How One IC Can Be Come A Lifesaver

The 4066 deserves special mention. I talked earlier about using the POV for 8 functions. Most POV are actually 4 switches, one up, one right, one down, one left. Right up is done by shorting 2 switches at the same time, right and up. Simply connecting 3 switches to 2 will not work, any switch will short both. I needed some kind of isolation. The 4066 provided the answer. When power is supplied to one pin of the IC, it will make a contact elsewhere. E.g. power on pin 12 will make a contact between 10 and 11. Using power on 2 pins will make 2 contacts. So to use POV right up I connect power to 2 pins with one switch. The 4066 will close the up and right switch. But the 4066 will keep these switches closed until power is gone from the input pins. So the input pins (e.g. 12 and 13) are also connected to ground with a small capacitor. So upon release of the switch the 4066 will open the contacts that were previously closed.

The grey bars are resistors. The rectangle is the 4066. Notice the notch which helps identify the pins.

Power on pin 5 closes contact between 3 and 4
Power on pin 6 closes contact between 8 and 9
Power on pin 12 closes contact between 10 and 11
Power on pin 13 closes contact between 1 and 2

Red and green wires are used to connect pin 13 to pin 5 and pin 12 to pin 6. (this can also be done with solder on the board). We want to close 2 switches with one (b1) so we use pin 13 and 5 to close and to as well as 3 and 4. When pressed, b2 applies voltage to 12 and 6 which will make the 4066 close 9 and 8 + 10 and 11. 5 and 6 are connected to ground via a resistor so when the button b1 or b2 is released the contacts made by the 4066 will be opened again. The buttons used got 2 pins. One is connected to the power supply from the game pad (the same one as our 4066 uses) the other to pin 13 or 12 of the 4066.

Toggle To Momentary

The 4066 served another purpose as well. The 4066 came in handy to convert a toggle switch to a momentary button pres. So flipping a switch will press a button for a second. Flipping it back will press the same button again. A way to make this without the 4066 but with a relay is described in this how to.

I've also seen people using optocouplers instead of the 4066 to connect to their keyboard. I did not use a keyboard so my requirements were different. I guess the keyboard responds a bit quicker than the joysticks and game pads. Using relays takes up a lot of space and I never got the optocouplers to do what I needed them to. The switches need double connections for this to work. The circuit is similar to the POV solution and it involves the charging of capacitors. Each time the switch is flipped one capacitor is charged and an other is discharged. When a capacitor is charged a current will flow until it is fully charged. Then the current stops. Now we need a means to turn these small current peaks into a switch. That's just what the 4066 does for us.

The switches are shown with their power and ground circuit. The connections on the corners are all + or - and the ones in the middle are the output. Depending on the position of the switch one middle connector provides + and the other -. When we flip the switch, it will be the other way round. The 2 output wires will be connected to the capacitors.

Circles are the capacitors and the bars are the resistors. The rectangle is the 4066. Notice the notch.

The 2 outputs of one switch (S2) end up at pin 12 and 6, so when flipping the switch 11 and 10 are closed or 8 and 9. 8, 9, 11 and 12 are connected to one switch, you can use 3 wires to save some on wiring. 9 and 10 can share 1 wire. Or even try to combine 11 and 8 and just use 2 wires.

We can connect 2 switches to one circuit. Again we use resistors which connect the capacitors to ground. So 1 4066, 4 capacitors and 4 resistors. The value of both determines the length of the pulse. I used 1000 uF capacitors and 220 ohm resistors which works well for me. Although FSUIPC sometimes misses a switch the joystick driver never misses one. So when using FSUIPC you may want a longer pulse.

This is the actual circuit. On the lower left are a few 4066's to accommodate the POV circuit.

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