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   |Is used in domain=Electronics

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   |Has function=Measurement

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   |Has icon=File:Electronics Workstation.png

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   |Has icondesc=Multimeter Icon

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   |Has image=File:Electronics Workstation.png

   |Has imagedesc=Weller WES51

   |Has imagedesc=Electronics Workstation

   |Has description=Standard electronics measurement and signal generation equipment.

   |Has description=Standard electronics measurement and signal generation equipment.

   |Has certification=https://georgefox.instructure.com/courses/1271

   |Has certification=https://georgefox.instructure.com/courses/1271

   |Has ace=Needed;Needed

   |Has ace=Needed;Needed

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==DC Power Supply==

==DC Power Supply==

The most basic function of a DC power supply is to provide a constant voltage to a device. “DC” stands for direct current; “AC” stands for alternating current. A 9V battery is an example of a DC voltage, and it will hold a constant 9 volts (at least until the battery starts to die). A 120V wall outlet is an example of an AC voltage, and it will fluctuate up and down from 120V to -120V and back to 120V over a set period of time. A DC power supply converts the alternating current from a wall outlet to a steady direct current through a system of transformers and filtering circuitry. We have a couple different models of DC power supplies in the Maker Hub—all of which will be able to supply 12 VDC for this electronics workbench certification.

The most basic function of a DC power supply is to provide a constant voltage to a device. “DC” stands for direct current; “AC” stands for alternating current. A 9V battery is an example of a DC voltage, and it will hold a constant 9 volts (at least until the battery starts to die). A 120V wall outlet is an example of an AC voltage, and it will fluctuate up and down from 120V to -120V and back to 120V over a set period of time. A DC power supply converts the alternating current from a wall outlet to a steady direct current through a system of transformers and filtering circuitry. We have a couple different models of DC power supplies in the Maker Hub.

===Setting Up a DC Power Supply===

===Setting Up a DC Power Supply===

===Safety Notes===

===Safety Notes===

It’s good practice to minimize the amount of bare, exposed wire in your circuit because this reduces the risk of shock or short circuits. Most projects that would use the DC power supplies would be considered low voltage, but that does not sanction careless “rat’s nest” wiring with exposed live wires. Design neat circuits that maintain a proper separation of line voltages and neutral/ground connections to reduce the chance of free-moving wires touching and creating a short circuit. A short circuit occurs when an electrical circuit of significantly lower resistance is completed (unintentionally); this is usually a result of accidental contact between electrical components or an internal component failure. Short circuits are dangerous high-current events and can cause fires, component damage, blown fuses, and tripped circuit breakers. We would like to avoid that.

It’s good practice to minimize the amount of bare, exposed wire in your circuit because this reduces the risk of shock or short circuits. Most projects that would use the DC power supplies in the Maker Hub would be considered low voltage, but that does not sanction careless “rat’s nest” wiring with exposed live wires. Design neat circuits that maintain a proper separation of line voltages and neutral/ground connections to reduce the chance of free-moving wires touching and creating a short circuit. A short circuit occurs when an electrical circuit of significantly lower resistance is completed (unintentionally); this is usually a result of accidental contact between electrical components or an internal component failure. Short circuits are dangerous high-current events and can cause fires, component damage, blown fuses, and tripped circuit breakers. We would like to avoid that.

If you are going to make a physical adjustment to a circuit, unplug or turn off the power to the circuit first. Certain electrical components (such as capacitors) can retain a voltage/charge even after the power to a circuit has been cut. You can test voltages with a multimeter to ensure that the circuit is discharged, or ask the Maker Hub staff for assistance if you are unsure. It is also good practice to work on circuitry with one hand. Using two hands increases the risk of completing a circuit across your heart from one arm to the other, which can be fatal. It only takes about 100mA across the heart to kill a human. However, this risk is extremely small when working with low voltages because low voltages are unable to drive that much current through a human body. Seek guidance from the Maker Hub staff before working with voltages above 50 V (AC or DC).

