routercnc_MK3

[routercnc]

Hi Neil

Thanks for that. Google search shows this is 12A which I think would be ok for continuous running just not sure about the inrush. Is yours powered up yet and running everything connected to it without problems? Thanks

[njhussey]

Unfortunately mine's had nothing done on it in the last 2 and a bit weeks as one of my colleagues (there's only 3 of us in the office) is on long term sick so I'm now doing all the design and engineering as well as all the other stuff I normally do so this has taken a backseat

I got the 12A one as I was going to put a soft start on my torroid....not got round to that yet. I'll probably do it if I have problems.....

[routercnc]

Hi Neil,

Sorry to hear that - it's so close to being finished.

On my machine I've re-drawn my circuit diagram to run the control side from 24V DC instead of 12V. I've ordered a 24V 5A SMPS and 2off 24V 4PDT DIN relays, laid out the 12V cooling pump and fan in series to give 24V load, and will drop a resistor (680ohm 1/2 Watt) onto the 12V LED line.


Those are the easy bits. But can anyone out there help with the following? I'm missing the contactor to switch on the 70V linear power supply and 30V SMPS for the 4 drivers. This will connect after the 6A type D MCB. I keep reading around on this and am getting no-where. There are 2 problems:

One is that I can't find a simple way to work out the inrush current on the power supply so don't know the peak current rating for the contactor.

Second is that contactors appear to be rated for different applications, labelled AC1, AC2,AC3 .. .AC6a, AC6b . . . For example AC3 is for motors, AC6a is for transformers etc. I can't seem to find any that are 24V DC coil with AC6a rating. All are AC3 rating which is really for motors?

I noticed Dean posted a drawing in Neil's build log (e-stop circuit) with a 25A contactor so that is my starting point. Is this an AC3 unit? If so does this work OK with a high inductive load such as the transformer?

All real world experiences and advice welcome as the Chint 25A (NC1-2510Z) AC3 24V DC coil is about £50 when you add delivery and VAT.
http://chaloncomponents.co.uk/epages...0Contactors%22

Finally is it best to isolate both the L and N as I've drawn? I assume I should leave the earth permanently connected to the devices being switched i.e. not run earth through the contactor?

Thanks

[routercnc]

Hi Dean - PM sent

[mitchejc]

Your box is looking VERY tidy and I've been watching this part of your build with a keen eye for ideas since I'm +- at the same stage with mine. Well done!

Can't advise you on the suitability of the SSR but I also got a 25A one (not the same make/model as yours) and I was unaware that it would still pass current when off so I exchanged it as faulty only to find out the new one does exactly the same. On mine its enough to light a 220V pilot light dimly an if I recall correctly I measured it at around 12V or 14V when in off position. For what its worth the guy at the shop told me to put a BIG heat sink on it if I plan to run 25amps thru it.

[routercnc]

Thanks for that Mitchejc,

For info here is where I got to using the SSR (small white square in the middle of the top DIN rail for those who don't use them):






But since these pictures were taken I've removed the SSR because as mentioned above I don't think it works well with the transformer. If it had worked then I didn't plan on using a heat sink because the 25A rating was just to help it survive the unrush current (which is momentarily 100s or 1000s of amps), but then it should settle to a couple of amps (?) for normal running. But if you've got a heat sink then I guess there is no harm in using it anyway.

New plan is to do what I should have done in the first place which is to run 24V DC control instead of 12V (as industry do) which means I can use a 24V DC contactor to switch the transformer and SMPS. The e-stop can then (through the relay) cut power to the drives in an emergency.
The proximity switches are happy on 24V and if I ever upgrade to something like the CS labs unit this also uses 24V. Just waiting for all the new bits to arrive from China.

At the moment I've laid the earth terminal blocks out to act as end stops/cover plates for the main grey terminals because in case you didn't know one end of each JXB4 terminal blocks is open so the last one in the row is 'exposed'. I've got some cover plates on order and when they arrive I can then cluster the earth terminals in the middle to make it as close to a star layout as possible.

Also when the new relays arrive I plan to re-do the diode layout and run it through a terminal block instead of hanging out the back piggy backed onto an cable.

[routercnc]

Got one of the drivers wired up for power and hooked the linear supply direct to the mains feed (just to check operation)
The driver green led came on and got 72V across the power terminals. Then switched off to see how long it would take to drain the caps. It was dropping just under 0.5V per second so took a couple of minutes to drop to a low level (obviously will be quicker with all three drivers). But strangely it stopped at just under 4V and stayed there. I waited but it did not go any further. In the end I held a 10K resistor across the cap terminal to drain it right down. Why did the voltage stop? Must be something in the drivers that stops drawing current at 4V?
This means there will always be a bit of energy stored in the supply long after it has been turned off. This bothers me a bit so I may add a bleed resistor permanently. Anyone else checked if their power supply drops to zero?