Cheapest motor drivers possible

Looks like those adapters don't have any connection to the heat pad on the bottom of the chip. You might find it is hard to keep the chips cool enough to drive your steppers. Plus I doubt you'd save much after buying the adapters, chips and passives. Maybe do away with the adapter and just get a through hole stepper driver in the first place like TB6560AHQ

stick on ram sinks would do. i'm not read enough on the tosh chip to make the circuit myself. it also makes more heat i think. another thought was maybe fitting two allegros on a single 48 pin adapter. or eventually even milling them myself.

I guess the main point was that once you get done with all that, you'll have a set of drivers that are less capable than the pololu's at about the same price and likely with a non-compatible pinout. If it's just an exercise in circuit design then go for it. But if the purpose is to save some money, I doubt the SM + Adapter route would save much if any. That's why we all buy from Pololu, cause they do them a few thousand at a time. Integrating SM or through hole drivers on the board would save money though if you leave out the adapter and do either a SM or a through hole board with matching components. I think Gen6, and others have done the integrated SM drivers pretty well, but there seems to be no through hole designs with integrated drivers. AKA47 has done a through hole design with the TB6560AHQ drivers but it is a separate driver board like Gen3. I think cooling would be far easier with the TB6560AHQ since they are much bigger and have a large heatsink pad, but since they are 2.5 amp drivers I think most could get by with no cooling at all.

I looked over the toshiba pdf. I think you need a diode array and a translator chip...

The allegro's are nice because they're a complete package. There's very little extra components needed. I like the pololu's but want to break the dependence and $13 hit every time one blows.

I would guess the majority of repraps are running 1amp or lower on their steppers anyway, I know every adjustment I've done has been to lower them. So one could skip the adjustable pot with the 1amp chips. I'd also skip the micro-stepping jumpers as the majority would get by just fine with hardwired 1\8 stepping.

That leaves you a diagram of the $3 chip and a few caps/resistors. That's it. And it would be fully STEP/DIR compatible.

Looking at aka47's design, there is this parade of diodes, but almost no further passive elements, so the design is even a bit simpler than a Pololu/StepStick.

Regarding microstepping jumpers, you can use solder jumpers to avoid soldering in jumper headers. This is just two pads close to each other, so you can put on a blob of solder to close the jumper.

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Generation 7 Electronics	Teacup Firmware	RepRap DIY

I think they are step/dir compatible. It just has different names on the pinout.

[www.rapidonline.com]

I was looking around for some low cost FETs and came across these at 15p (around $0.22 USD) each, I know various people have designed low cost PCBs for steppers, but are there any for sale? Otherwise I'm happy to design my own, is there still interest in reducing the electronics cost? I estimate the 12 FETs + a PIC MCU + other R&Cs = $35, maybe a kit could be sold for around $45, giving a small profit to cover the design costs?

Mike

4x TB6560 = $15: [forums.reprap.org]

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Generation 7 Electronics	Teacup Firmware	RepRap DIY

Good find on the TB6560s. I didn't make clear that my cost estimate included the components in a RePIC board as well as 4 drivers. I've found even cheaper transistors, so my estimate is still: 4 drivers + 16 FETs + a REPIC controller + other R&Cs = $35, if there's interest I can do a PCB design.

With four transistors you only have unipolar drive, so you get 40% less torque for the same size motor, which makes it a false economy unless you are using motors that cost less than your electronics.

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[www.hydraraptor.blogspot.com]

There's already a similar project, perhaps you want to join there: [reprap.org] I still can't see, though, why a board with an $12 PIC should be cheaper than one with an $8 ATmega.

Do these PICs have advantages over ATmegas? Like reasonably fast 32-bit processing, like synchronized parallel processing? I've read a few articles about PICs, but don't have a clear picture, yet.

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Generation 7 Electronics	Teacup Firmware	RepRap DIY

As much as I like PICs I don't know if there is a really good reason to do a PIC version of the RepRap electronics. The loss of all the development in firmwares seems to be too much of a negative. On the other hand the integrated USB is a plus. If you want to do a dirt cheap board (please do) I would probably pull from GEN7 or Sanguinololu as a base and add your FET drivers to that unless you need peripherals that aren't available on the ATmega to enable the drivers to run at a reasonable speed. Also I would echo the comment about bipolar steppers as that is the standard as of today.

Thanks for the feedback, I was planning to use the RePIC firmware unaltered, the PIC in that project is a similar price to an Atmel, (not $12 as on the repic page). I was looking at unipolar steppers to further reduce costs, unipolar steppers cost only a few $ each, a downside would be much slower acceleration, but that would be OK for a low budget Reprap. A Reprap for <£100 ($150) might be feasible?

Where do you find unipolar steppers for a few $ each?

[www.alltronics.com] has some unipolars for $3.50

Those will permanent magnet motors rather than the hybrid type we use. Typically they are 7.5 of 15 degree step angles and have far less accurate stop positions and micro stepping linearity. OK for Z but not really suitable for belt drive.

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[www.hydraraptor.blogspot.com]

Still in the "gathering salvaged parts left and right" phase here, but I found some really cheap steppers.

Here's what's on the label on the back:
hurst Model SAS P/N 4003-002, 12VDC, 8W

The motors have six wires.

