A little back ground on the project that i am about to start. It is based on this project: Automatic Pet Feeder. I am taking this project and making it a little larger. I will be expanding it to fill two pet bowls and also planning on a second version that i would like to include this RFID project: RFID Pet Food Bowl. The RFID part isn't on the radar yet but i would like to get enough power to run the complete project so I don't have to buy a power supply now and another one later on.
So the first version of the project will have 2 stepper motors, 1 servo, and a 16x2 lcd controlled by an arduino uno. Final version will add 2 additional steppers, a couple IR sensors, and most likely a ID-20LA reader.
Stepper Motors
Rated Current/phase: 1A at 3.4V
Phase Resistance: 3.5ohms
Stepper Drivers
A4988
8 V to 35 V and 1A -2A (with heat sink) output.
I am considering using an old dell power supply. I have two: one is 19.5V 3.34A and the other is 20V 4A. I would like to use the smaller one if possible, considering the fact that it'll be rare for more than 2 stepper motors being driven at the same time ever.
1.4A per coil at 3.5V = 9.8W per motor with some built in head room
so with 4 steppers that puts me at just under 40W with a decent amount of head room. To me the 19.5V power supply would be enough power for everything i want to do now and in the future for this project, If i understand everything correctly.
My main question is using the single power supply for the steppers and the Arduino. There are a couple DC-DC Step-down Regulator Modules that i have been looking at. Just want to have someone more knowledgeable tel me if i am understanding this correctly.
I cannot see the existing pet feeder at the moment (problem my end). Stepper motors are going to draw power all the time even if they are not moving, if you could use servos instead that would help keep your power bill down.
ardly:
I cannot see the existing pet feeder at the moment (problem my end). Stepper motors are going to draw power all the time even if they are not moving, if you could use servos instead that would help keep your power bill down.
Wouldn't i be able to use the Sleep pin on the A4988 driver to only energize when the motor needs to turn, or even the Enable pin to keep the board powered on but not outputting anything to the stepper. I do not need the motor to be actively held in place.
I decided to use a stepper instead of a servo because i figured it would be easier to control a set output. What i am trying to say is that if i know for example two full rotations equals 1/4 cup of pet food, then it would be two multiple that for addition servings if needed. I do not care what position the stepper is in because once the auger gear that pushs the food gets primed then its output will vary only a small amount depending on the position. The guy that created the project stated he had issues doing this with servos and switched the the stepper. Also the 3D printer files are only for the stepper and not for the servo mounting so that is why i am going that route.
Dsheumaker:
Wouldn't i be able to use the Sleep pin on the A4988 driver to only energize when the motor needs to turn, or even the Enable pin to keep the board powered on but not outputting anything to the stepper. I do not need the motor to be actively held in place.
Yes, you should be able to that if the motor does not need held in place. Does the design prevent the pets from working the mechanism, it is surprising how persistent animals can be when food is involved
Dsheumaker:
Wouldn't i be able to use the Sleep pin on the A4988 driver to only energize when the motor needs to turn,
If you do that you can't guarantee that the stepper is in the same position without making it go back to the ZERO or HOME switch whenever it is re-energized.
I agree with the idea that servos are likely to be more suitable unless you need something that can do multiple revolutions with position control. Even then, if you use a sail-winch servo it can do about 3 revolutions with position control.
ardly:
Does the design prevent the pets from working the mechanism...
Ardly the mechanism will be an auger gear mounted inside a tube, no way for the cats to activate it. There will be a manual feed button, just have to make sure they don't figure out how to press it haha.
Robin2:
If you do that you can't guarantee that the stepper is in the same position
Robin2 if the auger gears are primed with pet food and the code states at a feeding time the stepper move 400 steps eat. The movement would move the food and re-prime the auger gear.
Bringamosa:
60 wsstts output from your psu should be enough imo
Bringamosa do you have an opinion on the DC-DC step downs that i linked? i have now learned that i need something of quality. i have a super cheap power supply for my breadboard and it died on its second use.
Attached is the auger gear that i am referring to. It mounts inside a T section of PVC
Dsheumaker:
Robin2 if the auger gears are primed with pet food and the code states at a feeding time the stepper move 400 steps eat. The movement would move the food and re-prime the auger gear.
If I understand that description then it won't really matter if the motor moves 395 steps or 405 steps so any small loss of position when the motor is de-powered would not matter. In other applications requiring precise positions the loss or gain of a single step would matter,
