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Forum Index : Other Stuff : 24v logic inverter for cnc conversion

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mab1
Senior Member

Joined: 10/02/2015
Location: United Kingdom
Posts: 275

Posted: 01:08pm 20 Feb 2026

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Hello all,
Wondered if i could pick your the brains on this.

I'm converting an old pacer mill to a new control system, but the logic control lines (enable, drive reset) on the drives are actve high, whilst the output from the control board is open collector, active low. Similarly the fault out from the drive is active high whilst the faultin on the controller needs to be pulled low.

I can do this with 3 discrete transistors of course, but i was wondering, before i start soldering, is there a neater, more convenient solution?

The logic is 24v so i guess a simple cmos hex inverter ic wouldn't do. Could use a uln2002 instead of discrete transistors.

Any ideas of anything better?
Or what to google to find something ready made?

Bryan1

Guru

Joined: 22/02/2006
Location: Australia
Posts: 1777

Posted: 10:15pm 20 Feb 2026

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Mab the DM556 can be active high or low and with micro stepping makes for a smooth travel. The DM556 are pretty cheap and can get away with just direction and step pulse and ground for each axis.

With my CNC I bought a cheap control board off ebay which works with Mach3 and once the motion control driver is installed it just works.

Regards Bryan

mab1
Senior Member

Joined: 10/02/2015
Location: United Kingdom
Posts: 275

Posted: 02:49pm 21 Feb 2026

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Thanks bryan,

The existing drives and motors are really good quality, and i'd be reluctant to change them unless there was no other way. The new controller will work with them, it's just the diffrence in logic control lines means building little adaptor circuits.

I did find some ready made optoisolator modules on ebay which could work and are cheap, but it's swings vs roundabouts as to which is easier.

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