[Mariss Freimanis]

MrWild,

OK, you caught us and I confess: We use really really big, custom made matchbooks to make our drives look small. Please see the thumbnail; it shows the actual size of the matchbook. That is a G203V sitting on the matches.:-)

Mariss

[lagfish]

Mongkol,

Drive supply voltage = 32 * SQRT(mH inductance)

-Marcus Freimanis

If the supply voltage is lower than the recommended voltage here, what would be the consequences? Lower torque at high speeds? If I don't need to have high torque at faster speeds, is it ok to run the motors at a lower voltage than the voltage given by this formula?

[CoAMarcus]

lagfish,

You can definitely run the motor at a lower voltage, but as you stated you will not get the high speed torque you require. What kind of high inductance, low current motor do you have?

-Marcus

[the4thseal]

so when can we order some ......for those of us ho must pay? congrats to the winners

[CoAMarcus]

Here we go. In fitting with a new name, I suppose we need something snazzy with it on there. Here is a rough draft of a Mini-G poster, flier, ad, or whatever you want to call it. Enjoy!

-Marcus Freimanis

[.xXACEXx.]

awsome poster,flier,whatever i wasnt expecting to see the winners i guess..and when i scroll down ..and to be honest thought i saw my entry...i thought of that name..but didnt send it..lol...i prolly would have fell over if i had won..lol congrats guys on the wins...when can we expect to see the machine build log..lol....again congrats winners ,,and gecko drive...

pss.??? ...dang those are tiny drives!!!

[Mariss Freimanis]

the4thseal,

Here is the situation: The G250/G251s being passed out are REV3. The dimensions are 1.3" by 1.6" and 1.375" by 1.675" respectively, they do not have automatic current standby and the current set resistor has to be calculated from the weird formula. These come from the 200 or so drives we ran off to test some new production techniques. Once these are gone to contest winners and OEM recipients of complimentary evaluation drives, there will be no more REV3s.

The production G250/G251s will be REV5. The dimensions are 1.325" by 1.675" for both drives, they have automatic current reduction (70% of set current) and the current set resistor is a linear function of motor phase current (1,000 Ohms per Amp).

We cannot in good conscience sell the REV3 drives because of these differences. Were I a customer, I wouldn't be real happy if a month later an improved revision (REV5) were to appear. That is why we have chosen this method of dispersal.

Please everyone be patient. We are trying to do the fair thing for people. The REV5 panels (G250 and G251) arrive on May 23. Thousands of drives will become available a week to 10 days later.

Mariss

[Khalid]

Congratulations to all the winners

[lagfish]

lagfish,

You can definitely run the motor at a lower voltage, but as you stated you will not get the high speed torque you require. What kind of high inductance, low current motor do you have?

-Marcus

Hi,
I haven't bought any yet. But I'm thinking of using 270 oz-in, 2.8A, 3.6mH motors for my XY, and a 425 oz-in, 2.8A, 6.8mH motor for my Z. Would this be ok? Should I maybe go with 201s on the Z, and use a high current low inductance motor to get more high speed torque? Since I'm running a small benchtop mill, high speed torque is not as critical as say on a large wood router or something of that nature. Thanks.

[the4thseal]

thank you for the 411....you have done yeomen work. i look forward to the release....it is like Christmas .....in good time.......i will sit on my hands with a smile.

[alipavsky]

Okay, I need to put this up here real quick. Here is the formula for the current set resistor value on this version of the G251 and G250:

2.4 * I / (3.5 - I) = Current Set Resistor Value in KOhms

If you have a 3.5A motor, then leave it open. This is something I meant to post a couple days ago for the winners, but forgot to because there must have been one too many shiny objects nearby.

-Marcus Freimanis

Ok, I got bored. Here's a list of current-set resistors, in 0.1Amp increments. You may wish to double-check the math for yourselves.

-Andrey-

[LeeWay]

Congrats to the contest winners. Great job. Nice simple name as well.

My suggestion was firefly. That sounded good initially to me. I figured it was small and packed a lot of power. Then I looked at the literal meaning. I have already made some fire fly from some Vampire's by switching the DC side. :violin:

Firefly was really doomed at the start.

