# Making telephone mounted streetlights with LEDs



## wa2ise (Dec 1, 2013)

Here I'm building a telephone mounted streetlight using a tiny! surface mount LED. The two support arms are actually fine copper wires, one to feed the current to one side of the LED and the other takes the current away as a return to the power supply via a 10K resistor (necessary to limit the current). 







Carefully solder the arm wires to the LED, so the two arms don't get shorted together, and be aware that LEDs don't like to get very hot for more than a second or two. I find it easier to solder one arm wire to one end of the LED, then bend and form the lower arm, and melt it into the plastic pole, paying attention as to which way the LED is facing (you want its light to face down!). Then form the upper arm wire, and melt it into the plastic pole, be sure you don't short it to the first wire. Carefully bend and position the upper arm wire near the far end of the LED, and being careful not to short to the first arm connection to the LED, carefully solder it to the far end of the LED. Don't worry about LED polarity, we take care of that with the connections via a 10K resistor to the 12VDC supply under the layout. Less current thru the LED makes for longer life, and a reasonably realistic amount of light. LEDs must have resistors to limit the current, else they will burn out immediately.
And here it is lit:







looking like a sodium streetlight, as this is a yellow LED. 
The copper arms wire extends down the pole (as described above) so you can hook up the resistor and the power supply, my club's layout has 12VDC for uses like this. I melted gently these wires into the pole plastic, being sure they don't short together.
Here's a diagram showing the LED and arm wires in closer detail


----------



## midlifekrisiz (Jan 29, 2013)

that's a flippin good idea


----------



## Ray Haddad (Feb 19, 2014)

Really nice! Thanks for this.


----------



## golfermd (Apr 19, 2013)

Very cool. Like the idea of those 10k resistors to make the light intensity more realistic. :smilie_daumenpos:


----------



## gunrunnerjohn (Nov 10, 2010)

Nice work. I use the chip LED's for some tight places, that's a very good use for them.


----------



## Doc Holliday (Apr 6, 2014)

Great idea! 

Someone told me that you can protect the LEDs from the heat of the soldering iron by clipping a heat sink, like an alligator clip, on the lead between the solder location and the LED.


----------



## gunrunnerjohn (Nov 10, 2010)

That is correct Doc, I do that with some forceps.

This is a good idea with many electronic components, not just LEDs.


----------



## Hutch (Dec 19, 2012)

I don't think those forceps would work well on a surface mount LED. Where would you clip it without distroying it? With a regular/leaded LED you have some space between the LED and the solder joint.


----------



## gunrunnerjohn (Nov 10, 2010)

You obviously can't actually heatsink a SMT, since the pads are part of the package.


----------



## Hutch (Dec 19, 2012)

I've never felt the need for heatsinking during soldering. It's usually completed very fast, especially with SMTs. No problems _*that I'm aware of*_ so far.


----------



## wa2ise (Dec 1, 2013)

I've used some soldering rosin (Kester, in a squarish tin) to speed up the soldering process.  This stuff will clean the LED solder pad and the end of the wire you want to solder the LED to. I also have plenty of LEDs on hand, in case I destroy one  The forcepts would make handling the LED easier though.

When the LED streetlight is lit, it makes hardly any heat, and the connecting wires would absorb that heat as a kind of heatsink anyway.


----------



## gunrunnerjohn (Nov 10, 2010)

For SMT parts, I usually use a vacuum IC handling tool.


----------



## Hutch (Dec 19, 2012)

Great idea John. I have a few of those. Next time I solder leads on a surface mount I'll give it a try.


----------



## wingnut163 (Jan 3, 2013)

not to but in but even laying a pin on ether side will act as a heatsink.


----------



## Ray Haddad (Feb 19, 2014)

I use a very hard engineering pencil lead (#3HB) from Staedtler to hold parts in place while soldering.
http://www.amazon.com/Staedtler-Mar...d=1397589053&sr=1-3&keywords=staedtler+refill

You can find them much cheaper on eBay. The UK folks get the best deal.


----------



## wingnut163 (Jan 3, 2013)

Ray Haddad said:


> I use a very hard engineering pencil lead (#3HB) from Staedtler to hold parts in place while soldering.
> http://www.amazon.com/Staedtler-Mar...d=1397589053&sr=1-3&keywords=staedtler+refill
> 
> You can find them much cheaper on eBay. The UK folks get the best deal.


now there is a novel way. :appl::appl:


----------

