# Cross buck wiring using 555 timer IC chip??



## tr1 (Mar 9, 2013)

Does anyone here have a parts list/ or diagram for an operational
cross bucks grade crossing signal? What type of capacitor is used?
Any info provided is greatly appreciated!
I have a breadboard that should help here with its construction.
I also have a start on some components used.
Thank you! In advance! I thank you immensely!!!
I'll use the Bachman ho plastic cross bucks to work from. 
Regards,tr1


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## wvgca (Jan 21, 2013)

i suppose you could use a 1uf polarized from gnd to pin2 [tied to pin 6], won't drive a whole bunch of current, have to use leds, maybe a 10k from pwr [12v] to pin7, then a 1meg from pin 7 to pin 6 to set flash rate, you want it close to 50%


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## gregc (Apr 25, 2015)




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## tr1 (Mar 9, 2013)

*Yes,that pic looks very familiar*

Would it be possible for a parts list? I could take to my vendor, now.
Thank you,
tr1


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## tr1 (Mar 9, 2013)

*Pin#1?*

How is pin 1 determined?
Thank you,
tr1


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## MichaelE (Mar 7, 2018)

There is usually a notch or a tiny circle on the corner that determines pin one.

And sometimes they are all marked. Depends upon the manufacturer.


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## highvoltage (Apr 6, 2014)

tr1 said:


> How is pin 1 determined?...


Try this:


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## Bwells (Mar 30, 2014)

Another one:
http://www.mrollins.com/flash3.html


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## Dennis461 (Jan 5, 2018)

timing spreadsheet available,, 
wvcga suggested values are on the row just above 'seconds'
gives a period of 1.3958 seconds, high/low ratio of 0.499
R1	R2	C	f	T1	T	
1000	36000	5.00E-08	394.5205479	0.0012765	0.002534722	0.503605479
1000	33000	5.00E-08	429.8507463	0.001173	0.002326389	0.504214925
1000	28000	4.00E-08	631.5789474	0.0008004	0.001583333	0.505515789
1000	55000	3.00E-08	432.4324324	0.0011592	0.0023125	0.501275676
680	100000	1.00E-08	717.560295	0.000694692	0.001393611	0.498483396
10000 1,000,000.00 1.00E-06	0.71641791	0.6969	1.395833333	0.499271642
seconds ratio
1.44/(R1+2R2)*C 
R1 small compared to R2 for square wave with low=high


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## gregc (Apr 25, 2015)

Bwells said:


> Another one:
> http://www.mrollins.com/flash3.html


the circuit uses two 2n3055 transistor rated at 115W capable of driving a full-scale flasher.


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## Bwells (Mar 30, 2014)

gregc said:


> the circuit uses two 2n3055 transistor rated at 115W capable of driving a full-scale flasher.



Is that good or bad?


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## gregc (Apr 25, 2015)

they are large and there are two of them. A typical LED requires only 15 mW. 

In the circuit I posted, a single 8-pin 555 chip is capable of alternately driving both LEDs and performs the multivibrator function of the discrete component circuit you referenced.


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## Bwells (Mar 30, 2014)

Hmmm, sounds like overkill but I'll bet the Uber vehicles will see them!


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## Mark R. (Jan 26, 2013)

I had a circuit at one time for operating a cross buck using only two wires to the signal. The two leds were wired together with opposite leads. The circuit provided a DC flip-flop output.

Unfortunately, I now need it (signals were built in this fashion long ago) and cannot find it. Any help ?

Mark.


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## J.C. (Dec 24, 2016)

don't know it will work for everybody but I wired a 3mm flashing led in parallel with a standard 3mm led and with the proper resistor the standard led goes out when the flasher comes on and comes back on when flasher goes out.


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## T-Man (May 16, 2008)

This is the main electronic circuit page. but I cannot find the circuit. Just search google images . I used a 2n2222 transistors

Wikipedia has a flip flop circuit,


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## Mark R. (Jan 26, 2013)

That Wiki circuit still requires three wires to the pole. The circuit I had used two LEDs, the positive lead of one LED was attached to the negative lead of the other. The other positive and negative were connected together as well. Only two wires attached to the pair of LEDs and the circuit just flip-flopped the polarity.

Mark.


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## Dennis461 (Jan 5, 2018)

*2-wire*

You could build a circuit from 12VDC supply, with a 6VDC output terminal, say from a zener diode.
wire #1
Then use a 555 timer to cycle PNP and NPN which would connect other wire to either 12VDC or 0VDC.
wire#2

with LED's 6 volts in either direction will work.

the above is for a single ended DC supply, if you hade many such 2-wire flashers, I'd build a separate dual voltage supply +12VDC and -12VDC.


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## Mark R. (Jan 26, 2013)

FWIW - I finally found the Bi-polar LED flasher circuit again ....

http://www.talkingelectronics.com/projects/30%20LED%20Projects/images/BiPolarLED-Driver.gif

Instead of using a bi-polar LED, two separate LEDs are wired back to back with only two wires going to the pole.

Mark.


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## T-Man (May 16, 2008)

The 555 Timer chip is very common and useful. Amazon has books written on it with various applications all drawn out. With a little theory you can regulate the flash rate by changing components.


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