[CoAMarcus]

alipavsky,

We can not put the MOSFETs in sockets for many reasons, but the main one is the difficulty in soldering the sockets to the bottom and then plugging the MOSFETs in. This would make it take much longer to assemble, and would drive the cost up significantly because labor is the most expensive part of the assembly process.

Chances are, if it was socketed and someone blew a MOSFET up, they would just replace it rather than finding out why it did that. I view it as us promoting contemplative machining, because after something bad happens to your drive, you have to figure it out rather than just carrying on and doing it again. ;-)

-Marcus

[alipavsky]

Marcus,
Point well taken.

By the way, are you going to have any kind of advance ordering option or will you simply "drop the chedkered flag" and let the mayhem commence?

- Andrey -

[Mariss Freimanis]

Here's a progress report on the G250. We got the latest revision prototype boards in today at 2PM. We also got in at the same time bare sample mounting plates from our sheetmetal fabricators. I got right to work:-)

I decided a second prototype revision was necessary because I was not completely happy with the Kelvin ground connection to the current sense resistors (the 2 black horizontal things just below the left 2-56 Allen-head screw) in the original prototype. I moved the sense resistors into close proximity to get a much better Kelvin ground pick-off in this one. This will give a more accurate current sense voltage with less filtering required.

Since I opted for another prototype I also decided to do a variation on the main I/O connector. In this version it is a 3.5mm pitch screw terminal block, a miniature version of the 5mm terminal blocks on our standard drives. This version G250 is mounted on a 1.6" by 1.6" (40mm by 40mm) aluminum heat-spreader plate. This plate is bare aluminum and the size is a little smaller than a NEMA-17 motor. The production plates will be hard-anodized to provide electrical insulation for the MOSFET tabs.

The reason for this is we plan to offer the G250 in 'cheap' and 'dirt-cheap' versions. The 'dirt-cheap' version will have a 2 X 15 header (0.1" or 2.54mm) and bare MOSFETs. The 'cheap' version will look like the one in this picture.

Needless to say I didn't finish populating the board. Only the MOSFETS, CPLD, linear ICs, voltage regulators, trimpot and current sense resistors are soldered in place. The connector and purple 150uF/63VDC are unsoldered. The board has been 'solder-bumped' for hot-air hand-placement of the rest of the parts tomorrow.

Looking at the picture, I just noticed I missed bumping two pads, so how about a micro-contest? The first person in the next 24 hours (ending 9PM PDT Mar 19, 2008, one entry per person) to correctly identify where these 2 pads are wins three G250s from the first production run in April. You must give clear and unmistakable landmarks to describe the un-bumped pad locations. These are cheap drives so this is a cheap contest.:-)

This time tomorrow, the drive will be populated, tested and running. Friday we will order fabrication of the first 1,000 printed circuit boards. 3 weeks from this Friday we will have the boards and 2 weeks after that the G250s will be available for sale. Make it the last week of April or first week of May.

Mariss

G250 Specifications:

0 to 3.5A phase current
15VDC to 50VDC supply voltage
10-microstep drive, trimpot adjust for low-speed smoothness
Mid-band resonance compensated
Silent, 20-kHz synchronous PWM design (not a chopper)
All n-channel 20A rated discrete MOSFET bipolar power section (not a monolithic power IC)
3.3V to 5V STEP, DIRECTION and DISABLE inputs. 1mA load, (noise filtered but not optoisolated)
1.6" by 1.6" by 0.5" size
About $45 for the 'Cheap' version, about $35 for the 'Dirt-Cheap' version

[alipavsky]

How about this? The two pads directly under the yellow dot...

- Andrey -

[Mr.Chips]

I don't know what Bumping is but are they here?
Thanks

[skmetal7]

these two? too bad its not higher rez.. oh well

[holycross]

Is it the lower left hand corner of the board. Looks like the capacitor leads going to the board. Between the screw terminals and capacitor body.

Mark

[ddexd]

Mariss,

I could be wrong, but it looks like you missed 3 solder pads with the solder paste.

ddexd

[wolfdagon]

I had to Google bump pad to know what you were talking about. Unfortunately, I think Andrey got it on the first try. However, I will throw in a guess just in case. Say how about a weekly contest until they finally go into production. Or at the very least, another contest at some point giving away a G540?

Kenith

[eman5oh]

these two?

[eman5oh]

Well after looking at the others I think ddexd has the winner.

[CountZero]

Here is my entry.

[Mr.Chips]

Well after looking at the others I think ddexd has the winner.

Well I think it is Holycross. No solder there. (nuts) :rainfro:

[Mariss Freimanis]

Well, I can't keep the suspense going like this. Andrey (post #364) got it right just 17 minutes after the contest began. Andrey, please email me your shipping address and you'll get 3 drives when they become available.

Mariss

[LeeWay]

Congrats, Andre.
Hey Mariss, where does the DC switch go.

Nevermind. I think I know where you might suggest I put it.

[Mariss Freimanis]

Congrats, Andre.
Hey Mariss, where does the DC switch go.

Nevermind. I think I know where you might suggest I put it.

The DC switch is best placed in a fully shaded location where you can absolutely guarantee the sun will never shine.:-)

Mariss

[ddexd]

Well, I can't keep the suspense going like this. Andrey (post #364) got it right just 17 minutes after the contest began. Andrey, please email me your shipping address and you'll get 3 drives when they become available.

Mariss

Congratulations to Andrey. Mariss, I really thought I had you with the 3rd pad that didn't look like it had solder paste.

[alipavsky]

I'd like to thank the producer, the director, the accademy... oh wait, wrong soap box...

[CoAMarcus]

Okay, we have a new contest. This one has 6 brand new G250s up to win. First place will get three G250s, second place will get two G250s, and third will get one G250. All you have to do is guess the number of components in the G250. This means the total of parts that get soldered down to the board. I have attached a photo of the PCB so you can count the parts. There are no SMT components on the bottom side, so what you see is what you get. Here are the rules:

1.) This contest will begin at 10:30AM PDT Thursday, March 20 and runs until 5PM PDT Monday, March 24.

2.) There is one entry per person, and the first entry counts so make it a good one.

3.) In the event of a tie, only the first two winners in each category will be eligible for a prize. This means that there will be a maximum of two winners for first place, two for second, and two for third, for a maximum of 12 G250s to be awarded.

4.) First place will be awarded with three brand new G250s, second place will be awarded with two brand new G250s, and third place will win one brand new G250. All of the drives that will be awarded will be from our first production run available in early May.

5.) There are no exchanges for other drives, and only G250s will be awarded.

6.) The winners will be those who get closest to the actual number of components on the G250.

7.) This contest is only open the CNC Zone members who have been a member since before the contest started. This is to prevent people from creating a second handle on here and getting two guesses.

8.) There is no editing of answers. Any and all edited answers will be disqualified.

Good luck!

-Marcus Freimanis

[eman5oh]

By my count 86 parts if i did not miss any.