Running 12v over Cat6

[CanCuba]

I'm going to be hooking up an electric lock to my VTO. The VTO is located at the gate by the sidewalk and is powered via POE from the NVR. I have a second Cat6 cable running to the VTO in the same conduit as the Cat6 for the VTO. The second cable is to connect the VTO to the DEE1010B module which is to control the second electric lock for the front door. Really, I only need to use two wires on the second Cat6. This would be the RS485A and RS485B from the VTO to the DEE1010B. The DEE1010B and associated electric lock will be powered by a 12v 5amp power supply located inside the house.

My issue is the following:

I don't believe I could power the electric lock for the sidewalk gate off a POE splitter. After doing some research, an electric lock may require up to 3 amps (@ 12 volts) to fire the solonoid. It's a split second but it would probably be too much for the 18 watts I can get off of a POE splitter.

So I need to get power from the 12v 5amp PS inside the house to the electric lock outside at the gate. The second Cat6 will only have two wires in use (for the RS485 signal) and 6 free wires (24 awg wires). But my research is saying this won't be enough to carry the 12v 3amp current the 25 or so feet to the electric lock at the gate.

I'm not totally opposed to pulling two 18/2 cables (one cable for the RS485 and one cable for the 12v power) though the conduit to the gate electric lock replacing the second Cat6 cable as it would be come redudant.

My questions are the following:

Is there no chance the 6 spare wires (3 for +12v and 3 for ground) can carry the 12v 3amp current for the electric lock for the split second the solonoid needs to fire? I like to play it safe rather than sorry but I already have the second Cat6 in the conduit.

Would the induction load from the electric lock firing affect the signal to the VTO if the Cat6 and 12v power cables are running in the same conduit?

Any insight would be greatly appreciated.

 

[dmcIPCAM]

There is a discussion on Stack Exchange about what seems like a very similar situation:

Current over CAT6 ethernet cable

How much current can a CAT6 cable reliably handle? I want to use 3 of the cores for +5V and 3 cores for GND. I'm wondering at what current I need to think of another power solution.

electronics.stackexchange.com

 

[CanCuba]

There is a discussion on Stack Exchange about what seems like a very similar situation:

Current over CAT6 ethernet cable

How much current can a CAT6 cable reliably handle? I want to use 3 of the cores for +5V and 3 cores for GND. I'm wondering at what current I need to think of another power solution.

electronics.stackexchange.com

Thank you. Doesn't look hopeful for using the Cat6 to carry the 12v load despite it being maybe 1/10th of a second at full load. I guess I'll be pulling some 2-wire 20 gauge.

 

[tigerwillow1]

It's not clear to me if you're wondering if the paralleled catx conductors can carry the lock's current safely, or if the resistance will not allow the lock to operate reliably If it's the safety angle, I thought this would be easy to answer, but when I looked up current carrying capacity for a single conductor I found a range of 300 mA to 8 amps for AWG 24, depending on the application and who is providing the information. There's a section 840.160 in the NEC now that addresses this, with a maximum ampacity and a lot of derating factors, but it wasn't obvious to me if the numbers applied to each conductor individually or to the entire cable. As far as resistance goes, 3 paralleled 24 AWG wires is equivalent to about halfway between AWG 19 and AWG 20, so it's not a whole lot off from AWG 18 anyway. If I were doing this, I'd test it with a 50 foot hunk of the catx cable, and if it worked reliably with that, I'd assume it would be reliable at 25 feet. As far as knocking out the RS485 comm goes, the RS485 is supposed to be pretty tolerant of common-mode interference, but if the comm gets knocked out for less than a second, does that matter to you?

