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About Snerkel

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  1. I would look at installing a router doing NAT with the port for VPN being the only thing open. Setup a VPN server on one of the RSview PCs. Make a VPN connection from your PC to the RSview PC which will allow you to use RSlinx gateway to give you full access. This is about as secure as you can make it while still giving you full network access to those PCs snd PLCs.
  2. The 871TM is a two wire device isn't it ? I would suggest three wire devices for PLC inputs as the current drawn by the two wire proximity switch can be enough to cause the input to switch. You may be close to the switching curent with the two wire device, and slight noise on the wiring is enough to tip it over the edge.
  3. Energy Saving Ideas?

    One of the reasons these sort of things don't always get taken up is the different way they are assesed for tax purposes, though I think this may be changing. Fuel costs are taken in full from the annual profit. Assets are usually depreciated over a number of years, so only a percentage of the cost is set against profit each year, thus it takes a number of years for the bean counters to actually see the saving.
  4. 24VDC guard door circuit

    You should have taken your math one step further, the amount of voltage across the relay will be a tad over 20v, check the relay rating for the minimum pull-in voltage, if this is <= 20v then you should be OK
  5. SLC 5/03 Clearing Faults

    This may or may not work never tried it but.... Setup a fault routine. In the routine Latch S:1/8 Latch S:5/0 Unlatch S:1/13 This hopefully will set a minor error which will still stop the processor (but can be reset by key). Will unlatch the major error, and will set the reset on powerup bit.
  6. Circuit Breaker vs Fuse

    Using a breaker as you suggest will be fine. I assume the SCR is being used for a heater system? If it is then you will probably want to look at over temperature protection that controls a contactor in series with the SCR. In normal operation the contactor remains on and the SCR controls the heating, if an over temperature is detected then the contactor is used to isolate the heating circuit. Another idea for the over temperature protection is to use a circuit breaker with a shunt trip such as this Putting 24v onto the shunt trip turns off the circuit breaker so an external circuit (such as over temperature) can be used to "trip" the breaker.
  7. Circuit Breaker vs Fuse

    Also for SCR you should look at using Semiconductor Fuses for the best level of protection.
  8. Enclosure Water Drains

    Another addition may be to use a bagging over the water hoses, so you end up with a double skinned hose. End inside panel is sealed, end outside is open into a small tank or a bund. Level switch in the tank, any leaks no matter how small end up in the tank/bund, and even small leaks will eventually trigger level switch. System used a lot in chemical dosing.
  9. You could make a simple mod that satisfies both requirements. You would need an additional output from the PLC such that once you get the OK signal from your relay you short circuit the relay coil (using a relay driven from your PLC) thus illuminating the lamp. Of course your existing system will not detect a short circuit as the relay would still switch, my suggestion would cause a problem if you did have a short circuit. A better system would be a series resistor in place of the relay with a resistance approx = 50% of the lamp resistance. Using an analogue voltage input on the PLC measure the voltage across the resistor a good circuit will give you about 4v across the resistor, a bad circuit will give you less than say 2v or greater than say 6v across the resistor. This circuit will also light the lamps at a reduced brightness, the advantage of a reduced voltage across the lamps is that they don't get as hot. You would need to make sure the resistor had sufficent power handling to take the full 12volt across it. If you wanted to light the lamps at full brightness then place relay contacts across the resistor so as soon as you detect a good part you can switch the resistance out of circuit.
  10. No Reason being the description/rung comments are not stored in the PLC so unless you have the original software or a csv with the comments then you are stuffed.
  11. As far as I am concerned Ladder is a superb RISC language. For normal use you need to know a few instructions that can be built quickly and easily into a program for controlling a complex machine or process. The structured text and basic modules have their place, but for the actual control the PLCs are made to do ladder is by far the most robust, safe, programming launguage you could find. As far as engineering staff are concerned:- Our electricians need to at least be able to see why a process has failed, ladder with good comments make it simple for even the oldest technophobe to see the fault in a familiar language. Fault finding by MONITORING the PLC code is much quicker than the traditional electrical test methods.
  12. Panel Labels

    In the past I have used illuminated pushbuttons (with and without lamps). I then print laminated labels using a Brother P-Touch on laminate with clear background. The labels are cut to fit inside the pushbutton. I can generally create a symbol or get enough words in to convey use of button and it looks cool when illuminated.
  13. Simple may be best, a basket fitted to the lighting rig with the cables routed so that they drop down towards centre of basket. You would just have to take your time lowering the rig to ensure the cable comes out smoothly. Hopefully the random way the cable is stored in the basket will help prevent induction problems.
  14. Be careful if you decide to use any kind of drum as in operation you are likely to have 50% of the cable still on the drum. The inductance could easily melt your cables!
  15. good low cost DC Drive

    I have always found SSD drives to be good.