If you are going to make a physical adjustment to a circuit, unplug or turn off the power to the circuit first. Certain electrical components (such as capacitors) can retain a voltage/charge even after the power to a circuit has been cut. You can test voltages with a multimeter to ensure that the circuit is discharged, or ask the Maker Hub staff for assistance if you are unsure. It is also good practice to work on circuitry with one hand. Using two hands increases the risk of completing a circuit across your heart from one arm to the other, which can be fatal. It only takes about 100mA across the heart to kill a human. However, this risk is extremely small when working with low voltages because low voltages are unable to drive that much current through a human body. Seek guidance from the Maker Hub staff before working with voltages above 50 V (AC or DC).

With all voltage and current knobs set to minimum, turn on the power supply. If you need a very specific voltage, you may also connect the digital multimeter to the output of the DC power supply to give you a more accurate reading of the voltage. If your current knob is at the minimum, you may notice that nothing happens when you increase the voltage knob and a red LED turns on. This is because the current knob on a DC power supply operates as a current limiting function. At the minimum, the current knob will allow zero amps to flow, which means that the DC power supply will not provide any voltage. The purpose of the current limiter is to protect your circuit from damage. For example, if you know that your 100 Ω resistor is rated at 0.25 W, you might set your current limiter such that not more than 50 mA will flow through that particular resistor to avoid burning it out (letting out the magic smoke).

With all voltage and current knobs set to minimum, turn on the power supply. If you need a very specific voltage, you may also connect the digital multimeter to the output of the DC power supply to give you a more accurate reading of the voltage. If your current knob is at the minimum, you may notice that nothing happens when you increase the voltage knob and a red LED turns on. This is because the current knob on a DC power supply operates as a current limiting function. At the minimum, the current knob will allow zero amps to flow, which means that the DC power supply will not provide any voltage. The purpose of the current limiter is to protect your circuit from damage. For example, if you know that your 100 Ω resistor is rated at 0.25 W, you might set your current limiter such that not more than 50 mA will flow through that particular resistor to avoid burning it out (letting out the magic smoke).

If you’ve done your calculations, you may not need to be as cautious with the current limiter, but it’s always a good idea to start low with the current limiter every time you are powering an untested circuit. Rarely will an insufficient current or voltage ever cause damage to analog or digital circuits. Granted, the circuit probably won’t function as expected with insufficient current/voltage, but it should be fine to slowly increase the current/voltage to the desired amount when you are first setting your DC power.

If you’ve done your calculations, you may not need to be as cautious with the current limiter, but it’s always a good idea to start low with the current limiter every time you are powering an untested circuit. Rarely will an insufficient current or voltage ever cause damage to analog or digital circuits. Granted, the circuit probably won’t function as expected with insufficient current/voltage, but it should be fine to slowly increase the current/voltage to the desired amount when you are first setting your DC power.

Set the current limiter above it’s minimum, and slowly increase the voltage to the desired amount. After you have set your voltage and current correctly, you don’t need to change the settings at this point. Simply turn on/off the DC power supply as needed with the power switch or the voltage knob. Do not disconnect the leads from your circuit while the power supply is still on; free-floating leads are a short-circuit risk. Disconnecting live wires is a bad habit that becomes extremely dangerous if you work with higher voltages due to arcing hazards.

Set the current limiter above it’s minimum, and slowly increase the voltage to the desired amount. After you have set your voltage and current correctly, you don’t need to change the settings at this point. Simply turn on/off the DC power supply as needed with the power switch or the voltage knob. Do not disconnect the leads from your circuit while the power supply is still on; free-floating leads are a short-circuit risk. Disconnecting live wires is a bad habit that becomes extremely dangerous if you work with higher voltages due to arcing hazards.

