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Topic: how can i tell if device is rated for 5v or 3.3v ?  (Read 909 times) previous topic - next topic

amine2

Hello guys , i have this motor right here  :

motor encoder

the motor has an encoder wired to it .
these encoders tend to usually either be 5v encoders or 3.3v encoders .
at first i didn't think much of it , and powered the encoders with the Arduino's 5v power line .
and everything worked well .

then i tried to test it and powered them with the arduino's 3.3v power line , and surprisingly it also worked well !

both 5v and 3.3v gave me the same result . this god me worried that if it's meant to be powered by the 3.3v power line , it might get damaged on the long run .

i sent an email to the seller about 2 weeks ago and he doesn't seem to be willing to respond , is there any way i can practically tell whether this device is rated for 5v or 3.3v ?

thank you
it's all about the melons .

larryd

I do not see any data on this.

Quite expensive.

You may have to experiment to see if it works at the voltage you want to use.  :smiley-confuse:


No technical PMs.
The last thing you did is where you should start looking.

DVDdoug

Quote
how can i tell if device is rated for 5v or 3.3v ?
Buy from reputable suppliers that supply a datasheet, or a link to the datasheet, or a manufacturer's part number where you can find the datasheet.

If you can't find complete specs, you're taking a risk.    (There's nothing wrong with taking a risk, and long as you understand and accept the risk.)

I actually found the manufacturer's datasheet .

The motor is nominally rated for 6V but it says, "Usage 3-12V".  There is no information about what happens at the minimum & maximum but I assume the torque & speed specs are for 6V.

There's no information about the encoder.  And, the heading on the web page shows a different part number than the chart so that's not a good thing.  (I found it by clicking on a similar looking picture.)

Quote
i sent an email to the seller about 2 weeks ago...  
The seller probably doesn't know.

The manufacturer has an email contact form at the bottom of the datasheet page.    It's worth a try, but they may not respond to an end-user that bought one motor.    ...If they had the information "handy" it would probably be on the datasheet.

CurtCarpenter

Your motor uses hall effect sensors to detect speed and direction of rotation, so this article may be of some help: https://www.electronics-tutorials.ws/electromagnetism/hall-effect.html. 

The data sheet DVDdoug provides (well done!) indicates that you can connect the sensors to any 3.3v - 5v supply without worry.  Using 5v may offer you a little more noise margin over the 3.3V, and that might matter.

Curious:  do your sensors generate pulses of 5v or 3.3v depending on the supply voltage you use?

Looks like a nice motor!


amine2

Your motor uses hall effect sensors to detect speed and direction of rotation, so this article may be of some help: https://www.electronics-tutorials.ws/electromagnetism/hall-effect.html. 

The data sheet DVDdoug provides (well done!) indicates that you can connect the sensors to any 3.3v - 5v supply without worry.  Using 5v may offer you a little more noise margin over the 3.3V, and that might matter.

Curious:  do your sensors generate pulses of 5v or 3.3v depending on the supply voltage you use?

Looks like a nice motor!


hello Sir , thank you for your attention .
the pulse that the encoder outputs is a 5v one .
it's all about the melons .

amine2

it's all about the melons .

amine2

I do not see any data on this.

Quite expensive.

You may have to experiment to see if it works at the voltage you want to use.  :smiley-confuse:



Hello sir , thank you very much for your attention .

the encoder seems to work at a voltage of 5v . and gives the exact same output at 3.3v .
the edifice even has an LED diode , the diode lights up the exact same way with 5 and 3.3v .
it's all about the melons .

amine2

Hello guys , i thought i'd just post here instead of creating a new thread .

 - i am opting to make a printed circuit out of my design , and i don't know whether or not i should add the 3.3v line for the encoders  , it currently works well with 5v but who knows , what's the most reasonable thing to do ?

- a guy said to me that Hall sensors (such as the ones in the encoder) require 4.7K pull-up resistors . but for now everything seems to be working without those , should i add them anyway in my printed circuit design ?

- also about pull-up resistors , let's say i am willing to feed an arduino signal to 3 chip pins . which means that i am going to connect the same arduino pin to 3 different chip pins where the connection requires a pull-up resistor , should i use a single one on the arduino pin , or 3 different resistors on each and every one of the chip pins ? as some documents got me confused .

-since i am working with 5v and a maximum output frequency of about 10Khz , i won't be needing to modify the Clearance and drill parameters right ?

-one last thing , i have a 12V line in my circuit , so i need it to be extra wide . i can't find any document online that shows a clear correlation between voltage and line width though , can someone point me at the right direction to figure that out ?


thank you very much .


 

it's all about the melons .

CurtCarpenter

It looks to me (from the data sheet photo) like your motor encoder has the pull-up resistors already installed, and the fact that you are seeing 5V pulses from the encoder seems to confirm this.  So no, I   don't believe you need to provide the 4.7K pull-up resistors.

A single pull-up resistor at your Arduino pin should be adequate -- if you need it at all.  Check your Arduino datasheet to see if you can't enable an on-chip pull-up resistor.  But note:  we don't know what you're trying to connect that Arduino pin TO, and that could cause difficulties!

Since we don't know how much current you are trying to source at 12V, there's no way to determine whether you need to use a bigger line width or a smaller one.

