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Today I got a question from Garry on the Ohmify community.
[GARRY]:
“When I measure the voltage of my 9V battery using my multimeter I get a reading of 9.06 when it is not connected to any circuit. When I hook the battery up to a simple circuit (i.e. 325 Ohm resistor in series with a red LED) and measure the voltage drop across the battery I get a reading of 8.65 V – why the difference?”
I remember something I struggled with in the beginning.
The LED.
It’s supposed to have a fixed voltage drop, right?
Like 2V.
But what if I force 3V across its legs with a 3V battery?
I just published a new video where I answer the question:
“Does the resistor go before or after the LED?”
If you don’t want to watch the video, I’ve attached the script below so you can read it instead:
Imagine a circuit with two resistors in parallel.
If you’re not sure what that looks like, look at this image:
Let’s ignore the values above and instead say that R1 is 100 Ω and R2 is 100 000 Ω.
Can you quickly find the combined value of the two of them?
What if both of the values are 300 Ω?
You *could* use the formula for resistors in parallel and calculate it.
But there’s a quicker way.
Here’s a fun project.
Build a cool touch-sensitive lamp you can have on your desk.
Once you’ve built this project you can also apply the touch control to other things like a fan or a door bell.
The first thing you need to figure out is how to sense touch from a finger.
I like math.
But, I’m not an expert.
I know the basics.
But when it comes to more complicated stuff, like heavy derivation and integration, I think I’ve forgotten most of what I learned at the University.
These sensors are usually cheap.
And really easy to use!
An analog sensor is a sensor that gives you a voltage value that represents the measured value.
Per wrote me:
“What’s the easiest (cheapest) way to transfer a C program to a chip?”
Here’s my reply:
It depends on what chip it is.
Most microcontrollers require a programmer. This is a little thing you plug into the USB port that makes it possible to program the chip.
I really like the circuit that blinks a light with a relay.
Like this:
If you connect a battery to the electromagnet of a relay, through its normally closed contact, you will get a relay that switches on and off really fast.
If you add a big capacitor (like 1000 µF) over the electromagnet, the electromagnet will stay on longer.
I’ve done some research.
A couple of weeks ago Tek.no, a Norwegian tech-magazine, asked me if I could write an article for them.
There are a lot of people online claiming they have fixed broken graphic cards and other hardware, by baking it in an oven.
“What can you build with electronics?”, she asked me…
“Anything!” I said.
She looked at me with a blank stare. Apparently that was not a satisfying reply.
This happened to me a few days ago.
Sometimes I get too deep into electronics that I forget “normal” people don’t necessarily understand what you can do with electronics.
So…