Distance sensor power



  • the HC-SR04 distance sensor needs 5v so i can't use the 3.3 mini pro. I was just wondering if it also makes sense for the 5V minipro to remove leds and regulator to have a long lasting set of AA battery in series with this arduino.... wondering because so far i only saw this method adviced for the 3.3 mini pro.

    For the 5V arduino what is the best strategy to power it : 3 AA = 4.5V or 2 AA =3V and 5V step up boost module ?



  • step up modules ALWAYS consume more power than stepdown ,like a good voltage regulator.



  • sorry i should have re readen https://www.mysensors.org/build/battery
    where they say that the solution is still arduino 3.3V and step up regulator for the 5V sensor...



  • May be this post will help you finding a solution ;)

    Regards,

    QQ.



  • @qqlapraline thanks but i find it more simple and have a good experience feeding the arduino 3.3 with a step up 3.3 booster. Now of course i did not realize that the 3.3 logical levels would not work with the 5V sensor so that not only a 5V step up booster is needed for the sensor but also a logical converter ... it would be a little simpler if there was such low cost distance sensors working in 3.3V rather than 5V



  • @fhenryco
    Yet i can read for the HC_SR04 on some web pages:

    • Voltage : 3-5.5VDC
    • Logical lvel IO: 3.3V / 5V.

    so are you really sure guys that it does not work on 3.3 ?



  • @fhenryco, you have probably noticed in my post that the ultrasonic detector I use (ME007-ULS) is using 3.3v :)
    For your second question (does the HC-SR04 works under 3.3V), I would say try it :)
    But from my experience, it is quite unlikely that it works.

    QQ.



  • @fhenryco said in Distance sensor power:

    HC_SR04
    The SR04 series et al can be triggered by 3v3 logic but the 5v echo from the sensor must be stepped down by dropper resistors for the timing on the 3v3 pro-mini.
    It is regularly reported that these devices are unreliable with voltages below 5v, my project is to use the JSN version as it is in a very moist atmosphere, but the problem in using a 3v3 pro-mini was the same.
    5v boosters consume standby power, the question is how that is controlled, and I have limited experience of mosfet control.
    I am yet to build mine as still waiting on parts, but concept is a separate battery pack to 5v booster to the sensor fired up by a latching relay (Kemet EC2-3SNU or similar) so only the ground is common, and only the echo signal has to be stepped down.
    Hope this makes sense.



  • @zboblamont just to be sure i understand : the 5V echo from the sensor is because in the case you are speaking about the sensor is still powered in 5V even though it receives triggers in 3.3V ?
    And when you say that the sensor is unreliable in 3.3 , it's really when the sensor is both powered in 3.3 and receives triggers in 3.3, and of course should echo in 3.3V to the arduino then ? : strange that it does not work properly in this case ! ...



  • @fhenryco
    Yes to the first.
    The 5v supply will give a 5v logic output from the sensor on the echo pin. That must be reduced.
    Below a good 5v supply these sensors has been found to give unreliable results, although there are many different model numbers which look identical, so it is a bit of a minefield.

    No to the second, this particular sensor will not work reliably at other than a good 5v supply.
    The 3v3 is sufficient to give a logical high to the sensor to initiate measurement on this 5v device, a 5v trigger would also work from a 5v board. The echo output is at the sensor voltage of 5v level.
    If I recall one past thread on this, the poster was getting weird readings using a 3AA supply over time, the booster gave him rock solid readings until the batteries reached 1v.


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