LED Lighting a Trimphone dial...

[19and41]

I've used them to power LED's with decent results.  One could also use coin cell batteries for even less space taken.

[19and41]

I did a further search on Amazon and found this.  It looks like it's filling the bill...

https://www.amazon.com/Solid-Fiber-Optic-Indoor-Application/dp/B071FW1LRG/ref=sr_1_3?hvadid=78546413071281&hvbmt=be&hvdev=c&hvqmt=e&keywords=side+emitting+fiber+optic&qid=1558298447&s=gateway&sr=8-3#customerReviews

[twocvbloke]

if the LEDs were kept in parallel then they would probably work off a couple of AA batteries. I'm thinking there might be space for said batteries on top of the terminals inside the case. Would that be the way to do it? I'm not great with electronics, so just putting the idea out there.

That's essentially how I had the original "prototype" ring I assembled wired up to test my experimental light out in my dial, but not having a trimphone I don't know the size constraints inside the case for storing batteries internally...

I've used them to power LED's with decent results.  One could also use coin cell batteries for even less space taken.

I've thought of using coin cells too too, even using the rechargeable types, there's also LiPo battery packs & mobile phone batteries which can be pretty tiny with a decent amount of juice to give, it's just working out how to recharge them without having to add extra circuitry like a USB lithium charger...

[andy1702]

I wasn't thinking of recharging the batteries. I just thought if they were only powering a few LEDs they might last quite a while.

Regarding the voltage changing on the line when the phone is in different states, can anyone explain this so an idiot (i.e. me) can understand it please?

[twocvbloke]

I wasn't thinking of recharging the batteries. I just thought if they were only powering a few LEDs they might last quite a while.

I had the recharging idea in my head as a convenience approach, saving the need to open the phone up change the batteries when the battery runs out (plus a protected LiPo pack will just switch off at a low enough voltage to protect the pack from over-discharge damage), so like some other GPO telephones with battery packs in them for various functions, it'd be handy to recharge them from line power or something...

[andy1702]

The trouble with recharging from line power is that power changes depending on the state of the phone. The electronics to deal with that is definitely beyond me.

I know some phones based on the shell of a 746 had batteries inside them, usually to operate early push-button tone diallers. But as far as I know they didn't recharge, did they? All the ones I've seen have been flat as a pancake.

[twocvbloke]

The trouble with recharging from line power is that power changes depending on the state of the phone. The electronics to deal with that is definitely beyond me.

I know some phones based on the shell of a 746 had batteries inside them, usually to operate early push-button tone diallers. But as far as I know they didn't recharge, did they? All the ones I've seen have been flat as a pancake.

Yeah, the GPO had it figured out with the 764, but that's all detailed in my other thread on that, it's a few mA at most taken from the line so negligible really...

Other phones, I think there were some with non-rechargeable batteries but I don't recall which, but even so, a 764 that still has its' battery would be flat as a pancake too after having been disconnected for so long...

[Jim Stettler]

The trouble with recharging from line power is that power changes depending on the state of the phone.

Maybe use  a zener diode? A zener diode has a fixed voltage drop across the diode.
Just a thought
Jim

[twocvbloke]

I've become rather obsessed with the "Joule Thief" circuit which uses an NPN transistor, a 1K resistor and a small hand-wound inductor/transformer connected to a single battery (either rechargeable or non-rechargeable) to power LEDs, and, due to the compact size of the circuit, with the biggest component being the battery, it could be fitted somewhere inside a telephone...

Of course, I found the LEDs I want to use, can I find the dial though?? Nope, but it'll turn up I'm sure, eventually...

For those interested, here's a video on the circuit:
https://www.youtube.com/watch?v=K53beWYdIpc
From bigclivedotcom who coined the Joule Thief name...

[andy1702]

So assuming this circuit will make a battery last ages, what's the plan for actually lighting the dial? Are you still thinking of an LED behind each digit?

Trimphone dials are not totally opaque unlike those on a 746 for example. So I wonder if you lit the inside of the phone, would enough light enter the edge of the plastic dial faceplate to make it appear to glow in the dark?

[FABphones]

...I wonder if you lit the inside of the phone, would enough light enter the edge of the plastic dial faceplate to make it appear to glow in the dark?

A light inside the main body of the phone would quite possibly show more through the two openings for the plunger, and via the lower edges, particularly the lower front edge, where some had a lever. I would think it may be brighter also around the perimeter of the dial.

2CV, What dial do you need to find?

[Key2871]

Why can't you use phone line power ?
Your only talking about one volt anyway, and as long as the line maintains a balance it won't effect the line, or it shouldn't.

[twocvbloke]

2CV, What dial do you need to find?

I was just trying to find my dial, just my organisation skills being on the level of "chaos", found it now, but in the process I've yet again misplaced the LEDs!!! Serves me right for trying to tidy up my components trays and organise my mass of LEDs!!! 

Why can't you use phone line power ?

Just lack of knowledge and experience on my part, if using the Joule Thief, 1v is from the battery supply, if line power, the Joule Thief can't be used (It'd burn out the transistor) as it'd need to be dropped from 48v on-hook to about 2.5-3v, and then there's off-hook voltage too which probably would require a way to switch over from one circuit to another with extra switches, which overcomplicates things a tad...

So assuming this circuit will make a battery last ages, what's the plan for actually lighting the dial? Are you still thinking of an LED behind each digit?

Trimphone dials are not totally opaque unlike those on a 746 for example. So I wonder if you lit the inside of the phone, would enough light enter the edge of the plastic dial faceplate to make it appear to glow in the dark?

Yep, still looking at backlighting the dial, I've been playing with a single blue LED from the string I chopped up for the phosphor-green ones, and I've found placing the LED into the channel facing downwards actually does a better job at diffusing the light, so not such an obnoxious bright point of light as with my earlier experiments with my wrong-type-of-green LED string prototype...

As for lighting the inside, that'd be for another trial, I don't have a full trimphone, just the dial alone (I was more fascinated by the use of tritium tubes as part of my interest in low-danger radioactive materials), and the trimphone dials don't sit properly in a regular 700-type dial clamp ring so can't test it in those either...

That said, it wouldn't be the first time I lit a dial from inside the phone......

http://www.classicrotaryphones.com/forum/index.php?topic=7251

[twocvbloke]

Of course, being the smart dingbat I am, I put the LEDs into the "Bare LEDs" tray, and not the "Wired LEDs" one.........

[tallrick]

Years ago I was inspired by Protel payphone boards to build a charging circuit for a NiCad battery to operate my illuminated Princess phone which originally did not come with a light (1980's model) and it had plenty of power to run the Western Electric diodes I got from a broken 1970's phone. I used that phone for 7 years before the battery failed and I put the phone away.