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Topic: Interfacing 5v analog pressure sensor with 3,3v (Read 216 times) previous topic - next topic

mOskit

Hi,
guys, can any one confirm if 4050 level shifter will work to interface 5V sensor(0.5v-4.5v range) with DUE analog input??
If not, can some one please suggest simple, reliable solution?.
thank you.

dlloyd

The 4050 level shifter is for digital signals however you mention using an analog input. What is your sensor?

mOskit

You right. i used 4050 to power my display and spi signal.
the sensor i use is pressure sensor 3 wire 5V supply range 0.5v=0psi, 4.5v=150psi.

dlloyd

The simplest circuit would be a resistor voltage divider, however it would be good to know the part# or datasheet for the sensor in order to determine the appropriate values, or best approach.

mOskit

#4
Mar 19, 2015, 03:39 pm Last Edit: Mar 19, 2015, 03:40 pm by mOskit
http://www.ebay.co.uk/itm/5V-G1-4-0-1-2-MPa-0-150PSI-pressure-transmitter-Water-Gas-Oil-pressure-sensor-/181573150582?pt=LH_DefaultDomain_3&hash=item2a469a6776

This is all i know about it.

there is another thing i did not mention in the post as i thought it might be straight forward.
the design looks like this

Sensor(5V)->attiny85(ether 5v or 3.3v)-> i2c bus -> P82B71 booster -> P82B71 ->i2c bus -> arduino due(3.3v) -> screen(3.3v)

where i can make sensor + attiny 5v and than send data through i2c to due, but than i`m going to need some device btw 5v attiny and 3.3v due.

6 sensors in total.

Or as mentioned, keeps running everthing from 3,3v and just to step in linear fashion signal btw attiny and sensor.

dlloyd

Well, it's still not that staight forward. Detailed information like sensor specifications and diagram of your project would be useful.

Anyways, I'll do some guessing...

Perhaps the specifications are like this sensor:
http://www.aliexpress.com/item/Wholesale-price-5-pcs-DC-5V-0-1-2-MPa-pressure-transmitter-water-gas-pressure-sensor/1669537885.html

If so, then it mentions the Working Current <=10 mA ... is this the load current range?

If so, then a voltage divider like this should work fine without overloading the sensor output:

4.5V from sensor ●-------1K-------●-------2.7K-------● GND
                                  ↓
                        3.3V Due Analog Input

mOskit

Im not sure but they actually migh be 20mA as i saw someone mention it before.
if i use devider as you mentioned, am i still going to have linear fashion?

dlloyd

#7
Mar 19, 2015, 04:20 pm Last Edit: Mar 19, 2015, 04:24 pm by dlloyd
If the sensor has a current output, i.e. 0-20mA or 4-20mA, then it will take a certain loading resistor of low value to convert the output current to a voltage.

If the sensor has a voltage output, then a resistive voltage divider circuit could work, providing it doesn't overload the sensor's output signal. Also the impedance of this circuit must also be kept <= 10K in order to get accurate readings on the analog input.

Quote
if i use devider as you mentioned, am i still going to have linear fashion?
Yes, if your sensor has an analog voltage output (I think it does).

mOskit

could you point where i can find some info regarding choosing the right resistors for the voltage divider

dlloyd

I'm thinking the 1K and 2.7K as per reply#5 would work. Here's some reference material (lots available here and through various search engines).

Voltage Dividers

Voltage Divider Calculator


MarkT

If its voltage output you need to check the output impedance and max current
before deciding on voltage divider resistor values.  Go with 10k as the low resistor
as that is the highest value that will still work well with the ADC, so you impose
the lightest load on the sensor's output.  That would mean a top resistor of 5k
(or 4k7 if you can't find 5k0)
[ I won't respond to messages, use the forum please ]

mOskit

MarkT, sorry i dont get that -> low/top resistor?:)

MarkT

Draw a diagram of a resistor divider - one resistor is above the other, in voltage and in position
on the diagram.
[ I won't respond to messages, use the forum please ]

promacjoe

 not knowing anything about this sensor, I would like to make a suggestion. It may be a simple load sensor, a variable resistor that changes with pressure. You may be able to change the input voltage from 5V to 3.3V. Using a voltmeter check the voltage at different pressures. if it will work at 3.3V, your problem will be solved.

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