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There are cheap radio control servos available either new or not reliable enough for aircraft use and being discarded by fliers. These are a source of controllable electric motors that can be used in layout automation.
The servo requires a positive pulse of 1 to 2 milliseconds long every 20 milliseconds. The length of the pulse determines the position the motor drives too.The servo motor needs a 5 volt supply and this is derived from the 12 volt input.
The circuit uses the 555 timer set up in async continuous mode to produce a variable pulse.
For a fixed rotation application ie. points motor drive, a switch gives 2 timing reference voltages to the timer at pin 5. These are the standard voltage for pin 5 (Vc x 2/3) and a lower voltage determined by 20K adjustable when the transistor is on.
The other circuit gives variable position control by changing the pin 5 voltage between the max and min voltages. These are set to the throw limits that are required.
There are cheap radio control servos available either new or not reliable enough for aircraft use and being discarded by fliers. These are a source of controllable electric motors that can be used in layout automation.
The servo requires a positive pulse of 1 to 2 milliseconds long every 20 milliseconds. The length of the pulse determines the position the motor drives too.The servo motor needs a 5 volt supply and this is derived from the 12 volt input.
The circuit uses the 555 timer set up in async continuous mode to produce a variable pulse.
For a fixed rotation application ie. points motor drive, a switch gives 2 timing reference voltages to the timer at pin 5. These are the standard voltage for pin 5 (Vc x 2/3) and a lower voltage determined by 20K adjustable when the transistor is on.
The other circuit gives variable position control by changing the pin 5 voltage between the max and min voltages. These are set to the throw limits that are required.
LINK TO IMAGE - detect-vero.gif
Circuit Schematic
