Besides installing sound decoders in my engines, I also like other sounds on the layout: church bells, industrial whistles, coal breaker conveyor, running streams, crossing bells, etc. With the exception of the crossing bells, I have all of the sound modules activated by an on/off switch. I’ve been looking for some type of random timer or generator to activate them. Has anyone found a device that can do this or have a solution for one?
Chuck
Norfolk, VA
If you search for 555 timer circuits you should be able to find what you need.
As a fer-instance: http://www.555-timer-circuits.com/
Here’s another good site to search through: http://home.cogeco.ca/~rpaisley4/CircuitIndex.html
Hi Cacole,
Thanks for the recommendation. I have a decent grasp of basic electronics and have built some simple circuits, and could probably build one of these if pointed in the right direction. I’ve looked over the 555 sections of the websites, and understand the resistor and capacitor values will determine the on/off times. I was thinking of maybe 15 seconds on for a church bell and 5-10 minutes off, and without a lot of trial and error is this something achievable with a 555?
I also looked over the Walthers catalog and couldn’t find something like this which is commercially available.
Rob’s site has a ton of information on what you can do with a 555, with information on how to wire it and how to calculate the RC values.
He also has plenty of other really useful circuit ideas - like various forms of proximity detection which could also be used to trigger sound effects, so as when a train passes a specific point.
Depending on how the sound device is wired, on open collector output on the timer or detector can either simulate the closing of the pushbutton or just power the circuit on and off. If the sound circuit’s pushbutton connects to ground, then an open collector output will be a direct substitute, otherwise you will need to switch the power supply, or use a different output circuit on the timer, like a relay.
–Randy
Randy,
Rob was nice enough to answer an email and gave me a specific circuit, resistor and capicator values to try. I finally figured out how to calculate them and will be sending an order into Digi-key today. If I run into any problems installing them you may hear from me again. Thanks.
Chuck
Long delays with 555 based timers are problematic due to the very large values required of the RC components. You will need a very high quality capacitor, otherwise leakage currents will cause timing problems.
Rather than try to do this one 555, I would use two, or a 556, which is two 555s in the same package. Use the first timer for the long off delay and the second for the bell-on timer.
But my first choice would be a microcontroller, such as a PIC. They are dirt cheap and a lot more fun than messing with RC timing values for 555s, especially if you don’t have a junk box full of resistors and caps.
Take a look this starter kit. It’s also available assembled.