Power spliter for Raspberry pi and servo motor

I would like one plug to power a raspberry pi zero and also a servo motor… I know I need a transistor chip or something between the pi and the motor, but I want to be able to plug this into the same device, so what do I use to split the power?power-supplypowerraspberry-piservoChris Stratton82.9kThe concept of a “power splitter” is fundamentally mistaken for devices using voltage mode supplies. You need to concentrate instead on the specific supply requirements of your motor. If you really want to do this, get a mains supply which meets the motor’s needs, and then use a DC switching regulator to drop that down to what the pi needs, making sure that the first motor-voltage output is high enough that the pi regulator’s input requirement will be met even when the motor loads the supply. Using distinct mains supplies would typically be the simplest…Please edit the question to include the electrical specifications of your servomotor or its driver board, if that is external to the motor itself.@mguima until we know the nature of the asker’s motor, it is impossible for anyone to meaningfully help them. And that is not just a practical necessity, the requirement to include such information happens to be a fundamental rule of this site. Russell McMahon188kMatthew: It will greatly help people help you if you provide web links to anything you are using . The term “servo” can cover several quite different motor types and power and voltage and drive requirements for what you are probably using vary. Please provide brand & model of your servo motor and a web link to a data sheet (or a technical description if data sheet not available). A web link to a Pi Zero datasheet would also do no harm. || Note that what Chris says is valid – to get a good answer that works it is necessary to be sure of what the real requirement is. Chris StrattonWe don’t yet know that this is an “RC hobby servo” the term “servomotor” tends to mean the much more power hungry and capable industrial sort of device. Until the asker says what they have, anything posted is guesswork, and that’s not what this site is for. Russell McMahon@ChrisStratton I agree largely with what you say. I’m trying to steer the conversation in a way that a new user will feel comfortable with. Even very good advice can be fairly offputting when new to how things work. It’s still needed but … . I was about to add a “You need to …” comment. mguima@ChrisStratton and Russel, 99,999% chances that OP has a blue 9G servo. I edited my answer, because of course the circuit needed to isolate the SBC and the motor would be a lot complicated to OP build. Russell McMahon188kThu 12:33@mguima has provided a useful link in his answer. BUT do note Chris Stratton’s comments also. Any motor tends to make electrical “noise” which a microcontroller is very sensitive to. Also, usually the power needs of a motor exceed that which what can sensibly be fed from a Pi header directly. Finally, the voltage needs to be correct and may not match the Pi supply. Overall, when starting off, supplying the servo from a separate supply, batteries or other is a safe move. Grounds of Pi supply and servo supply MUST be connected. The servo control lead can usually be driven directly by the Pi. tlfong014345@Matthew, I like your little cute yellow cubes very much. I would give 5 stars (Top 1%) to your question. I guess, from your concise question and the use of the words “transistor chip”, “splitting power”, “servo motor” that it is very likely that you are like me, a hobbyist. You remind me of a recent StackOverflow blog saying the following: “It is a good idea to guide the newbie to arrive at a good question, and let them know what they don’t know that they don’t know. / to continue, …@Matthew, / continued, … It is only when the newbie sees the big picture, knows the basic things that he should know, and then uses a hobbyist friendly language to ask the question, then other newbies, ninjas, and pros can all join in to contribute a newbie language.@Matthew, / continue, … When I first read your question, I was surprised of two things: (1) How come this guy presents his question so succinctly and effectively, (using eye catching little yellow cubes etc), (2) But at the same time, this guy is using electronics amateurish language (eg, “transistor chips” instead of “transistor”, “servo motor” instead of, in short, “servo” which we hobbyists always use). / to continue, …@Matthew / to continue, … One of my hobbies is “technical presentation” and “effective communication”, so before I start answering any question, I almost always check the asker’s profile, to make sure we are talking the same “language”. When I skimmed your profile, I was surprised of another two things: (3) Your educational and career background, (4) Your long history with EESE and your very short list of questions and answers here. My surprise #3 of course make Surprises #1, #2 no longer surprising. / to continue, …@Matthew /continued, … And before I make an answer, I sometimes also let the asker know myself, a little bit more than my short profile in this EE SE. (1) I also have a MSc IT, at Imperial College London. I also once studies, (but dropped out after a year), in the Cybernetics Dept in Reading (UK’s Reading. :)) (2) It is only two years ago that I bought my first toy servo. I am a poor hobbyist, and I never played any RC toys, not to mention drones. / to continue, …@Matthew / continue, …The price of drones dropped so very much these years, that it has become a popular toy, and I would lose face if my 10 year old niece discovers that I don’t know nothing about drones. I know that drones use servos, but also BLDC (BrushLess DC) motors, which is another thing I don’t know nothing about (I do know toy DC motors very well, though).@Matthew, /continued, … (3) Now, my 3 year hobbyist learning and project plan: Make a cyber cat using 4 servos (You can find more details about my cyber cat project in the chat room chatting here: chat.stackexchange.com/rooms/112589/… ).@Matthew. / continue, …I will stop my TLDR pre-answer introduction here. You might like to tell me your learning/project plan, so that I can tailor my answer to fit the plan of yours and other future newbies. Cheers. mguima@tlfong01 I really appreciate your kind of approach and the very complete and documented hobbyst’s oriented answers that you write. I got to note that yellow duck from HK, since that remarkable answer when you told us about your struggle for hacking with GPS devices from home. Russell McMahon@tlfong01 provided this reference RpiZero Power Supply through 40 pin Power/GPIO Header or microUSB connector. || Note the warnings from Chris and in my answer.  1 hour later… tlfong014345Thu 13:37@RussellMcMahon Thank you for your help. I think it is a very good idea to open a chat room to clarify the user’s requirements and skills before me starting an answer. Actually I hope to know if the OP has a multi-meter and a bread board, and knows the basic techniques of soldering.(removed)(removed)@RussellMcMahon @mguima Actually just now I tried to open a chat room and invite everybody to discuss things. However I could not find any option to open a chat room. I know other users with higher reputation points can do that. I prefer to first draft an answer, casually upload pictures and programs in the chat room, so everybody can comment or make counter suggestions, to make sure I have not misunderstood the OP’s question. This is what I will be doing now in this chat room. Cheers.@RussellMcMahon Thank your for reminding me about the warnings when giving my answer. I will read them to see if I need to pay attention on something I am missing. I hope my to complete answer will no longer induce any warnings. Cheers. tlfong014345Thu 14:20@mguima Thank you very much for your nice words and encouragement. One reason that my answers are newbie friendly is that (1) I studied an EE diploma in a community college where, unlike universities, our teachers and text books used a language that “ordinary people” can easily understand. Later I also taught in a community college where I enjoyed telling the much disadvantaged, low privileged mature students / to continue, …about Ohm’s Law, how to blink a LED, and even NE555 timer, which gave them great joy and a big sense of achievement which they unfairly got so little in their real hard life, working 8 days a week, like a dog, youtube.com/…. Cheers.  14 hours later… Matthew3706yst 4:21Wow, thanks all for the discussion. I am into electronics as a hobby. I have studied software engineering, but the not familiar with too much electrical engineering. I am trying to design an automatic dog feeder… I want to plug in the device once, then power the raspberry pi and a 12 V dc motor. Matthew3706yst 4:44

