Operation of the 759 Danger Bell control There are 10 screw terminals located at the bottom of the board. They are numbered 1 through 10 starting from the left. There is a square pad on the bottom of the board for pin 1. The terminals are as follows for standard AC powered trains: 1 Base Post 2 Base Post 3 16 VAC from transformer 4 Connect to Base Post 5 Connect to 696 track trip 6 Base Post 7 Bell on 759 8 Right Lamp on 759 9 Left lamp on 759 10 Yellow wire to crossing gate In order to get the two lamps to flash separately, you will need to split the metal bracket on back of the 759 and run a wire for each of the lamps. The circuit is fairly straight forward. The 16 VAC from the transformer is rectified by the bridge rectifier diode and fed to a buck convertor which is adjusted to provide 5 VDC for the ATMega processor chip. The chip has four pins programmed as outputs and one pin programmed as an input. The input pin is connected to an opto isolater and when the track trip is pressed down, it provides a low to the input pin to start the program running. As long as the trip is pressed, the program will run continuously but as soon as it is released, the program will time out after a few more cycles. The 4 output pins drive opto isolated trigger chips which drives the four triacs. All this was done because we are switching 16 VAC on and off and the processor chip can only drive 5 volt devices. The chips are all socketed to make repair possible if one of them gets damaged. I could have done surface mount for everything but that is almost impossible for the average person to repair if needed. If you order boards through the easyeda.com website,(https://easyeda.com/gwcohn/af-759-danger-bell) here are some tips on how to assemble them. First install the bridge rectifier diode and the buck convertor. Then attach a train transformer to the first pin at the bottom (square pin) and the 3rd pin. This supplies 16 VAC to the rectifier which then powers the buck convertor. Adjust the blue poteniometer on the buck convertor to get 5 VDC from the output pins. If you do not do this, they come set to their maximum output voltage which would destroy the microproccesor chip. Once that is done, you can instll all of the resistors, capacitors, ic sockets, terminal strips and triacs. Then install the ic's making sure to observerve that pin one is to the upper left. After this is done, you can connect the board as shown above and it should be ready for operation. This the program for the ATMega processor chip: /* American Flyer 759 - 761 Danger Bell\Crossing gate control. When train runs over track trip, it starts a cycle of 10 light flashes and dings which continues until last car clears track trip. Also can control a crossing gate like a 592, 23601, etc. Requires modification to 759 or 761 to separate the two lights and/or the bell. Also requires a triac driver board to convert logic signals into controlled 16 volt AC pulses from transformer. George Cohn - April 8 2018 This code is in the public domain and can be used or modified as needed. By using this code, you accept all responsibility for damages if implemented incorrectly. */ // the setup function runs once when you press reset or power the board int cgate = 6; int llamp = 3; int rlamp = 4; int dbell = 5; void setup() { pinMode(6, OUTPUT); // Crossing Gate pinMode(5, OUTPUT); // Bell pinMode(4, OUTPUT); // Right Light pinMode(3, OUTPUT); // Left Light pinMode(7, INPUT); // Track trip or sensor, pull low to flash-ding //Apply 14 VAC from a track trip digitalWrite(4, HIGH); // Sets up at power on to turn Right light off digitalWrite(5, HIGH); // Sets up at power on to turn Left light off digitalWrite(6, HIGH); // Sets up at power on to turn Bell off digitalWrite(3, HIGH); // Sets up at power on to turn Crossing Gate off } // the loop function runs over and over again forever void loop() { { if((digitalRead(7) == LOW)){ // Waits for you to pull low to flash lights and ding bell for (int i = 0; i < 10; i++) { // Will flash-ding 10 times then stop after pin 4 goes HIGH digitalWrite(cgate,LOW); // Turns on crossing gate { digitalWrite(llamp,LOW); // Turn the LEFT Light on digitalWrite(dbell,LOW); // Dings bell delay(50); // Wait for 100 milliseconds digitalWrite(dbell,HIGH); // Turns Bell off-Short duty cycle prevents coil overheating delay(200); // Wait for 200 milliseconds digitalWrite(llamp,HIGH); // Turns Left Light off delay(250); // Wait for 250 milliseconds digitalWrite(rlamp,LOW); // Turn the RIGHT Light on digitalWrite(dbell,LOW); // Dings bell delay(50); // Wait for 100 milliseconds digitalWrite(dbell,HIGH); // Turns Bell off-Short duty cycle prevents coil overheating delay(200); // Wait for 200 milliseconds digitalWrite(rlamp,HIGH); // Turn the RIGHT light off delay(250); // Wait for 250 milliseconds then repeat } digitalWrite(cgate, HIGH); // Turns off crossing gate } } } }