Proximity Sensors
- Thread starter boxhead
- Start date
Amr Hassan
Member
- Join Date
- May 2005
- Posts
- 340
when i have these concerns i connect the to relays
ndzied1
Lifetime Supporting Member
At Turck they have some instructions.
Go to http://www.turck-usa.com/Support/Technical_Information.htm
And download the wiring information for AC switches. Unless Telemec is doing someting radically different, it should apply to them also.
Go to http://www.turck-usa.com/Support/Technical_Information.htm
And download the wiring information for AC switches. Unless Telemec is doing someting radically different, it should apply to them also.
rsdoran
Lifetime Supporting Member
NO not in series.
NOT power wise that is, the power can be connected normally if they are 3 wire sensors, then the "output(s)" can be in series.
NOT power wise that is, the power can be connected normally if they are 3 wire sensors, then the "output(s)" can be in series.
Last edited:
Eric Nelson
Lifetime Supporting Member + Moderator
You need a load in there somewhere!...boxhead said:
-Eric
Thomas Sullens
Member
yelp
YES
Eric Nelson
Lifetime Supporting Member + Moderator
As Thomas said, yes. Since you provided more info, I'll do the same:
-Eric
+---------------+
L1 <-------[ SENSOR ]--------| PLC INPUT |
| |
| --- PLC --- |
| |
L2/N <-----------------------| INPUT COMMON |
+---------------+
-Eric
There are ways around this problem that I have either used or seen used.
In order of preference:
1, wire each prox back individually. This is not the question you asked, but it is my preferred way of doing things.
2, Wire each prox individually to a relay, then connect the relays in either series or parallel, as needed by the logic.
3, For only series, it is often possible to wire a small number of two wire proximities in series. This will be on trial and error basis. Often, an interposing relay would also be needed.
One other problem I found with two wire proximity switches is that the off current is high enough to trigger the input, so I often wire the two wire proximity switches through relays as my normal policy.
In order of preference:
1, wire each prox back individually. This is not the question you asked, but it is my preferred way of doing things.
2, Wire each prox individually to a relay, then connect the relays in either series or parallel, as needed by the logic.
3, For only series, it is often possible to wire a small number of two wire proximities in series. This will be on trial and error basis. Often, an interposing relay would also be needed.
One other problem I found with two wire proximity switches is that the off current is high enough to trigger the input, so I often wire the two wire proximity switches through relays as my normal policy.
"One other problem I found with two wire proximity switches is that the off current is high enough to trigger the input, so I often wire the two wire proximity switches through relays as my normal policy."
Sometimes on the contrary - particularly with S7 400 series digital inputs , the input impedance is too high to drive the two wire device as well , I have seen ( but don't like) pull down resistors added to drive the device . Much better 3 wire or relay , anything else is trouble .
Of course it is never wise to wire PNP ( sinking ) open collector proxies in parallel as one will blow the collector up on the other ( i think I have that right)
Sometimes on the contrary - particularly with S7 400 series digital inputs , the input impedance is too high to drive the two wire device as well , I have seen ( but don't like) pull down resistors added to drive the device . Much better 3 wire or relay , anything else is trouble .
Of course it is never wise to wire PNP ( sinking ) open collector proxies in parallel as one will blow the collector up on the other ( i think I have that right)
Sensors
Thank-you everyone for your input, it has been more than helpful and i have it working fine at the moment. One minor glitch is that if the first sensor operates, it indicates i citect fine but when i reset it the second sensor operates ( although you can reset it straight away on citect)I assume this is because the plc scan is quick enough to pick up the second sensor before it powers up. Would this be correct?
Once again thank-you for the help, i find this site very informative.Also has anyone got the last series of the plc update newsletter? As i swithed providers a few months (about 5) back and forgot to change my email address here until recently.
If anyone has them could they email to
[email protected]
Cheers
Corey
Thank-you everyone for your input, it has been more than helpful and i have it working fine at the moment. One minor glitch is that if the first sensor operates, it indicates i citect fine but when i reset it the second sensor operates ( although you can reset it straight away on citect)I assume this is because the plc scan is quick enough to pick up the second sensor before it powers up. Would this be correct?
Once again thank-you for the help, i find this site very informative.Also has anyone got the last series of the plc update newsletter? As i swithed providers a few months (about 5) back and forgot to change my email address here until recently.
If anyone has them could they email to
[email protected]
Cheers
Corey
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