I want to put some LED lights on my sliding gate. I wondered if I could power them inductively, with a power 'transmitter' fixed to the gatepost and a power 'receiver' on the gate, positioned so when the gate's shut they are close together and the LEDs come on. The power requirement of the lights is 24W at 12VDC. The positional accuracy of the gate is good.
Bill
Magnetic switch if close enough, or some form of proximity sensor if farther away? Look at burglar alarm kit - plenty of that sort of thing. You might need to incorporate a small relay or transistor switch to handle the current though.
Have you considered whether or not ultraflexible wire might be suitable? Such as:
Just out of interest, why do you need the leds to be so bright? Leds using 24W would produce give thousand lumens. If you need that light level, why not have them fixed on posts?
What about solar?
See BigClive's solution. Needs water proofing though.
No. I don't think one could do this in any efficient way. I'd have thought some kind of simple mating connection would work fine at a low voltage. If you want them on when the gate is open but its only open for a while then one could use a UPS on the gate with the connection connecting the charging. To do power transfer well seems to require HF AC at quite a high current from what I recall. Looking at the inductive chargers for smart phones they do seem to have a lot of electronics involved in the detection of the tuned reception system as well. The question is, is the use case worth the hassle of building something big enough.
Note crosspost removed to satisfy Albersani server Brian
That seems to completely avoid the question of how the power jumps over to the gate ...
I think his issue is that in order to connect the lights on a sliding structure, he needs a long bit of cable, susceptible to damage, hence why he wants it to be wireless. Many years ago, and don't try this at home folks. I saw an electric helicopter being powered by a microwave beam from a modified oven. I somehow think that the power loss and danger involved in powering leds this way might be a slight issue though.
I still think some sliding contacts are the best bet myself, Low voltage, so no danger and if shrouded well, will probably last for years assuming the do not corrode, the sliding motion may keep them clean. Brian
Mmm.
Thet set me thinking alomgh te lones of a pair of contacts that are m,ade when the gate is fully (open? closed?) that charge a BATTERY on the gaste that powers the lights.
Its the wattage that will be the killer. Brian
You can buy 'commodity' induction coils in the 5W to 10W range that are intended for phone charging, rather than running the LEDs on 'live' power, maybe you could fit a battery on the back of the gate, and let it charge 24x7, if the gate spends a significant part of its life open, then have two receivers, so that its powered when fully open and when fully closed
e.g. a 5V 1A transmitter/receiver
a bit more googling ought to find 10W coils
I still think sliding contacts would be allot more efficient and less of a hassle to weather proof. Brian
You might be right, but that's not what bill asked for.
It's not 24w per led. It's 24w in total
I misunderstood the question. Having said that, for safety reasons the gate <should> have a bump stop on the leading edge so that if someone or thing gets in the way the gate either stops or withdraws. Such gates are heavy so need a fairly powerful motor (even if geared) to shift them ergo if it didn't stop it could do damage or serious injury. If the gate has such sensing then by definition it must already have some form of connection to it so that the bump sensor gets its message back to the controller, and if that connection exists then it shouldn't be difficult to get power for the LEDs as well surely?
My electric toothbrush has a base which is connected to the mains and a toothbrush which sits on the base to charge it. Effectively there is a coil in the bottom of the toothbrush that charges the toothbrush battery via a diode, and I imagine (I haven't dismantled one to find out) that there is a similar coil in the base, though as it is connected to the mains it will be a lot more turns of a much finer wire. When in close proximity they form an air cored transformer, and the mains going in the base charges the battery in the toothbrush.
In theory, a similar arrangement could light the diodes on the gate by having one transformer coil on the gate and one on the gatepost.
There are some snags: In order for a transformer to work (whether air cored or the more efficient iron cored), you need alternating current going into its primary winding. You will need either power originating from the mains or a DC supply with an oscillator between power and transformer coil.
LEDs require DC, so you are going to need a rectifier in the gate circuit, and unless you are prepared to put up with a 50Hz flicker it will need to be a full wave rectifier, and ideally a smoothing capacitor to protect the LEDs from spikes in the power input.
This is an outdoor gate, so you will have to make sure everything is weatherproof. It can be done, but I would be inclined to look for an alternative configuration: perhaps a battery pack for the LEDs on the gate charged by a solar panel, and a proximity switch based on a burglar alarm "door open" detector between gate and gate post? Or even a simple plug and socket arrangement between gate and gatepost so that DC arriving at the gate post gets to the LEDs on the gate when the gate is closed and the plug and socket marry up?
Just as an aside, 24W is a lot of light from LEDs (it is roughly the lumens equivalent to 4x60W incandescent light bulbs). Anybody shutting the gate in the dark is going to get suddenly dazzled. Anybody opening the gate and thus turning the previously lit LEDs off is going to find themselves night blind for a couple of minutes.
Jim
That doesn't mean it's not the best/simplest solution, though.
24W is a lot more poweer tha of the other LED ideas mentioned and I would imagine that losses would increase rapidly if the Rx/Tx spacing varied (and there has to be some play in the sliding arrangement, no matter how good it is).Carbon brushes would be ideal for one half of the sliding contact arrangement.
But if a battery is added, then charging can be done 24 hours a day, and the lights won't be on all the time, could be PIR or timer.
I know. That still equates to a couple of thousand lumens assuming around 80 lumens/w for a typical "domestic" led.
A catenary cable from end of gate to post a foot or so away from the rear of the gate should be resonably safe area but if the gate opens more than twice the height of the gate the bottom of the cateanry will touch the ground before the gate is open. Actually the less than twice as you'd want some slack in the cable with the gate fully closed.
I'm inclined to agree a mechanical solution is likely to be more reliable and easier to install, if only because the weather proofing requirements are almost non existant.
Corrosion can be elminated by choice of contact materials:
Stainless steel, recovered from the actual rubber blades of some old wipers? Rather small, less than 1/8" wide.
Springy copper strip "Copper traditional draught excluder". I have some, somewhere, but haven't seen it for quite a while. It wouldn't have got thrown out that's for sure! Advantage is that it's about an inch wide so easy to get a decent contact area and alignment. I could be persuaded to go looking and pop a some in the post.
Brass shim sheet, might be available in the DIY sheds with the angle, rod, tube other metal sheet stuff. But might not be springy enough. My metalurgy isn't up to knowing if heat treatment/quencing would make it springy.
Fixings, brass or stainless steel screws.
Or look at what is on offer for automatically connecting/disconnecting electric fences across gates (hinged or sliding). Might need careful selection of type and minor mods as an electric fence is high voltage low current rather than low voltge high current.
HomeOwnersHub website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.