Batteries are not an option… I believe there should be a way that I can integrate the R. PI with the motors. The motor is a 12 V one which will be controlled by that motor control chip.  17 hours later… mguima1230yst 21:46@Matthew Automatic pet feeders are one of the “holly grails” of DIY. I wished I still had the same confidence to trying to make one for my cats.There are a lot of glicthes. As the other users had said, a motor “backfires” a lot of “hazard” / disturbs to the very power lines that feeds it. This is the reason why is not adviseable that you power your motor with the same power lines that you will feed your RPi.But, which kind of motor are you using? Is it a servo motor? Is it a common DC motor (as in this second photo)? Is it a brushless DC motor? Is is a stepper motor? Every kind of motor has different requirements.In this new form of the question, the yellow cube would be a circuit that takes 12V from the wall-wart, convert it to 5V, has protections from the motor electric noises, and sends this 5V to the RPi. The 12V from the wall-wart also connects to the controller of the motor.A normal DC motor like this in the photo doesn’t have three wires. That kind of motor has only two wires. So, the power from the wall-wart goes to the controller of the motor; this controller receives a digital signal from RPi, and when this digital signal is on, the controller sends power to the motor.But at first you wrote “servo motor” in the question; after that, you put the photo of a DC motor; and recently the the photo in the question was changed again to a new kind of motor.The L293 chip can control a motor, but it is not reputed as a very efficient one.The IC or the module that will be used depends on the nature of the motor.Do you already have the physical fixtures, i.e., the parts that, controlled by the motor, will release the food? In my opinion, that should be the first part of the project. Only if you have the motor attached to the physical parts that will release the food to some kind of tray were the dog will eat, is that you should start to think about how to control this motor.You said that “I just need to spin the motor, one direction, for about a second. It is for an automatic food dispenser, so just a burst for a second or so, and I don’t know exactly what type of motor I need for that. “First you make your fixture and decide about the motor. Only after this you take the next step for the electronics control.As an IT professional, you know that computers can’t change things in the physical world by themselves. So, first, build the fixture to change physical things (the actuators or whatever else that will send a portion of food to the dog), and, second, think about the ways of put “brains” in it.  11 hours later… tlfong0143459:26@Matthew Ha, how nice to talk to a SE (Software Engineering) guy. I am a EE guy, but I did teach myself SE, many years ago. Actually we also need a ME guy, to design mechanical stuff. Perhaps we also need mechantronic guy. Or a in short a robotic guy. Anyway, I will tell my bad friends that I am building a robot cat food feeder, with the following features: (1) The cats should have a RFID chip implanted in the ear, or wearing RFID a collar. In other words: No RFID no food.Before moving on, let me show you a video:Homemade Dog Feeder with Arduino – 2015oct26, 27,983 Views
youtube.com/…, /to continue, … tlfong0143459:58So, if we want to also consider water feeder, we might need to consider solenoid valves. A solenoid (only, no valve) can also pull a door/window, to let food fall. In other words, we don’t need any motor altogether. The valve shown in the video is also a big over kill. You may like to see the light duty solenoid valve used is another cat food feeder.Cat food feeder and solenoid valves etc.(1) raspberrypi.org/forums/…
(2) raspberrypi.org/forums/…
(3) raspberrypi.org/forums/…My cat only drinks ice water direct from Fiji. So I need water pumps for the warm/cold water dispenser, actually one more pump for washing hands (claws):raspberrypi.org/forums/…My rooftop garden has jacuzzi for cats:(1) raspberrypi.org/forums/…
(2) raspberrypi.org/forums/…
(3) raspberrypi.org/forums/…
(4) raspberrypi.org/forums/…
(5) raspberrypi.org/forums/…
(6) raspberrypi.org/forums/…(see full text)Ah, morning tea time. See your later. Cheers.Before I go, the project log showing how me, the robotic engineer, designed the rooftop garden for my neighbours.

