Rods "Spaceship" Scratch built Plasma Cutter build

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28 Apr 2019 10:05 #132166 by rodw
Well I found some time to replace the mechanical relays with the opto isolated ones. Because they are single pole, I had to tie two together so I could isolate both side of the ohmic sensor switch



The LED's I added to the circuit board are now redundant as there are LED's built into the relays. Switching seems to be much cleaner now. I've got two more relays (for the torch and stepper controller disable) in the control box so I will replace them in due course as these came in a pack of 5. I feel more relaxed now I have opto isolated inputs and outputs.
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30 Apr 2019 15:50 #132357 by docwelch
Rod,
Can you share some information on those opto-isolated relays you are using?

Steven

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30 Apr 2019 20:19 #132368 by rodw

docwelch wrote: Rod,
Can you share some information on those opto-isolated relays you are using?

Steven


Steven certainly. here are the details:
RS Components 
Stock # 8886843  6.2mm Solid State Relay 24DC coil, HS Code 85364900
24VDC control, 0-60v load (sold in sets of 5)

Just search for the stock number on RS Components
au.rs-online.com/web/p/solid-state-relays/8886843

5 is a good number for a plasma machine. I've replaced my mechanical relay on the torch on signal so I have one left which I will use to replace the relay on my estop stepper disable signal so I can use them all.

Other guys are using opto22 input and output modules but I found they were way too expensive in Australia
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30 Apr 2019 20:48 #132372 by docwelch
I'm in the US and it looks like the Opto22 I&O modules are quite expensive here as well. Thanks for the link and additional information!

Steven

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30 Apr 2019 21:33 #132377 by islander261
Ebay for modules and racks.

John

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30 Apr 2019 21:35 #132378 by rodw
Ask jtknives where he bought his opto22's. Somewhere in the last few days, he said he only paid about $12 for 4 of them!

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05 May 2019 01:26 #132790 by tommylight
BTW, plenty of SSR for AC can be found on old photocopiers, usually 2 in the same package ranging from 5 to 15A, all controlled by 5V ( tested and they all do work with 3.3V form the parallel port ).
DC ones are much harder to find.
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06 May 2019 21:48 #133003 by andypugh
These look useful:
www.ebay.co.uk/itm/10DD-5-Channel-Din-ra...9:g:JtEAAOSwHMJYFvRJ
But it is worth noting that they switch to a common negative terminal, so your wiring needs to be suitable.
There is also an AC version of the same thing.
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07 May 2019 02:23 #133015 by rodw

andypugh wrote: These look useful:


Thanks Andy. They do look handy. I am also looking for a couple of relays to be used as dry contacts on my Arduino Rotary table controller. I need one input (say 5-36V but 10-36 would do) and one output. Small would be good though!

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09 May 2019 20:33 - 09 May 2019 20:39 #133286 by Grotius
@Rodw,

Maybe look at solid state relais, i see the previous post of Andy is also solid state, so good solution. They are 5v input and output is solid state. No mechanical clicking, just transistor technique.

I use them also with Ethercat for plasma start and to suit the plasma power by a combination of 2 fast solid state relais, connected in a c coded component to control digital plasma inverters that are non compatible with outside pc world. Like the new thermal dynamic 40-60i series with a Cat5 cable to the inverter. Modbuss is not fast.

I use in all plasma machine a 4 channel solid state relais : www.beckhoff.com/EL2794/
But you can order a standard solid state relais on ali too i think or maybe your interface provider has a solid state expansion set available.

How is your 120 amp's inverter doing the job? Did you cut 20mm already?
Last edit: 09 May 2019 20:39 by Grotius.

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