Timeline for Controlling a Piston Variable Pump with a Raspberry Pi
Current License: CC BY-SA 4.0
23 events
when toggle format | what | by | license | comment | |
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Oct 8, 2019 at 18:02 | history | bumped | CommunityBot | This question has answers that may be good or bad; the system has marked it active so that they can be reviewed. | |
Jun 10, 2019 at 5:01 | history | bumped | CommunityBot | This question has answers that may be good or bad; the system has marked it active so that they can be reviewed. | |
Feb 9, 2019 at 16:00 | history | bumped | CommunityBot | This question has answers that may be good or bad; the system has marked it active so that they can be reviewed. | |
Aug 31, 2018 at 18:58 | answer | added | user197175 | timeline score: 1 | |
May 23, 2018 at 21:12 | comment | added | Addison Crump | I'm not sure I follow why this would be the solution. What purpose does the rotary incremental encoder have in this system? | |
May 23, 2018 at 21:07 | comment | added | D.A.S. | Ok then you must use a rotary incremental encoder with a home switch and a MOSFET FULL BRIDGE rated for >12V and >= 1.5A which you can buy easily online | |
May 23, 2018 at 20:49 | comment | added | Addison Crump | @TonyStewartolderthandirt The force is applied to a control spool (which I assume implies back pressure). | |
May 23, 2018 at 20:44 | comment | added | D.A.S. | Is a spring tension or back pressure involved , since current controls force and voltage control controls speed affected by load | |
May 23, 2018 at 20:37 | comment | added | Addison Crump | The driving motor is effectively independent of this system (it's controlled by a physical motor which has a throttle determined by this RPi, but ultimately is unrelated to the displacement). The displacement is controlled by the current provided to the displacement input, which has a voltage of 12V. | |
May 23, 2018 at 20:34 | comment | added | MathieuL | @JRE Just saw that. So the whole system is a cascade system with an inner loop for the torque of the driving motor and the outer loop is the pump displacement if I get it correctly. | |
May 23, 2018 at 20:29 | comment | added | Addison Crump | @JRE is correct -- the pump is driven by a separate motor, all that this system controls is the displacement. | |
May 23, 2018 at 20:28 | comment | added | JRE | You could generate the control voltage for the voltage controlled current source using PWM and a low pass filter. You already have the DAC, though, so you could go ahead with that. | |
May 23, 2018 at 20:24 | comment | added | JRE | @MathieuL: The pump literally takes a current input. Think of it like a 4-20mA loop. The pump ouput pressure is proportional to the current. You aren't driving the pump motor with the current. You are providing a control signal to a device on the pump that regulates the output pressure. | |
May 23, 2018 at 20:18 | comment | added | Addison Crump | @MathieuL Would you please put this in an answer, possibly with appropriate components? | |
May 23, 2018 at 20:17 | comment | added | Addison Crump | @MathieuL The DAC is not a constraint, it was an attempt that clearly was incorrect. | |
May 23, 2018 at 20:16 | comment | added | MathieuL | @JRE IDK if the dac is an constraint in their project but to me if you can use PWM to drive the gate instead of an analogic signal you are making your life easier. | |
May 23, 2018 at 20:15 | comment | added | JRE | I think what you want is called a voltage controlled current source.. That's an example. I don't know enough about it to tell if it is a good design or not. I'll be watching this question to see what answers you get. | |
May 23, 2018 at 20:14 | comment | added | MathieuL | PWM resume to measure the current and than inject pulse into a transistor gate. The pulse of voltage will generate an average current which is controlling your displacement. | |
May 23, 2018 at 20:12 | comment | added | MathieuL | The basic strategy is to use PWM to drive the gate of an IGBT/MOSFET transistor which is connected to the pump. | |
May 23, 2018 at 20:11 | comment | added | Addison Crump | @MathieuL We need to convert a digital input to an analog output which scales current relative to the maximum of the digital input. This was the only way I understood how to do this, so if there is a better way I wouldn't be surprised. What would you suggest instead? | |
May 23, 2018 at 20:08 | comment | added | MathieuL | DAC isn't design to drive a piston.... DAC are made to generate analogic information signal from digital information signal. | |
May 23, 2018 at 19:50 | review | First posts | |||
May 23, 2018 at 23:03 | |||||
May 23, 2018 at 19:42 | history | asked | Addison Crump | CC BY-SA 4.0 |