I need to replicate the way a magnet is being energized by a controller, this magnet is part of an electrovalve used in a high pressure pump working with a 12VDC power supply.
The following figures show the waveform read by my portable hantek oscilloscope, which was connected to my laptop on battery power, therefore the osc's is floating in relation to the power supply. I first took measurements using one probe, and then another reading using two probes.
Figure #1 shows how the signal starts by delivering brief pulses of +120VDC to the right cable at 28 kHz (the osc's ground is connected to the left cable), then it goes into a steady +12V signal, then near the end it start pulsing again down to 0V, and finally, a brief -75V signal shows up.
Figure #2 shows the same measurement, but this time one probe was connected to the right cable, and the second probe to the left cable, while the osc's ground was connected to ground of the 12VDC power supply.
This is important: Using my multimeter, with the pump turned off, I found that neither one of the two wires is attached to the power supply's ground. This tells me that we're dealing with at least three separate circuits that produce three voltages: 12, 120 and -75V
The magnet's data is as follows.
As can be seen, the first thing that intrigues me is the initial pulsed 120V signal, since it peaks at that value at first, and then it gradually decreases to around 90V, this maybe tells me that a capacitor is being discharged into the magnet's coil.
Let me also say that I'm perfectly capable of programming and designing an MCU interface that will produce the necessary pulses at the right frequency and duration.
It is for the following four points that I'm requesting this forum's help.
I promise to do my homework and study all the recommended documents, and do the necessary research and calculations that are required of me.
So, step one:
How do I calculate the required current demanded by the coil in each section of the waveform, or should I simply go ahead and physically measure what's happening, or both?
Thank you all in advance for all your help.
The following figures show the waveform read by my portable hantek oscilloscope, which was connected to my laptop on battery power, therefore the osc's is floating in relation to the power supply. I first took measurements using one probe, and then another reading using two probes.
Figure #1 shows how the signal starts by delivering brief pulses of +120VDC to the right cable at 28 kHz (the osc's ground is connected to the left cable), then it goes into a steady +12V signal, then near the end it start pulsing again down to 0V, and finally, a brief -75V signal shows up.
Figure #2 shows the same measurement, but this time one probe was connected to the right cable, and the second probe to the left cable, while the osc's ground was connected to ground of the 12VDC power supply.
This is important: Using my multimeter, with the pump turned off, I found that neither one of the two wires is attached to the power supply's ground. This tells me that we're dealing with at least three separate circuits that produce three voltages: 12, 120 and -75V
The magnet's data is as follows.
As can be seen, the first thing that intrigues me is the initial pulsed 120V signal, since it peaks at that value at first, and then it gradually decreases to around 90V, this maybe tells me that a capacitor is being discharged into the magnet's coil.
Let me also say that I'm perfectly capable of programming and designing an MCU interface that will produce the necessary pulses at the right frequency and duration.
It is for the following four points that I'm requesting this forum's help.
- Calculate, if possible, the required current demanded by the coil in each stage. If this is too complicated, then I'll just measure the current using an ampsense sensor connected to my scope and then get back to this forum with the info.
- Develop a (preferably transformerless) 120V power supply capable of delivering the first series of pulses.
- Develop another power supply capable of delivering the final -75V pulse. This might have already been done, since people in this forum helped me design one several months ago, capable of continuously delivering 100 mA
- Develop a circuit with a bunch of mosfets that will be controlled by my MCU that will orchestrate the switching between these power supplies to produce the aforementioned waveform.
I promise to do my homework and study all the recommended documents, and do the necessary research and calculations that are required of me.
So, step one:
How do I calculate the required current demanded by the coil in each section of the waveform, or should I simply go ahead and physically measure what's happening, or both?
Thank you all in advance for all your help.
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