Baseplate blacksmithery

Much drilling and hacking of the baseplate this morning.

As I was preparing to make a start, the postman delivered this contactor. I bought it off ebay during the week for £20 - supposed to be about £60 + vat, so that was a reasonable deal. Cheapest I could find at CPC, RS etc was over £40. It's sold as Schneider Electric but it's a Telemechanique product (made in France) - Schneider own them these days. Brand new, unopened. Part number LC1D25BD - 25A, with 24VDC coil, so I can drive it directly with the e-stop circuit. It's primarily intended for use as a motor contactor or lighting relay. The AC3 rating is for motor applications.

In the Centroid wiring manual for the All-in-one controller (which has more detail than the Acorn manual), they recommend a Telemechanique LC1DT40B7A contactor. Couldn't find that part number on the Schneider website but there are a few very similar models eg the LC1DT406BL which seems to come in at a cool $250(!!). Couldn't see that available anyway convenient, so had to look for an alternative. For one thing, their part is a 40A device, which seems a bit OT. Admittedly, when using a contactor on a DC circuit, the current breaking rating will be (much) reduced but I don't think they are rated for DC operation anyway. So this one is probably good enough for my application.

The instructions / specs are printed on the inside of the box, which is neat!

There seems to be a modular snubber device that can be fitted. In its absence, there is a moulded link to complete the circuit on the std model:

Dug out the old soft start bits, as they contain a bit of DIN rail, which I'll be needing.

Looking at how to mount the Acorn's Mean Well power supply, I thought I'd take a closer look with the cover off. It's an open frame PSU with a mesh cover ie a classic OEM component. I used o designstuff just like this and although they have a good reputation, the technology would have been dated back in the 1980s when I started out. It's an absolutely bog standard flyback supply with TI / Eunuchtoad UC3842 PWM controller, primary side FET and one double diode on the output.

Lots of mounting holes required. If I ever need to remove any of the compts for repair or modification, I really won't want to be disconnecting all the I/O wiring and removing the baseplate just to access fixing nuts on the back face. So luckily I have a load of cinch nuts - you push one of these into the hole and a special tool rivets it into place. For some of the small parts, I just tapped the baseplate directly, as it's about 2 - 2.5mm thick. But for stuff like the transformer, VFD, heatsink etc, I need something a bit more secure.

This is what it looks like afterwards - very neat:

Starting to come together. I reused one of the sheet metal panel parts from the old console unit - this is one of those systems that keeps on giving! A couple of holes on the foot and a single fixing against the end servo drive and Bob's your auntie.

Dry fit up of the main components:

A couple of lengths of cable trunking and a terminal block:

Will need to figure out what goes on the DIN rail next. I've decided to put the soft start relay, soft start resistor and bridge rectifier in the space between the transformer and VFD. And the DC bus caps will sit under the Acorn, close to the drives, hence the bracket. As before, each servo drive will have its own wiring to the DC bus caps. Won't make a lot of difference but it's good practice.