The Twin Coil Switch Machine Driver Circuit allows toggle switches to control Twin Coil switch machine motors that have separate or common connected coils.
The handle of the toggle switch can used to indicate the selected route through the turnout.
The circuit can also control LEDs that indicate the selected route. The LEDs turn off instantly when the toggle switch is thrown.
Using the parts values shown below, a turnout can be reversed in about 5 seconds or less
This circuit board can also be used to drive Single Coil Switch machines.
The next diagram show the basic circuit for the Twin Coil Switch Machine Driver. Each printed circuit board has 5 switch machine driver circuits on it.
This circuit is not designed to allow rapid throwing of turnouts. It is designed to allow solenoid type switch machines to be thrown with toggle switches and have the handle of the switch indicate the position of the turnout.
If quick throws are needed then other capacitor discharge circuit designs might be a better choice.
If the toggle switch is thrown when no power is applied to the switch machine drivers, the turnout will be in the wrong position with respect to the toggles (and LEDs). Changing the position of the toggle switch after power is restored will correct the indication.
The Twin Coil Switch Machine Driver Circuit is designed to work from a 15 to 18 volt DC power supply. The standby current for the circuit board as shown is approximately 130 milliamps at 18 volts.
R1 and R2, limit the current resistors for the LEDs. They can be increased or decreased to control the brightness of the LEDs if needed.
R3 and R4, set the charging capacitor rate. They should have a 1/2 watt power rating for 1,000 ohm resistors.
The value of the R3 and R4, determines how quickly the turnout can be returned to its last position after being thrown.
For 1K ohm resistors, the voltage across the capacitors will be 90 percent of the supply voltage after 5.0 seconds.
If a turnout does not need to be thrown rapidly, a higher value resistor, such as 2.2K or 3.3K, can be used in place of R3 and R4. Their power rating can be reduced to 1/4 watt.
Increasing the values of R3 and R4, will also reduce the standby current needed for each circuit board.
Capacitors C1 and C2 should be 2,200 microfarads and have a lead spacing of 0.200 inches or 5 mm and should have a 25 volt rating.
The size of the capacitors depends on the power needed to throw the turnout and the supply voltage. In most cases, 2,200uF will be adequate but crossovers may require more power.
As crossover turnouts are thrown together, their coils can be wired in series so that each gets an identical current flow.
D1 and D2 prevent potentially damaging reverse currents from flowing through the LEDs when the power supply is switched off. This current comes from a charged C1 or C2.
D3 and D4 prevent current through the LEDs from charging capacitors C3 or C4. This allows the LEDs to turn off instantly when the toggle switch is thrown.
This circuit is designed to use DPDT toggle switches but a 3 pole Double Throw ( 3PDT ) switch could control frog power or signals using the third pole.
The circuit can also control auxiliary relays that can be used for frog polarity control.
The next schematic shows the 5 driver circuit board schematic and examples of switch machine circuits.
Another example circuit Multiple Location Control For Twin Coil Switch Machines
The next diagram shows a 12 volt relay connected to the circuit. The relay could be used to control frog or block power if needed.
The following is a suggested parts list for the Single Coil Switch Machine Driver's circuit board. Resistor values can be change so that the circuit uses less current when idle, see information above for details.
|Part||Qty.||Description||DigiKey Part #|
|D1, 2, 3, 4||-||1N4001 Diode||1N4001FSCT-ND|
|R1, 2||-||2.2K OHM 1/4W Resistor||2.2KQBK-ND|
|R3, 4||-||1K OHM 1/2W Resistor||1.0KH-ND|
|C1, 2||-||2,200uF 25V Aluminum Electrolytic||P5157-ND|
Anti-Ringing Diodes are not required for this circuit.
T42-1 Push-In Terminals Push-In Terminals can be substituted for the terminal blocks or wires can be soldered directly to the circuit board to reduce costs if desired.
For other information on other Capacitor Discharge type switch machine power supplies see: Basic Capacitor Discharge - switch machine power supplies.
The explanations for the circuits on these pages cannot hope to cover every situation on every layout. For this reason be prepared to do some experimenting to get the results you want. This is especially true of circuits such as the "Across Track Infrared Detection" circuits and any other circuit that relies on other than direct electronic inputs, such as switches.
If you use any of these circuit ideas, ask your parts supplier for a copy of the manufacturers data sheets for any components that you have not used before. These sheets contain a wealth of data and circuit design information that no electronic or print article could approach and will save time and perhaps damage to the components themselves. These data sheets can often be found on the web site of the device manufacturers.
Although the circuits are functional the pages are not meant to be full descriptions of each circuit but rather as guides for adapting them for use by others. If you have any questions or comments please send them to the email address on the Circuit Index page.
20 March, 2018