Inputs & outputs & relays ohmic

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22 Apr 2019 00:57 #131440 by JTknives
thy came out of a DC PWM so that makes sense. Guess i'm going to fire up the amazon app and get some stuff ordered. You know its the little things that seam to be killing the budget lol.

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22 Apr 2019 01:08 #131443 by tommylight
Relays are one of very few things that i can find locally. Everything else is a pain, have to order through friends abroad and wait and wait ........ i am to old for that wait $#@@. :)

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22 Apr 2019 01:30 #131446 by JTknives
i can order most stuff on amazon and have it here in 1-2 days.

What opto 22 are you using for the probing? i'm guessing something with a fast switch time.

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22 Apr 2019 01:57 #131449 by islander261
Well Tommy is correct you can't use a fullwave scr block to sense a DC voltage. You have to use a DC input block, they are available in several interface voltage ranges the ones I have came from ebay and are 15-32V interface ones, i think even the common 5V interface ones will work because the output is an open collector transistor. So on my system the pin is inverted, +24 is no contact and near 0 is contact, the Opto22 back plane provides the pull up to +24V.

John
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22 Apr 2019 05:23 #131456 by rodw

tommylight wrote:

JTknives wrote: Can I just run my probe sensing through a crydom M505012F.

Unfortunately no, those are SCR used for switching AC, not DC.
The problem with them is that once opened they will remain opened until there is not more current flowing through them and that is something that in AC happens 50 or 60 times per second while in DC it does not until the power is cut off.
Also that is a non isolated type so in the future if you use them, keep that in mind.


Hmm,I had a fairly brutal lesson about this a few days ago I did not realise the nice Solidstate relays were AC only until I saw them latching on just as Tommy describes.
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22 Apr 2019 16:42 - 22 Apr 2019 16:52 #131526 by islander261
This is the input module I use:

www.opto22.com/products/idc24

These should work if you want DIN rail module:

www.crydom.com/en/products/catalog/dr_input_modules.pdf

John
Last edit: 22 Apr 2019 16:52 by islander261.

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22 Apr 2019 22:07 #131559 by rodw
You would not believe how hard it is to find reasonably priced components here in Australia. The opto22 brand is quite expensive and not easy to find. I did find this one in a pack of 5. au.rs-online.com/web/p/solid-state-relays/8886843/
Very fast switching times way faster than our servo thread.

It says its DC switching and this article says mosfet can switch both AC and DC.
www.omron.com.au/service_support/FAQ/FAQ02243/index.asp

This is probably not a bad buy for an Aussie plasma builder. I'm already using 4 relays so would replace them all.

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22 Apr 2019 22:25 #131561 by islander261
Rod

That is an output module not an input module.

John

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23 Apr 2019 01:14 #131587 by tommylight

rodw wrote: You would not believe how hard it is to find reasonably priced components here in Australia. The opto22 brand is quite expensive and not easy to find. I did find this one in a pack of 5. au.rs-online.com/web/p/solid-state-relays/8886843/
Very fast switching times way faster than our servo thread.

It says its DC switching and this article says mosfet can switch both AC and DC.
www.omron.com.au/service_support/FAQ/FAQ02243/index.asp

That is a nice part/price/deal. And yes MosFet's can switch AC and DC, with the AC type having 2 mosfet's inside and DC one only a single one. Mosfet's have a diode inside always so that would let half of the sine wave through even when switched off when using AC, that is why they must have 2 of them wired ....contra !
Mosfet's also have the ability to remain opened by themself ( if the gate is not connected to anything, all it takes to open them is a touch ), but that is very easily dealt with, a single resistor between gate and drain will fix that.
Metal Oxide Semiconductor Field Effect Transistor, full name, i use them a lot, i still have plenty of them on some drives i made just to prove how easy and cheap a stepper motor can be run with Linuxcnc, 4 of them drive a motor, nothing more.
@ John
They can also be used for input sensing, it is basically a relay with no moving parts, and much, much faster.

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23 Apr 2019 02:12 #131591 by JTknives

islander261 wrote: This is the input module I use:

www.opto22.com/products/idc24

These should work if you want DIN rail module:

www.crydom.com/en/products/catalog/dr_input_modules.pdf

John


When I look up IDC24 I see some Thad ate prefixed with G4 and others that are just IDC24. Are there diffrent sizes that require diffrent racks?

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