.

[Byte_Butcher]

These RF parts need x amount of clearance from board components, so we had to go with 0402 to squeeze everything into a keyfob enclosure on a board 1/3 the size of a credit card. The CR2032 battery holder & UHF antenna sucked-up 50% of the
board space.

The board photo looks big, but it's definitely not.

You don't need to sell me on the NEED for small precisely placed components! I understand why small SMD parts are desirable.

Now I'm interested in good tools and techniques to make SMD more accessible for us mere mortals.
I wanna know how us wannabees can do it most efficiently, without a HUGE expense.

We do all SMD placement under a lab microscope,

Excellent! Does your microscope have a model number? Are there things you particularly like or dislike about it? Is it... horribly expensive?
These are the kind of tools I seek, but it's nice to have good reviews from folks who actually USE them, rather than blindly whipping out the credit card.

I love SMD components! But they can definitely push the limits of my eyesight and dexterity, so I'm in search of good tools and techniques to make things easier.


steve

[mackrackit]

I do not do stuff as small as Bruce and I am not building for certification....

I have a set of loupe and one of those headband magnifyers like jewelers use.
I also, do not laugh, use one of these.
http://www.intel.com/support/intelplay/qx3/

pretty much everything I do is custom, so all I have to be able to do is a good prototype.

For reflow I use a toaster oven from walmart.

That is how this newbee does it....

[ardhuru]

Bruce, thank you so much for sharing the code. But the reason I'm hoping to use the hardware UART for data transfer is that the receiver would then be able to receive data in the background, making the the dot-pattern display servicing much easier.

Intend to try out that; will keep you guys posted on the results!

Anand

[Bruce]

Steve,

A couple pair of SMD tweezers, a toaster oven, and a pair of the headband magnifiers like
mackrackit uses is all you really need. The microscope I've had for about 10 years now, and
the nameplate was peeled off a long time ago, so I don't know the manufacturer, but it
was around $400.00 new.

You can probably get one on eBay for a fraction of that if you want one. Get one with the
ring light if you do. I love the one I have. Really comes in handy when you're working with
very small SMD parts. The batch reflow oven is awesome, but it's pricey at >$5K. If you
have deep pockets a reflow oven is the way to go, and there are some good ones a lot less
expensive than the one we have. You probably don't need the high-temp lead-free type.

Anand,

Couldn't you use IR? A surface mount IR module like in the photo would work if mounted
dead center on the board, and you can connect it to the UART.

[ardhuru]

Anand,

Couldn't you use IR? A surface mount IR module like in the photo would work if mounted
dead center on the board, and you can connect it to the UART.

Absolutely; the only concern is it would interfere with the IR index pulses I currently use to sync the display frame. I could perhaps change the index sensor to a Hall effect device.

Regards,

Anand

[Bruce]

Cool looking clock. I've always wanted to build one myself, but keep getting interrupted by
things I have to do VS things I want to do....;o)

Do you have a video of your clock in action?

[Byte_Butcher]

Dave & Bruce,
Thanks for the SMD tips. I've already got a toaster oven (with homemade controller) to do reflow. That parts covered.
Got decent tweezers so I'm OK there.

I just need better eyes!

I've tried the headband magnifiers and haven't liked them much. It seems like the depth of focus wasn't very good and unless my head was just the right distance from the work then it wasn't focused. Maybe I just need better ones?
Right now I do my work under one of the magnifying lamps with the fluorescent tube around it, but that's not really ideal either. It's in the way a lot.

I think a good lab microscope may be my next adventure...

Dave, who's laughing at your Intel Play microscope? Not me! I already bought a Aven "Mighty Scope" for inspection. Up to 200x magnification...
http://www.weirdstuffwemake.com/swee...scope_0863.jpg

It gets in pretty close. The resistor in the lower right is 0603.
http://www.weirdstuffwemake.com/swee...closeup_01.jpg
Great for inspection, but it doesn't really respond quickly enough to work under "in real time", so I still need...something... else.


Anand,

I'm sorry I highjacked your thread to ask about SMD. But since Bruce brought up 0402 sized parts I just *had* to ask.

The question I'm wondering about, considering the *very* modest range requirement, would I need to modulate the Debugout signal, or just feed it to the MOSFET driving the coil every few 100s of ms (the rest of the time the coil wouldkeep getting its 32 KHz for power transfer).

I doubt you'll need to modulate the signal. I'd just stuff the signal direct into the MOSFET and I'll bet it works fine.
Certainly you could do IR too, but I don't see any reason why you can't couple the data through your transformer.
I'm looking forward to photos of the finished product in action.


steve