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| Digital Outputs can be used to drive LEDs, solid state relays, and transistors (or anything that will accept a CMOS signal).
| | #REDIRECT [[Digital Output Guide]] |
| Digital outputs can be used to control devices that accept a +5V control signal.
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| With transistors and some electronics experience, other devices can be controlled, such as buzzers, lights, larger LEDs, relays.
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| ==Specifications and Features==
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| [[Image:digital_output.jpg|right|thumb|A Phidgets digital output.]]
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| The 250 ohm resistance is internal to the PhidgetInterfaceKit 8/8/8, and limits the current that can flow through the output.
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| This is intended to protect the device from being damaged if there is a short to ground or if an LED is used.
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| The output is intended to drive TTL or CMOS inputs; it is not designed to provide power to an external circuit.
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| ===Ground Protection===
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| Ground terminals on the InterfaceKit share a common ground with USB ground.
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| Because they are not internally isolated, these terminals will expose the USB ground potential of the PC to which they are connected.
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| Be sure you are completely familiar with any circuit you intend to connect to the InterfaceKit before it is connected.
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| If a reverse voltage or dangerously high voltage is applied to the input or output terminals, damage to the Phidget or the PC may result.
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| ===5 Volt Terminal Block===
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| For users who need it, we provide 5V on the terminal block next to Digital Output 7.
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| ==Using the Digital Outputs==
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| Here are some circuit diagrams that illustrate how to connect various devices to the digital outputs on your Phidget.
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| ===Driving an LED with the Digital Output===
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| [[Image:LED_digital_output.jpg|right|thumb|Schematic for connecting to an LED.]]
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| Connecting an LED to a digital output is simple. Wire the anode to a digital output labeled 0 to 7 on the Interface Kit, and the cathode to a supplied ground, labeled G.
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| ===Using a 3052 SSR Board with a Digital Output===
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| [[Image:3052_digital_output.jpg|right|thumb|Schematic for connecting a 3052 board.]]
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| Setting the digital output to true causes the output of the 3052 to turn on.
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| This can be used to control AC or DC devices.
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| The load can also be switched with the 3052 on the high side.
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| High side switching is helpful for powering more complicated circuitry that cannot tolerate having multiple grounds.
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| ===Isolating a Digital Output with a MOSFET based SSR===
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| [[Image:isolating_digital_output_ssr.jpg|right|thumb|Schematic for isolating a digital input with an SSR.]] | |
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| It’s possible to wire up your own Solid State Relay to the digital output.
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| MOSFET based SSRs have the advantage that they can be understood as being a simple switch.
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| There are many other types of SSRs that are more suitable for controlling higher power, higher voltage AC devices that can also be controlled in the same fashion.
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| ===Isolating a Digital Output with an Optocoupler===
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| [[Image:isolating_digital_output_optocoupler.jpg|right|thumb|Schematic for isolating a digital input with an optocoupler.]]
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| In some applications, particularly where there is a lot of electrical noise (automotive), or where you want maximum protection of the circuitry (interactive installations, kiosks), electrical isolation buys you a huge margin of protection.
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| Driving the LED causes the output transistor to sink current.
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| The maximum current through the transistor will depend in part on the characteristics of the optocoupler.
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| ===Controlling a Relay with a N-Channel MOSFET===
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| [[Image:relay_nmos.jpg|right|thumb|Schematic for using a relay with an NMOS transistor.]]
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| A inexpensive mosfet and flyback diode can be used to control larger loads - relays for example - directly from the digital output.
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| Be sure to use a Logic-Level MOSFET so that the +5V Digital Output is able to turn it on.
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| ===Controlling a Relay with a NPN Transistor===
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| [[Image:relay_npn.jpg|right|thumb|Schematic for using a relay with an NPN transistor.]]
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| This circuit is very similar to the N-channel mosfet - but you may already have NPN transistors on hand.
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| ===Using a 3051 Dual Relay Board with one or two Digital Outputs===
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| [[Image:3051_digital_outputs.jpg|right|thumb|Schematic for using a 3051 board.]]
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| The 3051 Dual Relay Board is designed to be used with the PhidgetInterfaceKit 8/8/8.
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| An Analog Input can be used to supply power to the relays, and one or two digital outputs used to control the relays.
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| The 3051 is a good option if you need a couple relays in your project.
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| ==Known Issues==
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| {{KnownIssues|We need to tell users to pay attention to the update rate of their interface kit. If their program changes the state of a digital output twice without some kind of delay or other time-consuming instruction in between, the interface kit may not register the change.}}
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