#31
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Check Please.
This is the kitchen table I am currently considering.
I purchased an eBay torroidal transformer, Antek 6435 that is labeled: IP: 115V, 115V, OP 35V, 35V, 18V, 12V. For motors, I have about decided on 4 x MK 34HS 8801. Wired 1/2 coil I think these are 4 amp, 0.7 ohm phase resistance, 3.0 mh Inductance. IR = rated 28V. Driver(s), will be Gecko G-540 which would actually like no more than 3.5 amp (this can be remedied in the driver) and 18V to 50V; . Power Supply should be between 3 to 20 times rated voltage, or 8.4V to 56V. (I wonder if the current is limited to 3.5 amp, is that number to use in the power supply calcs, yielding 4.9V to 49V?) 3.5 amps times 4 motors gives me 14 amps needed. If I use one of the 35V outputs from the transformer, times 1.414 for 49 V DC that should be sufficient. A 25 amp x 140V rectifer, Mouser 512-GBPC 2502, and a Mouser Cap, 100V 10,000, mf, Mouser 539-CGS100V10,000, I'm hooping nothing will explode. I'm pretty sure I left something out,,,,Vmax? I'// be back shortly. Thanks, in advance, for helps, comment. roger Last edited by qroger; Tue 31 August 2010 at 12:25.. Reason: more clearer |
#32
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Houston is this a problem?
vmax, (for motor?) = sqrt (impedance)x 32 sqrt (.7) x 32 = 26.7
Back to the reading.. |
#33
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Hmm, pretty sure that I have this v max convused with power
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#34
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32 x sqrt(INDUCTANCE) = 32 x sqrt(3) = 55.4256 So you are very good at 49V.
8.4 to 56V for the motors was correct. 14 Amps, only if all motors drawing max at once. Experience tells us this doesn't happen, and 300 to 400W power supplies are adequate. Rough check then is that 300W / 50v = 6 Amps. If you're supplying above that, you should be in good shape. Last question then is do you have enough capacitance in 10k uF to smooth things out. See the helpful spreadsheet from MikeR, which recommends about twice that (two capacitors in parallel), if you are engineering conservatively. I think you'll be just fine as specified above. Note that each of the 36V windings on that transformer furnishes half of the rated current, so if it's 8.6A, you'll get 4.3A from each winding. You probably want to wire the two windings in parallel. Careful doing this; one way they work together; the other they short each other out. |
#35
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Thanks!
Now I have to go to the transformer and find out where you got 36 from and why 35+35 doesn't = 70. Dude! It's 'lectricity! It's not supposed to make sense! hehehe.
No Worries. roger |
#36
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36 is a typo. I meant 35. If you take the two windings and wire them in series, then 35V+35V = 70V at 4.3A. If you wire them in parallel, 4.3A + 4.3A = 8.6A at 35V.
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#37
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Thank you. I believe this has me squared away so I can order some parts!
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#38
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Another order
Yesterday I spent more money! hehehe. Ordered the capaciter(s) from Mouser as well as the rectifier. There was only one screw-type available so I went ahead and got the snap cap version, (so I wouldn't be back-ordered), and it was about 1/3 the cost for the same spec screw type.
I have to admit I wish I had had an electronic bill of materials on hand while I was ordering. Mouser has a project manager that would allow me, or admin, to post a project list, from which items are then checked off as ordered. I probably could have gotten some switches, etc, but now I will be forced to get organized for next time. Can someone rec a suitable wire size to connect the caps, the torroid, the rectifier, and items between the power in and the flexible cable riding in the cable carriers? Or is that a stupid question? I have a shopping trip to the scrap-yard planned for the weekend. Or there is this: http://charlotte.craigslist.org/tls/1931210450.html on the local craiglist. Cheap but big and would need a door. Check out the color though! Anyway the power supply parts are now on order, and as soon as the stock broker coughs up a check, I can plunge in for the rest of the kitchen table project. Man I hate letting a Windoze comp into the house, but the alternative would be tooo much distraction. There does not appear to be an easy Macintosh option, so Windoze it is, meh. This thing I came across is currently a key part in my fantasy of turning the MM into a cash machine: http://www.david-laserscanner.com/ current fantasy: 3d scan into 2d slices into 3d form into 3d object into money. Getting Excited Now, lol. |
#39
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Roger, a quick approach would be to match the gauge of the wires coming out of the toroidal transformer. Otherwise, you want to work out the amount of current you expect to use, and apply that. In a MM, you should be looking in the range of 14,16, and 18 gauge wires (15A, 13A, 10A as some safe working values).
