Gen7T or Toshiba drivers for Gen7?

Any thoughts on substituting through hole 2.5A continuous Toshiba drivers for pololu modules? Maybe a Gen7T sub-version (T for toshiba/tightwad Seems like a step in the direction of cheaper/easier. You would save $6-7 per driver or so and they are higher current drivers and easier to heatsink, so the dual stepper on the prusa would be less trouble. Plus Mouser and Digikey seem to keep a couple thousand in stock most of the time so the pololu stockage issues would go away. aka47 did up some separate driver boards gen3 style as below.

aka47.adsl24.co.uk/serendipity/index.php?/pages/stepdrv.html

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Any thoughts on substituting through hole 2.5A continuous Toshiba drivers for pololu modules?

The Pololus currently make up some 45% of the Gen7 price so I already searched a lot for a replacement and obviously, this Toshiba TB6560 is pretty much the only microstepping driver coming with a pin spacing sufficient for PCB manufacturing on a RepRap. Good choice!

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Maybe a Gen7T sub-version

I've just opened a "toshiba" branch in the Gen7 repo and if you give me your Github ID I'll add you as a collaborator.

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Generation 7 Electronics	Teacup Firmware	RepRap DIY

Well, I don't have a Github account, nor do I know how to use it other than downloading firmwares, but I'll get an account sometime soon. I will not likely have much time to start development in the near future, but I do plan on ordering some of the toshiba drivers and start breadboarding up some circuits to see if I can get them to work. It may be a while before I have anything worthy of a Github commit. I'm not enough of an electrical engineer to just design a circuit without messing with it IRL first. Also I am not currently familiar with the design software used for the board as I am a eagle user, so I'll have to get into that a bit before I can really contribute much I guess. Anyway, if no one does anything with it by the time I overcome all those hurdles in my "spare" time, I'll be there. I think it is a good sub-version for a sanguinololu too. (Sanguinoshiba?)

Well here's a first attempt. I have a github account now (bryanandaimee) It is completely untested. I'll try to etch one and test it sometime soon.

Great work, Bryanandaimee. Now I see what's the problem with the Toshiba's pin layout. Having motor coil pins on both pin rows can't be effective, as one always has to queeze the current track in between two pins, even on a multilayer board. This likely requires the track to go into the 3rd dimension by putting as much solder onto it as possible.

Worse for the 12V supply tracks, as the leftmost one carries current for all four motors ...

Nevertheless, worth an etch.

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Generation 7 Electronics	Teacup Firmware	RepRap DIY

I took a look at this chip and currently it's $ 4.20 for one $3.36ea. for 10 at mouser, for those in the usa that want to mess with it ask mouser to put your stuff in a small flat-rate box (and you can fit a bunch in there). and the shipping is like 5 bucks.
Pricing wise this might be a good alternative to the pololu drivers the geniuses here can make it work.

I think this one could be a winner if you use a milled style board and purposely make the jumper pins small traces and the current ones big triangles. and keep the distance to the outputs extra short, with thicker output pins. Might have to split the motor headers into two so they can be placed right next to the outputs. Resistance I understand, coding is a whole different story. I estimate the etched boards for the current version 7 vs your milled boards have much higher resistance values between any pcb connected points.
terramir

Yes, and I'm wondering if this design will eventually need to be a double sided design just for current carrying issues, but we'll see how it goes.

I've played around a bit with your footprint and it looks like I've found a solution which might allow inter-pin tracks 20mil wide while maitaining 0.4mm isolation gaps.



See your pins to the left, the experimental ones to the right. The footprint is in the .pcb file and might become even a bit better: pin copper width 46 mil (instead of 40 on the picture), track width 20 mil, makes 2x 17 mil for isolation, where 16 is sufficient. The drill hole is just 30 mil (0.76 mm), the Toshiba's pins are about the same size as those of 3 mm LEDs (which are thin) and 0.75 mm holes work fine, there. A matter of uncertainity are the Toshiba leg's tolerances.

