MicroLogix 1100

[Pulsar2003 0]

Hello everyone. I have an uncomplicated project that I want to make complicated. Yup! But let see what you all think of it. I have two small 120V motors that draw about 3 amp max. For that a simple relay with 10 amps contact will do for each one as they don't necessarily work simultaneously. As they are in a remote area it's not always easy to check if all is fine. Basically it is an oil burner and recirculating pump for a small boiler. The burner is protect by a UV sensor, therefore if there is no flame detected it will stop the motor. Easy! Only you find out that there is a problem when the water is cold. In other words: too late. I was wondering if a can use a simple current transformer to feed into the 0-10 VDC(0-32 760) inputs (model: 1763L16-AWA)? As the output is latched for each motors there should be a value in each of respective analog inputs. If a motor doesn't run I can have a alarm and if there should be an overload it too could trigger an alarm. I've read rapidly through the manual: 1763-RM001C-EN-P to look for any notes in the impedance value of the inputs. Nor I have found any details on the ML1100 itself also. Now if this current transformer would work, shouldn't I put a resistor to limit the current? What worries me also is should there be an overload the current drawn by the motor could possibly generate more than 10 VDC. Thank you.

[michael G 2]

how about using a spare contact on the relay after the uv sensor control, or even better some way of sensing directly that the temperature is not being controlled eg flow sensor on the recirculating pump and true burner status (actively running)

[Pulsar2003 0]

That could do the job. But I wonder....If I make an alteration to the electrical safety device can be an issue with the insurance company should something wrong happened? A flow meter could do also, yet I would need to make some plumbing. I plan to use thermocouples to monitor and control the water temperature and leave the actual thermostat (at 195F) as a safety device. I have that type of control on my electric water heater (there is a sensor a resistor outdoors) for the heat of one part of the duplex. An outdoor thermocouple will monitor the temperature, close to freezing point it maintains the water at about 130F with a few increments warmer as we get closer to 0F to obtain water at 195F. Writing this, you are correct, if the waster has to be heated up and takes too much time to heat up an alarm can be triggered. I have a current monitoring relay with a range of 2-20A but it's internal power supply is set at 220V while the circuit is on a 120V. Thanks.

[Ken Moore 23]

I do not recall how many high speed inputs the ML1100 has, but another options would be to mount a prox switch so that motor or pump rpm could be monitored. A simple collar with one pin and a prox switch, count the pulses to determine RPM, you do not have to be extremely accurate, since you are basically looking for a run/no run status. Just a thought.

[tip2112 0]

This is along the same lines as Ken suggested, but what about mounting a "zero-speed" switch to the shaft of the motor ?

[slcman 9]

I think all people here have a good and they are more cheaper than current transformer option. But if you still want to use current transformer for learn about micrologix analog pay attention on resolution. Extension IO have 12bits or more as resolution instead of base unit who have only 10 bits. You'll get 0-10V (0 - 1023) in the base unit (same for M1400), if you need more precision, use expension. I strongly suggest you to use current transformer with 0-10Vdc or 4-20mA output. This will prevent damage to unit.