stoubia
Member
Hello all,
I am putting together my first PLC/automation design at a company I recently started working for. I'm a EE (just graduated, little experience) so I have some knowledge of electronics, but I'm more experienced with microcontrollers and haven't touched PLCs before. The machine itself is very simple and straightforward for the most part, but I have some questions when it comes to the I guess you could call common industry practices (fuses and circuit breakers, safety relays, emergency stop switch, terminal blocks etc.) I'll give an overview of my project below and try and give specific questions, hopefully somebody with plenty of experience can help me out here.
Function
Control a hydraulic cylinder for a press fit assembly operation
Main components
CLICK PLC :
Hydraulic Components:
1 Hydraulic power unit (Parker-Hannifin, 10A @ 120VAC, similar model: here )
1 3 position - 4 way solenoid (built into hydraulic power unit, solenoid A and B controlled by 120VAC. 1.90A In Rush, 0.42A Holding, 21W. 3 positions are forward, back, and crossfeed/cylinder lock whatever)
1 hydraulic cylinder (double acting)
1 pressure transmitter (noshok, 4-20 mA out, 24VDC, attached to supply port on cylinder to measure force being applied)
Switches, indicators, safety relays:
1 magnetic safety switch (door safety lock, supplier)
1 LED tower lights (already have them, going to use them even if there was something simpler. link)
2 momentary pushbuttons w/ 1 N.O. contact block each (two handed activation for hydraulic link)
1 twist-release pushbutton w/ N.C. contact block (for e-stop)
1 Illuminated 2-position N.O. selector switch (probably will use for on/off)
1 2-position key-operated N.O. selector switch (might use for some safety precaution instead/in addition to other on/off selector switch)
1 Safety Relay, 110 VAC, 3 N.O.+1 N.C contact, 1 channel (probably for E-stop, link)
1 Safety Relay, 24VDC, 3 N.O.+1 N.C., 2-channel (for mag safety gate switch)
2 momentary limit switches with roller (stroke min and max of hydraulic cylinder)
Operation Sequence
Questions
1. How should I configure my safety relays and E-stop? I want to cut the power to the hydraulic pump when the door is open, when the start buttons are not pressed, and when the E-Stop is activated. The two safety relays I listed above are what I have on hand, I can add or subtract anything at this point.
1a. Is the best method of isolating the AC voltage to a motor to put a switch/relay on the load line?
1b. Each contact on the relay is rated for 5A (there are 3 NO contacts). The hydraulic pump is rated at 10 amps. Is it OK to split the load over the 3 contacts (assuming I only need to switch the load line), or do I need a relay with a higher rating?
1c. Could somebody recommend surge protection circuitry? The motor is definitely the heaviest load I have in this system, I will need something on the AC line I imagine.
1d. One of the relays I have has 2 channels, the other has 1. Should I use both relays, or just the 2 channel? Im using an encoded magnet switch and an emergency stop switch, but what about the on/off switch? Or would it ever be necessary to put a PLC output on one of the safety relay channels?
2. Input AC Voltage: there are 3 wires coming into the system (L, N, G). I understand I should put a fuse (or breaker?) on the incoming line.
2a. Is it only required on one of the lines (L)? or do I also need one on the neutral line.
2b. 120VAC is also needed to power the hydraulic power unit, the 2 hydraulic solenoids, and the stack lights. Do I need anything special to isolate the different modules?
2c. related to 2b, how do I size my fusus/breakers appropriately
3. PLC PSU:
3a. Do I need something on my +24V line between the PSU and the PLC?
3b. I have a second identical +24V PSU, is it recommended that I use that for non-PLC items to keep them isolated? (pushbuttons, safety switch)
4. Terminal Blocks: What are they, why would I want to use them?
5. Hydraulic Solenoids:
5a. What type of protection circuitry should I consider for these? Each of the 2 coils is rated at 1.90A inrush and .42A holding.
5b. The current rating seems within the ratings for my PLC's built in relay, so it should be fine to control it directly from the PLC (no external relay), right? I imagine the connection would be simply PLC out -> fuse/breaker -> solenoid.
6. The stacklight unit I have has a built in wiring, I was able to wire the whole thing to my relay I/O board to control the 3 lights, 1 buzzer, and a flashing mode for all 4 (8 lines in total). Wiring schematic found on the amazon page. I probed at it a little with a voltmeter, it seems like the common lines provide something like 50 VAC.
Should I bother putting any circuit protection on this device?
7. Any tips and tricks on putting together the enclosure? I want to make this thing look nice and organized. I was probably going to pick a box off of automation direct . Everything is getting mounted on the DIN Rails. I figure with the correct combination of terminal blocks, circuit breakers, cable management tricks etc. it will look very nice. Its a very simple system anyway, so it's good to start small.
Thanks for giving me your time, I appreciate any help I can get. I'm going to put together some block diagrams for various sections of the system and try and post them soon to try and show what I've got so far.
