Running power for a 24vdc swing gate opener

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rsouthgate

9 posts

Wannabe Geek

#197994 21-Jun-2016 17:58

Hi,
I'm thinking of getting a gate opener off aliexpress. The gate is about 30m from nearest mains supply. The motors are 24vdc and the control box looks to have a big coil transformer to take mains down to the 24v. I'm thinking of splitting this transformer into a separate box that I can mount near the mains power supply and then run simple twin 24vdc cable all the way to the control box at the gate.

It's either that or run a mains cable that distance. So I wanted to check if anyone knows of any regulations about concealed cables for 24v. Does it need to be shielded? Double insulated, etc? Or would it be legal to just staple it along a fence or drop into a shallow spade dug trough with no warning tape etc?

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1519 posts

Uber Geek

#1577828 21-Jun-2016 18:26

Have you got a link to the opener?

The voltage drop over 30m at 24v could be quite considerable, depending on the current draw of the motor. 30m will actually have 60m of cable when you count the supply and return wires.

You could possibly fit a pair of 12v batteries at the opener to reduce the voltage drop?

There are rules and regulations on running mains cables, but I don't believe that there are too many restrictions for 24v.

rsouthgate

9 posts

Wannabe Geek

#1577840 21-Jun-2016 18:52

Here's a link: https://m.aliexpress.com/item-desc/32644607041.html

Lists motor as 60w though it's hard to tell if that is each or both combined... I was going to use 22 gauge twin here:
http://s.aliexpress.com/zIJRzABJ

By my probably terrible calculations I was left with 19v at the opener... Can't tell if that would be enough... But does the maths sound right?

rsouthgate

9 posts

Wannabe Geek

#1577863 21-Jun-2016 19:22

I suppose as an alternative I could get a 30v driver... With same 22 gauge that should give me 24v at the end. Would that be more sensible? Actually that's not going to work is it - when the motors are off the control board will be getting close to 30v which it's probably not designed for.

deadlyllama

1263 posts

Uber Geek

Trusted

#1577904 21-Jun-2016 20:12

How much current is required? You could use a DC to DC converter at the gate to ensure the required voltage was available. Just make sure the converter is rated to silly the required current plus a comfortable margin

pipe60

127 posts

Master Geek

#1577947 21-Jun-2016 20:48

6mm would be more suitable to get 24V dc down to gate. Still better to run 240v down for gate, throw in a cat cable for a camera and think about a led flood light and pir.

deadlyllama

1263 posts

Uber Geek

Trusted

#1577948 21-Jun-2016 20:49

pipe60:

4mm or 6mm would be more suitable to get 24V dc down to gate. Still better to run 240v down for gate, throw in a cat cable for a camera and think about a led flood light and pir.

You have to care more about the electrical regulations when 240V gets involved...

MadEngineer

4278 posts

Uber Geek

Trusted

#1577970 21-Jun-2016 21:43

Gencalc

You're not on Atlantis anymore, Duncan Idaho.

Sharesies

Trade NZ and US shares and funds with Sharesies (affiliate link).

rsouthgate

9 posts

Wannabe Geek

#1577982 21-Jun-2016 22:10

$21 seems a bit steep for a calculator app!

Fred99

13684 posts

Uber Geek

#1578017 21-Jun-2016 22:38

pipe60:

6mm would be more suitable to get 24V dc down to gate. Still better to run 240v down for gate, throw in a cat cable for a camera and think about a led flood light and pir.

Yes - about 5-6mm (AWG #10) should be okay in my opinion, should keep voltage drop within about 5% with motors (60w x 2) running. They probably draw a bit more when they start, but the spec says soft start/stop.

In the end it's a bit of a guess as you don't know what's going to happen, but at least running 24v, easy to test by laying out cable on the ground to check it works.

I would probably not run 230v out. Even though I could get the regd sparky bit done for free, digging trenches and dealing with connecting an alibaba sourced PSU which probably doesn't have NZ SDoC would give me a bit of the creeps.

Jaycar etc sell 12v PIR led flood lamps, or just use LEDs without PIR which go on and off with the gate motors.

gzt

17125 posts

Uber Geek

Lifetime subscriber

#1578023 21-Jun-2016 22:43

From the spec:

Input voltage: DC24V
Motor's power: 60W
Rotational speed: 100PRM
Backup battery: 12V /(5.2 or 7.0AH)

If the battery backup runs the motor does that mean the motor is 12V? Then that is 12V/60W/5A. Unless it's a 24V motor running real slow on backup?

Fred99

13684 posts

Uber Geek

#1578029 21-Jun-2016 22:52

gzt: From the spec:

Input voltage: DC24V
Motor's power: 60W
Rotational speed: 100PRM
Backup battery: 12V /(5.2 or 7.0AH)

If the battery backup runs the motor does that mean the motor is 12V? Then that is 12V/60W/5A. Unless it's a 24V motor running real slow on backup?

Could be, but it's a guess. I'd assumed that the OP would want a dual gate system, so 2 x 60W.

MikeAqua

7779 posts

Uber Geek

#1578098 22-Jun-2016 09:43

I've done a bit of marine DC wiring (DIY, I am not a professional). I use the blue seas cable calculator, which has served me very well so far.

24VDC, 3A load, 200 ft run (there and back) in conduit and limiting voltage drop to 10% (acceptable for motor loads).

I got 14 AWG as the recommended wire gauge.

10AWG if we limit voltage drop to 3% (acceptable for electronic loads).

You could protect 14AWG cable at the supply end with a 10A circuit breaker or fuse.

The gate unit may have in-built protection. If it doesn't, another breaker or fuse will be required at the gate end to protect the motor etc.

Mike

SepticSceptic

2188 posts

Uber Geek

Trusted

#1578163 22-Jun-2016 10:47

The way I read it is if you use the battery backup part, all you will need is sufficient to keep the backup battery topped up, and the battery will be able to be used for the intermittent use of the gate ?

That way, you'd be able to use a smaller gauge wire, only to keep the battery topped up, and not for the instantaneous power for powering the motors

rsouthgate

9 posts

Wannabe Geek

#1578173 22-Jun-2016 10:59

It is strange that it says 12v battery. I asked the seller the question and they said the battery is typically used with a solar panel (300w) and a controller charging/ discharging a lead acid battery. When I looked into the cost of the panel and battery I was surprised how expensive that was going to be so I figured a long run of heavy gauge wire would be cheaper. I've ordered the thing now and I'll have a better idea once it's in front of me. But to go back a couple of comments I would prefer to not have to dig a 30m trench to code - that was my motivation to use a low voltage line.

MikeAqua

7779 posts

Uber Geek

#1578216 22-Jun-2016 11:38

The batteries will cost more than the heavier wire. But ... they will work when the power is out.

SepticSceptic:

The way I read it is if you use the battery backup part, all you will need is sufficient to keep the backup battery topped up, and the battery will be able to be used for the intermittent use of the gate ?

That way, you'd be able to use a smaller gauge wire, only to keep the battery topped up, and not for the instantaneous power for powering the motors

Mike

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