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The most widely used of all optoelectronic devices is the simple LED (light emitting diode). Here is a presentation of a variety of indicator and flasher circuits using LEDs.
Digikey has the yellow ones T 1 3/4 for about $1 ,8,400 in stock I think they also have some T1 $3 ,3 min. T1 is probably what you want for roof flashers ? in HO ?
or https://www.ebay.com/itm/182766199927
There are loads of 555 timer / modules / kits / boards on ebay,
the link Rico provided also has yellow flashing LEDs ,
Keep in mind , Its hard to recommend an exact fit without knowing what the application is .
looks very similar to the one I photographed, the capacitors might be a bit smaller, but not a big deal ...
the default rate was about 1 flash per second .. the price is a bit higher, but not much either ..
lol, just one ???? the things are less than a buck each?? i guess i could have sent you a free one, but the mailing cost would have been more than the buying cost .. think i have two or three dozen left over ... never thought of it till now ??
Recently when I installed that flashing warning light on the top of the water tower I used a 1.5 incandescent lamp. I like using a lamp for projects like this since the lamp first glows and then gets progressively brighter.
I already had the flasher circuit, but a flasher I purchased for ear warning light on a caboose cost me over $20.00.
Here's what I made. I replaced the blue LEDs with red. The sign is warning to visitors entering the retail side of the Stephens stone yard. The lights flash all the time a train might be present.
When the train comes back into view, you see the loco stall as it tries to climb the hill. There is no sound on this DC loco - that is the actual sound of the wheelslip!
I just acquired a BLI trackmobile at a reasonable price compared to some of those overpriced ones on ebay. I want to add flashing lights like this great installation,..
Well, a clone of the Arduino Pro Mini can be had for probably about $1.50, a small processor board that is factory programmed to blink the on board LED. So no programming is required if all you need is the blink. The blink is also available on a pin of the board, that you can simply connect to another LED with the usual resistor. It has an on board voltage regulator that can step down 12V to run the processor and LED. So all you would need is the board, a resistor, and an LED. Pretty simple. It is off the shelf working with no user programming required.
Edit - actually it's possible to drive LEDs alternately with an output pin, so that suggests crossing grade flasher too...