$20 wireless electronics

Hi everyone,

first time posting here in over 3 years, looks like a lot has change since I've been gone!

I've currently resumed building my second 3d printer (a Mini Prusa) and as a challenge I've decided to see if I can make functional electronics for under AUD$20. Here's what I've got so far:



BOM with current EBay prices are as follows:

328P Arduino Pro Mini ($2.73)
SD Card Module ($1.00)
ESP8266 serial wifi transceiver ($3.69)
4 A4988 stepper drivers w/ heat sinks ($7.96)
Proto board (AU$1.00)

Total: AUD$16.38

I'll need another couple of dollars to cover the power transistors and other discrete components but I should be able to come in on budget. One stumbling block I have encountered is the firmware: can anyone recommend one that's compatible with the 328P? I've had a brief look around and found a few for the Mega but nothing for the Uno. Worse case scenario I could always port my PIC-based Repic firmware to the AVR but there seems to be a ridiculously high number of different electronics to choose from these days and I don't feel there's much to be gained in contributing even more to the noise.

Edited 3 time(s). Last edit at 04/11/2015 03:37AM by Myndale.

I doubt you will find any suitable firmware that fits within the 2K RAM and 32K flash memory of the atmega328.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

Thanks for the response, I figured as much! There's no question in my mind the 328P can handle this, guess I'll just have to go do it myself. Cheers!

Teacup will work.

Teacup Firmware Wiki Link

Every time the UNO comes up for use as a 3D print controller, the thing that ends the thread every time is not having enough pins for everything. I don't know how the board you're using compares with the UNO, but you may want to count the pins before you put in any more time into this.....

There are several ways of saving pins:

- You can use a single pin for all the stepper driver DIR inputs, with no loss of functionality.
- You can share one stepper driver Enable pin between the XYZ drivers, because you don't really need to enable the XYZ motors individually.
- You only need one endstop switch per axis. At a push, you could share a single endstop input between all axes.
- You don't need a Z endstop switch if you have a Z probe, unless your printer is a delta.

So I think the comfortable minimum is 4 step pins, 1 DIR pin, 2 Enable pins, 2 thermistor inputs, 2 heater outputs, 2 endstop inputs, and one Z probe input. That's 14 pins. Add one if you want a controllable cooling fan. Add one for a delta printer, or subtract one for a non-delta if you are using a Z probe that can also be used for X homing , as the Ormerod does. So you still have around 4 spare pins - just enough to interface to an SD card.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

Quote
madmike8
Teacup will work.

Teacup looks really good but it doesn't seem to support printing directly from SD card.

Edited 1 time(s). Last edit at 04/11/2015 06:12PM by Myndale.

Quote
dc42
So I think the comfortable minimum is 4 step pins, 1 DIR pin, 2 Enable pins, 2 thermistor inputs, 2 heater outputs, 2 endstop inputs, and one Z probe input. That's 14 pins. Add one if you want a controllable cooling fan. Add one for a delta printer, or subtract one for a non-delta if you are using a Z probe that can also be used for X homing , as the Ormerod does. So you still have around 4 spare pins - just enough to interface to an SD card.

A lot of the Pro Minis (including mine) expose the A4-A7 analog pins, which along with D0-D13 and A0-A3 gives 22 GPIO pins in total. With that many pins you don't even need to use the DIR trick, you can use D0-D1 for serial, D2-D9 for the steppers, D10-D13 for SD card, A0-A2 for endstops/z-probe and A4-A7 for the extruder/heatbed thermistors and heaters (although in practice I'll swap the heater pins round for ones with PWM).

Edited 1 time(s). Last edit at 04/11/2015 06:36PM by Myndale.