Re: Pololu geared DC motor 30g prototype extruder May 25, 2016 12:04PM |
Registered: 14 years ago Posts: 351 |
Re: Pololu geared DC motor 30g prototype extruder May 25, 2016 12:35PM |
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Re: Pololu geared DC motor 30g prototype extruder May 25, 2016 12:44PM |
Registered: 7 years ago Posts: 78 |
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arthurwolf
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o_lampe
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If so you want as much of the work going on withing the firmware, or you'll meet problems very easily with synchronizatio, precision etc.
What synchronization?
The ATtiny gets the step/dir signal from the Atmega ( or other main controller ) and takes care of one motor in a closed loop. But AFAIK there is no feedback to the planner of the maincontroller that allows to sync the other axes with a skipping extruder. For the main controller it is still an open loop, right?
@rklauko
I'd make an e3d holder with integrated clamping holder for the motor/gear. That way you can easily change the motor when brushes or gears are worn out.
Sorry I thought you were going to use the QEI peripheral on the lpc1768.
Yeah if you use step/dir, the lpc1768 doesn't care a bit what's going on
Re: Pololu geared DC motor 30g prototype extruder May 25, 2016 05:00PM |
Registered: 9 years ago Posts: 93 |
Re: Pololu geared DC motor 30g prototype extruder May 25, 2016 05:01PM |
Registered: 14 years ago Posts: 351 |
Re: Pololu geared DC motor 30g prototype extruder May 26, 2016 03:29AM |
Registered: 8 years ago Posts: 181 |
My idea was a bit of a modification of your nr. 4 - I wanted to use analog input on ATtiny for very fast detection of position - it's much faster to read analog input then to read i2c value - time wise.Quote
ipcalit
4) my plan B based on the AS5600 specs - it has analog and I2C output that could be interfaced directly with the controller without any extra hardware (ATtiny). In this case you would need to poll regularly to get the position of the filament. This is already done for filament detection purposes in most firmware. The only question is whether this gives enough control precision to get reliable extrusion. If this works is cheaper than all the above.
Re: Pololu geared DC motor 30g prototype extruder May 26, 2016 05:11AM |
Registered: 10 years ago Posts: 18 |
Re: Pololu geared DC motor 30g prototype extruder May 26, 2016 10:40AM |
Registered: 7 years ago Posts: 78 |
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Risingphoenix
Been following with great interest - and thought I'd try to contribute.
There seems to be very similar motors (6V rather than 12V) available with dual shaft and encoder available from Polulu, with very differing gearings: https://www.pololu.com/blog/549/hpcb-micro-metal-gearmotors-with-extended-motor-shafts
Could this be not used to drive with for example a Arduino Nano, making for a small package?
I realize this can be done very cheaply with custom electronics - but as a proof of concept this might be easier...
Re: Pololu geared DC motor 30g prototype extruder May 26, 2016 10:50AM |
Registered: 7 years ago Posts: 78 |
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rklauco
My idea was a bit of a modification of your nr. 4 - I wanted to use analog input on ATtiny for very fast detection of position - it's much faster to read analog input then to read i2c value - time wise.Quote
ipcalit
4) my plan B based on the AS5600 specs - it has analog and I2C output that could be interfaced directly with the controller without any extra hardware (ATtiny). In this case you would need to poll regularly to get the position of the filament. This is already done for filament detection purposes in most firmware. The only question is whether this gives enough control precision to get reliable extrusion. If this works is cheaper than all the above.
That's why I asked about the resolution - the analog input of ATtiny85 has a resolution of 10bits, however I think reasonable resolution (considering the analog precision of AS5600 and ATtiny85) I expect to get more like 8-bit, therefore 256 values per revolution.
This is 1/2 of what misan suggests as reasonable. So if this is not enough, I'll switch to i2c.
Ah... you're right about the polarization issue. The typical rings we have have the poles on opposite faces of the magnet. Time to google for other magnets. Digikey may have some.Quote
rklauco
I have to get the magnet first - the AS5600 has to have a different polarization than the regular neodynium magnets I have
Re: Pololu geared DC motor 30g prototype extruder May 26, 2016 03:29PM |
Registered: 8 years ago Posts: 181 |
Re: Pololu geared DC motor 30g prototype extruder May 26, 2016 03:49PM |
Registered: 8 years ago Posts: 181 |
Re: Pololu geared DC motor 30g prototype extruder May 26, 2016 04:04PM |
Registered: 8 years ago Posts: 93 |
Could you save more weight by rounding those edges?Quote
rklauco
And this is how it looks like with Chinese cheap e3d v6.
Re: Pololu geared DC motor 30g prototype extruder May 26, 2016 05:05PM |
Registered: 8 years ago Posts: 181 |
My goal is to make it technically possible NOT to replace anything - you will just pull out your stepper, or redirect the step/direction outputs to free pin and that's it.Quote
asbo
This is rather exciting! Assuming it's possible, I think you should aim for being able to use these with pre-existing hardware, I'd love to run these but I wouldn't want to replace my Duet boards.
