# 3rd thread extending times of the simple dc reverse timer



## T-Man (May 16, 2008)

I went back to the circuits to understand how to lengthen the run times. The original with a 100uf cap runs 70 seconds out and 30 seconds on a return. 2 to 1 ratio which is determined with the two 470k resistors as r1 and r2 per the diagram.



out return

100 uf 75 sec 35 sec

220 uf 146 seconds 2.4 min 73 seconds 1.2 minutes

330 uf 219 3.6 109 1.8

470 uf 312 5.2 154 2.5


2.5 minutes is a long run or a very slow train.


This shows the new times with a simple capacitor change

Link to previous threads.


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## Big Ed (Jun 16, 2009)

It all makes sense to me now. 

Maybe I should buy one of those books...Electric for dummies.


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## T-Man (May 16, 2008)

You have your pigeons . 

Many have seen the threads but I wonder if anyone has done it.


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## Big Ed (Jun 16, 2009)

T-Man said:


> You have your pigeons .
> 
> Many have seen the threads but I wonder if anyone has done it.


And aren't they just beee u tifull pigeons? 

Probably the Gunrunner has done it. :smokin:

Maybe they are like me and don't understand it? 
I am the only one brave enough to admit it.


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## DonR (Oct 18, 2012)

T-man

My electronic understanding went murky with the demise of the
vacuum tube. I have put together a few solid state circuits
designed by others but only vaguely understand them.

Would you do a text summary of how this circuit works?

I see, for example, that a 100 uf cap affords a 75 sec run 
going out...but a return of 35 seconds...What does that mean?

Is it That the circuit will power the train for 75 seconds headed N and
at that point the cap is discharged and thus circuit stops the train. Then
the cap recharges and restarts the train going S but for only 35 seconds.
Why the diff?

Don


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## T-Man (May 16, 2008)

It has to with producing a square wave. The 555 timer is used in an astable circuit.

So in the astable circuit, practically quoting the electronics site, high is the charging of the cap to 2/3, the low is the discharging to 1/3. It charges using r1 and r2, but discharges using only r2.

I read this page to get a handle on it. My source.

Tm is the high part of the wave Ts is low. The time is determined from the size of the capacitor. So Ts is 75 seconds and Ts is 35 seconds. The rest is set with resistors. 

This is also the page I used to determine the flash rate of an LED.

I had to handle some theory but I just go for the results. If I say any more there is a good chance I would be wrong. So with a 100uf cap and 470k resistors at r1 and r2 it just does...

I go for copying circuits and have collected three books on the 555 timer. I am still shy on understanding.

The circuit is explained at the http://home.cogeco.ca/~rpaisley4/AutoRevCheap.html

Basically I used the two sites to achieve the goal of the trolley reverse. The power supply gave me headaches for some reason and I went to wall warts. Since then I have progressed on the voltage regulators on other projects.


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## T-Man (May 16, 2008)

big ed said:


> And aren't they just beee u tifull pigeons?
> 
> Probably the Gunrunner has done it. :smokin:
> 
> ...


You don't have to understand it. It helps. That is why I started with lighting an LED. I made it blink and now I make a train go back and forth.

If you want more assistance we can SKype it out.


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## T-Man (May 16, 2008)

One unit got the 220 uf upgrade.


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## T-Man (May 16, 2008)

*For circular track.*

This circuit can be modified for a simple circle track. The engine would run during one time period and rest on the so called reverse portion. Depending on the capacitor being used there is a short time and a longer time. I installed a double slide switch to the output of the relay. With a switch only one cycle will run the engine long or short time period. The output to the track is connected to the center of the switch. The output from the relay is connected to the outer pins of the switch.

The engine will run the circle then rest, then run again. The key is having an insulated rail. Hooking one wire from the relay. That gives you an ON and OFF, Flip the switch and the time sequence changes to rest then run and rest. You eliminate the reversing by not crossing the leads from the relay to the switch. Or you can keep it but you need to change the direction of the engine to keep it going forward.

The best part, you can run an AC motor with this. Locking out the e unit.


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