 

[CanCuba]

It's not clear to me if you're wondering if the paralleled catx conductors can carry the lock's current safely, or if the resistance will not allow the lock to operate reliably If it's the safety angle, I thought this would be easy to answer, but when I looked up current carrying capacity for a single conductor I found a range of 300 mA to 8 amps for AWG 24, depending on the application and who is providing the information. There's a section 840.160 in the NEC now that addresses this, with a maximum ampacity and a lot of derating factors, but it wasn't obvious to me if the numbers applied to each conductor individually or to the entire cable. As far as resistance goes, 3 paralleled 24 AWG wires is equivalent to about halfway between AWG 19 and AWG 20, so it's not a whole lot off from AWG 18 anyway. If I were doing this, I'd test it with a 50 foot hunk of the catx cable, and if it worked reliably with that, I'd assume it would be reliable at 25 feet. As far as knocking out the RS485 comm goes, the RS485 is supposed to be pretty tolerant of common-mode interference, but if the comm gets knocked out for less than a second, does that matter to you?

Great idea re: 50' test cable. I have the PS and electric lock online and wiring it up would take only a couple minutes.

Heat isn't a concern as the circuit is open for maybe 5 seconds. After the solonoid operates, which draws the maximum voltage of about 3amps, the current would drop to maybe 500ma at most. I'll have to take the lock apart, but some of them have a switch that cuts out the power when the solonoid fires so it doesn't burn out.

The NEC mainly deals with AC current over 120v and low-voltage allows for a lot more leeway, as it appears to me anyways.

Losing the RS485 signal for that little time wouldn't be an issue at all. I've tested the DEE1010B device and it doesn't need the RS485 signal to operate the second electric lock if operated by a button.

I forgot to mention that a concern maybe the 12v peak current on the second Cat6 affecting the signal on the Cat6 that feeds power and signal to the VTO. But POE is 57v generally before it's stepped down at the device. Knocking out that signal would be less than ideal as the VTO would need to handshake with the VTH and NVR again.

Looks like I'll have to tape the 50' 12v test cable and another cat6 together and see if there's a signal issue.

 

[Gimmons]

I have my door strikes running on 12v over twisted pair bell wire that isn't any thicker than cat6 wires. The run is about 12 feet, and I wondered if something would fry, but as the wire is accessible most of its run, and I had it on hand, I decided to try and see. It's been fine for a few months now.

As noted by others, use the 3 spare pairs in parallel for insurance, and maybe even put a fuse in somehow. If the Cuban electricity is anything like the Mexican variety, you're going to see some voltage spikes.

 

[bp2008]

Depending on how much it is worth to you to not need to run another cable, you could get an 802.3bt (a.k.a. PoE++) source (injector or switch) and a splitter capable of handling the power, like this for about $100. It would require a substantially large outdoor enclosure of course. Anyway this would give you 12v 5a at the far end to play with and not worry about it being out of spec for the cable.

 

[CanCuba]

I have my door strikes running on 12v over twisted pair bell wire that isn't any thicker than cat6 wires. The run is about 12 feet, and I wondered if something would fry, but as the wire is accessible most of its run, and I had it on hand, I decided to try and see. It's been fine for a few months now.

As noted by others, use the 3 spare pairs in parallel for insurance, and maybe even put a fuse in somehow. If the Cuban electricity is anything like the Mexican variety, you're going to see some voltage spikes.

Okay, that's reassuring. As I mentioned, the peak amp would be for a fraction of a second. Not a huge deal.

I have a UPS with a 150 amp hour battery array that powers the NVR and cameras so that's safe from spikes. Also, the PS that will power the electric locks, DEE1010B and front door RFID reader will have it's own UPS (much smaller battery as it will have almost zero draw) so that's safe, as well.

Yeah, sometimes the power flickers on and off a few times but I have surge suppresors on all my appliances and have never had an issue. A neighbour told me that about 20 years ago they replaced the transformer out front and ended up sending 220 on one phase. Utility ended up repairing and replacing a lot of appliances.

