Connecting an external trigger signal

The dispenser has an optically isolated input for triggering the controller remotely. It also provides power from the USB port, this makes it very flexible since it allows you connect simple switches, other systems with a wide signal input range (3-12V) and even sensors powered directly from the dispenser.

Note 1: Always check with a multimeter to see which strands in the cable correspond to which pins in the plug, a mix up can short the USB port and damage your power supply and/or device.

Note 2: Shut down the unit when plugging the cable to prevent accidental dispensing.

Troubleshoot: If the unit doesn’t respond with the foot switch or another external signal, make sure that the plug is inserted all the way in.

The first example is by using an external switch. You’ll need a regular 3.5mm cable with 3 conductors like this one:

4 conductor 3.5mm cable

To start dispensing you need to short the first two pins, 1 and 2 in this diagram:
(Block on the right represents the dispenser)

As you can see, the internal LED from the optocoupler is powered by the same USB 5V line as the dispenser but only when the switch is closed. Its ground is connected by the 3rd conductor in the plug.

Now to connect with a 3D printer or similar device:
Here you can isolate the input completely, you’ll need a 3.5mm jack with 4 conductors:

3.5mm 3 conductor cable

Please note the internal resistor is rated for 1/4W power dissipation and the LED voltage drop is around 1.2V
If you don’t have a 4 conductor cable you can also use a regular one, with the same connection shown above minus the 4th cable. The only difference is that the dispenser and printer grounds will be shared. There shouldn’t be problems with this but in some cases it could cause instability in the printer due to the extra noise of the motor.

If you want to extend the trigger voltage to 24V an external 1k resistor has to be added in series as shown in the illustration.