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#40
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big hoses into little hoses
Thank you. I think I remember that bigger wires have lower resistance and less line loss, so, in general there should be no harm in erring on the slightly bigger side #12awg?
Thanks again roger |
#41
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There is no electrical harm in using larger wire, as long as you dont create a situation where a large wire feeds an overly small wire. A common term for this is "fuse".
Larger wires don't bend as well as small ones. |
#42
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The Shopping continues
After removing the cubic foot or so of copper, + iron, I got an unused, air tight, transformer box at the scrapyard. (pictures to follow). I ordered the Gecko G540. Asked for a final official quote from MotionKing for the 8801's.
There is something i worry about: From Gecko: "]If your motor is below 3.5A, you can use the above drives as well as the G250, G251 or G540 drives. If you need an all in one solution then the G540 is the drive for you. It has a built in breakout board, short circuit protection, opto-isolation, parallel port connection and four axis operation via DB9 motor cable connectors.[/ [COLOR="Black"] If I read the Gecko correctly, current set resistors are used to make the Gecko suitable for amps below 3.5. For motor current above 3.5, (such as the MK 34HS 8801, what must be done to make everybody play nice together? I guess I should ask Gecko. Last edited by qroger; Mon 13 September 2010 at 12:47.. Reason: Make it mor better |
#43
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Roger, do you mean MotonKing 9801... I don't know the 8801
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#44
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MK 34hs 8801
http://www.motionking.com/show_produ...12&fenlei_ID=2
We will see if the link works. I believe the advantage is supposed to be that the lower inductance will get the motor down into g-540 range. All advice is gratefully accepted. |
#45
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Too big motor for Gecko
I found out the effect of too many amps for the Gecko. In my case if a 4 amp motor is used with a board with a 3.5 amp reccommendation, the torque is reduced, in this case 3.5amp/4 amp = 87.5%.
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#46
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Mk 34hs 8801
I found this link Kobus. There is more to it than just the author, but I forget what. I think it is partly cost.
http://www.mechmate.com/forums/showt...5&postcount=15 |
#47
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New Home for Kitchen Table: 50 cents / lb
In inches, it is, 20 high, 16 wide, 10 deep, with removable panel, 17 x 13. It was 1/2 dollar per pound. |
#48
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The Doghouse
I am trying mightily to get a photo in here. It is in the manage attachments slot, so far, so good...
Oh!! Happy Day! |
#49
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Another Check Please
I have on-hand, quotes from Motion King for the 34HS9801, the 34HS8801, and have a request in for prices on the 34HS6803
Specs are as follows and all I think are half coil. Motor length Current, (A) Phs Resistance Phs Inductance (ma) wt 6803 66 2.7a 1.2 ohm 3.5 mH 2.0 kg 8801 78 4.0a 0.7 ohm 3.0 mH 2.5 kg 9801 98 4.0a 0.98 ohm 4.1 mH 3.0 kg Kobus has run the 9801 with success. The 8801's have been kicked around in the forum but 1.) I don't find a record of anybody useing them, and 2.) MK says no availability for 3 weeks after payment. So My question is: For a belt reduction option, wouldn't the 6803's come closer to the G540 ideal? Thanks, roger |
#50
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Roger, I think you want to underdrive a larger motor, rather than overdriving (or just driving) a smaller motor. Otherwise, you're giving up torque you could have had.
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#51
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I'm wondering if belt drive reduction would take care of the torque issue. I think the lower induction, (relative to the 9801), maintains the torque out to higher rpms, so that's good for the belt drive, right? The little motors save a kg each for reduced momentum so that should be good, but probably not really significant.
Other than putting together a system that won't explode and burn to the ground, my other concern is that I have ordered the G540, and I have the power supply parts in hand, so I will need motors that fit within those constraints. From my point of blessed ignorance, I think any of these motors should work. I would have more confidence if Motion King had a conventional shopping interface. I presume they will eventually produce an invoice I can paypal off of. Thank you for your review, and as of now no motors have been purchase. roger |
#52
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34HS6803-G5 and G10
My mate has just got a quote back from Motion King about the 34HS6803 motors with a gearbox. They come in 5:1 or 10:1 reduction. The price we got is USD$115 for the G5 and USD$130 for the G10.
This would take care of the torque issue rather than putting a belt on it. At half the cost of the OM's they seem to be priced right. Does anyone know about the quality of these motors with the gearbox? Has anyone put these motors on a MM build? |
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