 

[Gimmons]

I've had to replace the electronics in my inverter-driven washing machine in Merida a couple of times. I leave it unplugged now, when not in use

 

[wpiman]

I'm going to be hooking up an electric lock to my VTO. The VTO is located at the gate by the sidewalk and is powered via POE from the NVR. I have a second Cat6 cable running to the VTO in the same conduit as the Cat6 for the VTO. The second cable is to connect the VTO to the DEE1010B module which is to control the second electric lock for the front door. Really, I only need to use two wires on the second Cat6. This would be the RS485A and RS485B from the VTO to the DEE1010B. The DEE1010B and associated electric lock will be powered by a 12v 5amp power supply located inside the house.

My issue is the following:

I don't believe I could power the electric lock for the sidewalk gate off a POE splitter. After doing some research, an electric lock may require up to 3 amps (@ 12 volts) to fire the solonoid. It's a split second but it would probably be too much for the 18 watts I can get off of a POE splitter.

So I need to get power from the 12v 5amp PS inside the house to the electric lock outside at the gate. The second Cat6 will only have two wires in use (for the RS485 signal) and 6 free wires (24 awg wires). But my research is saying this won't be enough to carry the 12v 3amp current the 25 or so feet to the electric lock at the gate.

I'm not totally opposed to pulling two 18/2 cables (one cable for the RS485 and one cable for the 12v power) though the conduit to the gate electric lock replacing the second Cat6 cable as it would be come redudant.

My questions are the following:

Is there no chance the 6 spare wires (3 for +12v and 3 for ground) can carry the 12v 3amp current for the electric lock for the split second the solonoid needs to fire? I like to play it safe rather than sorry but I already have the second Cat6 in the conduit.

Would the induction load from the electric lock firing affect the signal to the VTO if the Cat6 and 12v power cables are running in the same conduit?

Any insight would be greatly appreciated.

You could probably put a large capacitor at the end of the POE line after the splitter to provide that instantaneous currently see how short the burst will be.

This would go between the 12V and the ground after the splitter.

You thinking something like this?

https://www.amazon.com/Splitter-Compliant-Surveillance-5-5x2-1mm-PS5712TG/dp/B08HS4NT13/ref=sr_1_3?keywords=poe+12v+splitter&qid=1685926583&sr=8-3

 

[CanCuba]

You could probably put a large capacitor at the end of the POE line after the splitter to provide that instantaneous currently see how short the burst will be.

This would go between the 12V and the ground after the splitter.

You thinking something like this?

https://www.amazon.com/Splitter-Compliant-Surveillance-5-5x2-1mm-PS5712TG/dp/B08HS4NT13/ref=sr_1_3?keywords=poe+12v+splitter&qid=1685926583&sr=8-3

A capacitor is something I'd never had thought of! Any idea how'd I'd size such a capacitor?

That splitter is what I've been using around the house save for them being 18w output @ 12v. The splitter won't be used for the electric lock as I plan to use the 6 wires (3 +12v, 3 ground) of the Cat6 cable. If that's not possible, I'll run a 2-wire 20 awg cable in place of the Cat6 that's already there.

 

[wpiman]

A capacitor is something I'd never had thought of! Any idea how'd I'd size such a capacitor?

That splitter is what I've been using around the house save for them being 18w output @ 12v. The splitter won't be used for the electric lock as I plan to use the 6 wires (3 +12v, 3 ground) of the Cat6 cable. If that's not possible, I'll run a 2-wire 20 awg cable in place of the Cat6 that's already there.

What you probably want to do it measure the actual voltage at the end of the line, and then look at the minimum voltage the lock will operate and how long that is.

That POE thing will supply 2A or so-- but the instantaneous current is 3A. So, say you need 3A (lets just do all of it) for 100ms and can take a half volt swing, you are at around .6F.

You can plug your numbers into an online calculator if you don't want to solve a differential equation.

Simple Energy Storage Capacitor Formulae

 

[CanCuba]

What you probably want to do it measure the actual voltage at the end of the line, and then look at the minimum voltage the lock will operate and how long that is.

