SparkFun Forums

[pharmboyz]

Hi All,

In searching through the forums I have come across a couple of posts that mention an easydriver board that will have higher capacity than 0.75Amp. Hoping to confirm if this is true as we are looking for a board with up to 2A capacity.

Thanks
Pharmboyz

[EmbeddedMan]

Pharm,

Yes, such a board is in the works. I've got first four built up, but I'm unhappy with the performance (mainly heat dissipation) and will be re-designing it before building another bunch of prototypes. It will be based on the A4988 driver chip, which says it can do up to 2A, but so far I've only been able to push through about 1.3A/phase before it shuts down due to over temp. So I'm working on that. I do not have a timeframe for when the board will be for sale - as soon as possible, but getting a board into production takes way longer than you think.

*Brian

[pharmboyz]

Thanks Brian! Heat dissapation is a constant issue, but in my context it will not be running all the time, just intermittently from input received so looking forward to the new board. Thanks again, Pharmboyz

[mmcp42]

Hello Brian
I, too am very interested in a higher current Easy Driver
anything I can do to assist with the development?

cheers
Mike

[EmbeddedMan]

Sure, if you're good with kids, you could take care of my 3 girls so I can finish working on the board.

I kid, I kid. Seriously, I hope my wife never sees this message.

Honestly, I really could use some help finding a good heatsink. It needs to be surface mount solderable,

I really like this one : http://search.digikey.com/scripts/DkSea ... 45-1012-ND because it's so nice and cheap, but it's only 55C/watt which is pretty bad. They're about $0.53 each.

Now this one I've used before on some stepper boards for a client, and they work really well. (You can tell because they are really hard to solder to the board because they wick so much of the heat away) http://search.digikey.com/scripts/DkSea ... 45-1012-ND They're 18C/watt which is very nice. But they're $1.18 each.

Neither of those actually sit on top of the driver chip - the heat has to go from the die, through the package, down to the board, through the thermal vias to the center two layers of copper, then back up through more vias to the heatsink. You can see why we can't get enough heat off of these chips!

The driver chip to cool is an Allegro A4988 which is in a 28QFN package. Does anybody know of a cheap heatsink that you can put right on one of these chips?

*Brian

[mmcp42]

Happy to help research the heat sinks
(both links are the same btw - don't know if the second should be different?)

but 3 girls you say ... where's my silver cross and garlic?

update:
not sure if I'm barking up the wrong tree...
this sort of thing do the job?

£0.71 for 1
£0.59 in tens
£0.42 in hundreds

[EmbeddedMan]

Sorry, I did screw up the links. That second link was supposed to point to the one you linked. That's the pretty nice one that I use now, but it's too expensive. It's $1.02 in singles for me. It also sits pretty far away from the QFN part, so the heat has to travel through the board pretty far to get up to the heatsink.

I need to do some experiments with the boards I have assembled right now. In order to get closer to 2A/phase, we're going to have to go with a 4 layer board with 2oz copper (double the normal thickness). These will be more expensive to fab than the current EasyDrivers. However, the driver chip costs less (amazing isn't it) for the new board. We'll see how it all comes out in the wash - I'd love to keep the new EasyDriver priced at $15 if I can, but I'm not sure we can do it.

What I'd love is a tiny little anodized aluminum heatsink that you stick onto the top of the chip. They exists for BGA parts, but they're expensive and not small enough for these tiny 5mm x 5mm packages.

Hmmm. More research . . . .

*Brian

[mmcp42]

hello Brian
not heard form you for a while - any progress?

it if helps, I, for one, would be happy to pay > $15 for a high current EasyDriver
$20 would not be out of reach!
my machine is getting close to needing drivers - so I have a particular interest!

cheers
Mike

[EmbeddedMan]

Mike,

Thanks for reminding me. I have four of the first prototype Big Easy Drivers done. I have a couple big ooopsies on the board, but nothing that can't be fixed on the next rev.

With a heatsink and a fan, I can get 2A/phase out of it all day long at 24V. Without a heatsink or fan, I can do 1.4A. Without a heatsink and a fan, I can do about 1.6A.

So I'm going to go ahead with the next rev of the board, which hopefully will not have any errors. It's going to be a four layer 2-oz copper board, which means it will be great at getting rid of the heat, but it will be more expensive. With the heatsink, it will be even expensiver. I'm thinking of having a stick-on heatsink as an optional part.

When will it be ready? Not sure. I'm pushing hard to get it into SparkFun's hands before Maker Faire (end of May) and maybe even into production before then.

But I could use some help beta testing it. I want it to be rock solid. E-mail me in about 3 weeks with your address and I can probably send you one or two of the 2nd prototype version to test out if you'd like.

*Brian

[mmcp42]

be delighted to beta test
I'll drop you a PM with contact info
cheers
Mike

PS
I think making the heatsink an optional extra is a sound plan
that way people can trade off spend vs functionality

[phalanx]

I think making the heatsink an optional extra is a sound plan
that way people can trade off spend vs functionality

The only issue I see with that is Sparkfun targets users that may not have an engineering background and as such may not understand or appreciate the need for a heatsink. This can lead to people wondering why their new board just stopped working. Meeting price points is a tough issue but in this environment I would be inclined to design for reliability.

-Bill

[phalanx]

Sorry, I did screw up the links. That second link was supposed to point to the one you linked. That's the pretty nice one that I use now, but it's too expensive. It's $1.02 in singles for me.

If you are interested in that particular heat sink, Future Electronics has it for about $0.47 in singles. I buy most of my high powered LED components from them and have never had an issue. They are the main distributor for Lumileds.

http://www.futureelectronics.com/en/tec ... 0000G.aspx

I don't know if you are familiar with it but there is a website called http://www.findchips.com which lets you type in a manufacturers part number and it will search all the big distributors for stock and prices. It makes it easy to see if something is available and if it can be had for less money from another company.

-Bill

[EmbeddedMan]

Bill - good points about the heatsink. I have a Newark order on its way to me with tiny little stick-on heatsinks.

You are right about the possibility of a problem with not having a heatsink. However, I can make it clear in the product page text that if you're worried about power and heat you need a heatsink. Also, I've run several of these chips (A4988s) for multiple hours in severe over-temp situations, and they have never suffered any harm. Their built-in over-temp cutout works perfectly. So I'm not worried about damage.

*Brian

[mmcp42]

Hello Brian
did this ever get to production?

cheers
Mike

[EmbeddedMan]

Yup. Right here : http://www.sparkfun.com/products/10735

And it is pretty awesome - easy to add to a breadboard, or add screw terminals, mount permanently, or just hook up to try something. Will drive almost any size stepper motor.

Enjoy-

*Brian