voltage monitoring
in [Design]
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From: john1987 on 12 Jul 2010 18:25 Hi, Can you give me the part number on the rectifier and the capacitor or method to choose them. How about using a voltage divider? John
From: Joerg on 12 Jul 2010 19:38 john1987 wrote: > Hi, > Can you give me the part number on the rectifier and the capacitor or > method to choose them. How about using a voltage divider? > Well, if you don't need any isolation you can divide via resistor. But then you might as well rectify the pulses directly, into a cap, then hang a voltage divider across the cap. I normally use the BAS21 diode for such jobs, comes in a 250V variant. If the spikes can go higher than 200V I'd use one with more breakdown voltage. The cap should be a ceramic rated at 250VDC or higher. With the resistive divider being 1M a 1nF would give you a 1msec time constant. If that's too slow a reaction time drop the cap proportionately but you'll see more ripple. You can also reduce the resistor but then you'll start burning more serious power in the resistor. -- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM.
From: john1987 on 23 Jul 2010 18:17 Hi All, I am able to monitor the volatge across the coil and also can measure it with the help of an ADC on my micro. Now, I am looking for some kind of algorithm that can help to monitor the changes and act accordingly. Specs are : Input signal to the ADC (micro) is 2.5 volts peak (+ve only) and I would like to keep it that way. Now, if it drops to 2 volts than I need to get it to 2.5 volts again. It could be a simple if else instruction in C but I heard that algorithms like PID etc are availablr to this. How can these algorithms be helpful and what should I do to implement them. Please advice! Thanks John
From: Grant on 23 Jul 2010 19:10 On Fri, 23 Jul 2010 15:17:38 -0700 (PDT), john1987 <conphiloso(a)hotmail.com> wrote: >Hi All, > >I am able to monitor the volatge across the coil and also can measure >it with the help of an ADC on my micro. Now, I am looking for some >kind of algorithm that can help to monitor the changes and act >accordingly. > >Specs are : > >Input signal to the ADC (micro) is 2.5 volts peak (+ve only) and I >would like to keep it that way. Now, if it drops to 2 volts than I >need to get it to 2.5 volts again. It could be a simple if else >instruction in C but I heard that algorithms like PID etc are >availablr to this. How can these algorithms be helpful and what >should I do to implement them. > >Please advice! Advise what? Not enough context? People make switching converters with PIC chips, is that what you're after? Take a look at the application notes. There are PIC chips with onboard support for PWM, including the RS latch and comparator you need for driving the switch. Grant.
From: john1987 on 23 Jul 2010 19:43
Hi, I can do the PWM but I am confused about the control algorithm like would it be an over kill to do this with PID control algorithm. For example, right now I am doing that if the voltage is 2 volts than increase the duty cycle (using PWM) so that the voltage will increase to 2.5 volts and than when it reaches to 2.5 volts than keep the same duty cycle and keep looping to check any drop across the coil voltage. I know it also sounds like a speed control of the motor. John |