How many extruders do you need?

But as I can see so far the latency is the main problem for the stepper motors, that have to be exactly precise. I am planning to make a "standalone printbed", where a microcontroller only has to control the temperature of the bed and report it back to the main controller. This should be feasibel.

Hi bobc

Yeah I dont think trying to sync the step pulses across micros is a good idea but pwm for heaters and adc for temp does not need that level of sync.

Tony

Ok, so let's consider just the PWM and ADCs. The two chips I am using are £3.40 total for one off. A Mega644 would cost maybe £4.70, so already it's looking more expensive. You might be able to find a cheaper micro to do the job. But you still have the disadvantage of having to develop the code and have to program updates.

If the micro had more interesting processing to do it would make more sense, but using firmware to do a low level processing job is an unnecessary complication. One thing a micro could do is to manage set temperatures, but that is such a trivial task it is hardly worth offloading. What would be useful to offload is driving the steppers, but that is the hardest function to divide up and maintain synchronisation.

So I am really struggling to see what the advantage of the extra micro is, when you go into the analysis.

Before I found the PWM chip I did a search for a suitable micro and came up with some candidates. If the PWM chip is unsuitable, then I would look at again at using a micro. I think it would be a fun little project to do, but I already have plenty of those on the go I am currently looking at building an LPC1769 based board which is compatible with RAMPS-FD, then you could use more easily use Smoothieware etc. Then there is also a board with a Cortex M4 with hardware FPU which would be pretty interesting for non-cartesian geometries. So ideas for boards are plentiful, what takes time is writing the firmware, so my goal was to make one board which doesn't require firmware.

I'll make the same offer as before, if anyone wants to commit to writing the firmware, I'll design and build a board with the processor of their choice.

---

What is Open Source?
What is Open Source Hardware?
Open Source in a nutshell: the Four Freedoms
CC BY-NC is not an Open Source license

Quote
bobc
If the micro had more interesting processing to do it would make more sense, but using firmware to do a low level processing job is an unnecessary complication. One thing a micro could do is to manage set temperatures, but that is such a trivial task it is hardly worth offloading. What would be useful to offload is driving the steppers, but that is the hardest function to divide up and maintain synchronisation.

Yea, this is exctly what I am looking for. I want to build a polar bot with a heated bed (and maybe some additions later like a conveyor belt). The best way to transmit power to the build plate (if you want to spin it in one direction all the time) is a slip ring I guess. There are different slip rings available, some are designed for high power, some are designed for data signals. Slip rings that can deal with both are rare. So I would only transmit power via contacts to the build platform. For the data transfer I would use some kind of wireless transmission (maybe only transmit data once per rotation). For this reason I would need a micro controller that controls the temperature of the heat bed. But I am not sure what kind of communication protocol should be applied between the main controller and the bed (temperature) controller.

That's an interesting project!

You can get little RF modules which might be useful. The comms protocol could be quite simple, you just need to set and read temperature. I think you could use a small board like a sanguinololu to build a prototype, although you wouldn't need all the features on there.

---

What is Open Source?
What is Open Source Hardware?
Open Source in a nutshell: the Four Freedoms
CC BY-NC is not an Open Source license

Quote
bobc
That's an interesting project!

You can get little RF modules which might be useful. The comms protocol could be quite simple, you just need to set and read temperature. I think you could use a small board like a sanguinololu to build a prototype, although you wouldn't need all the features on there.

That is a nice and quite simple but powerful solution!

I have never done any wireless communication, so this might be a stupid question, but how would you connect the RF-Module to the MC? Would you take the I2C port or would you use just the plain digital pins?

The modules I am thinking of are these [www.ebay.com]. They connect with an SPI interface. There is already an Arduino library to support them, so it should in theory be quite easy to use.

I would not expect the data rate to be very high, but should be plenty for this.

---

What is Open Source?
What is Open Source Hardware?
Open Source in a nutshell: the Four Freedoms
CC BY-NC is not an Open Source license

Wow, they look cool! And they are really cheap! Do you have any experience how well they work?

I was thinking more about using 2 directions of Infrared, but I don't thinkt that it might be cheaper or easier than using these modules!

I have some of the modules, I haven't got round to trying them yet.

---

What is Open Source?
What is Open Source Hardware?
Open Source in a nutshell: the Four Freedoms
CC BY-NC is not an Open Source license