signals

[lordhinton]

hi to day in my electronics lesson i was learning about 555 timers and how they work, then i thought could i use an astable circuit for the pulse connected to a 555 for the timing then to another chip that goes through its legs 1 by 1 send out pulses to the out put component.

 

i thought could this be done with a 2 aspect signal so the light is on green but when a train passes over the sensor or magnet buried in the ballast it acts as a switch which then sets off the circut then timer so it goes red counts its little time then goes back to green after the timer is up (or with 3 aspect yellow then green).

 

 

sounds complicated but i get it but will it work ??????

 

 

 

dan

[lordhinton]

the signals i plan to use are the ercon? type that come with a little circuit board attached

[Lady_Ava_Hay]

hi to day in my electronics lesson i was learning about 555 timers and how they work, then i thought could i use an astable circuit for the pulse connected to a 555 for the timing then to another chip that goes through its legs 1 by 1 send out pulses to the out put component.

 

i thought could this be done with a 2 aspect signal so the light is on green but when a train passes over the sensor or magnet buried in the ballast it acts as a switch which then sets off the circut then timer so it goes red counts its little time then goes back to green after the timer is up (or with 3 aspect yellow then green).

 

 

sounds complicated but i get it but will it work ??????

 

 

 

dan

 

Probably but why not use Traintronics signals and BDL68 sensor boards which do much the same job and are ready to go with a warranty if they don't?

[Guest baldrick25]

Probably but why not use Traintronics signals and BDL68 sensor boards which do much the same job and are ready to go with a warranty if they don't?

I don't see any reason why it shouldn't work, except you would need to use the CMOS version of the 555 or 556, because of the long time constants required.

Use quality capacitors for the RC network as they most likely will be in the uF region, and keep them away from any hot components like regulators, otherwise the time constants may vary a lot.

[noiseboy72]

I have just built a similar system on my layout.

 

A very poor video is here

(sorry, filmed on my mobile, and also it seems I can't drive trains and film at the same time!)

 

The first clip is an automatic signal. It uses an LDR and relay kit from Maplin (About £8 I think) to detect the train. I used a simple method to incorporate a variable time delay, dependant upon the speed of the train. As the train passes over the sensor, the capacitor starts to charge. As soon as the last part of the train clears the LDR, the capacitor will start to discharge. When it reaches about 1.6V, the relay is disengaged and the signal resets to green. A long, slow moving train will allow more charge to build up and the light will stay red for longer.

 

The second clip is of a semi-automatic junction signal with interlocking. The same detection method is used, with the sensor just beyond the converging junction. To operate the signals, there are 2 switches. A basic interlock is provided as in order to set a route to clear (Green), the other switch must be set to red. The switches are latched red and momentary green.

 

The system works using DPDT relays wired to latch when energised. Provided the switches are operated correctly, the relay will latch, setting the route to clear and preventing the other route from being selected until the train has passed over the LDR.

 

Very simple and cheap to build, about £30 plus the cost of the 3 signals.