Hello,
I want to power sensor (custom sensor) with arduino.
The sensor is designed so that output signal is sensitive to input voltage. In addition higher input voltage gives higher resolution on the output (max Vin allowed is 20 V).
What scheme (what ICs) would you recommend to use to stabilize output from arduino but keeping it at least at 5V level? Desired accuracy level is 1% or lower. And it should not be noisy.
Thanks.
Any circuit attached to the output 5v is likely to reduce the voltage unless it is simply a capacitor.
You may be better off to design an independent supply.
Weedpharma
Use a linear regulator from a high voltage - switch mode regulators are inherently noisy and
should be avoided for precision analog circuitry in general.
If you have a 12V supply, drop it to say 10V with a low-drop-out linear regulator. Then a 1:1
voltage divider would bring the output to the 5V range.
Circuit design would depend on the sensor.
What is the current draw, is it constant or not.
Are you reading an analogue or digital value from the sensor.
How much noise can you tolerate. Noise value of a common 7808 regulator is ~40uV.
Way below the digital steps of an Arduino pin.
If you want proper advice, you should post more details about the sensor.
Leo..
Thanks for the replies.
The problem is exactly that you pointed out:
In order to get regulated output of at least 5V I need to have voltage higher than 5V, so have to use step-up regulator which is switch-type - noisy.
Current does not have to be high: 3 - 5 mA is enough. Sensor outputs analogue signal - I use external ADC to get the signal to arduino.
Can I use precise voltage reference IC after step-up switch regulator to power such sensor? Would it reduce noise from switch regulator?
Step-up (boost) regulators are noisy. Step-down (buck) regulators not so.
I assume you power the Arduino with a higher voltage than 5volts. Maybe 9 or 12 volts.
Can't you use that to make a separate 5volt rail with e.g. an adjustable LM317.
If your sensor draws a constant current, a simple RC or LC filter can be used to further reduce noise.
But maybe load- and line regulation are worse enemies.
How is your external A/D powered.
More info (schematic diagram) is better advice.
Leo..
Wawa:
Step-up (boost) regulators are noisy. Step-down (buck) regulators not so.
I assume you power the Arduino with a higher voltage than 5volts. Maybe 9 or 12 volts.
Can't you use that to make a separate 5volt rail with e.g. an adjustable LM317.
If your sensor draws a constant current, a simple RC or LC filter can be used to further reduce noise.
But maybe load- and line regulation are worse enemies.
How is your external A/D powered.
More info (schematic diagram) is better advice.
I power everything from USB. I do not want to use external power supply. And I also plan in future to power everything from a battery. So step-up conversion will be needed anyway.
Have you used switching-linear combined ICs (e.g. MAX1765)? Will it do the job?
Thanks
This one has 4% accuracy. Does this mean that it may be off by 360 mV from 9V?
I found the answer in this thread:
http://forum.arduino.cc/index.php?topic=327394.msg2259947#msg2259947
pavelkh:
This one has 4% accuracy. Does this mean that it may be off by 360 mV from 9V?
Yes. Something like that is made with calculated parts, and not trimmed to 9.000volt afterwards.
Leo..