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@Holly Good afternoon from Suffolk, VA! Working on lab 3 (Programming). I’m in the “circuits” portion. On that page, there is a link to a video explaining the differences of DC and AC electricity. When I hit the link, it crashes the browser on the RPi. FYSA!
@Holly Good afternoon again… Still going through the lab. Working on “Build a circuit”. Down towards the bottom under “Task: Build a Circuit”…7th task down “Connect to Ground”… the image shown shows the ground jumper connecting to the “positive” rail… not the “negative” rail as stated in the paragraph. Am I seeing this correctly? If so… I’m confused about HOW power is supposed to go in a circuit. Or… was this picture taken and morphed into another purpose?
@Holly Disregard… Its me in my interpretation f the image.
@Holly Lab three, “Build a Circuit”, “Equipment Needed”, 5th bubble/slide…. “Wires”. I didn’t use them as the jumper wire kit on the 9th bubble/slide facilitated the ‘jumper’ requirement. Redundant?
Lab three, “Write a Computer Program with a Circuit and GPIO Pins”, “Gather Materials”… states that ANY LED color will do., along with the 100 Ohm resistor. LED forward power range between 1.8V for RED to 4.0V for white.
“Task: Build a Circuit” , you state that forward voltage for GREEN is 2.2V. I thought 2.2 is for YELLOW? (The picture in this section shows a GREEN LED, not YELLOW.
In a prior portion of the lab…. under “Build a Circuit”, “Ohm’s Law”… are voltage values for varying LEDs… and are corroborated on the website link that you provided… https://www.electronics-tutorials.ws/diode/diode_8.html
Doing the calcs… YELLOW: Voltage supplied = 3.3-2.2 (forward voltage) = 1.1V R = V / I = 1.1V / 0.02ma = 55 Ω
GREEN: ” ” ” 3.3-3.5 ( ” ” ) ” -0.2V Doesn’t this mean that there’s not enough juice to pump through from the 3v3 power tap?
You would have to use a 5V tap, right? Which would mean that we’d have to figure out own resistor measurements, right?
So… for this portion of the lab… is the YELLOW LED the LED of choice?
Your thoughts?
@Holly… Good morning! Doing some reading in the Raspberry Pi book. Page 11… 1st para… “4 pins…” it says that the 3v3 can supply only up to 50mA.
Lab three… “Intro to GPIO Pins”, second section down, “Raspberry Pi GPIO Pins”… the external link https://pinout.xyz/pinout/3v3_power#, on that page for 3v3… it states that all pi’s since the B+ can go up to 500mA due to switching regulator.
Kind’a a big power difference. The book has a copyright of 2016. Is it safe to say that there has been some component upgrades over all… just like color coding to GPIO pins… that are transparent to most people? If so… how can I tell if I have an older model of an RPi… model 3 and older (As the book topped out on a model 3)?
Am I getting too much into the weeds on this?
Your thoughts?
Leo
Hi Leo, Plenty of things to address here. Thank you for bringing these things to our attention.
- I changed the link in the Intro to Circuits Topic to open in a separate tab. It seems to have helped on my end, please confirm if that has been fixed on yours.
- The image should show that the black (dark grey) wire connects the bottom leg of the LED to the far right power rail. The far right power rail connects to ground on the power supply that is connected to the top of the breadboard.
- The slide that has the wires on them is redundant; you are correct. I’ve removed it.
- Regarding the “LED of choice,” you make an excellent point. Being consistent is one of our biggest goals in this phase. I’ve changed the instruction.
- Finally, you are right about the book being a little outdated. After extensive research, this was the textbook that aligned most with the content of BISKit. Unfortunately the 2016 is so far the most current version of the book. And yes, it caps out at RPi 3 Model. I believe it is mentioned somewhere in Lab 1. The website is more likely to have the most accurate information. As far as our instruction goes, we strive to have the most up-to-date and accurate information. As for this specific detail, I would want to verify that every RPi we purchased has the switching regulator before I edit any informational details on the website. I believe it would be safer across the board to assume that 3v3 supplies at least 50 mA.
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