Modular Stepper Motor Driver.

In an effort to make the design more flexible, I decided to breakup my original circuit and make it modular.

Download PCB Layout Files. UPDATE Please read the update text on the download page...!

Interconnection.

In the above photo I have tried to show how it is possible to have up to 4 Driver modules connected to

one "Motherboard" (for want of a better name!).

The overall circuit is the same as my original three driver circuit.

The motherboard.

This design uses the printer port to control the Stepper driver. I wrote a small program to help in debugging any printer port issues follow this link to LPT_SPY.exe

This is where all the switches and relays are connected. The relay drivers are Darlington transistors ( TIP122) with built in snubber diode and are made to work with 12Volt relays. The 12Volt relay supply is protected by a "polyswitch" and can deliver up to 1.5 Amp.

The Enable/Disable motors switch, allows motor current to be switched off without shutting down the entire system.

It could also be wired to an emergency stop switch.

Each motor driver module is connected using a simple 10way ribbon cable.

Size

Smart Current Monitor

I added a small microcontroller to monitor activity on the X,Y,Z and 4th axis Step Pulse lines.

After a period of inactivity the current drive to all motors is shut down.

The inactivity monitoring periods are 1 minute or 5 minutes.

The Smart Current Sensor HEX file is available on the Download Page

After current drive is shut down, the microcontroller continues to monitor, only this time it waits for activity, and applies current drive to all motors as soon as a pulse is detected on X,Y,Z or 4th Axis. The first pulse is not missed.

Note! it could be argued that it's just as easy to switch off the power. This system does it for you, even when you are away and when the program has stopped.

There can also be a problem when switching power on/off. During the power on phase there can be random pulses, and these will move the motors and the previous position is then changed. With the Smart Current Monitor, this does not happen..

The Smart Current Monitor

The HEX code file is available for download

Motor Driver Module.

For a better view I removed the simple heat sink.

Each motor driver module has its own power supply plug and is designed to work the a PC power supply type connector, but regular screw terminal can also be used.

If two or more Motor Driver modules are used, they can share a common heat sink, or use individual heat sinks as shown here.

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