That POE thing will supply 2A or so-- but the instantaneous current is 3A. So, say you need 3A (lets just do all of it) for 100ms and can take a half volt swing, you are at around .6F.

You can plug your numbers into an online calculator if you don't want to solve a differential equation.

Simple Energy Storage Capacitor Formulae

Very helpful, thanks again!

Having trouble finding a .6F capacitor. Could I use a 1F capacitor? Is oversizing a capacitor bad?

 

[tigerwillow1]

0.6F is a monster. Are you sure there isn't a slipped decimal there? Electrolytic caps are most often rated in microfarads, and 1,000 microfarads is pretty darn big.

 

[Alaska Country]

Agree, that is one big capacitor.

Another issue will be initial charging current as that capacitor will look like a dead short to a 2 amp power supply. Which in turn may shut down the power supply if it has over current protection. Or it not, it could end up being a smoke test!

One could use a current limiting resistor or IMO a better choice would be a 12 volt DC tail or brake light (incandescent filament type) for current limiting. Select one that when supplied with 12 VDC take about 1 to 2 amps to fully illuminate. Then place it is series between the power supply and the capacitor.

However, the overall solution is to use the correct wire size and power supply for your needs and not try to reinvent the wheel.

 

[wpiman]

Very helpful, thanks again!

Having trouble finding a .6F capacitor. Could I use a 1F capacitor? Is oversizing a capacitor bad?

Yes, you can go up but sometimes the larger once have a large charge up times and may totally sink your power when charging up. That might really throw electronics at the end for a loop. You could also do 6 100mF caps in parallel. Any my guess was a total swag, I think you could cut it by 2/3rds realistically.

As others have said, yeah that is a big boy. For 12V, you can get some really big ones designed for car audio systems.

Honestly, I would just try it without it. My guess is the lock probably has a rather large internal capacitor.

 

[tigerwillow1]

You could also do 6 100mF caps in parallel

Assuming mF means microfarad, 6 100mF in parallel is 600 mF, or 1/1000th of 0.6F. I've never seen caps rated in millifarads.

 

[wpiman]

Assuming mF means microfarad, 6 100mF in parallel is 600 mF, or 1/1000th of 0.6F. I've never seen caps rated in millifarads.

I mean milli. 1/1000 of a farad. 1000uF.

I am not talking the little electrolytic ones on a PCB here you use for decoupling caps.

Car Audio Capacitors - Capacitor Industries

These long life, high ripple current car audio capacitors are great additions to any audio system that is in need of extra power.

www.capacitorindustries.com

But I had a lot of assumptions that could be wrong.

 

[CanCuba]

I should have been a bit clearer. I'm having trouble finding a 0.6F (600 micro F) capacitor here in Cuba. lol

They're out there but difficult to locate sometimes. Going to take the lock apart later today to see if there's a capacitor.

Either way, I won't be using the POE splitter to activate the lock. It would be the extra wires in the second Cat6. If that works without adding a capacitor, I'll be golden. But it will have to wait until I'm back from the beach next week! lol

 

[CanCuba]

Here's why I wonder where my head's been! I've had an electric lock on the front door for quite a while now. And powering it using the same 12v 5a PS that I will be using for the installation at the gate. The ethernet cable that I've been using has a run longer than what I need for the front gate and I've been using 2 wires for each +12v and GND.

So we know that 3 wires for +12v and the same for GND will work fine. I feel so foolish for forgetting how I set up the front door lock!

Also, I opened the electric lock that's going on the front gate. No capacitor, the power goes straight to the two solonoids. Interestingly, this particular lock has a switch to that when the power is applied and the mechanism is engaged, power is removed so as to prevent burnout. Switch is circled in green.




So, in closing, the cat6 will carry the 12v just fine with 3 wires each 12v and GND. Only concern is that jolt of electricity interfering with the cat6 that feeds the VTO. But I'll figure that out next week.