[alipavsky]

So, according to the formula, these drives are good for motors with inductance up to about 2.44mH, right?

[Mariss Freimanis]

alipavsky,

You are mixing things up a bit. The equation (V = 32 SQRT mH) gives the maximum practical power supply voltage for a given motor inductance; i.e. it guarantees the motor will not burn down from overheating. Unless you are planning to run motors at 3,000 RPM with 50VDC you can use a lower supply voltage. That is the reason why step motor drives have a wide supply power supply range, 15VDC to 50VDC for the G250. The lower supply voltages are there because they are very usable.

Example 1: You have a 0.8 mH motor rated at 3.5A. The equation gives 28VDC as a maximum supply voltage. Use a 28VDC supply and you get everything the motor has to give. Go higher and the motor will overheat.

Example 2: You have a 10mH motor rated at 2A. The equation gives 101VDC as a max voltage. You can go to 50VDC and still get decent speed from the motor. It may not have much usable torque at 3,000 RPM but it certainly will have it at 1,500 RPM. At 500 RPM and below you wouldn't see any difference.

Mariss

[Burn]

Even though I own servo motors, Mariss (hint hint ), I admire your work in trying to reach the lower-end of the market for entry-level home shop machinists.

I'll be buying 2 more G320's in the near future, since I only ordered 1 to test it out. I wish you the best of luck in getting these out to people on the market.

[Khalid]

Marcus and Mariss...Please advice me what i do with my Chameleon?...I kept the name of my new machine Chameleon, and u kept the drive name Mini-G...My machine is not Mini.......

[CoAMarcus]

Hey all, I just wanted to post a recap post. This is just so everyone can stay current on what the drive is going to offer.

1) The G250/G251 now also includes Automatic Standby Current. The phase current folds back to 70% of set value one second after the last step pulse. This cuts motor resistive heating and drive heating 50%.

2) The Current Set resistor is now a linear function of current; 1K equals 1A. You want 3.3A, you use a 3.3K resistor, you want 1.2A, you use a 1.2K resistor, etc.

We have been running the test production drives with no heatsinking whatsoever at 3.5A and 50VDC; the power MOSFETs get warm but not hot. To summarize:

CPLD based 10-microstep drive.
15VDC to 50VDC supply voltage.
0 to 3.5A motor phase current.
Mid-band resonance compensation.
Microstep to Full-step morphing at higher speeds.
Automatic Stanby Current.
Silent synchronous clocked design; no hissing, squealing, grunting or whistling. Ever.
Trimpot Adjust for low-speed smoothness.
Premium 4-layer printed circuit board.
NEMA-23 motor speeds tested to 10,000 RPM.
Very small size: 1/3 the size of a credit card.
Very efficient, very low drive heating.
Survives motor disconnect while powered.
All surface mount component (0603) design.
$31 for the G250 in large quantities, a little more for the G251.

We will have single quantity pricing soon, once we figure out what is up with the OEMs. If you guys have any questions, just let me know. Thanks!

-Marcus Freimanis

[tauntdesigns]

Marcus,

Do you have any PDF's done yet? Manuals, wiring, etc.......

Just wanting some new stuff to read. I can also start getting everything together for my controller build.

Thanks,
Jack

[CoAMarcus]

Jack,

As requested, I modified a G201 manual for the G251. This includes the correct pinout and all other info pertaining to the drive. This is for the current revision, so there will be changes made before the new one comes out, including drawings of the drive and other pertinent information.

This has had a brief 5PM proof read, and my mind is not firing on all cylinders so I am sure there are quite a few mistakes in there, so if you find any please let me know. I will be making one for the G250 some time soon as well, and will be posting any stuff I think of regarding the new drives.

The G540 manual will take a little longer, because I have no idea where to begin. Haha, it is kind of the freak of the litter because it is not like anything we have produced before, so I will have to type a completely new manual for that from scratch. Enjoy!

-Marcus Freimanis

[tauntdesigns]

Thanks

Jack