Single Sided 4 Axis Interface PCB What this board does: Simply put, utilizing an off the shelf PC parallel printer cable, this board handles quick and neat connections for up to 4 of the single axis driver boards found on this website via a simple 10 pin IDC cable for each axis. In addition:
1. It also has connections for limit and home switches, filtering and LED's for those switches.
2. A TIP122 transistor driver that can be used to control a relay for spindle control.
3. Onboard 5VDC regulator
4. A transistor latch that can be hooked to a simple spst Estop Switch and a simple spst Estop reset switch.
DIY build information and details:
The DB25 connector on this pcb HAS to be female!!!!!
A commercially build version
Two users DIY boards
How the estop circuit works. The basics: Q1 and Q2 comprise a Set-Reset flip flop. The reset switch (when closed) across X7 forces Q2 to turn off by starving base current, the set switch (when closed) across X6 forces Q1 to turn off by starving base current. Holding both switches will hold both Q1 and Q2 off. The flip flop action works in that when one of the transistors is off, it allows a base current in the opposite transistor that will turn that opposite transistor on. An on transistor starves the base current to the opposite transistor holding it off. Consequently, the collectors of each Q1 and Q2 (and corresponding pads L and J) will toggle between a lo and high 5V logic state. This is just the set-reset latch portion of the circuit.
When it powers up, C9 acts as a short to force Q2 to hold an off state as the power supply comes to it's regulated value. Below is the result state of the power up. It should be noted, that a quick power cycle may not bring the circuit to the power up state.
How the circuit behaves when the Set switch is pressed:
When the set switch is released the latching action of the flip flop holds the base of Q1 starved similar to the switch press. Q4 and associated components, make up the LED7 driver to indicate the state of the set reset flipflop.
The follow image shows all the components that make up AUX1.
By jumpering JP5 you can control AUX1 to drive a relay, or solid state relay. If the relay is a 5V relay, you can simply hook the coil across X2 with the positive side to Pin 2 if the relay has a built in diode. By setting pin 1 of the parallel port high, Q3 will turn on and provide sink drive to a relay coil. For an SSR, utilizing the Pin 2 as positive and pin 1 as the minus input you can control via LPT Pin 1. By setting pin1 high, Q3 will be on provide a current path for the SSR to turn on.
Simple Logic Probe
Aux1 can also be used for troubleshooting. By removing JP5 and connecting a wire probe to Pin2 of JP5, you can test logic states. LED6 will illuminate when Pin2 is touched to a Hi state node and be off when open of touched to a low state node.