Modeltown Lamps

[Sylvian Tennant]

Hi there

I bought two Modeltown station lamps and a wall lamp. I tried them out with a 9 volt battery and two went blue and have stopped working but one is okay.

I'm guessing I did a bit of a whoopsie and over powered the LEDs inside as they're only 3 volts but is this the actual case or could it be a manufacturing fault.

[bazzer42]

I guess they are frazzled, my dear old dad always told me to use resistors. Perhaps modeltown can sell you a couple, failing that I must have some somewhere as i used to use them before discovering boy racer strips.
The sealed 12 volt strips make excellent lighting as they give a warm light with a 9 volt battery, i have 3 lgb coaches that have interconnecting strips in the roof fired by an under slung pp3 ( or the modern equivalent) .
Sorry for the poor typing, stroking a needy westie with the left hand.[/b]

[Sylvian Tennant]

Don't worry I'm reply via phone so this grammar could interesting!

dear ! It was the first thing to hand and I hadn't realised till after model town lamps are just 3v! I've ordered some more which I'd like to wire up in series and would like to know if a resistor would still be nesearry. In fact I was considering making them solar powered as I have a spare solar panel from some lights I accidently snapped.

Cheers for the help and advice.

[philipy]

I've ordered some more which I'd like to wire up in series and would like to know if a resistor would still be nesearry. In fact I was considering making them solar powered as I have a spare solar panel from some lights I accidently snapped.

.

Whether or not a resistor is required depends on the spec of the LED's and the way they are wired i.e series or parallel, as well as the voltage of the battery. LEDs vary from colour to colour in respect of the voltage they will operate on/tolerate.
This site will allow to you to calculate the resistor value:
http://ledcalc.com/#calc

As for the solar panel, I believe that most cheapo chinese garden lights incorporate a 'joule thief' circuit which allows LED's with a nominal voltage of around 2.3 volts to operate on a rechargeable battery with a nominal voltage of 1.2volts. Most garden lights use a single 600ma 1.2v battery so you are unlikely to blow your modeltown lights with one, but it may or may not work, depending on the actual parameters of the chinky electronics. Try it and see.

[MDLR]

I've been using LEDs for many years on 2 x AA or AAA batteries, and I've never needed a resistor.....................

[Soar Valley Light]

I have yet to find a garden solar power pack that lasts more than six months. I've got tons of LED lights - just nothing to power them!

[philipy]

I have yet to find a garden solar power pack that lasts more than six months. I've got tons of LED lights - just nothing to power them!

I tend to agree with that, Andrew. My other half likes our back garden to look like Blackpool prom and spends a small fortune in Poundstretcher replacing failures! However even expensive stuff from garden centres has no more life expectancy.

There seem to be 3 problems, the major one is that the chinese ones are rarely anything like waterproof which leads the components corroding PDQ. 2nd problem is the battery, usually only 600mah and of poor quality and lasting relatively few charge cycles, plus 3rdly, in my ant-ridden clay soil, the little @*$% love to carry little balls of clay into the lamp bodies and completely fill them, creating a permanent short of everything to everything!
The other issue of course is the limited time for direct sunlight to charge them up.

I recently came across a youtube item about increasing the efficiency by changing the inductor and using a better quality and higher capacity battery. A couple of weeks ago I acquired the necessary 'chip' on ebay and have constructed a customised power unit for my station lights. It worked well from the start but only time will tell on the longevity/efficiency. Can't do anything about the sunlight levels, unfortunately.

[Soar Valley Light]

That's interesting Phillip and pretty much mirrors my experiences. Keep us posted about your modification please as the year progresses.

What voltage do these things work on by the way? I'm tempted to chop off the solar wizzardry and simply put a battery across the wires!

Andrew

[markoteal]

I reckon for some, they do about 3v - I've already had a go at that with some 'lightbulb' style solar lights - like others on here - after a few recharges, things become very dim.