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Generation 7 Electronics	Teacup Firmware	RepRap DIY

Looks good. I didn't do that footprint from scratch, it's just a ZIP24 with an added pin. I think your version is much better. Data sheet says pins are .55 +/- .1 so up to .65, and looks like a drill of .25 mill is suggested, so .3 should work.

Got a footprint built for oval pads. It looks like a winner. I also added a second footprint for the heater FET's to fit IPAK transistors because I bought a bunch of these for 17 cents each. They work fine in my Gen7 V1.3 board for the hot end. Haven't tried them with a heated bed yet. IPAK is 90 mil spacing instead of 100 so I had to drill the board out quite a bit to get them in. I also routed the 5V for the thermistors from the chip supply so that the thermistors don't stop reading when the ATX supply is off. Pretty close to an etchable board now. I hope to etch tomorrow.

Have a question about these drivers is there a way to make these plug-in compatible with all the electronics but especially gen 7 because this would be cool is it doable?
terramir

I think the point of these drivers is to no longer requiring something to plug in. They're on the main board.

Also, the electrical advances of these chips are few, A4988s work just as fine.

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Generation 7 Electronics	Teacup Firmware	RepRap DIY

I thought that the drivers were to reduce cost? They significantly cheaper than the pololu given they are £2.30 vs £11 for pololu. They are also easier to heatsink plus have a higher current handling. I know that the A4988's have current limiting circuits but this allows the board to drive higher current motors for milling ect.

I also think that developing an alternative driver to the pololu is a good idea, after personally blowing a few of them over the build for my Prusa they are expensive and the chips cannot be replaced so a board must be brought new again. At least the Toshiba ones can be easily replaced should you blow one. I'm not denying the the A4988s are more than capable for controlling the current versions of the reprap, and that for 3d printing alone the power draw should only reduce as designs become more optimised and efficient. I just feel that the stepper drivers seem to blow quite regularly (although mostly through user error) and as such I think that designing a new circuit in which drivers which are harder to replace would be a mistake.

As an aside I also think that it would be great if a board could be designed which allows the Toshiba chips to be used as a direct replacement for the pololu.

Having said that, what is the current limit for plastic headers? Is 2.5A too greater power draw for that type of connection?

I don't think a plug in replacement would be doable with the through hole version of the toshiba chip. It is too long to run sideways, and turning it vertical would mean it would interfere with pins going to the socket. You could certainly do it with the SMT chip but I don't know what that would get you other than an alternative, likely as expensive or more expensive but with slightly higher current capabilities.

fair enough. I'm using Sanguinololu 1.3a as opposed to Gen7 but I dont think that makes a difference. Is there any chance it could overhang the socket? I know it would look messy as hell but could it work? Just I'm planning another Reprap soon and have a spare Sanguinololu board but no stepper drivers and the Toshiba are so much cheaper!

I guess that could work, but by the time you make a daughter board and populate it with the caps and resistors and stuff you aren't likely to have saved much. Most of the savings is in integration since the drivers all cost about the same for bare chips.

Well I powered up a board and promptly let out the smoke. Not sure yet what's up. I'm guessing it's either my design or my build quality. So I'll be troubleshooting for the next little while. Needless to say don't build these electronics yet.

Bad luck with the first design, but then these things take time to perfect! And yeah your right about the daughter board, I'll just rebuild with the current state of the art when I get round to making it, and to be honest that seems the best way with reprap by far!

Hope you do get these working though, it would be great if there was a 2nd option to pololu.

Have a look at this one:

[cgi.ebay.fr]

Thanks to the keen insight of droftarts, I have a "working" board. It has passed the initial movement test on one axis without emitting smoke. Turns out I had neglected to set the enable pin to non inverting. I didn't notice that the logic for enable was inverted from the way the pololu drivers work. And it seems that the toshiba drivers really dislike being enabled before the motor voltage is turned on.

