Hello all,

I'm trying to finish up a project left for our technology department. We have a project that requires 4 relays that are rated for 12vdc at 158 mA and my power supply is 12vdc at 2A. The wire used is copper 24 AWG and is 4 strands, but we only use 2 out of the 4.

The length of the wire (from power supply to relay) goes about 450-650 feet. I measured the voltage at each relay and the closet one gets about 12vdc while the furthest gets 10.6vdc.

Can anyone help? I'm not an electrician and this project was put in my lap. Should I look for a relay that requires less power (I tried calling and finding some) or should I just try and find a power supply that is a little larger? Any help is appreciated.

Thanks,

 

Is the relay getting only 10.6V a problem?
The vast majority of 12V relays will work just fine on 10.6V.

 

It appears to be I'm unsure. I can send power and then go to the relay and tap the button that actuates the relay and then it will pull and fire. Seems like it's almost enough juice, but just not enough.

This is the relay I'm working with: Omron G7L-2A-BUBJ-CB DC12

 

Is the relay getting only 10.6V a problem?
The vast majority of 12V relays will work just fine on 10.6V.

Also thank you for the fast reply!

 

From the datasheet, the relay should pull in at 75% of the rated voltage - 9V - so if there is 10.6V across the relay coil I don't know why it doesn't pull in.

 

From the datasheet, the relay should pull in at 75% of the rated voltage - 9V - so if there is 10.6V across the relay coil I don't know why it doesn't pull in.
View attachment 143320

One other suggestion that I might try is taking the 2 unused strands and pairing them with positive and negative? Would that increase the likelihood of it actuating?

 

Your relays have a "must operate" coil working voltage of 75% or with a 12 volt coil 9 volts. The coil current is about 160 mA.

We have a project that requires 4 relays that are rated for 12vdc at 158 mA and my power supply is 12vdc at 2A. The wire used is copper 24 AWG and is 4 strands, but we only use 2 out of the 4.

I assume you are referring to 24 AWG 4 Conductor cable using 2 of the 4 conductors. Should that be the case I would parallel the unused pair with the used pair and reduce the line resistance and subsequent voltage drop. I see as I typed Albert already covered the minimum pull in voltage.

Ron

 

Your relays have a "must operate" coil working voltage of 75% or with a 12 volt coil 9 volts. The coil current is about 160 mA.


I assume you are referring to 24 AWG 4 Conductor cable using 2 of the 4 conductors. Should that be the case I would parallel the unused pair with the used pair and reduce the line resistance and subsequent voltage drop. I see as I typed Albert already covered the minimum pull in voltage.

Ron

Yes thank you very much. I'm going to try that and then let you know how that works. Didn't even cross my mind was going to just have the pair for wire break, but as long as it functions I can pull more wire if needed!

 

1000 ft of 24 ga (you have double the distance) has about 25 ohms. With a 191 ohm coil, you would expect the coil to see 10.6V. Relay is probably out of spec. Try doubling the wire (use two strands for each leg), that should kick the voltage up to 11.2V. Alternatively, increase the voltage to around 13.2V or so.

24 Ga wire isn't a very good solution for long runs. I'd use something like 18 Ga.which would get you 11.6V and am pretty sure the relay would work.

Just a thought, you aren't trying to power both coils in parallel (one swtich with 2 coils)?

[edit] should have checked, ron beat me to it[/edit]

 

1000 ft of 24 ga (you have double the distance) has about 25 ohms. With a 191 ohm coil, you would expect the coil to see 10.6V. Relay is probably out of spec. Try doubling the wire (use two strands for each leg), that should kick the voltage up to 11.2V. Alternatively, increase the voltage to around 13.2V or so.

24 Ga wire isn't a very good solution for long runs. I'd use something like 18 Ga.which would get you 11.6V and am pretty sure the relay would work.

Just a thought, you aren't trying to power both coils in parallel (one swtich with 2 coils)?

[edit] should have checked, ron beat me to it[/edit]

Noted for the wire! Thanks. And yes there are a total of 3 coils off of 1 power source. It is wired in a way that hits a center point and then branches to the 3 relays.