So, I'm making a little x-y plotter, using the 28byj-48 5V steppers (with the drive module)
It is all working beautifully .. But I really want to ask about power, as I'm finding this the trickiest to get right.
So I have been using some 9V batteries, into either the vin, or the dc in
The motor is 5V and runs out of the 5V pin
But, I have to replace the batteries fairly regularly... More than I'd like to since I am calibrating the drawing mechanism.
I got a 12V adaptor today, and ran that through the vin, and motor from the 5V. The DC plug and the little 5V regulator got hot, so I think it's possibly a not very accurate 12V, or else it really is just too much.
Tomorrow, I'm going to try to find an adjustable adaptor, or maybe a 9V. But I wanted to put the question out there about running quite low voltage things, like small steppers, but getting the appropriate power source.
What kind of solution did you find. Do you worry about the heat?
The other thing I don't like is my adaptor seemed to 'surge'. Even though it was switched off at the mains, when I just plugged in the DC cable, I got a blink of lights. Any advice for stopping that kind of thing happening?
Claudia:
So, I'm making a little x-y plotter, using the 28byj-48 5V steppers (with the drive module)
It is all working beautifully .. But I really want to ask about power, as I'm finding this the trickiest to get right.
So I have been using some 9V batteries, into either the vin, or the dc in
The motor is 5V and runs out of the 5V pin
It would be very useful to know the worst case current demand for the two motors as there is a limit of how much +5vdc current you can draw from the arduino 5V pin and it's a different value if the board is USB powered Vs powered from the external DC power connector. Assuming it has been working for you except for short battery life I guess you may be OK, but it's best to always have and incorporate all the information required to make the best design decisions.
But, I have to replace the batteries fairly regularly... More than I'd like to since I am calibrating the drawing mechanism.
Those small 9vdc batteries were designed to power smoke alarms and other very low current devices, they really suck for arduino projects and they are the most expensive battery choice possible from a capacity Vs cost basis.
I got a 12V adaptor today, and ran that through the vin, and motor from the 5V. The DC plug and the little 5V regulator got hot, so I think it's possibly a not very accurate 12V, or else it really is just too much.
Tomorrow, I'm going to try to find an adjustable adaptor, or maybe a 9V. But I wanted to put the question out there about running quite low voltage things, like small steppers, but getting the appropriate power source.
What kind of solution did you find. Do you worry about the heat?
I don't worry about the heat, but many do. The on-board +5vdc voltage regulator has build in protection against over temp and over output current limits, it just shuts off it's output if either limit is reached. But that aside, heat is never an advantage (unless your building a heater ) so it best to try and run as cool as it can. The recommended input voltage for the Arduino DC connector is 7.5vdc to 12vdc. The closer your adapter runs at the 7.5v value the cooler the on-board +5vdc will run, as that is it's function, to 'waste' the difference of input voltage to +5vdc output voltage via heat dissipation.
The other thing I don't like is my adaptor seemed to 'surge'. Even though it was switched off at the mains, when I just plugged in the DC cable, I got a blink of lights. Any advice for stopping that kind of thing happening?
Not sure what you are seeing, but it could be the main filter capacitor inside the adaptor still retaining some charge even though unplugged from the AC mains. Not sure of a easy fix for that, unless you switch to a more modern switching regulator type power adapter, as they usually use a small filter cap(s).
Thanks so much for your reply... It was so comforting that I was much bolder....
In the end I got two different adapters, one 9V and one adjustable, which I can take down to 7.5V.
The 9V ... The regulator gets hot, but think it's not a big problem. The 7.5 is pretty perfect, it gets warm.. But I think that's the thing doing its job.
So, what I was doing was running each stepper on a separate Arduino, today I put them both on one Arduino on what I believe is a parallel circuit. Seems to work perfectly, nothing getting too hot, motors seem to be running at the same even speed as before, so I think I must have got it right. And this is running off the 7.5V setting.
A 5V regulator acts like a controlled variable resistor. What I mean is as the voltage goes up the regulator changes its resistance so the output stays at 5V. that wasted energy gets tuned into heat. What you can do is attach the tab on the regulator to a piece of metal and give it a bigger radiator to get rid of the heat. Just be careful what the metal touches as it coulf short against the pins of the regulator and short out.
Depending on the output rating of your wall transformer (wall wart...) they will run warm when used at near their rating. A 5V regulator is not very efficient and supplying one with 12 V means abut half the output of the transformer is heating the regulator.
You don't need to regulate the power to the stepper motor/driver and feeding it a voltage higher than 5V should improve its speed a bit. The darlington array should be capable of 50V/500ma; the limitation of the stepper itself is heat.
Your controller board has a mysterious little jumper on it; if necessary, you can remove this jumper and add a resistor between those two pins to reduce the current through the motor and thus bring the heat of the motor under control. You'd want to add somewhere around 26 ohms for each volt over 5V you run the motor -- but again only if it seems like the motor is getting too hot.
) so it best to try and run as cool as it can. The recommended input voltage for the Arduino DC connector is 7.5vdc to 12vdc. The closer your adapter runs at the 7.5v value the cooler the on-board +5vdc will run, as that is it's function, to 'waste' the difference of input voltage to +5vdc output voltage via heat dissipation.