How to reduce voltage of 30mV to 10mV?(im a beginner)

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garygothic

New Member

• Oct 23, 2009

• #1

Hi there.Im a beginner in electronic stuff. May I know what are the options that I can do to reduce a very low voltage of 30mV to 10mV?Can I use resistor?or voltage regulator?If yes,what type of resistor/voltage regulator can I use?for your information,im doing a project on reading sensor output voltage.

 

Last edited: Oct 23, 2009

Nigel Goodwin

Super Moderator

Most Helpful Member

• Oct 23, 2009

• #2

Just two resistors, called an 'attenuator' or 'potential divider'.

Values depend on the source and load impedances, which is why your question is far too vague.

 

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garygothic

New Member

• Oct 23, 2009

• #3

Im using two sensors to run a sequential step motor: **broken link removed** and sensor2. Sensor1 produce Vout (voltage output) ≈ 30mV for every 1% increase meanwhile sensor2 produce Vout of =10mV for 1C increase. Im planning to lower the sensor1 voltage so that it will have almost the same Vout as sensor2. Your help is very much appreciated.

 

Gayan Soyza

Active Member

• Oct 23, 2009

• #4

Whats the maximum percentage for humidity & maximum Celsius for temperature?

Are you using any micro controllers for this?

 

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garygothic

New Member

• Oct 23, 2009

• #5

Maximum humidity percentage is 100% and maximum temperature value is 125C.Im using pic16f917 microcontroller and Im using **broken link removed** demo board to run my motor. Im planning to run humidity sensor using the demo board (Replacing the light sensor) but the Vout for humidity sensor is different compared to light and temperature. So the only way I can run the humidity sensor is by lowering down the Vout .

 

Gayan Soyza

Active Member

• Oct 23, 2009

• #6

Why can't you measure the AD readings from the humidity sensor? 30mV is easier to measure from a 10bit AD channel.

 

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garygothic

New Member

• Oct 23, 2009

• #7

The thing is the demo board has set the ADC value fix for both temperature and light sensor which is 10mV.

 

Gayan Soyza

Active Member

• Oct 24, 2009

• #8

That means demo board supports 10mV increments?

If you give 30mV humidity output what does the value that demo board out to PIC input?

 

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garygothic

New Member

• Oct 25, 2009

• #9

The value for humidity are not accurate when it is shown on the demo board.A value from 120 to 255 keeps popping out.It is suppose to be a value from 0 to 100 only.Unlike temperature and light,the demo board will shows both sensor's value that I wanted.

 

Gayan Soyza

Active Member

• Oct 30, 2009

• #10

To show the humidity 1% you have to wait 30mV.But the problem is your hardware gives 10mV increments.To show humidity wait 3 times the 10mV increments.Or divide the AD reading by 30.

Ex:if AD reading 75mV then show = 2.5% (75/30)

 

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garygothic

New Member

• Oct 31, 2009

• #11

May I know how to divide using assembly language?My converted value would be taken from ADRESH and move to w (movf ADRESH,w) then I will show it on the LCD.

 

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garygothic

New Member

• Nov 1, 2009

• #12

I have found the solution for my problem.Thanks for those who had commented on my thread.

 

Gayan Soyza

Active Member

• Nov 1, 2009

• #13

Have you found division codes?

 

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garygothic

New Member

• Nov 1, 2009

• #14

No. I did not used division codes in my program. I just found out that the pic16f917 can read the analogue voltage from the humidity sensor.I can manually compute the humidity value using this formula: %RH = ((Vout/5)-0.16)/0.0062 But now I'm having problem with the Vout from the humidity. Since the Vout value are not steady,the output value from ADC displayed on the LCD keeps fluctuating up and down (random numbers from 0-255). By the way,I'm using this formula to compute the value that are displayed on the LCD = (Vout/5)*255. So now I'm planning to make the ADC to read one value at an interval times and convert it but do not know how to do this. Someone told me to use sample-and-hold,other told me to use RC circuit.I have a very little knowledge on these terms and usage. Anyone can help me on this?