Saturday 9-5

This was my day to work on the crossing lights. I am trying to clean up the installation and convert it over to a solid state system. The existing system was little understoood at the track and was undocumented. I started by drawing out the layout last weekend and after adding to it what I thought the new system should be wired like, I proceeded to get the parts needed to change it over to a more modular systemk and group all of the electronics inside the building and just have the displays out on the poles. I also want to add a bell for notifying the pedestrians when a train is comming. I looked into electronic modulkes to sysenthisize the bell sound and ordered a kit to do so. When the kit arrived, it was not as I had expected. Several companies advertise a sound board that makes several railroad sounds including a crossing bell. The illustrations and circuit descriptions all memtioned a COB (chip-on-board) technology for the sound generation and several solder pads to wire switches for selecting the sound desired. I finally ordered a kit from a Canadian company that claimed it produced 3 railroad sounds. When it arrived I found that the kit did not have more than one switch! I was at a loss as to how you select the sound that you want but I put it together to see just how it went together and provided the sounds. The directions were in Asian/English and did not read well. I made the two boards up and noted that either 12V or 3V could power the board. I hooked up the 12V and listened to the speaker and nothing recognizable came from it. Sort of a high-pitched dqueeling sound emenated from the loudspeaker. I first checked over all my instructiuons and traced the board to see if I left something out or had a solder bridge on the board but to no avail.

     At this point, I called the company and left a voice mail explaining that I was unhappy with the kits, so far, and why I was unhappy. I then went back to trouble shooting and found that the author had mentioned that the power supply for the chip was critical at no more then 3VDC. There was a voltage devider to provide the three volts if you used 12 volts. I got out the trusty meter and found that the 3 volt point was above three and decided to put in a potentiometer so I could adjust the voltage to get the critical 3 volts for the chip. I also wondered if the audio amplifier transistor was shorted or damaged during the assembly process. I replaced the transistor and and as I turned the control up and down, I was able to get a faintly remotely sounding locomotive chugging as well as sort of a bell ringing sound out of the speaker. When I got the return E-mail form Q-Kits about the board, they comfirmed thatg this kit simply simply provided three railroad sound sequentially in a loop. They also mentioned that the 3VDC is critical and the speaker only work properly when the circuit is run on 3VDC and not 12VDC! In fact, they show the board being used without the output resistor and have the signal connected to a power amplifier.I am  having  hard time with an electronic bell for the grade crossing in the first place and apparently this boards will not work for anything at the track - except for a souvenier perhaps.

     I started looking at mechanical bells as an offshoot of my curosity about the light and bell frequency. I understand the railroad mechanical bells had a motor driven clapper that rotated at a fairly slow speed as the bells were about a second apart. I remembered fire alarm and burglar alarm bells featured mechanical clappers and wondered if they had spec sheets that mentioned frequency but alas the only frequency talked about for burglar alarm or fire alarms is a rapid ringing causing an annoying sound to drive people avay frim the area being protected. I am looking for a slower, perhaps more melodic, sound from a clear bell. The bell should be between four and eight inches for the right pitch. but getting a ringer at the right frequency may take a little more legwork. I could order a bell and remove the factory ringer and add small motor of about 6 to 10 RPM and hang a clapper from its shaft and that should get me the authentic crossing bell sound.

     I finally removed the old wiring and circuit boards that were damaged and prepared the area for the new wires. I drew up two different schematics of the system and had to make a choice. After the first version I realized there was no compelling reason to wire it that way again. I then startd out with a white sheet of paper and drew it as I would have designed it for the most part and added in shorting out the leads external to the building when it is not activated so as to lessen the chance of a weather related outage. With the two leads shorted to each other and ground, The differential voltage should be close to nil and hopefully any potential would get shunted to ground before it could get into our components.

     Of course, the plastic sunshades are getting worn and need replacement. I have added that to my projrct list and have some aluminum roofing flashing and have cut several pieces to the general size and now I have to shape them and paint them grayish black so they look authentic, Fred Wright offered to help me with the target's shades and their mounting on the units.

     I reburried the cables by the Grelson building and the old car barn so it looks much better again.

On Sunday I came back with Tom Prescott and hoped to finish up the work on the crossing signals but it seems something kept going wrong, One of the LEDs has gone out for some reason and one on the control card has as well. I tried replacing the oscillator chip that contains the drivers transistors but it did not fix the issues. I also tested the LEDS to see what current made them bright enough for actual use and discovered that I have to raise the current flow to 25% above the existing limit to get  bright enough display. Tommy thinks the LEDs spectrum may also be a problem in that the light frequency is being selected by the red lens which makes it appear dim. Therefore, I have a quandry. Should I raise the current to the LEDs because the supply is off half the time? Should I look for another LED that has much brighter output? Should I look at different output device such as an incandescent lamp again?

     I decided to try the higher output LEDs that All Electronics has for sale that can use 10 times the current and mounts on a flat surface so I can put them on the back of the light box and it gives the light a chance to spread out before hitting the red lens. The 555 chip says it has a current rating of 1000ma and the new LEDs are up to 300 ma so two LEDs should work OK.