connecting analog sensor to digital input

kenny_Powers

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Feb 2017
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Hello everybody.
for an asignment we are using a s7 1200 siemens starterkit to connect sensores to create a program. we were hoping to save some money and connect 16 analog npn diffuse sensores to the digital input add on. i understand that we have to connect the sensores to a 24v supply and ground, but is it possible to connect the 300mA output of the sensores to the digital input on the plc, and if not what is the cheapest way to change it so this is possible?
this information is from the di add-on data sheet.
● Type of input voltage DC
● Rated value (DC) 24 V
● for signal "0" 5 V DC at 1 mA
● for signal "1" 15 VDC at 2.5 mA
Input current
● for signal "0", max. (permissible quiescent
current)
1 mA
● for signal "1", min. 2.5 mA
● for signal "1", typ. 4 mA; Typical

thank you in advanced
 
Last edited:
They wouldn't work. They are analogue sensors and you have digital inputs.

You need at least 1 analogue input and a load of relays if you want to save money and not buy 16 analogue inputs.
 
The specs you provided is for the PLC input. We don't need that. What is the part number of the sensor? You said it's NPN. It may have an analog output and digital setpoint.
 
The cost of analog inputs nowadays is so low that you will be better off doing it right and buying analog inputs. By the time you get done screwing around you will spend more on time than you will save.
 
the sensore

CHE18-30NA-B710 (E3F-DS30C4).
this is the sensor. this is the translation of the specs for the sensore

Name Infrared photoelectric switch Model CHE18-30NA- B710 Power supply 6-36VDC Current consumption 13MA The following power protection power supply reverse protection control output 300MA detection distance 5-30CM (adjustable). Output mode NPN NO (Permanent detection object opaque object output indication LED (red) Dimensions-M 18-1168 (MM) Housing material ABS detection surface material PMMA lead length 1.2M Origin Maide Hao Electric (Yueqing) Co., Ltd. Code (ZI by OMDHON trademark owners, authorized Shanghai Mai Dehao Industrial Co., Ltd. engaged in the Asia-Pacific region related industry brand licensing (license: related product development, manufacturing and sales)

We havent connected sensores before so we are a bit unsure about the methode. would it be better to scrap the four sensores and just buy all digital ones? the di addon module is alot cheaper than the ai. thank you for all your answeres. it is much appreciated.
 
We havent connected sensores before so we are a bit unsure about the methode. would it be better to scrap the four sensores and just buy all digital ones? the di addon module is alot cheaper than the ai. thank you for all your answeres. it is much appreciated.

You've got digital ones. The only "analog" feature of these sensors is the measuring distance. You're good to go.
 

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