FSR current draw

Other Hardware General Electronics
1

How can I calculate the current draw of this fsr sensor?
1 pin is connected with a 10k pull-up resistor to Vcc+(5V) and to analog pin of the Arduino and the other pin is connected to ground

Thanks

2

Ohm's Law?

3

I guess. Is it 5V / 10k (pull up resistor) = 0.5mA ? or I should also find the resistant of the fsr itself and add it to the value of the pull up resistor?

4

here is the data sheet of the fsr

Screen Shot 2022-12-26 at 20.52.53
Screen Shot 2022-12-26 at 20.52.532602×1198 284 KB

at no pressure the resistanse is higher then 20M ohm meaning almost no current draw. assuming at maximum pressure the resistance of the fsr is 0 ohm the maximum current drew will be 5V/10k = 0.5mA ?

5

To avoid misinterpretation please provide a schematic or block diagram showing exactly how you have the devices connected to the Arduino.

6

Screen Shot 2022-12-26 at 21.22.56
edit: VCC = +5V from Arduino

7

Perfect! Thanks. Don't worry about current draw. Just look for the A/D reading on A0. If you want more than just a random reading, do not connect to VCC, connect to the Arduino 5 volt pin. Or enable the internal 1.1 volt reference voltage.

8

Yes I connect it to arduino +5V.
But am my calculating was right?
5V /10k? = 0.5mA maximum current draw ?

9

My calculator shows 0.5 ma. Will be hard to measure!

10

Why do you need current?
All what your need - a resistance of your FSR, it should be calculated from analog voltage on arduino A0 pin

11

I don't need current I just wanted to see if I understand the calculation to determine how much is the max current the fsr will draw

12

To calculate current you should add the FSR resistance to the value of 10K pillup. If the FSR resistance is varied, to find the maximum current you should take the minimum FSR resistance.
Only If the minimum FSR is zero - the current will be 5V / 10k = 0.5mA, otherwise the value will be lower than 0.5mA

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13

I might be wrong, but I remembered I have been told that is generally better to connect sensors with one terminal to ground and the other to GPIO (as in the schematic I shared above) and not to Vcc.

Can someone explain me why is better doing so? is it somewhat related to interfaces of electricity?

14

Pin and ground connections are generally safer in practical builds.
No 5volt running everywere that could short out to ground (metal case etc.)
You could then also use the internal pull up of the processor, so external pull up is not always needed.

pinMode(sensorPin, INPUT_PULLUP);

Pin and VCC connections work the same, but you must use an external pull down resistor.

Note that one way results in 0-1023 and the other way 1023-0.
You can flip that in code.

sensorValue = analogRead(A0);
sensorValue = 1023 - analogRead(A0);

Leo..

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15

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