Extending Plip Range

Post by **Defender110** » Wed Oct 26, 2011 1:28 pm

So how do we get an IR plip to travel 10metres like some claims on here? I know it is possible with RF plips but never heard of an IR traveling 10 metres before?

Post by **mat_fenwick** » Wed Oct 26, 2011 3:09 pm

Defender110 wrote:So how do we get an IR plip to travel 10metres like some claims on here? I know it is possible with RF plips but never heard of an IR traveling 10 metres before?

Well, the technology is obviously capable of more than a few feet - think of your TV remote. LEDs do drop in output over time but we're talking hundreds of thousands of hours, so unlikely to be that. Battery life, and poor transmission of the beam through the window are the only other things I can think of; might try it with an open window to see if there's any difference. But so long as I can unlock it before I actually get to the door, that's all I need so I'm not massively bothered either way.

Matt H · Post by **Matt H** » Wed Oct 26, 2011 4:42 pm

I took mine apart and cleaned it, especially behind the plastic window that covers the LED, and the LED itself... Made a surprising difference. Still not great, but it works from a couple of feet away. It's better than using the key, especially if your hands are full!

Although my drivers door doesn't unlock with it, but that's a different story...

Way2go · Post by **Way2go** » Wed Oct 26, 2011 4:58 pm

mat_fenwick wrote:
Defender110 wrote:So how do we get an IR plip to travel 10metres like some claims on here? I know it is possible with RF plips but never heard of an IR traveling 10 metres before?
Well, the technology is obviously capable of more than a few feet - think of your TV remote. LEDs do drop in output over time but we're talking hundreds of thousands of hours, so unlikely to be that. Battery life, and poor transmission of the beam through the window are the only other things I can think of; might try it with an open window to see if there's any difference. But so long as I can unlock it before I actually get to the door, that's all I need so I'm not massively bothered either way.

Quite right Mat!

The longer the distance, the more critical the position and angle aiming of the plip need to be. So most of us will use it close to the car when the acceptance angle is not so critical.
The most critical angle is when opening the tailgate. The plip has to be aimed through the aerofoil aperture and between the rear headrests.

Post by **mat_fenwick** » Tue Nov 01, 2011 10:22 am

As a bit of an aside, I said I would check to see if I had saved the JPGs from Bob Smith's site. I couldn't find them, so as I have just done the job I've jotted down a quick guide on how to do it.

Regarding the range, I wonder if the advances in LED technology mean it would be worth swapping the IR LED in the fob? So long as it has a similar forward voltage and operating current, it should give more output without any downsides.

Way2go · Post by **Way2go** » Tue Nov 01, 2011 9:25 pm

mat_fenwick wrote: Regarding the range, I wonder if the advances in LED technology mean it would be worth swapping the IR LED in the fob? So long as it has a similar forward voltage and operating current, it should give more output without any downsides.

That sounds to be a valid hypothesis Mat.

Post by **Defender110** » Tue Nov 01, 2011 11:02 pm

Sounds like a good idea to me, do your's first Mat and if it works out i'll post you my fob

Post by **mat_fenwick** » Wed Nov 02, 2011 9:43 am

After doing a bit of research it seems like IR LEDs of that era would have probably had a maximum output in the region of 15-30mW. If we limit the search to LEDs of the same size then it's not difficult to find some with an output of 150mW (designed for night vision applications).

Getting a more powerful LED means that you can choose one with a wider viewing angle and (hopefully!) still have a reasonable range, so it should mean that it's not so critical exactly where you point it. If you really just want maximum range then it would be better to go for a narrow angle one, which would focus the IR radiation in a tight beam. But that may not be so useful in this application?

The only thing I'm unsure of is the wavelength emitted, and whether it matters to the receiver. Still, at under a fiver for 10 delivered it's not too expensive to find out!

Watch this space...

Post by **mat_fenwick** » Thu Nov 03, 2011 1:18 pm

I measured the voltage at the IR LED in the fob, and found it to be surprisingly low at 0.9V. I didn't know if this is an artificially low figure because the meter is averaging the pulses emitted, so I decided to buy some replacements with a Vf of 1.2 -1.5V (seems to be a fairly typical figure) just to try one. They arrived today but unfortunately do not give any output when in the circuit. I've tested them at 1.5V and they do, so I can only assume the voltage is too low for them to operate when installed.

We do have some better meters at work which are capable of measuring voltage sampling at up to 500 times a second, so will try those to see whether I can get an accurate voltage reading.

Jaba · Post by **Jaba** » Fri Nov 04, 2011 6:29 pm

I actually have a ripped copy of the above mentioned site. So if anyone needs any thing from it then it is still available, but not online of course unless..................
It could be assimilated into the DIY pages. Which could be done with a little work.

Way2go · Post by **Way2go** » Sat Nov 05, 2011 4:58 am

That sounds a good plan.......Jim, Xac?

Mike E (uk) · Post by **Mike E (uk)** » Sat Nov 05, 2011 3:34 pm

Mat's plan is sound, I expect a useful increase in range could be made.

But I still think an RF fob is superior, because you don't need to point it and it works from 50 feet or so, which an IR device will never be able to do.

Use a remote control alarm, or CPO.co.uk sell a suitable transmitter & receiver pair for about £20, which can be wired to the central locking interface.

Mike

Way2go · Post by **Way2go** » Sat Nov 05, 2011 3:54 pm

Mike E (uk) wrote: But I still think an RF fob is superior, because you don't need to point it and it works from 50 feet or so, which an IR device will never be able to do.
Mike

I can't see that on the basis that you can operate the locks from 50 feet away that that makes the RF fob superior. How far away from the car do you need to operate the locks?

It could also be argued that the IR fob is superior because it offers you extra security, as:
1) After locking the car, you cannot accidentally unlock it again by inadvertently pressing the button when in you pocket.
2) If a stranger nicks your keys when in the pub with a view to nicking a car, your car will not flash "Hey I'm here" identification (as is the norm for RF) when the fob is pressed in the car park!