This project overcomes some of the limitations of the XY-PWM Pulse Signal Generator. See my article on the PWM & Pulse Signal Generator (XY-PWM).
The output of the XY-PWM module is suitable only as a signal source and can't drive high current devices. The ZK-PP2K module can drive devices up to 8 Amps or 150W.
PWM definitionPulse-width modulation is a digital technique to control a signal by repeatedly toggling a signal between a HIGH and a LOW state in a consistent pattern. We can portray new information by changing how long the signal is HIGH versus LOW. The PWM signal has two key parameters - frequency and duty cycle.
The period of the PWM signal(measured in seconds) indicates the amount of time it takes for the signal to complete one cycle. Refer to the image above. We can see that a period is a complete cycle of the signal, changing from LOW signal to a HIGH signal and back to a LOW signal. The signal pattern of each period is repeated over and over again.
The frequency of the PWM signal, measured in Hertz (Hz), indicates the number of complete periods that occur in 1 second. In our LaunchPad, the PWM signal typically has a frequency of 490 Hz. This means that our PWM signal completes 490 periods every second. The period and frequency of a signal are closely related, in that the faster the frequency, the smaller the period. The slower the frequency, the larger the period.
The relationship between period and frequency is realized with this equation:
For example, the period of a 1-kHz (1000 Hz) signal is 1/(1000 Hz) = 0.001 s or 1 ms.
The Duty Cycle of the PWM signal is the percentage of time that our PWM signal is in a HIGH state versus a LOW state. For example, a simple square wave has a duty cycle of 50%. However, we can change the duty cycle of our PWM signal, anywhere from 0% (for always OFF) to 100% (for always ON) and anywhere in between, depending on what type of information we want to portray.
PWM can also be used to control the power that is fed into certain electrical devices. By changing the duty cycle of a PWM signal, we can actually simulate an average voltage (or current) output. The longer the duty cycle is, relative to the period, means that, on average, the signal is more HIGH than LOW. This means on average more voltage (or current) is seen at the digital output pin. If we start at a duty cycle of 0%, we should see an effective average voltage of 0 V. Increasing duty cycle to 50%, we’ll start to see an effective average voltage of VCC/2. And lastly, at a duty cycle of 100%, we should see an effective voltage of VCC.
(extract from ScienceDirect)
The ZK-PP2K is a low cost module that provides electrical signals at a variety of frequencies, square wave, pulse and output levels. It supports dual mode - PWM mode and PULSE mode. It supports high current output and can be directly connected to the motor.
- PWM mode / PULSE mode (1 to 9999)
- LCD high definition display
- Support frequency adjustment (1Hz to 150kHz - accuracy 2%)
- Support duty cycle adjustment (0% to 100%)
- High current output: 8A (Max)
- Support power-down memory function
- 1-Channel signal output
- Support reverse protection
- Support enabled/disabled output
- Direct drive LED/Motor/solenoid valve
The module has an input voltage from 3.3 to 30V. The output signal drives a power MOSFET configured as a open drain. Because of this configuration, it won't show an output signal until a load is added between the output and the output supply voltage.
Like the XY-PWM module, the ZK-PP2K module does a great job at generating a PWM signal. However it's real advantage is in its output stage allowing it to drive high current devices directly. The output voltage is controlled by a adjustable buck/boost converter. It supports a constant current feature so as to protect the output and/or the load that is connected. This is incorporated into a 3D printed case based on a clam shell design. This results in a unit can neatly sit on a shelf or workbench.
The power supply is a 12V 5A power brick that has been opened up and glued into the bottom of the case. This feeds the ZK-PP2K module and also a ZK-4KX DC to DC 4A 0.5-30V Adjustable Buck Boost Converter with constant current support. This provides the OUT+ supply while the ZK-PP2K module controls the OUT- supply.
The STL files for 3D printing are attached. All printing was sliced with a 0.2mm layer and no supports. You will need to orientate the parts to sit flat on the build plate.
I added another set of terminals from the ZK-4KX module so you can use the power supply part if you don't want to use the ZK-PP2K module
Using a 1000 ohm resistor as the load, the module generates a clean precise waveform. The only issue I have with the module is there is no contrast setting for the LCD screen. It's viewing angle is not good and you almost need to be directly in front of the screen to read it. Contrast was better than the XY-PWM module used in my other project. It is a great value module and is a useful addition to any workshop.
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