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Author Topic: 14.4V ground reference for ADC  (Read 12460 times)

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Offline Arjunan M RTopic starter

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Re: 14.4V ground reference for ADC
« Reply #150 on: June 02, 2019, 05:12:59 am »
Can you suggest a low cost feature i can add to my PSU?
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Offline Arjunan M RTopic starter

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Re: 14.4V ground reference for ADC
« Reply #151 on: June 02, 2019, 05:29:20 am »
Look at this , I was looking for a switch.
3D image in a pdf format. 8)
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Offline Simon

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Re: 14.4V ground reference for ADC
« Reply #152 on: June 02, 2019, 08:01:17 am »
what's your minimum voltage going to be?
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Offline Arjunan M RTopic starter

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Re: 14.4V ground reference for ADC
« Reply #153 on: June 02, 2019, 08:05:46 am »
Quote from: Simon on June 02, 2019, 08:01:17 am
what's your minimum voltage going to be?
Lt3080 can go down to near zero.
I need my minimum voltage to be one or less than one.
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Offline Simon

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Re: 14.4V ground reference for ADC
« Reply #154 on: June 02, 2019, 09:09:50 am »
a crude solution could be a resistor. To stop the resistor drawing a lot of power at higher voltages you can use comparators that switch in and out different resistors.
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Offline Arjunan M RTopic starter

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Re: 14.4V ground reference for ADC
« Reply #155 on: June 02, 2019, 09:57:59 am »
Quote from: Simon on June 02, 2019, 09:09:50 am
a crude solution could be a resistor. To stop the resistor drawing a lot of power at higher voltages you can use comparators that switch in and out different resistors.
The problem with resistors are that i will get false readings in m current measurement.If it is a constant current  source or circuit i can just subtract the current of the constant current source.
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Offline Simon

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Re: 14.4V ground reference for ADC
« Reply #156 on: June 02, 2019, 10:04:10 am »
Well you are shoehorning one thing on top of another. If this was designed properly it would not be a problem. The current sense could come after all of the regulation with the feedback being taken from the final output.
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Offline Arjunan M RTopic starter

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Re: 14.4V ground reference for ADC
« Reply #157 on: June 02, 2019, 10:09:07 am »
Okay, i will not worry about the current measurement.
Is there any way to constantly sink 1mA to a opamp?
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Offline Simon

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Re: 14.4V ground reference for ADC
« Reply #158 on: June 02, 2019, 10:14:09 am »
There probably is but i can't be bothered right now.
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Offline Arjunan M RTopic starter

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Re: 14.4V ground reference for ADC
« Reply #159 on: June 02, 2019, 10:16:20 am »
Quote from: Simon on June 02, 2019, 10:14:09 am
There probably is but i can't be bothered right now.
I will try to make it myself.
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Offline Simon

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Re: 14.4V ground reference for ADC
« Reply #160 on: June 02, 2019, 10:19:41 am »
that would be a good idea.  Something along the lines of driving a BJT powering a resistor from the output while sensing the voltage across the resistor to keep the voltage constant.
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Offline Arjunan M RTopic starter

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Re: 14.4V ground reference for ADC
« Reply #161 on: June 02, 2019, 11:23:40 am »
MADE IT!!!! :)
What it does is subtract 100mV(1mA x 100Ω = 100mV) from the output voltage of the regulator.And feeds it into the other side of the resistor.So that the current flowing through the resistor is always 1mA.
The opamp used in the real circuit will be lm358.
In the simulation it can work below even 500mV.
I will build it using lm358 and test it out, i think it will work in lower than 1V.

Here is the circuit (image)↓↓↓↓
« Last Edit: June 02, 2019, 11:51:23 am by Arjunan M R »
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Offline Arjunan M RTopic starter

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Re: 14.4V ground reference for ADC
« Reply #162 on: June 02, 2019, 11:25:40 am »
Here is the simulation in LTspice
Edit:Added buffered input to the differential amplifier and added the voltage divider.
« Last Edit: June 02, 2019, 11:52:54 am by Arjunan M R »
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