Specifications

TECHNICAL SPECIFICATIONS

Input voltage: 220 to 240 VAC

Board Input Current: 0.5A RMS maximum

Output current for external power supplies: 8 A RMS maximum

Operating temperature: 0 ° to 50 ° C

Maximum driving current for each output towards driver: 20 mA continuous

Maximum heating element current: 2.8 A

Maximum 12 VDC “Services” output current: 0.4 A

Power supply: 220 VAC, 80 W (maximum consumption) protected by fuse.

Operating temperature: 0 ° to 50 °.

Internal power supplies: N ° 2 (5 V and 12 V), high efficiency switching type. The 12 V power supply can be replaced, in case of maintenance, with a simple screwdriver.

Drivers piloted: N ° 1 X Axis, N ° 2 Y Axis, N ° 4 Z Axis (max. Driving current: 20 mA for single signal).

Output for external 220 VAC power supplies: present, timed and protected with fuse (max load 1500 W real).

Limit-stroke inputs: minimum and maximum on all axes, possibility of choosing the common polarity (currently set to ground).

Extruder fan output: controlled by firmware and signaled by LED.

Heating element output: controlled by firmware and signaled by LED, protected by fuse (2.5 A max.).

12 V 0.4 A output for external fans: present, protected by fuse.

12V main power supply cooling: present, active above 50 ° with fan installed on board.

ARDUINO reset button: present and accessible.

Possible replacement of ARDUINO board: manual removal with a simple screwdriver.

Isolation of parts powered by 220 VAC mains: present, removable for maintenance.

Connectors: with extractable terminal (in case of disconnection from the board, the wired part must not be removed and remains isolated).

Mounting: vertical or horizontal, at the user’s choice

PROJECT SPECIFICATIONS

The imaginbot controller card is able to control stepper motors operating in parallel, to be exact:

1 on the X axis;

2 on Y axis;

4 on the Z axis;

1 of the extruder.

The “Controller for imaginbot 3D printer” is made up of 2 separate boards: “Controller” board and “Power supplies” tab.

Both units are connected, by means of simple insulated cables, and must work simultaneously.

This choice was made to facilitate the installation of the whole and to avoid having to produce a printed circuit outside the production standards, therefore very expensive.

The dragging kinematics of the 3D printer, to which the entire project refers, must respond to fairly stringent mechanical stresses as all the axes must move masses of considerable size compared to the standard of this type of machine.

This premise is even more valid for the movements of the Z axis.

All this, as expected, requires considerable torque.

This condition has imposed on the Y axis and on the Z axis the use of stepper motors operating in parallel, to be exact 2 on the Y axis and 4 on the Z axis.

Each motor is equipped with a dedicated controller, this is not installed on the boards object of this description.

187/5000The solution of mounting external controllers near their motors has the undoubted advantage of keeping the spinning lines (all motors are 4-wire bipolar) short and compact.

Considering the currents involved and the electromagnetic pollution resulting from maintaining long connections, combined with ease of maintenance, makes this design choice not questionable.

The controller power supplies are drawn from power supplies placed in an external cabinet.

This solution also aims to make the system, as a whole, easier for any maintenance and to keep all the parts more installable and scalable, since the bulkier and heavier components are separated.

The current supplied by each power supply unit, compared to the needs of the stepper motors, is abundant.

In order to do this, it was possible to use a power supply unit for two driver / stepper motor groups.

Table 1 summarizes what has been said (refer to figs. 1 and 2).

To ensure a safe and reliable system start-up, the 220 VAC voltage supplied to the S350-36 power supplies is delayed by about 1.5 seconds with respect to the start of the controller board containing the programmable section, that is the board ARDUINO MEGA 2560.

In fact, the simultaneous connection of loads with a strong capacitive component, as are the power supplies seen above, entails the risk that disturbances and glitches may assume such amplitude as to disturb the normal start-up of microprocessor units.

To remain in a perspective of maximum safety (necessary when printing proceeds with expensive materials) the DC power supplies of the programmable and display / memory section are different from those of the motors.

Upper and lower limit switches must be installed on all axes.

This precaution is necessary, as well as for the calibration of the axes, for obvious safety reasons.

The controller board acquires the signals coming from these micro-switches, obviously of a digital nature (ON / OFF), verifying or not the presence of a 5 VDC voltage.

However, it is possible, by means of simple hardware predispositions, to invert the logic of the signal, or to supply 5 VDC if the kinematics has reached its limit switch or to have 5 VDC in normal operating conditions.

Obviously, in the latter case, the reached limit switch will inform the microprocessor with a voltage of 0 VDC.

All the inputs of the limit switches are suitably filtered for RF with adequate capacity.

All signals arriving at the external drivers are interfaced by photo-couplers in order to cancel the effect of eddy currents circulating between different electrical masses and keep immunity to line noise high.

Furthermore, the optical coupling gives the “Controller” unit great flexibility of use.

Furthermore, the “Controller” board is completely independent from the choice of stepper motors in order to power and working voltage.

These parameters in fact depend on the external power supply used and the stepper motor chosen.

Obviously, the external drivers must also have adequate power for the installed motors.

The input of graphic data and the necessary software settings is made by means of an SD type memory.

This is entered in the display / memory card which also allows, by means of an encoder, data entry.

The ARDUINO MEGA 2560 set and the 12864 display / encoder card, containing a dot matrix LCD display (128 x 64 dots), constitute a sort of computer with mass memory, i.e. SD memory.

The software Marlin of print management is completely freeware and the source, written in “C ++” language is widely commented.

These peculiarities make it easily modifiable according to personal printing needs.

I summarize the characteristics of the “Controller” card in table 2, those of the “Power supplies” card in table 3.