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tlfong01
tlfong01
1:26 AM
@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
https://www.youtube.com/watch?v=TcqbZ_y5WI0, /to continue, ...
 
tlfong01
tlfong01
1:58 AM
So, 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) https://www.raspberrypi.org/forums/viewtopic.php?f=37&t=231541&p=1418624&hilit=solenoid+valves+tlfong01#p1418727
(2) https://www.raspberrypi.org/forums/viewtopic.php?f=37&t=230984&hilit=cat+food+feeder#p1415973
(3) https://www.raspberrypi.org/forums/viewtopic.php?f=37&t=230984&hilit=cat+food+feeder#p1415270
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):
My rooftop garden has jacuzzi for cats:
(1) https://www.raspberrypi.org/forums/viewtopic.php?f=37&t=77158&start=425#p1382243
(2) https://www.raspberrypi.org/forums/viewtopic.php?f=37&t=77158&start=425#p1377308
(3) https://www.raspberrypi.org/forums/viewtopic.php?f=37&t=77158&start=425#p1380907
(4) https://www.raspberrypi.org/forums/viewtopic.php?f=37&t=77158&start=425#p1381407
(5) https://www.raspberrypi.org/forums/viewtopic.php?f=37&t=77158&start=450#p1384933
(6) https://www.raspberrypi.org/forums/viewtopic.php?f=37&t=77158&start=450#p1389079
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:
 
 
2 hours later…
tlfong01
tlfong01
4:57 AM
Now 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
https://www.amazon.com/MEAN-WELL-original-RS-25-5-Switching/dp/B01NBRTCIT/ref=sr_1_3?dchild=1&keywords=mean+well+rs25-5&qid=1601700802&sr=8-3

(b) Amazon MeanWell LRS-150-12 12V 12.5A 150W Enclosed Switchable Power Supply - US$25
https://www.amazon.com/MEAN-WELL-LRS-150-12-Enclosed-Switchable/dp/B00M8TBJLK/ref=sr_1_2?dchild=1&keywords=mean+well+rs35-12&qid=1601700563&sr=8-2
(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.
 
tlfong01
tlfong01
5:19 AM
Of 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…
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 Tester
Ah, locking down lunch time! See you later.
 
tlfong01
tlfong01
6:19 AM
In case you wish to consider higher current rating, such as 6A to 12A. You can consider regulators like these below:
(1) https://www.amazon.com/DROK-Adjustable-Converter-Transformer-Protective/dp/B07JZ2GQJF
(2) https://www.amazon.com/DROK-Converter-5-3V-32V-Regulator-Transformer/dp/B078Q1624B/ref=pd_lpo_60_img_0/144-0786939-9118234?_encoding=UTF8&pd_rd_i=B078Q1624B&pd_rd_r=0e88d5b4-6b7f-4fe0-afa5-cdf80e31bae3&pd_rd_w=iOXyg&pd_rd_wg=6GREO&pf_rd_p=7b36d496-f366-4631-94d3-61b87b52511b&pf_rd_r=27JDHBHESNYDAN028KWJ&psc=1&refRID=27JDHBHESNYDAN028KWJ
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.
 
tlfong01
tlfong01
6:35 AM
If 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.
 
tlfong01
tlfong01
6:46 AM
 
 
2 hours later…
tlfong01
tlfong01
8:39 AM
Your 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)
https://www.amazon.com/dp/B01LXV085F?psc=1&pf_rd_p=0341f622-1508-4712-8614-4588a55d8cf4&pf_rd_r=XK3GNSW7XEEJPXD5GYAQ&pd_rd_wg=AGGiK&pd_rd_i=B01LXV085F&pd_rd_w=k5XLc&pd_rd_r=54cf5bb7-b947-48f3-8dc9-35d3a4c51f9b&ref_=pd_luc_rh_ci_mcx_mr_huc_d_03_02_t_img_lh
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
https://www.amazon.com/Greartisan-Electric-Reduction-Eccentric-Diameter/dp/B071KFSM8V/ref=sr_1_1_sspa?dchild=1&keywords=gear+motor&qid=1601714444&sr=8-1-spons&psc=1&spLa=ZW5jcnlwdGVkUXVhbGlmaWVyPUEzVVNKV1pGSkxITUxRJmVuY3J5cHRlZElkPUExMDIxMzIwQUxROU5QOFhLVkE5JmVuY3J5cHRlZEFkSWQ9QTA3MTU5MTFKUUY2VjBRNk8wQzQmd2lkZ2V0TmFtZT1zcF9hdGYmYWN0aW9uPWNsaWNrUmVkaXJlY3QmZG9Ob3RMb2dDbGljaz10cnVl
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
https://www.pololu.com/search/compare/22
The 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
https://www.pololu.com/product/4780
 
tlfong01
tlfong01
9:11 AM
As 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.
 

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