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Author Topic: hooking up limits  (Read 8213 times)

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Offline Hood

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Re: hooking up limits
« Reply #10 on: September 04, 2008, 01:53:50 PM »
I have used several methods, one is a board that cncbuildingblocks made, it is used on my lathe to convert the limits switch 24v to 5v, sadly Ed is no longer making his boards :( I also use relays to convert the 5v to 24v and vice versa. On the mill I am presently doing I made up a board with 7 relays on it, I can have the switched contacts of the relays either all in series, all seperate or a mixture of both just by placing jumpers accordingly. The idea behind this was I could connect a load of limit switches to the board and as the switched contacts were in series I would only need 1 input to Mach. I also have a similar one that takes outputs from Mach at 5V and has 24V accross the switched contacts, I use this for the Inputs to my servo drives which are 12 to 24V.
Hood

Offline Kristin D

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Re: hooking up limits
« Reply #11 on: September 04, 2008, 02:26:17 PM »
I have used several methods, one is a board that cncbuildingblocks made, it is used on my lathe to convert the limits switch 24v to 5v, sadly Ed is no longer making his boards :( I also use relays to convert the 5v to 24v and vice versa. On the mill I am presently doing I made up a board with 7 relays on it, I can have the switched contacts of the relays either all in series, all seperate or a mixture of both just by placing jumpers accordingly. The idea behind this was I could connect a load of limit switches to the board and as the switched contacts were in series I would only need 1 input to Mach. I also have a similar one that takes outputs from Mach at 5V and has 24V accross the switched contacts, I use this for the Inputs to my servo drives which are 12 to 24V.
Hood

What sort of buffer/driver do you use for the outputs? Another thought (dangerous stuff this thinking!) way back I was building automated handling equipment with TTL logic, we used gold plated switch contacts on all our limit switches, one fine day our purchasing agent "got a deal" on a batch of microswitches that were silver plate, within a month I was running all over the country replacing 10-12 switches on every machine as the switches oxidized and were not working reliably. So that brings me to the relays, since there is so little current flowing I wonder if the contacts exhibit similar behaviours with out using some higher current by way of a resistor network and transistor or IC buffer.

Kristin

Offline Hood

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Re: hooking up limits
« Reply #12 on: September 04, 2008, 02:44:55 PM »
The outputs from Mach are through the breakout boards I have, one is a PMDX122 and the other a CNC Building Blocks Acustep, from there they go to the relay coils.
 The relays I have have gold plated contacts and so far no problems :)

Hood

Offline Kristin D

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Re: hooking up limits
« Reply #13 on: September 04, 2008, 02:57:40 PM »
The outputs from Mach are through the breakout boards I have, one is a PMDX122 and the other a CNC Building Blocks Acustep, from there they go to the relay coils.
 The relays I have have gold plated contacts and so far no problems :)

Hood

Thanks,

That answered all my questions. Now for the relay hunt to begin!

Kristin

Offline Hood

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Re: hooking up limits
« Reply #14 on: September 04, 2008, 03:01:42 PM »
I use these ones, nice and compact for fitting on the board I made :)
http://www.rapidonline.com/Electronic-Components/Relays-Solenoids/PCB-Relays/Subminiature-relay-SPCO-1A/29518/kw/60-0795#techspec
 Not sure how easy they are to get in other parts of the world.

Hood

Offline Kristin D

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Re: hooking up limits
« Reply #15 on: September 04, 2008, 04:55:49 PM »
I just saw some fijutsu relays in a surplus catalog now I need go to their website and check the P/N as it has a different suffix than the ones on your catalog page. But they also have some others and all about $1USD ea or 10/$8.50 so it may pay to order up a bunch if they have gold contacts. They also had an inexpensive solid state contactor I could use direct for spindle control for $6.50 ea.

Kristin