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Adding Limit Switches to the BE-SP6
You can use Computer signals instead
of Direction and Clock switches.
Direction
Switch
Control connector
Clock Switch
Run / Stop
Stepper Connector
Power (+ and -)
4 Stepper Wires
7 to 18 VDC power for the
BE-SP6 circuit.
BE-SP6 Circuit
20K resistor
Main Speed
Adjust Pot.
Max Speed
Adjust Pot.
Set once.
(2) 500K Pots
Optional
NO
Com
NC
2 Momentary Push Button
Limit Switches. For left and
right travel limits.
WARNING:
Don’t press “both”
switches at same time.
Stepper Motor
Power Supply
NO
Com
NC
Stepper Motor Driving Belt
NO Normally Open
Com Common
NC Normally Closed
This is a wiring diagram to help you connect wires to parts.
You can use 22ga wire for anything connected to the control connector.
Red lines are only +5 volts .
Black lines are Ground (0v)
Green lines = Digital signals, can be only 5 or 0 volts
Gray lines are for the Stepper and Stepper power.
Blue lines = Analog signals, any voltage between 0 and 5 volts. Used to adjust the slowest and fastest speeds.
If you don’t use the two pots you will be running the Stepper at a slow speed.
This circuit will run the Stepper in one direction until one of the Limit switches is pushed.
Then it will reverse the stepper until that switch is not pushed any more.
It will continue to push and release the switch as long as the Clock switch is in the run position.
If you flip the Direction switch the Stepper will travel in other direction until it gets to the other Limit switch.
You can get several things reversed and it wont work right.
Test the circuit wires first, find what Limit Switch will reverse the motor when pushed.
Only one switch will reverse Stepper depending on the direction it was going before it hit that switch.
The Clockwise limit switch will not stop a Stepper going Counterclockwise.
Same for other direction.
Copywrite Robert D. Roan 2007
Bob’s Engineering Colorado USA
Limit Switches for the BE-SP6 Circuit
2 of 2
Example:
If you set the Direction switch to make Stepper go Clockwise, then flip the Clock switch to run, the Stepper will turn
Clockwise until something hits the “Clockwise Limit” switch. Same for Counterclockwise.
If you placed the Clockwise Limit switch in the right place the Stepper will reverse then chatter at that place until
you stop the clock or you change direction with the Direction switch.
When pushed, both limit switches will “electrically reverse” the direction switch.
If you were going Clockwise and you hit the “Counterclockwise” limit switch, Stepper would just keep going.
We designed this circuit to override the direction signal going into the BE-SP6 if the limits are hit.
DON’T do the “lets see what happens” thing and press both the limit switches at the same time.
In real life the motor can’t be at both limits at the same time.
Pressing both will SHORT the 5volt power that runs the BE-SP6 circuit. Not good for it.
It wont destroy the circuit but it can overheat the 5 volt regulator.
If it didn’t work?
Make sure the motor is moving the object toward correct limit Switch.
One way to fix it:
Swap limit Switch Positions or swap the wires going to the “NO pins”.
Second way to fix it:
Swap only the wires going to the M1 And M3 pins on the Stepper connector.
Swapping Stepper connector wires will only reverse Stepper Direction.
Or do both if you already have fancy labels on your Direction and Clock control panel switches.
NOTE:
We assume the solder jumper on the back of the BE-SP6 circuit board is in the standard shipped position.
That is when the internal clock will be used to run the Stepper when +5V is on the “Clk” input.
CLKout
CLK/En
0.1uF
4
5
RA
RB
500k
14
1
2
CLK/En
2
3
A
4
5
B
6
7
CLKout
1k
13
12
C
11
10
9
D
8
(Switch up) Uses Gates A and B to produce
a CLOCK to the Driver.
This Switch is a solder jumper between 2 of
the 3 pads on back of board.
The Switch (on back of board) selects between the output of (Gate A ) or (Gate D)
To change switch position, move the solder short from pad1 and pad2 to pad3 and pad2
Gates (A and B) are part of a oscillator circuit that will only run if pin 2 has a high (5V) on it.
Adding resistor(s) or a pot, across RA and RB will speed up the oscillator.
When the switch is up, the clock pulses from gate B go into the control circuit of the Driver.
Each CLK pulse moves the Stepper one Step. It will run until the CLK/En input goes low.
Gates (C and D) are part of a de-bounce (latch) circuit that will clean up outside clocks.
When the switch is down, the output from gate D goes into the control circuit of the Driver.
Copyright Robert D. Roan 2007
Bob’s Engineering Colorado USA