Hello All,
In my project I want 0 to 5 VDC output to generate 4-20 mA signal. This signal is finally triggering an Industrial thyristor unit.
I am using Arduino Mega2560(v3) (digital Pin9) to generate PWM signals. These signals are fed into an OpAmp (LM358) you can find the reference circuit at
http://henrys,bench.capnfatz.com/henrys-bench/arduino-projects-tips-and-more/arduino-lm358-op-amp-pwm-to-voltage-converter/
I have implemented the circuit and now checking with the outputs.
On 100% duty cycle I am getting around 3.8VDC output at Arduino Pin 9 and thus it carries over to rest of circuit resulting only 16.16mA signals instade of 20mA.
I checked with other duty cycles too but result is same.
(Please read colums in order of, Duty Cycle -- Actual Voltage o/p at Arduino Pin9 -- Actual Final current O/p -- Expected Arduino o/p V -- Expected Final Current O/p
10% -- 0.38VDC -- 1.60mA -- ~0.50V -- ~5.6mA
25% -- 0.95VDC -- 6.80mA -- ~1.25V -- ~8.0mA
50% -- 1.90VDC -- 9.12mA -- ~2.50V -- ~12mA
What I cant figure out is If I run the arduino without any load (or with small load of RC Filter with LED at output) I can read correct voltage on Pin9 but as I connect OpAmp circuit The allover there is a voltage drop of 36%.
Will expert please guide me?
In my project I want 0 to 5 VDC output to generate 4-20 mA signal. This signal is finally triggering an Industrial thyristor unit.
I am using Arduino Mega2560(v3) (digital Pin9) to generate PWM signals. These signals are fed into an OpAmp (LM358) you can find the reference circuit at
http://henrys,bench.capnfatz.com/henrys-bench/arduino-projects-tips-and-more/arduino-lm358-op-amp-pwm-to-voltage-converter/
I have implemented the circuit and now checking with the outputs.
On 100% duty cycle I am getting around 3.8VDC output at Arduino Pin 9 and thus it carries over to rest of circuit resulting only 16.16mA signals instade of 20mA.
I checked with other duty cycles too but result is same.
(Please read colums in order of, Duty Cycle -- Actual Voltage o/p at Arduino Pin9 -- Actual Final current O/p -- Expected Arduino o/p V -- Expected Final Current O/p
10% -- 0.38VDC -- 1.60mA -- ~0.50V -- ~5.6mA
25% -- 0.95VDC -- 6.80mA -- ~1.25V -- ~8.0mA
50% -- 1.90VDC -- 9.12mA -- ~2.50V -- ~12mA
What I cant figure out is If I run the arduino without any load (or with small load of RC Filter with LED at output) I can read correct voltage on Pin9 but as I connect OpAmp circuit The allover there is a voltage drop of 36%.
Will expert please guide me?