Running power for a 24vdc swing gate opener

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MikeAqua

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#1578219 22-Jun-2016 11:42

For a DC cable you could use irrigation hose (cheap as chips) as a conduit.

Depending on location you could leave it on the surface, run along a fence or shallow bury.

If you do use conduit you may wish to buy a heavier than required cable to get something stiff enough to push through.

rsouthgate: 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.

Mike

frankv

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#1578262 22-Jun-2016 12:14

I'd be concerned about safety before legality. Although there's (probably) no regulations covering 24V wiring, you could potentially be putting enough energy down the wire to start a fire. If you separate the transformer from the motor, you really should add a fuse at the transformer end.

Looks like you can connect up two 60W motors (for two gates) to a single controller.

Some DC motors (depending on type) can be speed-controlled by varying the voltage, so running on 12V probably means running at low speed.

There's a current-sensor for safety... running at low voltage may mean higher current, and that might trigger the current sensor?

There's no limit switches, so presumably it just turns on the motor for 3 seconds and assumes that the gate is then open. If the motor is run from low voltage, it might open more slowly, and consequently not open all the way. Or maybe they just run until the current-sensor is triggered?

Calculating from the specs (2.4cm/s) installation instructions (72.5-83.5cm travel), it looks like it takes about 3 seconds to open the gate? Say 10 seconds to open and close the gate, at 120W (2 motors) = 120*10/24*24 = about 2Farad. Supercaps for 24+V seem to be expensive though.

I wonder if there's any reason not to put two 12V batteries in series? But then I guess you would need more than 24V to charge the batteries. Plus presumably some kind of circuitry to control the charging.

I'd suggest that IP55 (especially from AliExpress) might not be adequately rainproof. I'd check any joints and cable entry points and probably seal them up with hot-glue.

deadlyllama

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#1578369 22-Jun-2016 14:46

The really clever thing to do would be to modify the control box to work on 24VDC or whatever its internal power supply puts out, then put that by the gate.

MadEngineer

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#1578379 22-Jun-2016 14:57

rsouthgate: $21 seems a bit steep for a calculator app!

the Windows app is free

You're not on Atlantis anymore, Duncan Idaho.

frankv

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#1578406 22-Jun-2016 15:49

deadlyllama:

The really clever thing to do would be to modify the control box to work on 24VDC or whatever its internal power supply puts out, then put that by the gate.

I assume that the control box does run off the 24VDC... probably a 7805 regulator something like that to make 5VDC for the logic and radio receiver and so on. Otherwise, you'd need another AC-to-DC converter for the control board.

MikeAqua

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#1578431 22-Jun-2016 16:13

The Blueseas calc is free too (website, iOS or Android) and there are a few other web calcs designed for marine electrical out there.

MadEngineer:
rsouthgate: $21 seems a bit steep for a calculator app!
the Windows app is free

Mike

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richms

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#1578434 22-Jun-2016 16:23

A friend had one and the 24V was just so it had enough to charge the battery, all the motors were 12v and ran from the battery, so that it could have tiny wire from the house to the motor control box as it was only carrying a few 100mA.

You sure that is not how this one is designed to work?

Richard rich.ms

Fred99

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#1578466 22-Jun-2016 17:00

richms:

A friend had one and the 24V was just so it had enough to charge the battery, all the motors were 12v and ran from the battery, so that it could have tiny wire from the house to the motor control box as it was only carrying a few 100mA.

You sure that is not how this one is designed to work?

Maybe you're right. The toroidal transformer in the PSU looks kind of small, and it's very common for the Chinese to use small 12v DC motors that look like the one in the picture in garage door opener etc, they're much the same as 12v car wiper motors.

rsouthgate

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#1578589 22-Jun-2016 18:32

I'll have a better idea when it's in front of me but I'm thinking if it's 12v motors with a regulator for those and a 5v regulator for the control board then the voltage drop from 24 doesn't matter and I'll use some cheap 22awg cable. Let's see when it gets here!

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