Having populated the board with a couple drivers and stuff there are some issues with component placement that need to be resolved before it's functional. The drivers overhang more on the ends than I allowed for when I placed some of the jumpers so you can't actually install pin headers, and it's a bit cramped in spots. But that's just a matter of moving stuff around a bit.

this web-link may be helpful
[www.cuteminds.com]

Thinking more about the issue of power on / power off sequencing which seems to be more critical for the toshiba drivers, (though I guess the pololus emit smoke fairly frequently too) It seems that the main requirement is that the 12V power lag the 5V on start up and lead it on shut down. Secondarily that the enable and reset pins be low until 5V and 12V stabilize. Running off ATX supply seems to generally enforce these requirements most of the time, but I imagine that people running off a dedicated 12V supply and USB for 5V could get into trouble as the 12V supply would not be controlled from the board. Also on the regular Gen7 board I find that if I run off USB for 5V the ATX control floats when USB is disconnected and ATX turns on.

So a pull up resistor will likely be needed from ATX standby 5V to the power-on line for these electronics. I think that will generally solve power on sequencing for ATX supplies.

For 12V supplies that have no control line I'm unsure how to enforce the power on sequence. I'm thinking maybe putting another FET on the board to connect 12V to the drivers controlled by the ATX power on control line. That way the power on sequence should be enforced the same no matter what power supply is used.

I'm not sure if these precautions are sufficient, but I'll be doing some more testing soon. Some destructive testing is in order I think.

Can anyone think of any holes in my power on assumptions? I'm wondering if any of the software packages have smoke emitting buttons I haven't thought about, or possibly firmwares whos behaviour doesn't jibe with what I'm assuming here.

Just a thought on the notion of safety features, would it be possible incorporate any kind of debugging on the board, like green LED for working and Red for blown or similar?

That way the novice stands a much better chance of debugging dead ICs

Well I'm going to blow a few in as many ways as I can think of. I'll do some testing afterwards and see if there are any consistencies in which pins short or open when the driver goes. It may be possible, but I'm guessing that while there will be some patterns there may be no definitive pin you could stick an LED on to tell you if it was bad. It may short when blown sometimes and open other times, or different pins blow due to different circumstances. Probably the best I can do will be some troubleshooting tips.

bryanandaimee Wrote:
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> Well I'm going to blow a few in as many ways as I
> can think of. I'll do some testing afterwards and
> see if there are any consistencies in which pins
> short or open when the driver goes. It may be
> possible, but I'm guessing that while there will
> be some patterns there may be no definitive pin
> you could stick an LED on to tell you if it was
> bad. It may short when blown sometimes and open
> other times, or different pins blow due to
> different circumstances. Probably the best I can
> do will be some troubleshooting tips.

Yes I concur with the atx, power supply can solve some of the problems however for safety considering the sequence mentioned here you might want to use the 5Vsb rail (it usually can deliver 0.5A to 2A max which should be enough for the atmega as well as the toshiba drivers. if I'm reading the data sheet correctly the max used on VDD is like 80 mA times 4 that's like 400mA max so as long as the power supply can hack 1A we could power everything on Vsb slap a resistor on the 5V rail and run the whole thing with the atmega steering the power on sequence, but I had a thought since pc psu's can hack quite a bit of throughput and well having to load the 5V line with a resistor is quite wasteful, so I was thinking we could use the 5V line to heat the bed , depending on the bed design we could use 5V and a minimum let's say load for the atx supply for PLA and just have it switch higher for abs :s that could be wired up by creating one fixed heater (always on limited heating capacity let's say a preheat that drain's off the power needed to keep the psu stable without buring off the power uselessly ( example one 10 ohm 10 W resistor ) the heated bed will still switch on and off but there would be no need for wasting electricity, and the bed would stay warm while the psu is on.
Question is what will 2.5W of power really do much warming of the bed might want to use 2 10 ohm resistors in parallel this would be 5W and well that would even further help stablize the psu and well 5W of warming power hmmm that Could be enough for PLA if there is not much cold airflow over the bed if we enclosed the reprap maybe it will be enough to maintain the temp might have to boost it a bit in the beginning. I wonder if this could work in a pcb design (let's say MKIII)
Just some ideas
terramir

Actually I think the ATX standby line is probably a safer 5V source since you would know that the ATX supply is powered if that is on, and off when the ATX supply is off, and there would be no way to have 12V on when 5V was off. With USB you might disconnect the 5V while the ATX supply is still connected, and with current Gen7 boards that results in the control line floating to ground and the ATX supply turns on. That's why I'll need a pull up resistor on the ATX contol line.