Ah, I forgot to say where the cartoon comes from:pinterest.com/pin/…  2 hours later… tlfong01434512:57Now the short answer for your question.(1) Use two separate power supplies, one for Rpi, the other for motor and solenoids.(a) Amazon MeanWell RS-25-5 5V 5A 25W Single Output Switching Power Supply – US$10
amazon.com/…

(b) Amazon MeanWell LRS-150-12 12V 12.5A 150W Enclosed Switchable Power Supply – US$25
amazon.com/…(2) Don’t use plastic cased wall warts, for at least two reasons:(a) Wall warts usually have two grounding, even though they have a insulated plastic casing.(b) Anything plastic looks cheap, may damage your reputation.(3) So I am suggesting to “split the power” at the 110VAC mains point. Use a power bar with individual power on off switches, indicator status lamps, and fused “everywhere”.(4) MeanWell USA is a good brand, designed in US, manufactured in CN, with good quality assurance and control. tlfong01434513:19Of course you can use just one 12V PSU, and “split” or “forked” out a 5V to Rpi, using a popular LM2596 based switching power supply. But it is always a good idea to “decouple” MCU/SBC/logic power from Motor/Relay/Solenoid power which as
EMI/Back EMF/Noise Problems. Usually mains/actuator voltage spikes and noises will escape through ground wires, so it is a good idea to decouple power/ground wires as much as possible. So let the (mains) grounding at the 110AC power bar is the best you can do. There are other tricks to avoid noise etc, eg. Using optical isolation at input side. But the…(see full text)For rich newbies, I usually recommend the following LM2596 adjustable 5V/12V PSU for playing with RpiZ/W and motors. It is handy to have button digital control and LED numerical display. There are other variations with higher current capacity, say up to 10A, but they are not LM2596, but other brands, and usually need big heat sinks.Just an example.Amazon LM2596 Numerical Control Voltage Converter DC 5/12/24/32V to Adjustable 0-30V/12V/5V Switching Regulator Module 1.5A Volt Transformer with Red LED Voltage Testeramazon.com/…Ah, locking down lunch time! See you later. tlfong01434514:19In case you wish to consider higher current rating, such as 6A to 12A. You can consider regulators like these below:(1) amazon.com/…
(2) amazon.com/…The good thing with the above voltage regulators is that they have a LCD Voltage and Ampere meter, so you can easily check current vs voltage when testing things like motor etc. tlfong0114:35If your are using a 6A or 10A power supply, it is a good idea to provide you own fuses, say 2A or 3A. As shown in the following picture. Rpi 2/3/4 has polyfuse on PCB, but not RpiZ/W. tlfong01434514:46

  2 hours later… tlfong01434516:39Your motor is similar to the one below. It is a 12V geared DC motor, usually very low speed, self locked. If you are driving in one direction, you can use a N-Channel power MOSFET, such as IRL540N, with low Vgs(th). If you drive CW and CCW, you can use a full bridge DC motor driver such as L298N.Amazon – High Torque Turbo Geared Motor Gearbox DC 12V Motor 2/3/5/6/10/20/30/40/62/100RPM (2 RPM)
amazon.com/dp/…The motor used the above “Homemade Dog Food Feeder”, uses also a low speed DC gear motor, but with eccentric shaft.Amazon DC 12V 2RPM Gear Motor High Torque Eccentric Output Shaft 37mm Diameter Gearbox – US$14
amazon.com/…You can see a big picture of the hobbyist motors in the following Polulu motor comparison chart, which include stepping motors which is high precision, eg, used in 3D printers.Polulu Comparing Products Chart in 34 Categories
pololu.com/search/compare/22The two motors mentioned use 6mm shaft diameter, and gear box 370 diameter. In your application, 2mm to 4mm diameter motor should be enough.A popular 6V small power DC gear motor such as the following is popular in house hold applications, eg, smart curtain, where speed is not important, and low speed, high gear ratio can easily drive heavy loads.Polulu 15:1 Micro Metal Gearmotor LP 6V
pololu.com/product/4780tlfong01434517:11As I said, you might not need any motor, perhaps a solenoid is easier to implement. But I would suggest you to google around tutorials, instructables, and YouTube videos for inspirations.