nilclass

joined 1 year ago
[–] nilclass@discuss.tchncs.de 5 points 2 weeks ago (1 children)

Sounds like you dodged a bullet, if that's how the CEO reacts to you declining the offer. Just imagine how they'd react to somone actually making a mistake at work

[–] nilclass@discuss.tchncs.de 7 points 1 month ago

It's a conspiracy, orchestrated by Big Adapter

[–] nilclass@discuss.tchncs.de 4 points 2 months ago (4 children)

ISS, as in: you get shot into space?

[–] nilclass@discuss.tchncs.de 35 points 2 months ago (6 children)

Oh, so they can't get autonomous driving to work, thus the next step is to get people who are sleeping to steer the cars remotely

[–] nilclass@discuss.tchncs.de 1 points 2 months ago

Great, good luck with that :)

Another thing that comes to mind: for audio purposes another technique used in ring modulators for audio effects is to use a mosfet switch to mix the signal with a square wave. This has more byproducts than mixing with a pure sine, but is a lot easier to do. Since you are downconcerting, it should not matter at all if you use a square wave, since the byproducts will all be (higher-order) harmonics of the local oscillator, which you'll filter out anyway.

[–] nilclass@discuss.tchncs.de 3 points 2 months ago (2 children)

I'm not sure I understand what you are trying to do... do you want to build a radio? Or are all your signals in the audio range?

Anyway:

Regarding Gilbert cells, the two popular chips are MC1496 and SA631. The 631 comes with a built-in oscillator, so it's quite handy. Unfortunately both are hard to come by these days.

[–] nilclass@discuss.tchncs.de 19 points 3 months ago

Sounds great, except i think this whole thing is about some punching game.. Not sure though, i'm not a sports person

[–] nilclass@discuss.tchncs.de 35 points 3 months ago (1 children)

Heresy! Australia will always be a planet.

[–] nilclass@discuss.tchncs.de 1 points 3 months ago

Growing plants with LEDs certainly works, I'm just wondering if the power of a USB port is enough

[–] nilclass@discuss.tchncs.de 1 points 3 months ago (2 children)

there's no need for relays if you have low voltage

That's a good point. Also makes me wonder if those lights will actually make a difference when it comes to plant growth, given the low power.

[–] nilclass@discuss.tchncs.de 6 points 3 months ago (2 children)

It's not completely stupid. One pissible issue: when the light level is around the threshold, slight variations (think: cloud passing by) will cause the relay to switch back and forth quickly. This can be solved with some additional parts (keyword: hysteresis).

I would recommend using a microcontroller, it makes this problem easy to solve, plus you can have more logic to trigger the lights (eg time based).

Another thing is turning off: if it's purely based on light level, you need to make sure the sensor does not "see" any of the LED light, otherwise it thinks the sun is back up

[–] nilclass@discuss.tchncs.de 6 points 5 months ago

I'm mindlessly scrolling through lemmy, for the glory of the empire!

 

I am powering a 5V microcontroller (arduino clone, atmega328p) using a 9V block and a buck converter. Now I want to let the microcontroller occasionally measure the battery voltage, so I can get an idea of how full it is.

My first idea was to use a simple voltage divider:

I've chosen the resistor values so that:

  • the voltage at the measure output is < 1.1V, to be able to use the 1.1V internal reference of the atmega's ADC
  • R1 || R2 < 10kΩ, since the atmega datasheet says "The ADC is optimized for analog signals with an output impedance of approximately 10 kΩ or less"

This is great and all, but what bothers me is that this circuit will constantly draw ~100µA from the battery.

So, my next thought was to add a mosfet to the divider, to switch it on only while measuring:

This is obviously bad, because now when the mosfet is off, the ADC input sees the whole battery voltage.

To address that issue, I've added a second mosfet into the measure path:

This works, and it does not draw any current, except while measuring.

However, it's quite a few parts. So I'm curious if anyone has an idea how to do this with just a single mosfet. It seems to me like it should be possible, but I haven't figured out how.

Oh, and if I'm doing something stupid here, please tell me :)

 

I have a whole bunch of them. They are possibly a bit older (70s, 80s) judging by other contents of the junk box they are from.

There are no labels of any kind, but on the top they have stripes that look hand painted.

For at least some of them the resistance roughly corresponds to the color code.

So, I'm just curious why I can't find anything about these on the internet.

 
 

I'm taking apart a broken tape recorder produced in the 70s (a Tesla B57, made in Czechoslovakia), to harvest some parts (inductors, switches, ...) and maybe reuse the case for some project.

Which made me wonder: are there any dangers to protect myself against? I know about lead, so I'll take precautions when desoldering things. Is there anything else to be aware of? Some fumes, other toxic materials, ...?

I'm not planning to connect the device to power in any way, so from an electrical perspective there should be nothing to worry about (except for caps maybe). Am I wrong?

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