Interfacing an ultrasonic sensor to a Micrologix 1000.

[tsmartin_98 0]

I did a rough search of the forums and didn't see anything close to what I need to do so I thought I'd ask. I am prototyping a machine out of parts salvaged from other decommissioned machines to keep the cost down. With that in mind, buying the "correct" parts isn't really an option at this phase of development. What I have in my parts bins is: 1) An Allen Bradley Micrologix 1000 with 120 volt ac inputs and relay outputs. 2) A Telemechanique VM18PNO 24 volt dc ultrasonic sensor with PNP output, 40mA current consumption, 100mA max switching current. 3) A 24 volt dc relay. 4) A 24 volt dc power supply. I have done some research online and from what I've been able to gather I should be able to use the sensor to operate the relay which in turn would be used to switch 120 volts to the input of the PLC. This is strictly an on/off circuit. Not analog. What gets me is I see resistors and diodes in the circuits and my eyes glaze over. I'm not an electrical engineer so I'm wondering if any of you out there can verify that this will indeed work and put down in plain English how to do it. Thanks in advance. TS

[chantecler 15]

Could you post the diagram? I'm pretty sure many of us will be able to tell if the circuit will work and what the resistors and diodes are for.

[tsmartin_98 0]

I'll try and attach a pic of the circuit I got off the web that I think is what I'm looking for. I'm beginning to think some of the circuitry is handled inside the sensor. Thanks TS

[chantecler 15]

Hello, First of all, I hope my English be understandable enough. I have attached a hand drawing of the circuit that I utilize, it's really simple. In this case you don't need any extra components since they are already inside the sensor. In case you are curious about the components in your drawing (the one you posted): one is a NPN transistor, the resistor is needed to limit the current fed into the transistor base and the diode is used to protect the transistor against the stress produced by the relay coil when the current flow is abruptly cut. Bye

[PortenoSuenos 1]

Muy Bueno..!!

[tsmartin_98 0]

Thanks TS