Voltage to digital reading - Electronic Circuits Projects Diagrams Free

richacm · 20th May 2008, 01:09 AM

Hi all, my first post.

I've got a project I am working on which measures the water level in a tank by using a piezo pressure sensor (Honeywell 24PCBFA1D http://docs-asia.electrocomponents.c...6b80026163.pdf ) connected to an open ended tube inserted in to the tank. I calculated that the maximum pressure for 3m of water is about 4.5 psi so I got this 5psi max component.

The component measures pressure by a range of voltages, from what I can see. 85mV to 145mV, where 85mv is no pressure and 145mV is 5psi.

What I want to do is have some indication (LED's or Computer interface) as to the value. How do I go about converting say 100mV to a digital value I can do something with? E.g. light up the first 3 of 10 LED's to show the tank is 1/4 full. Or take the raw 100mv value in to the computer and calculate the height of water in the tank.

Thanks heaps,

Craig

Super_voip · 20th May 2008, 06:32 PM

you could start with a cheap multimeter, I can can get one for $6, rip it apart and remount it in another box. If re-scaling is the problem ie you want 100mV (or 100 somethings) to represent 100% full you could do it with an op-amp(even a 741).

ericgibbs · 20th May 2008, 06:43 PM

hi,
If you amplify the signal, you can configure a LM3914 LED driver to display the 'depth' on a LED bar.

Get the LM3914 datasheet from DatasheetArchive :: Free Datasheet Search Engine :: Electronic Components

richacm · 20th May 2008, 08:54 PM

Thanks for the input. I think that LM3914 will work a treat in conjunction with that Op-Amp....just need to figure out how to convert the 100mV to a reading within the range for the LM3914.

That multimeter idea is interesting also, what components does that use?

ericgibbs · 21st May 2008, 06:41 AM

Quote:

Originally Posted by richacm

Thanks for the input. I think that LM3914 will work a treat in conjunction with that Op-Amp....just need to figure out how to convert the 100mV to a reading within the range for the LM3914.

hi,
After a little amplification, the LM3914 resistor values can be configured to remove that 'bottom end' offset voltage of 85mV.
The LM3914 LED's will show 'zero' [say LED #1] and the 'top end' 145mV should light LED #10

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20th May 2008, 01:09 AM	(permalink)
richacm	Voltage to digital reading Hi all, my first post. I've got a project I am working on which measures the water level in a tank by using a piezo pressure sensor (Honeywell 24PCBFA1D http://docs-asia.electrocomponents.c...6b80026163.pdf ) connected to an open ended tube inserted in to the tank. I calculated that the maximum pressure for 3m of water is about 4.5 psi so I got this 5psi max component. The component measures pressure by a range of voltages, from what I can see. 85mV to 145mV, where 85mv is no pressure and 145mV is 5psi. What I want to do is have some indication (LED's or Computer interface) as to the value. How do I go about converting say 100mV to a digital value I can do something with? E.g. light up the first 3 of 10 LED's to show the tank is 1/4 full. Or take the raw 100mv value in to the computer and calculate the height of water in the tank. Thanks heaps, Craig

20th May 2008, 06:32 PM	(permalink)
Super_voip	you could start with a cheap multimeter, I can can get one for $6, rip it apart and remount it in another box. If re-scaling is the problem ie you want 100mV (or 100 somethings) to represent 100% full you could do it with an op-amp(even a 741). Last edited by Super_voip; 20th May 2008 at 06:35 PM.

20th May 2008, 06:43 PM	(permalink)
ericgibbs	hi, If you amplify the signal, you can configure a LM3914 LED driver to display the 'depth' on a LED bar. Get the LM3914 datasheet from DatasheetArchive :: Free Datasheet Search Engine :: Electronic Components __________________ Eric "Good enough is Perfect" PIC tutorials: Gramo's: www.digital-diy.net/ Bill's: www.blueroomelectronics.com/ Last edited by ericgibbs; 20th May 2008 at 06:44 PM.

20th May 2008, 08:54 PM	(permalink)
richacm	Thanks for the input. I think that LM3914 will work a treat in conjunction with that Op-Amp....just need to figure out how to convert the 100mV to a reading within the range for the LM3914. That multimeter idea is interesting also, what components does that use?