I'd advise you to get everything working on a breadboard before you start thinking about making a printed circuit board.  Without more detail about what you're working on, I don't think anyone can help you in that area.  We're already guessing a lot  :) 

amine2

Hello again Curt , thank you again for your attention ! and i am sorry for my late feed-back as i've been highly over-burdened this past time .

the circuit indeed works on the breadboard . even without the pull- resistors for the encoder pins . only at very high motor speeds does the readings become rather erroneous . sometimes the Microcontroller skips pulses or reads pulses in reverse . though at low speeds the readings are very accurate . since i have 6 encoders and am using other interrupts to create PWM signals i don't have the luxury of Hardware PWM , therefore i am taking readings using a timer interrupt at nearly 10Khz . yet surprisingly at high motor speeds i still get incorrect reads (faulty by a limited margin) .

here is the schematic :



currently i removed the pull- resistors that were connected to encoder pins from the design .

i am using the 5V rail to feed the encoders . and i removed the 3.3v signal line , i also am worried about that .

i am also worried about there not being any capacitors  near the atmega328 (not an arduino board , the printed circuit has a standalone Atmega chip) is that really required ?

the 5V and 12V signals are provided by an other independent circuit .

there are some missing connections in the schematic but they are straightforward , from the 74HC595 to the L293D and then from that to the pin-header .

 so my questions are :

          - the manufacturer says the maximum continuous draw per motor is 60mA , the 12V rail is only used to power 6 Motors through the L293D chips . though i get a reading of nearly 1A when all of the motors are ON during a test . so how wide should the 12V rail be ?
          - is it necessairy to have a 10uf capacitor near the Atmega IC ?
          - can i get away with powering the encoders with 5V ? or must i add a 3.3v line ?
          - is there anything else you may recommend to be added to the circuit ? maybe an other capacitor somewhere ?


thank you very much .

it's all about the melons .

CurtCarpenter

Looks interesting!

1) About circuit board trace width on your 12V line, look here:  https://www.7pcb.com/trace-width-calculator.php .  Note that the width depends on how thick the copper layer is on your circuit board.  Play with the calculator a little bit and it will help you get comfortable with some choice of width.  (It looks to me like a 15mil trace on 2oz copper would give you plenty of safety margin -- but play with the calculator -- its cool!  :)

2) It can't hurt to put a 10uF (more or less) capacitor, in parallel with a 0.1uF capacitor (more or less), close to your ATMega.  The big capacitor helps smooth out any slow fluctuations that might happen on your power rail, and the 0.1uF capacitor can help with any high-frequency noise from your circuit.  Look at the capacitors as insurance.

3) Based on everything you've told us, powering your encoder with 5V ought to be just fine -- no worries.

4) I'm not sure why you need R1 and R3.  Why not just ground those two pins on the ATMega if they need to be held low?  Otherwise, looks good to me, and as the old saying goes, if it works, don't fix it!

If the problem you're having with skipped pulses seems random, it may be timing related.  Too many things happening all at once.  Maybe a way to check would be to see if the problem changes if you turn off two or three of your encoders? 

Hope that helps.






amine2

4) I'm not sure why you need R1 and R3.  Why not just ground those two pins on the ATMega if they need to be held low?  Otherwise, looks good to me, and as the old saying goes, if it works, don't fix it!


thank you very much sir . this project is a Bionic upper hand . it has 5 fingers but the thumb also does adduction and abduction and therefore it needs two motors . so in total we have 6 motors and 6 encoders . i will post all about it in the forum when done and will sure give you credit for this valuable help .

yes that helps very very much , i will make sure to add the two capacitors .
though about R1 and R3 :

          - one of them is connected to the ENABLE pin . the motors i have don't support 12V very well , so the PWM signal from the arduino has a duty cycle that doesn't surpass 50% for me to get a maximum voltage of 6v . the thing is on bootup , the arduino pins turn to high impedance , therefore the 74HC595 starts to get random signals and i always end up with 12V being fed to the motors for a very short amount of time .
to fix that i added a pull- resistor on the enable pin . that totally fixed the problem , you told me about the innate option to add that in the Atmega datasheet and thank you for that . but i had already added the resistor in the board by then and as long as it solved my problem i kept it (thank you very much though i learned that option from you and i didn't know it existed)

          - now MISO seems to receive some random signals if kept un-wired and therefore rendering the SPI transmission more prone to Noise , so therefore i connected it to ground . but then i remembered that i may have to reburn the bootloader on the chip , so i might need to actually use MISO . so i added a resistor . so that when i place wires to program the CHIP via SPI i'd have access to the MISO pin and when the wire isn't there the MISO would be reconnected to ground .

i didn't route the MOSI and SCK pins out , if i'd ever need them , i thought i'd just attach a snapper to the DIP pins and use those , since those signals are connected to the 74HC595 chips .



Thank you very much sir (y)

 
it's all about the melons .

CurtCarpenter

Sounds like an amazing project!  I'll look forward to your post about it.

MarkT

Flippant answer to the original question:  Power it from 7V, if it blows up its a 3.3V part, if it works its a
5V part (probably a somewhat damaged 5V part, but hey).

Slightly less flippant answer:  Test a bunch of them at a range of voltages and plot the results.  In other
words do the work of characterizing the parts in detail.
[ I will NOT respond to personal messages, I WILL delete them, use the forum please ]

Paul__B

Thank you very much sir.  This project is a Bionic upper hand.  It has 5 fingers but the thumb also does adduction and abduction and therefore it needs two motors.  So in total we have 6 motors and 6 encoders.
Of course you realise that to do a real hand, you arguably need twin motors for each finger - the superficialis and profundus for each finger, not to mention the lumbricals and interossei.   :smiley-lol:

Cannot live long and prosper without.

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