Measuring Output Power Using Atmel Tiny45 and Boost Converter

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Discussion Overview

The discussion revolves around measuring output power using an Atmel Tiny45 microcontroller in conjunction with a boost converter. Participants explore methods for feeding current information into the microcontroller's ADC to calculate total power, addressing both theoretical and practical aspects of the measurement process.

Discussion Character

  • Technical explanation
  • Homework-related
  • Exploratory

Main Points Raised

  • One participant inquires about how to input current information into the ADC of the Atmel Tiny45 to calculate output power from a boost converter.
  • Another participant suggests connecting the ADC across a suitable resistor to measure voltage, emphasizing the need for a balance between resistor size and voltage measurement accuracy.
  • A participant proposes using a current-sensing resistor for current limiting and suggests differential voltage measurement across it, recommending low-pass filtering for averaging the current.
  • One participant notes the absence of a current-sensing resistor and asks how to measure output current, indicating they have resistors in series for voltage measurement.
  • Another participant states that without a series current sensing resistor, calculating power is not feasible, and requests a schematic for further assistance.
  • A participant expresses the need for more information and outlines a plan to measure voltage drop across a resistor to derive current, aiming to optimize power output by adjusting the duty cycle based on measured power.

Areas of Agreement / Disagreement

Participants generally agree on the necessity of a current-sensing resistor for accurate power calculations. However, there is no consensus on alternative methods to measure current without it, and the discussion remains unresolved regarding the best approach to achieve the desired measurements.

Contextual Notes

Limitations include the lack of a current-sensing resistor and the dependency on specific circuit configurations, which may affect the feasibility of proposed solutions. The discussion also highlights the need for further clarification on the relationship between duty cycle and output voltage.

carvinrose
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HI,

How do i feed the current information into micro-controllers ADC input to calculate the total power?


Please help. I am using atmel tiny45 and its a boost converter output current i want to measure for output power.

Thanks.
 
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ADCs measure voltage, just connect the ADC across a suitable resistor with the current flowing through it.
It's a balance between a resistor that's small enough not to use too much power and to produce a voltage difference big enough to measure accurately
 
carvinrose said:
HI,

How do i feed the current information into micro-controllers ADC input to calculate the total power?


Please help. I am using atmel tiny45 and its a boost converter output current i want to measure for output power.

Thanks.

Does your boost DC-DC use a current-sensing resistor for current liminting? If so, you can do a differential voltage measurement across it (like with an opamp), and drive that voltage into the ADC to sense the current. You may want to do some filtering of that signal, to lowpass to get the average current.
 
berkeman said:
Does your boost DC-DC use a current-sensing resistor for current liminting? If so, you can do a differential voltage measurement across it (like with an opamp), and drive that voltage into the ADC to sense the current. You may want to do some filtering of that signal, to lowpass to get the average current.

No i don't have a current sensing resistor. Although i have two resistors in series to measure the output voltage. But how do i measure the current at the output?
 
carvinrose said:
No i don't have a current sensing resistor. Although i have two resistors in series to measure the output voltage. But how do i measure the current at the output?

Without a series current sensing resistor, you won't be able to calculate power (barring a CT). Can you post your schematic? We can't do your student work for you, but we can post hints and suggestions for you to consider to solve your problem.

Quiz Question for extra credit -- how is the duty cycle of your boost related to the output voltage?
 
berkeman said:
Without a series current sensing resistor, you won't be able to calculate power (barring a CT). Can you post your schematic? We can't do your student work for you, but we can post hints and suggestions for you to consider to solve your problem.

Quiz Question for extra credit -- how is the duty cycle of your boost related to the output voltage?

Lol i know i need a resistor but i need more information i guess what i have to do is measure the voltage drop then divide by the resistor to get the current value? i have searched the net but haven't found anything. Well my goal is to extract maximum power so all i am planning to do is measure the output voltage and measure the output current multiply them to get output power than increase the duty cycle and measure the output power again. Then compare them if power increased then increase duty cycle further then compare again if power decreased than decrease duty cycle to change the output voltage. It's pretty simple. But how to get the current information into micro controller is the problem right now.

Thanks
 

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