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I have an electric gate opener that takes a 15-18v AC input. Around 100m from the gate I have a 240v outdoor circuit that I'd like to use to power the gate and some garden lighting.

I can't find any specifications on exactly what current the gate will draw, however the readily available transformer for it is rated at 16v, 3.75A. It's only supposed to be located approx 20m from the gate though and I'm concerned that even with expensive 6mm cable, the voltage drop will be too great using this transformer. Overseas they use an 18v transformer and locate it up to 100m from the gate, however I'm struggling to find a suitable one in Australia. There are, however, plenty of outdoor rated (IP67) 24v AC transformers.

So I'm wondering is there any relatively cheap and reliable way to take this 24V AC which, when the gate and lights are operating, might drop to as low as 20V AC at the end of the cable run and get a voltage that stays in the 15-18V AC range from it to power the gate?

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  • \$\begingroup\$ How much current does the gate require? What voltage are the lights able to run from? That is: how high can the voltage be that powers the lights? How much current do the lights need? \$\endgroup\$
    – Dwayne Reid
    Commented Sep 10, 2015 at 6:14
  • \$\begingroup\$ Can you run the 240 Vac all the way to the gate? \$\endgroup\$
    – Dwayne Reid
    Commented Sep 10, 2015 at 6:15
  • \$\begingroup\$ As stated I dont know exact gate current. Something up to 3.75A. Probably 2-3A. Lights are LED, so low overall current, drivers will accept anything between 12v and 24V so not too worried about them. Unfortunately I can't get 240v to gate due to trench depth requirements \$\endgroup\$
    – madz
    Commented Sep 10, 2015 at 6:28
  • \$\begingroup\$ Take pic of the guts of the gate control pcb and you may get more inspiration.' \$\endgroup\$
    – KalleMP
    Commented Sep 12, 2015 at 14:15

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A suitable transformer should be available online for shipping to you.

What you propose is a bit risky as under light load the voltage may rise higher than you hope.

However depending on the gate circuitry it may be tolerant of 24V at some increase in operating speed and decrease in motor and/or gearbox lifetime.

Gate circuitry might possibly accept DC in which case you can add in a diode bridge, smoothing capacitor and a regulator to your transformer to get the ideal voltage.

An alternative might be to find a suitable size (bigger than what you think you need) transformer with multiple taps and use it as an autotransformer to adjust your voltage to suit. You can use taps designed for higher voltages as long as the current rating is adequate. Say 48V and 36V taps would work to bring 24V to 18V as well.

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    \$\begingroup\$ I didnt know about autotransformers, they sound interesting. It's likely to be the answer I think, will wait for a little bit though and see if there are any other ideas. I wish I could tell more about the tolerances of the gate circuitry. I don't have any schematics though and am not experienced enough to know what to look for on the pcb \$\endgroup\$
    – madz
    Commented Sep 10, 2015 at 6:43
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    \$\begingroup\$ Bear in mind with an autotransformer that the ELV side is not isolated from the LV (mains) side. This may have safety implications, depending on the insulation on the gate opener. \$\endgroup\$
    – Simon B
    Commented Sep 10, 2015 at 8:20
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    \$\begingroup\$ @SimonB -- the autotransformer would be sitting on the secondary side of an isolating transformer, so it wouldn't be an issue \$\endgroup\$
    – ThreePhaseEel
    Commented Sep 10, 2015 at 15:22

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