I'm starting this week with some of the logistics of parts collecting to build your robot. I'm going to start with the brain. Our team has a robot that kinda works already, but is missing one major coolness feature. I'll be getting to that in future posts, but for now, the brain.
You will need a team of a half dozen once you get to the more advanced teams, and will need to focus on the mechanical and the brain at the same time to be able to have the robot ready for the big day. And so, on the brain we will start, and in the hope, I can give some clues as to the motorization side next week.
Every project requires a lot of tea, and some berry jam. Right now, you can see I'm just setting up my own rig, we want to have 2 rigs for the team to work on, to allow not a backup, but to allow parallel development, and to learn as quickly as possible.
1. Raspberry pi 4 in this build.
2. A display, anything HDMI ready is a good start, but regardless you will now need a micro HDMI cable. I'm using a old display here that takes a HDMI/VGA source, it worked perfectly, no need to mess with display config.
2. micro HDMI adapter (must be micro, not mini!)
3. 16 GB SD card (you want at least 2 cards prepared, they do fail a unlucky times.) Between your team you will have more cards, but be careful with them, they do get lost easily.
4. Keyboard - any one will do
5. Mouse Optional, but nice to have attached at various times.
6. USB-C cable. Cannot emphasize this one enough.
7. Camera, this will be the eyes of your robot. Any spare webcam will do to bootstrap us for now.
8. Heatsink . Yes, the pi4 overheats easily.
If you don't have a webcam , get the official pi one, the normal infrared filter version. Some of the original cameras are missing an IR (Infrared) filter. There's a story in how that happened: the first batch of pi cameras had a fault, they were missing a thin film which filters out infrared. That gave the camera the ability to actually see better in the dark. Which made it a hit with makers, because that turns out to be very useful in almost every maker application. It's possible to remove this filter in some cases, fiddly, but for this project, we want the one that comes without the filter. A USB webcam is bulky, but easier to work with to start out at this point.
You can buy everything online from a great number of sources. I'm going to be impartial as possible without being dishonest. I like to support the smaller businesses out there, amazon are easy to use, but are not a great role model. When we get to the mechanical post, I'll share more tips on where to buy parts from the smaller sellers, but all the basics can be bought by following links from the raspberry pi foundations' website. They have made it easy. You may end up a PiHut, Pimoroni, Element14 (Farnell) amongst others, but it's pretty much the same deal with very little variation.
Because our robot is going to be consuming a lot of power it's going to need batteries, but to save us messing about, I have a 12A supply handy. Notice the missing USBC power cable inlet and my GPIO hack.
You can grab a GPIO digram off the web and power the pi directly on the GPIO 5V pins as show in the image below. No risk of brownouts on account I have a super high capacity supply. We don't want brownouts either. more on that later. I'm going to show you a few tricks to reduce the prototyping costs as we go along. Because not everyone has access to an electronics parts bin. And the idea is not to have to need loads of spare parts anyway, it all costs. I am always scavenging old machines of all kinds. Most modern electronics are not good scavenge, the older it is, the better in general.
We are going to be using 18650 batteries, they are easy to get hold of, most laptop battery packs are made up of around 6 of them or something similar. You don't want damaged ones, new batteries will probably set you back £40 for a set.
Here you can also see my NOT aftermarket heatsink. It's clearly not a kit, because it's missing the second heatsink, because this heatsink came out of a dead power supply. It will need upgrading later, but for now, we are booted and can start coding. And that's the key, you need to work out how to start coding early while the rest of your team find the motors and other parts. It's all going to take longer than you think.
(CB)
