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bewaesserungssteuerung [2021/08/25 16:51]
sebastian
bewaesserungssteuerung [2021/08/25 20:04] (aktuell)
sebastian
Zeile 178: Zeile 178:
 According to discussion in https://e2e.ti.com/support/motor-drivers-group/motor-drivers/f/motor-drivers-forum, VPROPI has a bandwidth of 1MHz but is very weak (<100uA).  According to discussion in https://e2e.ti.com/support/motor-drivers-group/motor-drivers/f/motor-drivers-forum, VPROPI has a bandwidth of 1MHz but is very weak (<100uA). 
  
-What I find is that CS is rather stable due to being buffered behind the 10k by 33nF to ground. But I also find that VPROPI is being distorted by the load imposed by the 33nF through the 10k. At 66% duty cycle SENSE alternates between 180mV and 0mV, VPROPI alternates between 670mV and 395mV, and CS reads 575mV (close to the expected 600mV of five times 120mV average SENSE). At 33% duty cycle SENSE alternates between 90mV and 0mV, VPROPI alternates between 235mV and 95V, and CS it at 145mV (again close to the expected 150mV of five times 30mV average SENSE).+What I find is that at 30kHz PWM CS is rather stable due to being buffered behind the 10k by 33nF to ground. But I also find that VPROPI is being distorted by the load imposed by the 33nF through the 10k. At 66% duty cycle SENSE alternates between 180mV and 0mV, VPROPI alternates between 670mV and 395mV, and CS reads 575mV (close to the expected 600mV of five times 120mV average SENSE). At 33% duty cycle SENSE alternates between 90mV and 0mV, VPROPI alternates between 235mV and 95V, and CS it at 145mV (again close to the expected 150mV of five times 30mV average SENSE).
  
-Unsoldering the 33nF makes VPROPI follow SENSE much more accurately.+The [[pgv-100|Hunter PGV-100 valve]] (24Ω, 55mH) requires 300mA to switch on and then 80mA to stay on. With 15V supply and the DRV8801 (with a 500mΩ Rsense, PHASE HIGH and MODE1 HIGH) a 55% PWM duty cycle gives 290mA current through the valve in steady state (SENSE 145mV/0mV, CS 400mV), and a 15% PWM duty cycle gives 80mA (SENSE 40mV/0mV, CS 30mV).
  
bewaesserungssteuerung.txt · Zuletzt geändert: 2021/08/25 20:04 von sebastian