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Topic: how can i tell if device is rated for 5v or 3.3v ?  (Read 651 times) previous topic - next topic

Southpark

#15
Sep 10, 2018, 11:24 am Last Edit: Sep 10, 2018, 11:30 am by Southpark
- 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 ?

One way to find out is to measure the DC voltage at one of the hall sensor output pins (relative to the gnd pin) for a case where the hall sensor supply voltage is 3.3V. As you rotate the disk, the voltage will probably switch from 0V to 3.3V or vice versa. Then do the same thing for a hall sensor supply voltage of 5V. If you get sensor output voltages that switch between 0V and 5V, then chances are that your hall sensor can work with either 3.3V or 5V. This means that you would be free to choose what voltage you want to operate with, by choosing your hall sensor supply voltage.

Those pin-out sheets are at least helpful in that they tell you what the wires are, and provide some clues about voltage levels. Otherwise, it's a bit of fail on their part on providing adequate details. It's probably a fail on their suppliers.

The other thing is ..... maybe you've thought about it already ---- such as what sort of measurements are planned for those encoders. Relatively constant angular velocity measurements?

amine2

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.
Yes thank you very much Sir ! i am sorry for the late response
it's all about the melons .

amine2

One way to find out is to measure the DC voltage at one of the hall sensor output pins (relative to the gnd pin) for a case where the hall sensor supply voltage is 3.3V. As you rotate the disk, the voltage will probably switch from 0V to 3.3V or vice versa. Then do the same thing for a hall sensor supply voltage of 5V. If you get sensor output voltages that switch between 0V and 5V, then chances are that your hall sensor can work with either 3.3V or 5V. This means that you would be free to choose what voltage you want to operate with, by choosing your hall sensor supply voltage.

Those pin-out sheets are at least helpful in that they tell you what the wires are, and provide some clues about voltage levels. Otherwise, it's a bit of fail on their part on providing adequate details. It's probably a fail on their suppliers.

The other thing is ..... maybe you've thought about it already ---- such as what sort of measurements are planned for those encoders. Relatively constant angular velocity measurements?
Yes that actually did work !
it turned out that encoders were equally rated for 3.3v or 5v .
it's all about the melons .

amine2

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.


Well yeah in the human body that's how it works xD the superficialis and profundus are for finger precision , while when it comes to extension and flexion it depends on the muscle group ! either the flexors or the extenders . that's mainly because muscle can only apply force when they contract . there for a single muscle can only move the joint in one direction ! though Motors can turn in both directions . i am using a 4 Bar linking mechanism . the motor motor flexes and extends the finger . in other designs they use an elastic substance to extend the finger , and a motor to flex it !

it's all about the melons .

amine2

Hello again :) since its the same project i didn't want to make an other thread .
ima just post my question here .

it is time now to make a printed circuit for the hand . and we're gunna get the made in china . the making doesn't take more than 2 days but the delivery takes more than a month ! that's why i wanna make sure that everything is done correctly to avoid a major delay of an other month after the  circuit comes in !

the PCB house has two parameters in the making process that i can't quite grasp :

 - the copper weight and the surface finish , i have no idea how to pick the right ones . i even tried searching online without any hope .



- the clearance for everything on the board is 0.2mm which is around 6mil . even with the +12V line the clearance is also 6mil .  that wouldn't cause any problems right ?


-for a copper weight of 1oz , the width of the 12V line is 1.7mm . i just wanted something more than enough to avoid problems , that would work right ?
when it comes to the 5v line , i used used the standard width of 0.4mm .


- one last thing , i used many connectors on this board , the thing is : two of them are not on the edge of the board , they are inside it as you can see , i marked them with green arrows in this photo :



the connectors will still snap correctly right ?




Thank you very much for your attention .


it's all about the melons .

srnet

the connectors will still snap correctly right ?
How can anyone know, without knowing exactly which connectors they are, and the other exact components that are nearby ?

Print out the board, at 1:1 scale, stick the printout to a bit of foam and actually check that all the actual components that you are using will fit, simple.
$50SAT is now Silent (but probably still running)
http://www.50dollarsat.info/
http://www.loratracker.uk/

srnet

- the copper weight and the surface finish , i have no idea how to pick the right ones . i even tried searching online without any hope
Where were you searching ?

If you type 'HASL with lead'

Into Google is already knows you are asking about PCB surface finishes, and suggests several explanatory links.

For the full answers however, you should tell us if this is  DIY project or something you intend to sell.
$50SAT is now Silent (but probably still running)
http://www.50dollarsat.info/
http://www.loratracker.uk/

amine2

Hello , thank you very much for your Attention Srnet , i am sorry for the lack of detail .

this is the exact connector that i have :
connector



you can ignore all the nearby components , my question is whether or not it can slide on the surface . because the connector is in the middle of the board and not on any of the edges .




- i am not intending to sell this , neither is it for a DIY project . we are constructing these hands for local amputees . so it must be long lasting and the design has to be as reliable as it can be .



- what about the clearance and the routing width sir ?
it's all about the melons .

MarkT

Maybe go for gold plating and conformal coating for reliability - will be more robust to getting
damp and less likely to corrode if it does.  Certainly all connectors must be gold plated sort
for long term reliability in harsh environments.
[ I will NOT respond to personal messages, I WILL delete them, use the forum please ]

srnet

my question is whether or not it can slide on the surface . because the connector is in the middle of the board and not on any of the edges .
They will (normally) fit flush, but it depends on the wires used and other stuff nearby.

But as I am sure you were going to do a trial component fit (see post #20) you can check at that time if the wires are intefering with other stuff.
$50SAT is now Silent (but probably still running)
http://www.50dollarsat.info/
http://www.loratracker.uk/

amine2

Thank you very much guys , this is what i finally went with for the design .

- 2oz copper is an extreme , and this design can do well with just 1oz
.
- i went with HASL with lead , it seems to have sufficient endurance . also went with that to avoid the higher temperatures and lack of compatibility of some parts with ROHS surface finishes .

- a 0.2mm clearance is more than enough for this application , even near the 12v+ rail .

- i ramped the 12V line width to 2.1mm just for extra safety .
 
- the connector will fit just fine .


if you guys have any remarks i would like to hear them .
thank you .

it's all about the melons .

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