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    Boost Converter design help ...

    Battery or Input voltage: 9V
    Output voltage : 24V
    Output current: 24 mA

    What could be the current drawn from the battery? Please help.

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    Re: Boost Converter design help ...

    Output power 24 volts x .024 amps = 0.576 watts.

    Input power 0.576 watts divided by 9 volts = .064 amps if it was 100% efficient which it will not be.

    My guess would be about 80 to 100 mA.
    Cheers, Tony.



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    Re: Boost Converter design help ...

    Output power 24 V x .024 A = 0.576 VA.

    Input power = 0.576VA/90% = 0.64 VA
    Input current = 0.64VA/9V = .071 A = 71mA

    Battery drown current is 71mA
    Minimum battery capacity require in mAH = 71*9 = 639
    Approximately 1000mAH battery would be safe



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    Re: Boost Converter design help ...

    If its the case, how the loop calibrators will work?



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    Re: Boost Converter design help ...

    Hi,

    where exactely do you see the problem?

    Battery current is not loop current.

    Klaus



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    Re: Boost Converter design help ...

    I thought, the battery current will be included into the loop current to operate the transmitter. Can you please show me any schematic or block diagram representation?



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    Re: Boost Converter design help ...

    Hi,

    please give informations what you want to do.

    Be more descriptive.
    Use a paper and a pencil, a picture, a datasheet, a link ... to show us your ideas.

    Klaus



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    Re: Boost Converter design help ...

    Quote Originally Posted by smijesh View Post
    Battery drown current is 71mA
    Minimum battery capacity require in mAH = 71*9 = 639
    Approximately 1000mAH battery would be safe
    Insufficient information.

    If you want the battery to survive 24 hours, you will need 71*24=1700 mAH; just round up to 2000 mAH. 2000mAH 9V battery is uncommon and you may need two in parallel. I do not recommend connecting cells in parallel. You may use 6 1.5V 2000mAH AA cells in series.

    Your calculation of minimum battery capacity calculation is suspect.



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    Re: Boost Converter design help ...

    Quote Originally Posted by hemnath View Post
    I thought, the battery current will be included into the loop current to operate the transmitter. .............
    Generally in a boost converter the battery current is in a separate loop from the output current, even though they share the same ground.
    Zapper
    Curmudgeon Elektroniker



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    Loop Calibrator design help

    Hi I am designing a loop calibrator. Controlling of 4 to 20mA using 16 bit AD5060 DAC and using opamp.

    How to use in loop using DAC and opamp or should i use XTR transmitter IC?

    any reference schematic?

    Please help.



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    Re: Loop Calibrator design help

    A loop transmitter is a current source. So the question refers to "do you know to design a precision current source"? What are your specifications? Emulating self-powered or loop-powered transmitters, accuracy?

    TI XTR ICs can be surely used. Also any other dedicated 4-20 mA transmitter or DAC with current loop output like AD420.



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    Re: Loop Calibrator design help

    Hi,

    one possible solution.

    Self powered. So it is very precise.
    Click image for larger version. 

Name:	ConstCurrDAC.png 
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ID:	136494

    Klaus


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    Re: Boost Converter design help ...

    I can understand now how it works after doing some search and from your post.
    You may use 6 1.5V 2000mAH AA cells in series.
    I shall use 6 1.5V AA cell and boost the voltage to 30V using buck boost IC. Can you specify any better IC?

    I shall provide this 30V to opamp supply voltage and I shall create howland current source for 0 to 20mA with varying load of 0 to 1KOhm.

    Please clarify this doubt. I assume this 30V won't be very stable. Does it affect the output current?



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    Re: Boost Converter design help ...

    I guess you would start the design with a specification of the planned loop calibrator. Current source/sink? Maximal load resistance for source mode, maximal external voltage for sink mode, current range, accuracy. You did in part by saying 1k load, 20 mA. Consider that commercial calibrators support 22 or 24 mA.

    I see that some commercial calibrators are using a 9V battery, presume they have a boost converter for current source mode. Battery lifetime is in a 10 hours range, acceptable for a portable instrument.

    A howland current source has the disadvantage that accuracy depends on the tracking of multiple resistors. Better make an unipolar current source with a single precision shunt resistor.



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    Re: Loop Calibrator design help

    Yes I have the specification with me.
    mA source/simulate and measure: 0 to 24mA, Voltage source and measure: 0 to 30 VDC
    Accuracy: 0.01%

    Building and testing the project with stage by stage. Now building the circuit on source side. Voltage source: I have connected LTC1655 16 bit DAC to a microcontroller. Measured the maximum output voltage of the DAC is 4.098V. Provided a buffer at the output with LTC1151. And using non-inverting configuration and voltage is amplified with the gain of 2(just for testing purpose to check the stability). Am I going on right Path?

    - - - Updated - - -

    any reference circuit for unipolar current source with single precision shunt resistor?



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    Re: Loop Calibrator design help

    any reference circuit for unipolar current source with single precision shunt resistor?
    Basically like post #12 in the merged thread which works as current sink for two-wire loop interface, add a positive supply voltage to make a current source. I presume that the current source output of a portable instrument must not necessarily be grounded.



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    Re: Loop Calibrator design help

    Thank you.

    Does the circuit on page 4 (voltage controlled current source) will work for my problem.

    - - - Updated - - -

    Please check page 3 Boosted Bidirectional Controlled Current Source ..



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    Re: Loop Calibrator design help

    Hi,

    it will work.
    But it wonīt give you the specified 0.01% accuracy.
    (At least Iīve never seen a voltage regulator with 0.01% accuracy)

    You still didnīt follow our recommendations to show us what you want to build. Is it asking too much?

    Klaus



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    Re: Loop Calibrator design help

    I am designing a lab grade multifunction loop calibrator. Which has the capability to measure/source 0 to 24mA. Voltage measure: 30V DC. And loop powered.

    - - - Updated - - -

    Like Fluke 709



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    Re: Loop Calibrator design help

    Pls check the attached. Does it work for my application?

    will this circuit acheives 0.01% accuracy?



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