trying to work out how much power a 28byj-48 stepper motor uses

[jumpingjimmy]

im trying to use this stepper motor to put a chicken door up and down and want to know how much power it uses to get an appropriately sized battery and solar panel for it but my voltmeter is broken and haven't been able to fix it, so i figured i could try to guess how many amps it uses and use that to get the battery roughly correct hopefully instead.

i just randomly searched the internet for the specs and found these.  i wanted the 5v version but accidentally got the 12v version and it's run through a 5v output on arduino uno annd still works.  it has a resistance of 200ohm which i think makes the current (V/R) = 0.025amp but im not sure how many amps that uses in total or is that just for one rotation or its resting state?  apparently the resting power use is quite greedy.  It would only turn maybe 20-25 times twice a day to put the door up and down but im not sure how to guess the rest.

 

[JCA34F]

Do you have a 12V power supply? Are you using a driver like a ULN2003 between motor and Arduino?
https://www.elecrow.com/uln2003-stepper-motor-driver-p-262.html
If I recall correctly the 5V 28BYJ-28 draws around 120mA, so 5 * .12 = 0.6 Watts input and about 0.4 ~ 0.5W mechanical output (?). How heavy is your coop door and how fast to raise it?

[jumpingjimmy]

Do you have a 12V power supply? Are you using a driver like a ULN2003 between motor and Arduino?
https://www.elecrow.com/uln2003-stepper-motor-driver-p-262.html
If I recall correctly the 5V 28BYJ-28 draws around 120mA, so 5 * .12 = 0.6 Watts input and about 0.4 ~ 0.5W mechanical output (?). How heavy is your coop door and how fast to raise it?

yep that's the one im using, i stole the idea from this guy.  i'm just using the usb connection to test it out which i thought was 5v and it works fine, i figured as i have it running off the 5v pin of arduino uno it didn't need more,  i haven't picked the power supply yet i'm wondering if i should buy a 6V battery or 12v or possibly find another way if the battery demands are too big by the stepper.  i have it set on 7 rpm if that's a speed the top it can go is about 11-12 i didn't set that speed for any particular reason i just figured going the slowest or quickest wouldn't be good for it.  the door is a thin sheet of aluminum probably not more than 400 grams.

[JCA34F]

Running motors from the 5V pin is not good, could burn out the 5V regulator if running from batteries or damage your computer's USB if running from that. 12V motor needs 12V (at least 1 Amp) supply and a driver like ULN2003 to handle the current, don't try to run it from the output pins, they cannot supply enough current, also driver boards have spike suppressing diodes built in. I've gotten about 13 RPM before it starts missing steps but YMMV. If you're planning to use a hoist arrangement, what will your windlass drum diameter be?

[HermannSW]

I have only the 5V version of 28BYJ-48.
I read somewhere that even that version can be powered with 12V.
Since you said powering your 12V stepper with 5V is possible, it is likely to turn a bit slower than powerded with 12V.

In general I read that it is dangerous to drive the stepper from Arduino 5V rail.
I have several Arduino Unos and take the risk until really something breaks.
I do drive 2 such steppers from single Uno 5V and have not seen any issues sofar.

First I did control the stepper PT camera system from Arduino.
Lately I changed to Raspberry Pi (for real time automatic camera centering).
I did not want to risk my PIs, so I still use the Uno, but just as 5V power supply.

The bottom stepper has to turn top stepper and 70mm lens, both together 55.5g weight:
https://forum.arduino.cc/index.php?topic=647703.msg4369656#msg4369656

[JCA34F]

The 5V 28BYJ-28 (50Ω coils) draws about 100 ~ 110mA so I would wild guess the 12V model will draw about 5 / 12 * 100 = 42mA.
Also, I wouldn't try to run the door very fast, remember, there are very few chickens who are Mensa candidates.

[jumpingjimmy]

Running motors from the 5V pin is not good, could burn out the 5V regulator if running from batteries or damage your computer's USB if running from that. 12V motor needs 12V (at least 1 Amp) supply and a driver like ULN2003 to handle the current, don't try to run it from the output pins, they cannot supply enough current, also driver boards have spike suppressing diodes built in. I've gotten about 13 RPM before it starts missing steps but YMMV. If you're planning to use a hoist arrangement, what will your windlass drum diameter be?

i was thinking of getting a 12v acid lead battery and splitting the wire if this possible or having two wires one to the stepper motor as 12v and the other to a drop down converter which connects to the 5v pin of the arduino uno.  i am using a small pulley about 1.5cm in diameter to keep the torque required by the stepper for each rotation low.

