# Understanding a circuit diagram for a breadboard connection

#### tobe_sta

Joined Jan 9, 2019
2
Hi. I'm in the process of building an automatic dog feeder using this tutorial - https://www.instructables.com/id/Internet-Enabled-Raspberry-Pi-Pet-Feeder/. I'm OK with the Raspberry Pi and physical construction of the feeder side of things, but the electrical connections with the motor is new to me.

Looking at this diagram (https://cdn.instructables.com/FO1/0KOH/IIQC965A/FO10KOHIIQC965A.LARGE.jpg), I already have the motor, jumper wires and breadboard. I'm trying to work out 1. what other parts I need and 2. how I would connect them.

For 1. I believe I still need the following:
• 270 Ohm resistor (I can only find 330 online, is that fine?)
• 10K Ohm resistor
• NPN Bipolar Transistors (PN2222)
• Diode 1N4003 (I can only find 1N4001 or 1N4007)
For 2. I've been looking online for walkthroughs for connecting a motor to a breadboard as electronics are foreign territory to me.

Any help or advice is much appreciated!

#### ericgibbs

Joined Jan 29, 2010
12,264
hi tobe,
Welcome to AAC.
Do you have any details of your motor, ie: current/voltage, for checking that a PN2222 is suitable.?
Are you ask for a image of the bread board layout for this circuit.?
E

#### Raymond Genovese

Joined Mar 5, 2016
1,658
Because your Q2 has a lot to do with Q1, it is important to determine exactly the motor you have. Do you have this motor as per the Instructable? https://www.amazon.com/gp/product/B006W2HLSY?psc=1&redirect=true&ref_=oh_aui_detailpage_o03_s01

If so, look carefully at their picture:

Those two prongs are where you will connect the +12 and GND. Look carefully and you will see the + mark on one of the prongs. That is where the connection to +12V is made.

Note also that in the comments, some people reported that the RPM of what they were sent was much higher than the advertised RPM. Just be aware of that.

If you have a different motor, then you have to find out the characteristics of the motor that you have first. If you have the one pictured, then some of the specifications are in the advert - including the .07A rating which is a very important one.

The 330 ohm resistor will probably work just fine, but note that you can get 270 ohm resistors on line and sometimes it is recommended that a beginner get a collection of common values so that you will have them for other projects that you might undertake - see for example https://www.amazon.com/Ltvystore-15...d=1547125699&sr=1-9&keywords=resistor+package

Given a choice between the two diodes, choose the 1N4007.

You have not asked anything about how that small circuit works (the transistor switch), but this forum is a very good place to ask those questions. When you understand a bit more about the fundamentals, you will get a handle on some of the connection issues, so ask away.

Hope this helps.

#### tobe_sta

Joined Jan 9, 2019
2
Thanks for the replies.

Yep, that is the motor that I have purchased. I didn't know that about the prongs +/-, good to know. I think the tutorial expects you to have a decent background knowledge of electronics which I'm now trying to get my head around.

I'm trying to find a quick crash course on how these components work together and how I would then connect everything together on the breadboard. If there is an image of how a motor connects to a breadboard, that would be awesome. I'm happy to learn, but it's also a matter of I don't know what I don't know.

#### dl324

Joined Mar 30, 2015
12,682
270 Ohm resistor (I can only find 330 online, is that fine?)
10K Ohm resistor
NPN Bipolar Transistors (PN2222)
Diode 1N4003 (I can only find 1N4001 or 1N4007)
Before we can answer any of your questions, we need to know the current required by the motor, the HIGH level output voltage from the Pi, and how much current it can source.

Edited schematic:

#### Raymond Genovese

Joined Mar 5, 2016
1,658
Thanks for the replies.

Yep, that is the motor that I have purchased. I didn't know that about the prongs +/-, good to know. I think the tutorial expects you to have a decent background knowledge of electronics which I'm now trying to get my head around.

I'm trying to find a quick crash course on how these components work together and how I would then connect everything together on the breadboard. If there is an image of how a motor connects to a breadboard, that would be awesome. I'm happy to learn, but it's also a matter of I don't know what I don't know.
I think that you might benefit from some background first. Although that Instructable has a lot of pictures and is not a particularly advanced project, it might be hard to construct some of it if you have no experience at all.