I have a 24 volt 2.5 amp AC power supply, and I need to control 2 12 volt stepper motors and 4 24 volt DC motors. (The steppers each draw a little less than a third of an amp.) And I need 5 volts for my Arduino. So I need to convert the 24 volts to both 12 and 5 volts. Is there a switching voltage regulator that could give me both the 12 and the 5 (two outputs)? Or should I do it with two different voltage regulators/DC-DC converters? Or since I am running off of AC power, should I not worry about the inefficiency of a linear regulator and use that for one or both of my conversions?
Rectify the voltage, this will give you about 33V. Use a 5v switching step down regulator for the arduino and a a current controlling stepper motor driver like a Big easy driver. There is no need for 12V since stepper motors should be driven with current, not with voltage, the stepper driver takes care of that.
I already said the higher voltage would be better for the stepper driver in your other Thread
If you had continued this question in the other Thread everyone would have all the background info.
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Sorry Robin! This seemed like a different topic, so I started a new thread. as per my other thread, I also have a 5 volt stepper that I have been testing with. I really don't want to mess with the 12 volt steppers in the machine I'm controlling, until I'm sure I won't damage them when I connect them to my controller.
So when I commect my controller prototype to the 5 volt stepper and try to run it with 24 volts of power, it gets VERY hot. Can you explain? That is why I didn't want to run the 12 volt steppers with 24 volts of power.
What controller? A linear regulator gets hotter as the voltage difference increases. A switching/chopping controller/regulator does not. On a Big easy driver there is both a chopping controller for the stepper and a linear voltage regulator. The latter can get quite hot for high input voltages
I'm building a controller for a robot. I have 24 volts coming into the controller and am using a Pololu A4988 to control the stepper motors. I'm using a 5 volt stepper motor for testing but the motors in the robot are 24 volts. The 5 volt motor gets very hot when testing.
There is no such thing as a 5V or 24V stepper motor. All stepper motors are controlled by current. And you seen to contradict yourself, first you are writing that the controller gets hot, now it is the motor. Of course a motor will get hot when fed too much current. And it will get hot very quickly, the formula is P=I^2*R where R is he winding resistance. You will have to adjust the current according to the motor you are using. Set the motor to a moderate rotation rate and adjust the current potentiometer until the motor runs smoothly that will be a good setting in most cases.
You must set the current limit on the A4988 to match the requirement of the motor it is controlling.
I can't remember if you provided the specifications for what you are calling the 5v motor?
(If this was the other Thread I could probably just scroll back ! )
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nilton61:
There is no such thing as a 5V or 24V stepper motor. All stepper motors are controlled by current. And you seen to contradict yourself, first you are writing that the controller gets hot, now it is the motor. Of course a motor will get hot when fed too much current. And it will get hot very quickly, the formula is P=I^2*R where R is he winding resistance. You will have to adjust the current according to the motor you are using. Set the motor to a moderate rotation rate and adjust the current potentiometer until the motor runs smoothly that will be a good setting in most cases.
The "rated voltage" in the specs for the motor is what I'm referring to. And that seems to tie into the voltage if I compare the poles going into the stepper with a multimeter.
dptdpt:
The "rated voltage" in the specs for the motor is what I'm referring to. And that seems to tie into the voltage if I compare the poles going into the stepper with a multimeter.
Robin2:
You must set the current limit on the A4988 to match the requirement of the motor it is controlling.I can't remember if you provided the specifications for what you are calling the 5v motor?
(If this was the other Thread I could probably just scroll back ! )...R
The motor is the SY39ST34-0166A, specs on this page. So I understand that I need to set the current limit. Seems tricky, but I'll give it a shot. I'm also wondering if it might be easier to just send the motor its reference voltage and be done with it, then I wouldn't have to play with the current limit on the Pololu controller.
dptdpt:
I'm also wondering if it might be easier to just send the motor its reference voltage and be done with it, then I wouldn't have to play with the current limit on the Pololu controller.
NO. The reference voltage is meaningless. It is just derived from Ohm's law when you know the resistance and allowed max current. And it is only relevant if the motor is not moving. Once the motor starts moving the reference voltage will not be able to force the permitted current to flow against the back-emf and the inductance of the coils. Use the highest convenient voltage - in your case 30 something from the unregulated but rectified AC supply.
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Wow. I do have a lot to learn. So the important thing is that I need to adjust the current limit on the Polulu controller? So as per the specs for the stepper motor, linked to above - it says "Current/Phase = .16 amps". So there are two phases, so I should set the current limit on the Polulu controllers to .32 ohms - correct?
Hmmm. Or - does the controller only energize one phase at a time, so the current limit should be the .16 amps?
Currents are always specified, adjusted and measured per phase. The stepper driver enegizes both motor phases. The currents are sinus and cosinus functions (90 degrees apart). You can adjust the current by specifications and/or measurement but i recommend fine tuning the current until the motor runs smooth and then checking the temperature.
Ok. It seems easiest to go with the specs for the motor, at least to start. So my motor's current limit is .16 amps per phase. So, according to Pololu's website here, I want to set the current limit to .16/.7 = .23. Which would give me a measurement at the "ref" pin of .092 volts. Yikes, that's small.
Does anyone have experience adjusting the trimpot on the Pololu controller? I'm having a hard time adjusting it to get a voltage of .092 at the ref pin. It is unclear how many turns the trimpot will take...
As far as i can see the potentiometer is NOT a multiturn
dptdpt:
Does anyone have experience adjusting the trimpot on the Pololu controller? I'm having a hard time adjusting it to get a voltage of .092 at the ref pin. It is unclear how many turns the trimpot will take..
My motors take 0.33 amps and I have had no trouble setting the pot - apart from it's very small. It is only a regular single turn preset pot. I'm not going to comment on your calculations in case I make a mistake and I don't have time now to re-educate myself with the Pololu instructions.
...R