[jumpingjimmy]

I have only the 5V version of 28BYJ-48.
I read somewhere that even that version can be powered with 12V.
Since you said powering your 12V stepper with 5V is possible, it is likely to turn a bit slower than powerded with 12V.

In general I read that it is dangerous to drive the stepper from Arduino 5V rail.
I have several Arduino Unos and take the risk until really something breaks.
I do drive 2 such steppers from single Uno 5V and have not seen any issues sofar.

First I did control the stepper PT camera system from Arduino.
Lately I changed to Raspberry Pi (for real time automatic camera centering).
I did not want to risk my PIs, so I still use the Uno, but just as 5V power supply.

The bottom stepper has to turn top stepper and 70mm lens, both together 55.5g weight:
https://forum.arduino.cc/index.php?topic=647703.msg4369656#msg4369656

i didn't know anything about arduino so i didn't know about the stepper motor running from 5v being a problem.  i'm hoping to use two wires or take one wire and divide it from a 12v acid lead battery and use one for the stepper and the other for the arduino either connected to a drop down convertor and to the 5v pin as an input or to the barrel jack directly.  if i can get it right i prefer it rather than take the chance of it damaging the board even though your setup (the camera looks like a tank gun) seems to work nice

 

[jumpingjimmy]

The 5V 28BYJ-28 (50Ω coils) draws about 100 ~ 110mA so I would wild guess the 12V model will draw about 5 / 12 * 100 = 42mA.
Also, I wouldn't try to run the door very fast, remember, there are very few chickens who are Mensa candidates.

they are surprisingly good at getting inside when it gets dark.  thanks for working it out.  what does the 42mA mean is it the measurement for one rotation of the stepper?  if i did 20 rotations twice a day that's still under 2A if that is correct then i think i could get away with a 12V 4.5Ah lead acid battery possibly.

[MarkT]

Stepper motors pull full current continuously.  They are not usually chosen for low power applications.

[JCA34F]

42mA is the estimated current for a 12V 28BYJ-48, with a 400g (3.94N) door and pulley radius of .75cm, required lifting torque will be about 2.943 Newton cm or 0.0293 Nm. If you roll on more layers of cable, torque will go higher with each layer (greater diameter), if you wind on 4.5 cm torque will be about 8.83 Ncm. I have no idea of the 28BYJ-48's torque. 
EDIT: You may be able to turn motor power OFF at the top IF the motor's gear reducer has enough drag to keep the door from sneaking down.

[jumpingjimmy]

Stepper motors pull full current continuously.  They are not usually chosen for low power applications.

yes i know when looking how to do the stepper i've seen you say "gear motor with encoder and lead screw" is the way to go to people on here (some of these were years ago so your opinion might be different now) but i know the stepper is a bad choice for energy but i'd already bought all the stuff for the stepper before i found out so i thought i'd give it a go at least, plus your suggestion is not within my capability for now. also not many examples on youtube or here for what you said.  the only ones that use dc motors seem to use limit switches instead which i think you are saying to avoid by mentioning the encoder part.  i figured i can use reuse the battery and solar and arduino which are the most expensive bits when i get on top of it anyway.   i assume using a leadscrew with the stepper then switching it off to provide a mechanical backup is no good because the stepper would need to turn a lot.  

[jumpingjimmy]

42mA is the estimated current for a 12V 28BYJ-48, with a 400g (3.94N) door and pulley radius of .75cm, required lifting torque will be about 2.943 Newton cm or 0.0293 Nm. If you roll on more layers of cable, torque will go higher with each layer (greater diameter), if you wind on 4.5 cm torque will be about 8.83 Ncm. I have no idea of the 28BYJ-48's torque.  
EDIT: You may be able to turn motor power OFF at the top IF the motor's gear reducer has enough drag to keep the door from sneaking down.

i managed to get a smaller pulley (0.5cm radius) and it only needs to turn 9 times to pull up the door which is great and i powered it with 12v too after what you said about the 5v pin thing so it really has no problems plus the door is tiny deliberately.  i used fishing line so the string hardly rolls on top of each other (don't think there's enough of it too to be a major problem).  and that's exactly what i did turned off the stepper off and it holds, probably not the best situation in terms it could accidentally fall one day but it works for now.  thanks for working it out for me because i was quite unsure what to do if i was wasting my time getting the battery if it wasn't going to be enough and i wouldn't have bought it if i didn't have some confidence in it.