Probably. But I am too lazy to do so But the OpenSCAD files are linked in my previous post, feel free to edit them and provide a pull request if you'd like. I think the rounded edges would saved me just miligrams. But I can remove the whole top structure - originally designed as the top holder of the extruder. Now, when I think of it, it's useless...Quote
asbo
Could you save more weight by rounding those edges?
Re: Pololu geared DC motor 30g prototype extruder May 27, 2016 01:52AM |
Registered: 7 years ago Posts: 78 |
The ATtiny85 would have to be collocated on a board with the AS5600 to get the analog input to work properly. Any plans to make such board and add the DC driver there too?Quote
rklauco
My goal is to make it technically possible NOT to replace anything - you will just pull out your stepper, or redirect the step/direction outputs to free pin and that's it. The driving of the DC motor and position sensing will be done by external HW - in this case ATtiny85, AS5600 and some DC motor driver (on its way from China for a week already).
Re: Pololu geared DC motor 30g prototype extruder May 27, 2016 02:11AM |
Registered: 8 years ago Posts: 181 |
Re: Pololu geared DC motor 30g prototype extruder May 27, 2016 05:32AM |
Registered: 8 years ago Posts: 93 |
That sounds excellentQuote
rklauco
My goal is to make it technically possible NOT to replace anything - you will just pull out your stepper, or redirect the step/direction outputs to free pin and that's it.Quote
asbo
This is rather exciting! Assuming it's possible, I think you should aim for being able to use these with pre-existing hardware, I'd love to run these but I wouldn't want to replace my Duet boards.
The driving of the DC motor and position sensing will be done by external HW - in this case ATtiny85, AS5600 and some DC motor driver (on its way from China for a week already).
Unfortunately I could never wrap my head around OpenSCAD, I am quite good with SolidWorks though.Quote
rklauco
Probably. But I am too lazy to do so But the OpenSCAD files are linked in my previous post, feel free to edit them and provide a pull request if you'd like. I think the rounded edges would saved me just miligrams. But I can remove the whole top structure - originally designed as the top holder of the extruder. Now, when I think of it, it's useless...Quote
asbo
Could you save more weight by rounding those edges?
Re: Pololu geared DC motor 30g prototype extruder May 27, 2016 05:49AM |
Registered: 8 years ago Posts: 181 |
Could the STL export help you? I can make one no problem - even using OpenJSCAD.org I can do it online...Quote
asbo
Unfortunately I could never wrap my head around OpenSCAD, I am quite good with SolidWorks though.
I bought most of them already.Quote
asbo
Out of curiosity I typed motor encoder into aliexpress and there are some cheap motors with encoders already attached. I've no idea if they're any good for this purpose, and you've probably already stumbled across them, but I thought I'd mention it just in case.
[www.aliexpress.com]
Re: Pololu geared DC motor 30g prototype extruder May 27, 2016 07:21AM |
Registered: 10 years ago Posts: 18 |
Re: Pololu geared DC motor 30g prototype extruder May 27, 2016 07:22AM |
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Re: Pololu geared DC motor 30g prototype extruder May 27, 2016 07:58AM |
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Re: Pololu geared DC motor 30g prototype extruder May 27, 2016 08:59AM |
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Re: Pololu geared DC motor 30g prototype extruder May 27, 2016 12:37PM |
Registered: 8 years ago Posts: 93 |
Re: Pololu geared DC motor 30g prototype extruder May 27, 2016 01:01PM |
Registered: 7 years ago Posts: 78 |
Re: Pololu geared DC motor 30g prototype extruder May 27, 2016 01:15PM |
Registered: 8 years ago Posts: 181 |
Re: Pololu geared DC motor 30g prototype extruder May 27, 2016 01:22PM |
Registered: 8 years ago Posts: 181 |
The problem here is that the $3 motors do not have the extended shaft. So you have no place to put the encoder to.Quote
ipcalit
1) if the motors burn (at some point) you have to replace it along with the encoder as the long shaft motor is more expensive from Pololu than the bundle from Aliexpress. If we could get the encoder off the motor, then you can get plenty of N20 geared down to 30rpm for $3 each.
Re: Pololu geared DC motor 30g prototype extruder May 27, 2016 01:26PM |
Registered: 12 years ago Posts: 972 |
Re: Pololu geared DC motor 30g prototype extruder May 27, 2016 02:01PM |
Registered: 7 years ago Posts: 78 |
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rklauco
The problem here is that the $3 motors do not have the extended shaft. So you have no place to put the encoder to.Quote
ipcalit
1) if the motors burn (at some point) you have to replace it along with the encoder as the long shaft motor is more expensive from Pololu than the bundle from Aliexpress. If we could get the encoder off the motor, then you can get plenty of N20 geared down to 30rpm for $3 each.
Anyhow, for now the AS5600 seems most viable. I'll try to test it as soon as I got the magnets from china...
Re: Pololu geared DC motor 30g prototype extruder May 27, 2016 02:08PM |
Registered: 8 years ago Posts: 181 |
Re: Pololu geared DC motor 30g prototype extruder May 27, 2016 02:14PM |
Registered: 12 years ago Posts: 972 |
Re: Pololu geared DC motor 30g prototype extruder May 27, 2016 02:17PM |
Registered: 7 years ago Posts: 78 |
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misan
Take a look at the AS5601 too, as it provides regular AB encoder outputs too.