==Function Generator==

==Function Generator==

There are eight range switches that select output frequencies from <1 Hz to 10 MHz. The coarse frequency knob adjusts the frequency within a range from 10% of the maximum to the maximum. For example, if the 100 kHz range is selected, the output frequency can be adjusted from 10 kHz to 100 kHz. The duty cycle, CMOS level, DC offset, and -20 dB functions are only active if their corresponding switches are pressed in. The duty cycle knob alters the symmetry of the waveform through skewing or changing the ratio of “on” time versus “off” time. The DC offset changes the mean amplitude of the waveform. Reference the manual for information on more advanced capabilities such as the sweep functions, TTL/CMOS, and voltage-controlled generation.

There are eight range switches that select output frequencies from <1 Hz to 10 MHz. The coarse frequency knob adjusts the frequency within a range from 10% of the maximum to the maximum. For example, if the 100 kHz range is selected, the output frequency can be adjusted from 10 kHz to 100 kHz. The duty cycle, CMOS level, DC offset, and -20 dB functions are only active if their corresponding switches are pressed in. The duty cycle knob alters the symmetry of the waveform through skewing or changing the ratio of “on” time versus “off” time. The DC offset changes the mean amplitude of the waveform. Reference the manual for information on more advanced capabilities such as the sweep functions, TTL/CMOS, and voltage-controlled generation.

The best way to “see” the output of a function generator is to use an oscilloscope. An oscilloscope will show you a graphical representation of the signal, and allow you to understand the effects of the waveform shape, frequency range switches, coarse/fine adjustment, duty cycle, DC offset, etc.

The best way to “see” the output of a function generator is to use an oscilloscope. An oscilloscope will show you a graphical representation of the signal, and allow you to understand the effects of the waveform shape, frequency range switches, coarse/fine adjustment, duty cycle, DC offset, etc.

A signal generator is designed as a precision device that can produce very specific waveforms; it is not designed as a powering device capable of generating large voltages or currents from its output. This is one of the reasons why a signal generator is commonly used alongside a DC power supply. A common benchtop DC power supply excels at providing a precise DC voltage at a moderate current (usually less than 10 A), but it cannot produce waveforms on its own. If you want to produce a waveform with moderate voltage/current, one great method is to design an amplifier circuit. An amplifier circuit commonly uses a transistor (or series of transistors) to turn small low-power signals into larger moderate-power signals. The signal generator provides the small signal to the input of the transistor, which modulates the DC voltage at the output of the transistor to create a larger moderate-power signal. This is the type of circuit you will be testing to complete this certification.

A signal generator is designed as a precision device that can produce very specific waveforms; it is not designed as a powering device capable of generating large voltages or currents from its output. This is one of the reasons why a signal generator is commonly used alongside a DC power supply. A common benchtop DC power supply excels at providing a precise DC voltage at a moderate current (usually less than 10 A), but it cannot produce waveforms on its own. If you want to produce a waveform with moderate voltage/current, one great method is to design an amplifier circuit. An amplifier circuit commonly uses a transistor (or series of transistors) to turn small low-power signals into larger moderate-power signals. The signal generator provides the small signal to the input of the transistor, which modulates the DC voltage at the output of the transistor to create a larger moderate-power signal.

===Impedance===

===Impedance===

You can test the function generator by connecting it directly to the leads of an oscilloscope. Just remember that the function generator will be impedance bridged with the oscilloscope, so you may observe a slight reduction in your signal’s amplitude after connecting the function generator to your circuit. After checking your circuit, connect the leads from the function generator to the circuit before turning on the power. On our particular model of function generator, the output is always on, so keep that in mind as you use it.

You can test the function generator by connecting it directly to the leads of an oscilloscope. Just remember that the function generator will be impedance bridged with the oscilloscope, so you may observe a slight reduction in your signal’s amplitude after connecting the function generator to your circuit. After checking your circuit, connect the leads from the function generator to the circuit before turning on the power. On our particular model of function generator, the output is always on, so keep that in mind as you use it.

==Oscilloscope==

==Oscilloscope==

==Digital Multimeter==

==Digital Multimeter==