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control signal over long distance

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rjvh

New Member
Hi I just want some ideas on transfer a control signal (just on off)

the thing is it have to be safe voltage its a level switch in a water tank the distance is 300+ meter and i will have a voltage drop that will effect the working of the contacters and relais

normaly i work with 24V control voltage and have big problems to work with 220V control voltage (did it only one time under protest on demand of acustomer and no responsability paper from him)

the aplication is in laos so radio transmitting is not Alowed by law

my idea is to step up the voltage on one side of the line just for the transportation and step it down on the other side also to keep cable to a minimum size (see drawing)

are there any other solutions to this problem?

Robert-Jan
 

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ericgibbs

Well-Known Member
Most Helpful Member
hi R-J,

This is one alternative.
 
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crutschow

Well-Known Member
Most Helpful Member
You could also use a 28v or 48v transformer and add a resistor (if needed based upon the calculated line resistance) to give 24vac at the relay.
 

mneary

New Member
Consider that 24aWG (0.5mm) wire is only 60 ohms round trip for 300m. What is your relay resistance (impedance?).

If that doesn't deliver enough current to the contactor, use it to operate a relay which in turn operates the contactor. Small 24V relays are cheap.
 

rjvh

New Member
Consider that 24aWG (0.5mm) wire is only 60 ohms round trip for 300m. What is your relay resistance (impedance?).

If that doesn't deliver enough current to the contactor, use it to operate a relay which in turn operates the contactor. Small 24V relays are cheap.
relay impendance is 80:eek:hm: so +/- 0.3 Amp will be the current

the distance is 300 meter so total wire lengt is 600m

i calculated with gauge nr23 (I am not familiar with this type of writing the wire size) 0.5 sqr mm

that comes down on a resistance of +/- 40:eek:hm: (according online tables)

so if i have a output from 36V than it should work

i still keep it optional to put a resistor (Value unknown yet 5 Watt) in series to fine tune the whole thing on site situation as the lenkt of the cable could vary a bit

Thanks for the replies and sugestions

Robert-Jan
 
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