So I disconnected the solar panel and wired in a 2032 x2 Penny Battery holder and hey pesto - nice bright LEDS that do the job they were originally designed for - then when the event is over, Is lip a bit of card between the gripper on the battery and the battery itself and store away ready for the next event.

I've also got some from eBay to replace LEDS and use some of these (not the pink ones!) as house lighting on the railway

http://www.ebay.co.uk/itm/New-10-LED-Ba ... 2cba238e9e

[Soar Valley Light]

Cheers Mark,

I'll follow your example and bring a little light back into the life of the local wildlife!

Andrew

[philipy]

That's interesting Phillip and pretty much mirrors my experiences. Keep us posted about your modification please as the year progresses.

As requested, a quick update on things.
To put it in a nutshell, so far it works! After 3 months everything is fine so far.

Basically, I followed the instructions in this Youtube video ( there are loads of similar ones, but this works for me):
https://www.youtube.com/watch?v=3BKKwEm1n6E

I got a 5v PV panel from ebay, plus the other components that he specifies, and used one 1700mah Duracell NiMh rechargeable that I had lying around.
Made a small box from 2mm styrene sheet to fit everything in and it has been happily powering 7 LED's on my station ( 2 platform lamps, 2 in the building, the telephone box and 2 in the pub behind) from dusk until dawn ever since.

It's worth playing with the value of the inductor - changing it alters the 'brightness:illumination time' ratio.

[oldchadders]

I've been using LEDs for many years on 2 x AA or AAA batteries, and I've never needed a resistor.....................

In basic terms - LEDs are current -operated devices, most common ones have a forward voltage drop across them of about 3 volts when working (the actual figure depends on the type, size and colour of the LED. For the above reasons, most LEDs can be safely powered by a 3volt battery. However this is extremely bad practice. When using an LED you should ascertain its recommended operating current (usually around 10 to 20mA) and its forward voltage drop. The brightness of the LED is determined by the current passing through it. All the calculations required involve basic ohms law. To determine the value of the series resistor, subtract the LED forward voltage from the battery voltage (let's express that as Vb - Vf = Vx) The value of the series resistor can then be calculated as R = Vx /If, where If is the operating current in mA and R is the value of the series resistor in Kohms (kilohms = thousands of ohms) the other factor you may come up against is the wattage rating of the resistor. Generally for the normal range of voltages used for our applications a 1/4 watt resistor should be perfectly adequate.
If anyone needs any help working out anything like this, drop me a PM and I will be happy to help.
Peter

[oldchadders]

I have yet to find a garden solar power pack that lasts more than six months. I've got tons of LED lights - just nothing to power them!

I tend to agree with that, Andrew. My other half likes our back garden to look like Blackpool prom and spends a small fortune in Poundstretcher replacing failures! However even expensive stuff from garden centres has no more life expectancy.

There seem to be 3 problems, the major one is that the chinese ones are rarely anything like waterproof which leads the components corroding PDQ. 2nd problem is the battery, usually only 600mah and of poor quality and lasting relatively few charge cycles, plus 3rdly, in my ant-ridden clay soil, the little @*$% love to carry little balls of clay into the lamp bodies and completely fill them, creating a permanent short of everything to everything!
The other issue of course is the limited time for direct sunlight to charge them up.

I recently came across a youtube item about increasing the efficiency by changing the inductor and using a better quality and higher capacity battery. A couple of weeks ago I acquired the necessary 'chip' on ebay and have constructed a customised power unit for my station lights. It worked well from the start but only time will tell on the longevity/efficiency. Can't do anything about the sunlight levels, unfortunately.

In commercial applications (like garden lighting) a solar panel is usually used to keep a rechargeable battery charged up (often a single 1.5v cell). In my experience this requires more sunlight than we tend to get in the UK and the poor charging characteristics of the circuit often leads to early failure of the rechargeable battery. A total no-win situation.