From the datasheet:
- 7.5 degrees/48 steps per revolution
- 2-Phase Holding Torque (oz-in) is 10.5
- Rated Torque @ 4-5 p/s (oz-in) is 7.5
- Nominal Voltage (volts) is 12
- Winding Resistance (ohms) is 36
- Rotor Inertia (oz-in2) is 0.17
- Temp Rise (°C )* is 65

Now I know it's too imprecise to drive a belt directly, but I'm guessing that I could either lower the speed via gears or by using a threaded rod.

And since it's only 48 steps per revolution, wouldn't a threaded rod be a valid alternative if it can get as many pulses per second as a 200 steps motor? Wouldn't it be about four times faster at turning the rod?

Also, I'm trying to find a good stepper driver schematic using something really cheap like TIP122's or IRLZ44 (unipolar setup). I've already done a few tests with TIP122's and an ATtiny85 for the logic part of the stepping (I plan on going with maybe an ATtiny84 for the decoding+driving, the ATtiny85 doesn't have enough pins for both inputs+outputs) if I want to keep ISP abilities.

An M8 threaded rod is 32 times slower than a T5 belt and an 8 tooth pulley. Even so if it stepped at the same rate it would still be 8 times slower . Because it is a 12V motor instead of a 2.8V motor it will have much higher inductance so will actually step much slower unless you use a higher supply voltage.

Don't you think Reprap would already be using these if they were viable?

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[www.hydraraptor.blogspot.com]

Well, those are surplus motors I found, I thought they were a good deal at 4$CAD each. Maybe I could use them for the vertical axis?

About a week ago I was able to find three Sanyo Denki motors (one 103H5208-0842 and two 103H5208-0841) with a small gear already on the shaft, they were on a small assembly using short S2M belts. There is absolutely zero play (backlash) between the gear and the belt, I'm guessing "S2M" means synchronous belt, 2mm? From what I've read it's better than a timing belt.

Are those motors better for building a RepStrap?

I'm thinking about building a Mendel90, it seems to be easier to build, requires a lot less parts, cost a lot less and should be a lot stronger. I already have one 10mm rod from an old Agfa 1212U scanner, as well as about two dozen 608 bearings and 8mm bolts.

Yes I think those are suitable, see [www.youtube.com]

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[www.hydraraptor.blogspot.com]

Not sure if these are any good, but the price seems right so the information might be useful to some. They're unipolar but they do have six wires, so AFAIK they could also be used in bipolar mode.

[www.alltronics.com]

Yes, six-wire-motors are unipolar as well as bipolar. In which mode they operate depends on how you wire them.

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Generation 7 Electronics	Teacup Firmware	RepRap DIY

Never mind those motors...

The good news: they're listed at 8.95$USD each, they're NEMA 17 and have a 0.9° step.

The bad news: the datasheet says they're 10.78 oz-in while the RepRap motor page mentions a minimum of 19.4 oz-in for a Mendel.

I was thinking..
The arduino is complex enough to send complex i/o commands
And it only takes 4 pins to stear 12 leds idependetly using a Charlieplexing.
Please take a look here to see how that works http://labs.stijncoppens.com/thesis/charlieplexing-leds/

Thats 12 leds using 4 pins, it might be possible to stear 3 stepper motors with pins !
Just replace each led with 2 leds or diodes and a mosfet as like :

----|>|----+---|>|---- 
           |
+12v-------D------     (D= a mosfet or perhaps a hexfet)

If not made it jet (i dont have a stepper motor, still waiting for one to arive)

During previous post i had trouble to login, i prefer to track this so what about using Cahrlie plexing
with charlie plexing 4 digital pins is enough to control 12 leds
And with 5 pins one would be able to control 20 leds
like

what i wonder is instead of lighting a led, how about controling a mosfet to stear a magnet inside a stepper motor

Won't work: MOSFETs share the source pin between control (gate-source) and high current (drain-source) paths, so can't be Charlieplexed without passing the full motor current through a control pin (which is likely to damage the processor).

Shipping cost is too high for me in Canada, but perhaps it's more reasonable for people in the USA:

[www.ebay.com]

Yvan256 Wrote:
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> Shipping cost is too high for me in Canada, but
> perhaps it's more reasonable for people in the
> USA:
>
> [www.ebay.com]
> er-Motor-103H5208-2PH-NEMA-17-/130712613103?pt=LH_
> DefaultDomain_0&hash=item1e6f1430ef&_uhb=1#ht_1401
> wt_956

Those are unipolar, so won't work with standard RepRap drivers. At $14 each including shipping (in the US) they aren't that great of a deal.

Edited 1 time(s). Last edit at 07/22/2012 03:02AM by NewPerfection.

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NewPerfection Wrote:
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> Those are unipolar, so won't work with standard
> RepRap drivers.

They are six wire so they would be fine. Eight wire work just fine too. It is only five wire that do not work unless you open them up and rewire the coils.

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NewPerfection Wrote:
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> Those are unipolar, so won't work with standard RepRap drivers.

See Sublime's reply about six wires.

Also, they're listed at 6.99$USD each, no idea what the shipping cost is for the USA but it's 24.25$USD for USPS Priority Mail International. However, the seller also says "I will try to combine shipping where possible", so it might end up at much lower than 14$USD each. It's not like all the other places have free shipping either. That's why I posted the link.

Edited 2 time(s). Last edit at 07/23/2012 11:18AM by Yvan256.