I am putting together my first PLC/automation design at a company I recently started working for. I'm a EE (just graduated, little experience) so I have some knowledge of electronics, but I'm more experienced with microcontrollers and haven't touched PLCs before. The machine itself is very simple and straightforward for the most part, but I have some questions when it comes to the I guess you could call common industry practices (fuses and circuit breakers, safety relays, emergency stop switch, terminal blocks etc.) I'll give an overview of my project below and try and give specific questions, hopefully somebody with plenty of experience can help me out here.
Function
Control a hydraulic cylinder for a press fit assembly operation
Main components
CLICK PLC :
- CPU: C0-02DR-D link
- 8 Relay In/Out: C0-08TR link
- 8 DC Input: c0-08ND3 link
- 24V, 1.3A PSU: C0-01AC link
Hydraulic Components:
1 Hydraulic power unit (Parker-Hannifin, 10A @ 120VAC, similar model: here )
1 3 position - 4 way solenoid (built into hydraulic power unit, solenoid A and B controlled by 120VAC. 1.90A In Rush, 0.42A Holding, 21W. 3 positions are forward, back, and crossfeed/cylinder lock whatever)
1 hydraulic cylinder (double acting)
1 pressure transmitter (noshok, 4-20 mA out, 24VDC, attached to supply port on cylinder to measure force being applied)
Switches, indicators, safety relays:
1 magnetic safety switch (door safety lock, supplier)
1 LED tower lights (already have them, going to use them even if there was something simpler. link)
2 momentary pushbuttons w/ 1 N.O. contact block each (two handed activation for hydraulic link)
1 twist-release pushbutton w/ N.C. contact block (for e-stop)
1 Illuminated 2-position N.O. selector switch (probably will use for on/off)
1 2-position key-operated N.O. selector switch (might use for some safety precaution instead/in addition to other on/off selector switch)
1 Safety Relay, 110 VAC, 3 N.O.+1 N.C contact, 1 channel (probably for E-stop, link)
1 Safety Relay, 24VDC, 3 N.O.+1 N.C., 2-channel (for mag safety gate switch)
2 momentary limit switches with roller (stroke min and max of hydraulic cylinder)
Operation Sequence
- Operator loads part to be press fit
- operator closes door
- operator presses both buttons to initiate pressing
- hydraulic cylinder powers on and extends until pressure reading reaches desired value/max stroke limit reached
- cylinder retracts (only while door remains closed)
- part is unloaded
Questions
1. How should I configure my safety relays and E-stop? I want to cut the power to the hydraulic pump when the door is open, when the start buttons are not pressed, and when the E-Stop is activated. The two safety relays I listed above are what I have on hand, I can add or subtract anything at this point.
1a. Is the best method of isolating the AC voltage to a motor to put a switch/relay on the load line?
1b. Each contact on the relay is rated for 5A (there are 3 NO contacts). The hydraulic pump is rated at 10 amps. Is it OK to split the load over the 3 contacts (assuming I only need to switch the load line), or do I need a relay with a higher rating?
1c. Could somebody recommend surge protection circuitry? The motor is definitely the heaviest load I have in this system, I will need something on the AC line I imagine.
1d. One of the relays I have has 2 channels, the other has 1. Should I use both relays, or just the 2 channel? Im using an encoded magnet switch and an emergency stop switch, but what about the on/off switch? Or would it ever be necessary to put a PLC output on one of the safety relay channels?
2. Input AC Voltage: there are 3 wires coming into the system (L, N, G). I understand I should put a fuse (or breaker?) on the incoming line.
2a. Is it only required on one of the lines (L)? or do I also need one on the neutral line.
2b. 120VAC is also needed to power the hydraulic power unit, the 2 hydraulic solenoids, and the stack lights. Do I need anything special to isolate the different modules?
2c. related to 2b, how do I size my fusus/breakers appropriately
3. PLC PSU:
3a. Do I need something on my +24V line between the PSU and the PLC?
3b. I have a second identical +24V PSU, is it recommended that I use that for non-PLC items to keep them isolated? (pushbuttons, safety switch)
4. Terminal Blocks: What are they, why would I want to use them?
5. Hydraulic Solenoids:
5a. What type of protection circuitry should I consider for these? Each of the 2 coils is rated at 1.90A inrush and .42A holding.
5b. The current rating seems within the ratings for my PLC's built in relay, so it should be fine to control it directly from the PLC (no external relay), right? I imagine the connection would be simply PLC out -> fuse/breaker -> solenoid.
6. The stacklight unit I have has a built in wiring, I was able to wire the whole thing to my relay I/O board to control the 3 lights, 1 buzzer, and a flashing mode for all 4 (8 lines in total). Wiring schematic found on the amazon page. I probed at it a little with a voltmeter, it seems like the common lines provide something like 50 VAC.
Should I bother putting any circuit protection on this device?
7. Any tips and tricks on putting together the enclosure? I want to make this thing look nice and organized. I was probably going to pick a box off of automation direct . Everything is getting mounted on the DIN Rails. I figure with the correct combination of terminal blocks, circuit breakers, cable management tricks etc. it will look very nice. Its a very simple system anyway, so it's good to start small.
Thanks for giving me your time, I appreciate any help I can get. I'm going to put together some block diagrams for various sections of the system and try and post them soon to try and show what I've got so far.