Yes a 5V HBP or hot end is a good idea for ATX supplies since there needs to be a good load on 5V anyway. It wouldn't be too hard to design a custom board with stripboard. I did a 12V one for the vertical x axis contest and put some basic design rules up as well.

[www.thingiverse.com]

I'm planning on trying a 5V ghetto HBP sometime soon.

By tying more strips in parallel you could get whatever wattage you want for any voltage you care to design for. The prusa HBP is about 80W so I would guess you'd need at least 40W or so for PLA. Most ATX supplies will do 30A on 5V so that shouldn't be a problem, you might even use both 5V and 3.3v if you want to spread the load really evenly but that would be a bit tricky to design. Or 5V for the HBP and 3.3v for the hot end. Of course that would mean a change in heating resistors for the hot end. Not sure if the FET's would like driving a load that was on a voltage lower than the gate voltage. And if you want to do temp control on the HBP you would have to either separate the supplies or drive both hot end and HPB from the same voltage.

The control line of an ATX should be driven low with an open collector / drain transistor, not direct from the Atmel. To avoid inverting the firmware you can pull the base / gate to 5V and switch the emitter / source with the Atmel.

A MOSFET will not mind switching a lower voltage than its gate.

I am taking a leaf out of Adrian's book and using a 12V 20A lighting PSU from China for my next machine. Only £14, doesn't need dummy loads, doesn't have a fan AFAIK, so quiet and a more convenient form factor. The only downside is you need to be electrically competent to make a safe mains connection with a switch.

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[www.hydraraptor.blogspot.com]

according to the atx spec the 5Vsb is usable for a light load, most cheaply made atx psu's need a load on 5V 10Watts should be sufficent to stablize the psu (i.e. make sure the voltages are with-in atx spec (which is like +/- 5 % for most).
What I was proposing was an always on (as long as the green wire is shorted to ground preheater for the bed. which means 5W or a little more constant load on the 5V line. the main heating of the bed would be steered by the electronics, but as long as the psu is up the bed would be fed 5W of heating (this could work with separate leads to a strip board design two additional resistors 10 ohm resistors in a sand resistor design. yes it would add some wires, but just think about this when the "thermostat" is triggered the 5 volt load will disappear all together this can cause voltage fluctuations and resets. But if you use a constant load (5 to 10 W) on the 5V the heatbed reaches a certain temp with the "switched" 12V heater the 5 to 10 W will keep the temperature stable longer while keeping the psu in check. using a switched load on the 5V line of a psu will cause problems during a no load condition.
so what I would propose is a 2.5W or 5W constant load (the 10 ohm resistor many people use is 2.5W ) so 2.5W maybe sufficient, and the rest on a gen 7 or gen7 T (or other electronics switched 12V heater. this way we can save on wireing too (12V 8 amps needs a heck of a lot less wire than 5V 16amp) it's like quadruple the wire needed to cut down on resistance losses getting to the bed.. (see voltage/ resistance and ohms law google is your friend).
terramir

I start work on my own MoBo with TB6560, based Gen7. Please check my PCB's project - GENTIBA v1.0

Edited 3 time(s). Last edit at 01/24/2012 09:30AM by codec.

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Hey codec, good to see another design out there. Pretty soon we'll have some good alternatives to pololu electronics. How big is that board?

nophead, informative as always. Thanks

terramir, I agree that is a good idea. I actually just leave my heated be on all the time while the ATX supply is on. It's not currently temperature regulated or FET controlled. It heats up to whatever the equilibrium temperature is and stays there. I think that is a common though probably not an optimum approach. So you could do it your way with a thermistor and dual supplies, or just plug the HBP directly to 5V and it will heat whenever the ATX is powered.